AUTOMATIC ACQUISITION OF CT RADIATION DOSE DATA: USING THE DIAGNOSTIC REFERENCE LEVEL FOR RADIATION DOSE OPTIMIZATION

AUTOMATIC ACQUISITION OF CT RADIATION DOSE DATA: USING THE DIAGNOSTIC REFERENCE LEVEL FOR... Abstract The present work describes that we try to construct a system that collects dose information that performed CT examination from multiple facilities and unified management. The results of analysis are compared with other National diagnostic reference level (DRL), and the results are fed back to each facility and the cause of the abnormal value is investigated for dose optimization. Medical information collected 139 144 tests from 33 CT devices in 13 facilities. Although the DRL of this study is lower than that of Japan DRL, it was higher than the DRL of each country. When collecting all the examination, it is thought that the variation of the dose due to the error other than the intended imaging site is large. In future, we should continue to collect information in order to DRL renewal and we also think that it is desirable to collect information on physique and detailed scan region as well. INTRODUCTION Computed tomography (CT) is about 40 years old. Japan’s annual medical radiation dose per capita is the world’s largest, and most of the exposure is from CT examinations(1). Diagnostic reference level (DRL) recommendations to restrict exposure to that which is medically necessary have been made by the International Commission on Radiological Protection (ICRP)(2, 3). Regarding the role of DRL, if the typical dose used in the institution exceeds DRL, it is necessary to review to determine whether the dose is optimized unless there is a clinically valid cause is there. In general, investigate the performance and examination protocols (procedures) of the equipment used, find the cause of high dose (low dose), and take countermeasures to use a more appropriate dose. After taking countermeasures, dose optimization is achieved by reassessing the typical dose of the facility and confirming that it is lower than DRL. DRLs of CT examinations are expressed as volume CT dose index (CTDIvol, mGy) and dose-length products (DLP, mGy cm); for pediatrics, limits may be extrapolated from adult values, or set using pediatric phantoms(4–17). DRLs for Japan were published in 2015 using the 75th percentile of dosimetry data collected by questionnaire(18). There are three types of DRL: national DRL (NDRL), set at the national level; regional DRL (RDRL), set at the regional/academic level; and local DRL (LDRL), set at the individual center level(19). Dose indices from many centers are required to establish NDRL and RDRL, but rules on how to determine NDRL and RDRL have not been finalized. Modern radiographic diagnostic equipment records information including patient demographics, scan parameters and dose index. It is important to collect information on radiological examinations from several centers(20), and to build a dose management system capable of calculating RDRL and aggregating and managing dose information. There are several methods of collecting dosimetry data: Digital Imaging and Communications in Medicine (DICOM) headers(21, 22). Reading dose information from an image file containing data from the CT device(23). DICOM modality performed procedure step (MPPS)(24). DICOM structured report (DICOM SR)(25). We can easily read patient information and scan parameter information from a DICOM header, but the information on the dose index is often not recorded. The data recorded in the CT scanner of each manufacturers vary, and the examination information, the patient information, and the dose information are recorded as image data called ‘Dose report’ or ‘Dose sheet’. MPPS is a protocol for managing the information of the examination. The types of tags that can be handled are small in number and insufficient for dose management. DICOM standardized ‘CT Radiation Dose Reporting (Dose SR)’ in 2007 for the purpose of unifying the information output format used for dose management(26). And defined a template structure for the information to be output at DICOM part 16: content mapping resource(27). This template structure was summarizing different exposure doses and related information for each device into a unit called Information Object Definition (IOD) and defined as ‘CT Radiation Dose SR IOD templates’ (Figure 1). Furthermore, the International Electrotechnical Commission (IEC) was recommended outputting dose information according to the Dose SR standard for CT device in 2012(28). Figure 1. View largeDownload slide Fundamental structure of ‘CT radiation dose SRa Information Object Description (IOD) templates’. This is part of the CT dose SR template. The templates have a hierarchical structure, and there are other contents showing X-ray, mammography and fluoroscopy. As the hierarchy progresses, scan parameters other than dose information and patient information are also described. aSR = structured report; bTID = template ID. Figure 1. View largeDownload slide Fundamental structure of ‘CT radiation dose SRa Information Object Description (IOD) templates’. This is part of the CT dose SR template. The templates have a hierarchical structure, and there are other contents showing X-ray, mammography and fluoroscopy. As the hierarchy progresses, scan parameters other than dose information and patient information are also described. aSR = structured report; bTID = template ID. We collected RDSR on dose index for CT examination and attempted to construct an aggregation system that collects dose information and scan parameter of multiple facilities by collecting information by image capture of dose sheet for noncompliant CT devices. For dose optimization, we set regional DRL and the results of analysis were compared with other National DRL, and the results were fed back to each facility and the cause of the abnormal value was investigated. METHODS AND MATERIALS Patients This retrospective study was approved by the National Institute of Radiological Sciences (NIRS) and the ethics committees of the target centers. Target patients were those who underwent CT examination from October 2014 to December 2015. Patients 0 to ≤15 years of age were classified as pediatric, and were subdivided into 0–≤1 year old, 1–≤6 years old, 6–≤11 years old and 11–≤15 years old groups. Patients over 15 years old were classified as adults. Protocols All centers had CT scanners with >16 detectors, adjusted to the most appropriate scan parameters according to age, physique and examination(17). About protocol name, in the case of RDSR we referred to ‘Target region’ mentioned in CT irradiation event data of TID10013 and the case of Dose sheet we referred to ‘Body part examination’ of DICOM header. For the dose index, the collected data included contrast-enhanced examinations when a patient underwent an examination with >2 scans (i.e. three-phase contrast examination) both CTDIvol and DLP were calculated from the mean dose. Data acquisition Two types of collection tools were used, corresponding to Japan Dose Index Registry (J-DIR). One is the National Institute of Radiological Sciences Tool ‘NIRS Tool’ (Carestream Health, Tokyo, Japan) that we developed originally. It corresponds to collection of RDSR and information collection by image capture of CT Dose sheet. The other is a commercially available ‘Dose Manager’ (Cure Hope, Osaka, Japan), which supports collection of only RDSR. Both tools collect RDSR for a certain period and output, there is no difference in accuracy. For facilities that use models that cannot output RDSR from CT, we used the image capture version of NIRS Tool. The collection tool connected to each center’s network and acquires information in real time by collecting the RDSRs or dose sheets outputted from the CT device (Figure 2). We selected 13 centers equipped with CT scanners with different manufacturers roughly representative of the distribution throughout Japan (Figure 3). The collection period of each center varied depending on the permission of the center and the burden on the personnel (Table 1). Figure 2. View largeDownload slide RDSR acquisition system. This is the connection diagram of the Tool used in this study. We collected SR data from CT or PACS in real time. CT scanners not equipped to issue SRs were handled by image capture of the dose sheet. The acquisition data was compressed and anonymized the current day between 0 o’clock and 3 o’clock every day. In addition, we made anonymization that data cannot be concatenated. The technician uploads the anonymized data on SafeSync. NIRS aggregates the SR data from each facility to the server and uploads the analysis data again. Figure 2. View largeDownload slide RDSR acquisition system. This is the connection diagram of the Tool used in this study. We collected SR data from CT or PACS in real time. CT scanners not equipped to issue SRs were handled by image capture of the dose sheet. The acquisition data was compressed and anonymized the current day between 0 o’clock and 3 o’clock every day. In addition, we made anonymization that data cannot be concatenated. The technician uploads the anonymized data on SafeSync. NIRS aggregates the SR data from each facility to the server and uploads the analysis data again. Figure 3. View largeDownload slide Distribution of CT venders. (a) Distribution of CT venders in Japan(29), n = 11 349. (b) Distribution of CT venders in this study, n = 33. Figure 3. View largeDownload slide Distribution of CT venders. (a) Distribution of CT venders in Japan(29), n = 11 349. (b) Distribution of CT venders in this study, n = 33. Table 1. Collection period and examination number, age of adult and pediatric patients. Center  Bed  Scanner number  Toola  Acquisition period  Examination number of adult  Nunmber/scanner/dayb  Age (year old)  Examination number of pediatric  Nunmber/scanner/dayb  Age (year old)  Start  End  Male  Female  Total  Mean ± SD  Male  Female  Total  Mean ± SD  A  749  2  N  1/16/15  4/9/15  4575  3415  7990  48  64.07 ± 16.56  96  61  157  0.9  6.66 ± 4.84  B  712  1  N  7/9/15  12/30/15  7138  5335  12 473  72  66.48 ± 17.36  219  118  337  1.9  6.55 ± 4.88  Cc  740  3  N  7/8/15  12/31/15  7572  4588  12 160  23  64.21 ± 15.43  259  145  404  0.8  6.55 ± 4.48  D  676  2  N  8/19/15  9/29/15  902  752  1654  20  66.29 ± 17.61  23  12  35  0.4  6.49 ± 4.94  E  227  1  N  9/15/15  12/30/15  1306  1301  2607  25  68.81 ± 14.65  33  29  62  0.6  5.21 ± 4.54  F  715  2  Ncap  12/18/14  1/30/15  1205  910  2115  25  64.66 ± 15.03  11  17  28  0.3  8.96 ± 4.86  G  580  2  N  1/20/15  12/31/15  26 785  20 806  47 591  69  66.6 ± 15.53  264  144  408  0.6  9.54 ± 3.88  H  388  1  D  4/20/15  7/28/15  1596  1331  2927  30  64.87 ± 17.38  49  25  74  0.7  7.11 ± 4.76  Ic  600  2  D  11/18/15  12/31/15  1040  788  1828  21  61.46 ± 17.02  28  32  60  0.7  8.53 ± 4.49  J  269  2  N  9/29/15  12/31/15  2109  2041  4150  22  71.23 ± 14.57  6  0  6  0.03  11.17 ± 2.93  K  1001  6  N  10/29/15  12/30/15  4412  3526  7938  21  67.47 ± 14.26  28  13  41  0.1  9.07 ± 4.53  Lc  1225  4  N  10/28/14  2/2/15  8648  6958  15 606  40  60.93 ± 16.90  165  125  290  0.7  7.63 ± 4.34  Mc  600  5  N  2/19/15  12/31/15  9164  6673  15 837  10  65.24 ± 14.96  97  135  232  0.1  7.56 ± 4.79  Total  652.5 ± 271.27d  33    10/28/14  12/31/15  76 452  58 424  134 876  32.8 ± 19.15d  65.50 ± 15.92  1278  856  2134  0.62 ± 0.49 d  7.52 ± 0.43  Center  Bed  Scanner number  Toola  Acquisition period  Examination number of adult  Nunmber/scanner/dayb  Age (year old)  Examination number of pediatric  Nunmber/scanner/dayb  Age (year old)  Start  End  Male  Female  Total  Mean ± SD  Male  Female  Total  Mean ± SD  A  749  2  N  1/16/15  4/9/15  4575  3415  7990  48  64.07 ± 16.56  96  61  157  0.9  6.66 ± 4.84  B  712  1  N  7/9/15  12/30/15  7138  5335  12 473  72  66.48 ± 17.36  219  118  337  1.9  6.55 ± 4.88  Cc  740  3  N  7/8/15  12/31/15  7572  4588  12 160  23  64.21 ± 15.43  259  145  404  0.8  6.55 ± 4.48  D  676  2  N  8/19/15  9/29/15  902  752  1654  20  66.29 ± 17.61  23  12  35  0.4  6.49 ± 4.94  E  227  1  N  9/15/15  12/30/15  1306  1301  2607  25  68.81 ± 14.65  33  29  62  0.6  5.21 ± 4.54  F  715  2  Ncap  12/18/14  1/30/15  1205  910  2115  25  64.66 ± 15.03  11  17  28  0.3  8.96 ± 4.86  G  580  2  N  1/20/15  12/31/15  26 785  20 806  47 591  69  66.6 ± 15.53  264  144  408  0.6  9.54 ± 3.88  H  388  1  D  4/20/15  7/28/15  1596  1331  2927  30  64.87 ± 17.38  49  25  74  0.7  7.11 ± 4.76  Ic  600  2  D  11/18/15  12/31/15  1040  788  1828  21  61.46 ± 17.02  28  32  60  0.7  8.53 ± 4.49  J  269  2  N  9/29/15  12/31/15  2109  2041  4150  22  71.23 ± 14.57  6  0  6  0.03  11.17 ± 2.93  K  1001  6  N  10/29/15  12/30/15  4412  3526  7938  21  67.47 ± 14.26  28  13  41  0.1  9.07 ± 4.53  Lc  1225  4  N  10/28/14  2/2/15  8648  6958  15 606  40  60.93 ± 16.90  165  125  290  0.7  7.63 ± 4.34  Mc  600  5  N  2/19/15  12/31/15  9164  6673  15 837  10  65.24 ± 14.96  97  135  232  0.1  7.56 ± 4.79  Total  652.5 ± 271.27d  33    10/28/14  12/31/15  76 452  58 424  134 876  32.8 ± 19.15d  65.50 ± 15.92  1278  856  2134  0.62 ± 0.49 d  7.52 ± 0.43  aN, NIRS Tool; Ncap, NIRS Tool capture version; D, Dose Manager. bThe value is total examination number per acquisition period day and scaner number. cThe center is a university hospital. dThe value is mean value ± SD. View Large Table 1. Collection period and examination number, age of adult and pediatric patients. Center  Bed  Scanner number  Toola  Acquisition period  Examination number of adult  Nunmber/scanner/dayb  Age (year old)  Examination number of pediatric  Nunmber/scanner/dayb  Age (year old)  Start  End  Male  Female  Total  Mean ± SD  Male  Female  Total  Mean ± SD  A  749  2  N  1/16/15  4/9/15  4575  3415  7990  48  64.07 ± 16.56  96  61  157  0.9  6.66 ± 4.84  B  712  1  N  7/9/15  12/30/15  7138  5335  12 473  72  66.48 ± 17.36  219  118  337  1.9  6.55 ± 4.88  Cc  740  3  N  7/8/15  12/31/15  7572  4588  12 160  23  64.21 ± 15.43  259  145  404  0.8  6.55 ± 4.48  D  676  2  N  8/19/15  9/29/15  902  752  1654  20  66.29 ± 17.61  23  12  35  0.4  6.49 ± 4.94  E  227  1  N  9/15/15  12/30/15  1306  1301  2607  25  68.81 ± 14.65  33  29  62  0.6  5.21 ± 4.54  F  715  2  Ncap  12/18/14  1/30/15  1205  910  2115  25  64.66 ± 15.03  11  17  28  0.3  8.96 ± 4.86  G  580  2  N  1/20/15  12/31/15  26 785  20 806  47 591  69  66.6 ± 15.53  264  144  408  0.6  9.54 ± 3.88  H  388  1  D  4/20/15  7/28/15  1596  1331  2927  30  64.87 ± 17.38  49  25  74  0.7  7.11 ± 4.76  Ic  600  2  D  11/18/15  12/31/15  1040  788  1828  21  61.46 ± 17.02  28  32  60  0.7  8.53 ± 4.49  J  269  2  N  9/29/15  12/31/15  2109  2041  4150  22  71.23 ± 14.57  6  0  6  0.03  11.17 ± 2.93  K  1001  6  N  10/29/15  12/30/15  4412  3526  7938  21  67.47 ± 14.26  28  13  41  0.1  9.07 ± 4.53  Lc  1225  4  N  10/28/14  2/2/15  8648  6958  15 606  40  60.93 ± 16.90  165  125  290  0.7  7.63 ± 4.34  Mc  600  5  N  2/19/15  12/31/15  9164  6673  15 837  10  65.24 ± 14.96  97  135  232  0.1  7.56 ± 4.79  Total  652.5 ± 271.27d  33    10/28/14  12/31/15  76 452  58 424  134 876  32.8 ± 19.15d  65.50 ± 15.92  1278  856  2134  0.62 ± 0.49 d  7.52 ± 0.43  Center  Bed  Scanner number  Toola  Acquisition period  Examination number of adult  Nunmber/scanner/dayb  Age (year old)  Examination number of pediatric  Nunmber/scanner/dayb  Age (year old)  Start  End  Male  Female  Total  Mean ± SD  Male  Female  Total  Mean ± SD  A  749  2  N  1/16/15  4/9/15  4575  3415  7990  48  64.07 ± 16.56  96  61  157  0.9  6.66 ± 4.84  B  712  1  N  7/9/15  12/30/15  7138  5335  12 473  72  66.48 ± 17.36  219  118  337  1.9  6.55 ± 4.88  Cc  740  3  N  7/8/15  12/31/15  7572  4588  12 160  23  64.21 ± 15.43  259  145  404  0.8  6.55 ± 4.48  D  676  2  N  8/19/15  9/29/15  902  752  1654  20  66.29 ± 17.61  23  12  35  0.4  6.49 ± 4.94  E  227  1  N  9/15/15  12/30/15  1306  1301  2607  25  68.81 ± 14.65  33  29  62  0.6  5.21 ± 4.54  F  715  2  Ncap  12/18/14  1/30/15  1205  910  2115  25  64.66 ± 15.03  11  17  28  0.3  8.96 ± 4.86  G  580  2  N  1/20/15  12/31/15  26 785  20 806  47 591  69  66.6 ± 15.53  264  144  408  0.6  9.54 ± 3.88  H  388  1  D  4/20/15  7/28/15  1596  1331  2927  30  64.87 ± 17.38  49  25  74  0.7  7.11 ± 4.76  Ic  600  2  D  11/18/15  12/31/15  1040  788  1828  21  61.46 ± 17.02  28  32  60  0.7  8.53 ± 4.49  J  269  2  N  9/29/15  12/31/15  2109  2041  4150  22  71.23 ± 14.57  6  0  6  0.03  11.17 ± 2.93  K  1001  6  N  10/29/15  12/30/15  4412  3526  7938  21  67.47 ± 14.26  28  13  41  0.1  9.07 ± 4.53  Lc  1225  4  N  10/28/14  2/2/15  8648  6958  15 606  40  60.93 ± 16.90  165  125  290  0.7  7.63 ± 4.34  Mc  600  5  N  2/19/15  12/31/15  9164  6673  15 837  10  65.24 ± 14.96  97  135  232  0.1  7.56 ± 4.79  Total  652.5 ± 271.27d  33    10/28/14  12/31/15  76 452  58 424  134 876  32.8 ± 19.15d  65.50 ± 15.92  1278  856  2134  0.62 ± 0.49 d  7.52 ± 0.43  aN, NIRS Tool; Ncap, NIRS Tool capture version; D, Dose Manager. bThe value is total examination number per acquisition period day and scaner number. cThe center is a university hospital. dThe value is mean value ± SD. View Large The NIRS tool compresses and anonymizes the current day’s RDSR between midnight and 3:00 am. Also, performs anonymization that cannot be concatenated. The information acquired from each facilities should be aggregated in the RDSR server in NIRS via the network, but it was impossible to realize because the clinical network did not allow connection with the external network due to facility policy problem. Therefore, as a method of acquiring information collected by each facility, we thought that it was safe to share it with NIRS by another PC connected to the virtual private network (VPN). Sharing is one to one with NIRS and each facility, and facility sharing is not done. In order to realize these sharing we used SafeSync (Trend Micro Incorporated, Tokyo, Japan). The data were aggregated into the RDSR System of a dedicated server. Dose Manager was able to output RDSR collected from CT at all times in anonymous state and shared by SafeSync. Data analysis The data of each center aggregated in the RDSR System were output with comma separated values (csv) and analyzed with spreadsheet software (Excel 2013, Microsoft Office, Redmond WA, USA). Data are expressed as mean ± standard deviation (SD). We used the VPN to summarize each center on a spreadsheet, and examined analytic data from each center. Comparison of dose-related data to DRLs RDSR and dose sheets included CTDIvol and DLP for the dose index, calculated the mean and SD for each anatomical region in adults and children, the representative value of each center. For CTDIvol and DLP of ‘Head and Brain’, ‘Circle of Willis’, ‘Eye region’ and ‘Orbit region’ in adults, the dose index value normalized to a 16-cm phantom standard is shown. For the other anatomical regions, it shows the values normalized to a 32-cm phantom. For the CTDIvol and DLP of pediatric patients, the values derived with the 32-cm phantom were doubled to simulate a 16-cm phantom(17). The mean and SD values, minimum value, 25th percentile, 50th percentile, 75th percentile and maximum value were calculated from the dose indices of each center. The mean value of each center was used as a representative value, and its 75th percentile values were taken as adult and pediatric DRLs in this study. We compared our findings with DRLs of the head, chest, abdomen and heart in adults from data published by 10 countries. The pediatric DRL was compared with DRLs of head, chest and abdominal CT published from six countries. RESULTS The total number of centers participating in the survey was 13, of which four were university hospitals. The number of beds was 227 in the smallest center and 1225 in the largest (Table 1). There were 134 876 examinations of patients over 15 years old (males: 76 452, females: 58 424) with RDSR obtained during the survey period from October 2014 to December 2015, and there were 2134 examinations of patients ≤15 years old (males: 1278, females: 856). There were 84 203 adult (males: 47 213, females: 36 990) and 1316 pediatric (males: 745, females: 571) subjects. The mean value for all centers was 32.8 ± 19.15 cases per day. The mean value for pediatric cases at all centers was 0.6 cases. The mean age of adults was 65.5 ± 15.92 years and the mean age of pediatric subjects was 7.5 ± 0.43 years. Figure 4 shows the age ranges in more detail. Figure 4. View largeDownload slide Distribution of examinations by age and sex. Figure 4. View largeDownload slide Distribution of examinations by age and sex. The total number of CT devices targeted for collection was 33, and all had more than 16 rows of detectors. Figure 3 shows the vendor breakdown and departures from the average. No Hitachi scanners were included. Table 2 shows the 20 target regions acquired from all the centers. ‘Unknown’ cases were excluded from the analysis. Table 2. Acquisition of CT target region and patient number of adult and pediatric patients. Target region (SRTa)  Adult examination number  Pediatric examination number  M  F  Total  M  F  Total  Head (T-D1100), brain (T-A0100)  14 302  11 826  26 128  535  374  909  Circle of Willis (T-45526)  0  9  9  0  0  0  Eye region (T-D0801)  1002  977  1979  83  45  128  Orbit region (T-D0801)  297  245  542  30  21  51  Neck (T-D1600)  2177  1580  3757  49  24  73  Heart (T-32000)  182  97  279  0  0  0  Chest (T-D3000)  29 726  22 592  52 318  193  145  338  Abdomen (T-D4000)  19 745  14 145  33 890  110  80  190  Chest and abdomen (R-FAB55)  3974  3355  7329  50  41  91  Chest, abdomen and pelvis (R-FAB56)  1940  1143  3083  82  33  115  Entire body (T-D0010)  216  90  306  22  16  38  Pelvis (T-D6000)  311  356  667  11  4  15  Lumbar spine (T-11503)  551  437  988  11  8  19  Spine (T-D0146)  13  22  35  2  0  2  Extremity (T-D0300)  537  556  1093  23  13  36  Arm (T-D8200)  26  23  49  4  1  5  Shoulder (T-D2220)  519  257  776  17  8  25  Leg (T-D9400)  116  67  183  12  7  19  Unknown (00001,99GEMS)  818  647  1465  44  36  80  Total examination number  76 452  58 424  134 876  1278  856  2134  Target region (SRTa)  Adult examination number  Pediatric examination number  M  F  Total  M  F  Total  Head (T-D1100), brain (T-A0100)  14 302  11 826  26 128  535  374  909  Circle of Willis (T-45526)  0  9  9  0  0  0  Eye region (T-D0801)  1002  977  1979  83  45  128  Orbit region (T-D0801)  297  245  542  30  21  51  Neck (T-D1600)  2177  1580  3757  49  24  73  Heart (T-32000)  182  97  279  0  0  0  Chest (T-D3000)  29 726  22 592  52 318  193  145  338  Abdomen (T-D4000)  19 745  14 145  33 890  110  80  190  Chest and abdomen (R-FAB55)  3974  3355  7329  50  41  91  Chest, abdomen and pelvis (R-FAB56)  1940  1143  3083  82  33  115  Entire body (T-D0010)  216  90  306  22  16  38  Pelvis (T-D6000)  311  356  667  11  4  15  Lumbar spine (T-11503)  551  437  988  11  8  19  Spine (T-D0146)  13  22  35  2  0  2  Extremity (T-D0300)  537  556  1093  23  13  36  Arm (T-D8200)  26  23  49  4  1  5  Shoulder (T-D2220)  519  257  776  17  8  25  Leg (T-D9400)  116  67  183  12  7  19  Unknown (00001,99GEMS)  818  647  1465  44  36  80  Total examination number  76 452  58 424  134 876  1278  856  2134  aSRT is structured reporting templates. Table 2. Acquisition of CT target region and patient number of adult and pediatric patients. Target region (SRTa)  Adult examination number  Pediatric examination number  M  F  Total  M  F  Total  Head (T-D1100), brain (T-A0100)  14 302  11 826  26 128  535  374  909  Circle of Willis (T-45526)  0  9  9  0  0  0  Eye region (T-D0801)  1002  977  1979  83  45  128  Orbit region (T-D0801)  297  245  542  30  21  51  Neck (T-D1600)  2177  1580  3757  49  24  73  Heart (T-32000)  182  97  279  0  0  0  Chest (T-D3000)  29 726  22 592  52 318  193  145  338  Abdomen (T-D4000)  19 745  14 145  33 890  110  80  190  Chest and abdomen (R-FAB55)  3974  3355  7329  50  41  91  Chest, abdomen and pelvis (R-FAB56)  1940  1143  3083  82  33  115  Entire body (T-D0010)  216  90  306  22  16  38  Pelvis (T-D6000)  311  356  667  11  4  15  Lumbar spine (T-11503)  551  437  988  11  8  19  Spine (T-D0146)  13  22  35  2  0  2  Extremity (T-D0300)  537  556  1093  23  13  36  Arm (T-D8200)  26  23  49  4  1  5  Shoulder (T-D2220)  519  257  776  17  8  25  Leg (T-D9400)  116  67  183  12  7  19  Unknown (00001,99GEMS)  818  647  1465  44  36  80  Total examination number  76 452  58 424  134 876  1278  856  2134  Target region (SRTa)  Adult examination number  Pediatric examination number  M  F  Total  M  F  Total  Head (T-D1100), brain (T-A0100)  14 302  11 826  26 128  535  374  909  Circle of Willis (T-45526)  0  9  9  0  0  0  Eye region (T-D0801)  1002  977  1979  83  45  128  Orbit region (T-D0801)  297  245  542  30  21  51  Neck (T-D1600)  2177  1580  3757  49  24  73  Heart (T-32000)  182  97  279  0  0  0  Chest (T-D3000)  29 726  22 592  52 318  193  145  338  Abdomen (T-D4000)  19 745  14 145  33 890  110  80  190  Chest and abdomen (R-FAB55)  3974  3355  7329  50  41  91  Chest, abdomen and pelvis (R-FAB56)  1940  1143  3083  82  33  115  Entire body (T-D0010)  216  90  306  22  16  38  Pelvis (T-D6000)  311  356  667  11  4  15  Lumbar spine (T-11503)  551  437  988  11  8  19  Spine (T-D0146)  13  22  35  2  0  2  Extremity (T-D0300)  537  556  1093  23  13  36  Arm (T-D8200)  26  23  49  4  1  5  Shoulder (T-D2220)  519  257  776  17  8  25  Leg (T-D9400)  116  67  183  12  7  19  Unknown (00001,99GEMS)  818  647  1465  44  36  80  Total examination number  76 452  58 424  134 876  1278  856  2134  aSRT is structured reporting templates. Table 3 shows the ranges and values of the CTDIvol and DLP of each target region at each center as a representative value in adults. Table 4 shows the pediatric values. Table 3. CTDIvol and DLP for single scan of each anatomical region for adult. Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)  DLP (mGy cm)  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  Head (T-D1100)b, Brain (T-A0100)b  13  26 128  68.9  11.26  47  62  67  78  88  1170.7  268.81  655  1059  1174  1292  1684  Circle of Willis (T-45526)b  1  9  29.2  0  29  29  29  29  29  558.3  0  558  558  558  558  558  Eye region (T-D0801)b  4  1979  35.0  11.52  20  29  37  44  45  624.3  205.52  344  563  658  720  836  Orbit region (T-D0801)b  5  542  39.9  19.15  19  29  36  46  69  719.2  636.24  293  351  520  596  1836  Neck (T-D1600)  13  3757  20.1  12.85  9  12  18  24  58  566.3  376.04  236  392  513  553  1741  Heart (T-32000)  3  279  41.6  27.12  18  27  36  54  71  983.6  292.97  653  871  1089  1149  1210  Chest (T-D3000)  13  52 318  16.3  14.66  8  11  12  15  63  721.5  337.52  290  587  659  689  1660  Abdomen (T-D4000)  13  33 890  15.4  15.03  8  10  11  12  65  641.3  344.54  351  485  549  640  1706  Chest and abdomen (R-FAB55)  2  7329  36.4  41.28  7  22  36  51  66  1039.3  963.45  358  699  1039  1380  1721  Chest, abdomen and pelvis (R-FAB56)  2  3083  17.0  0.73  17  17  17  17  18  877.3  20.63  863  870  877  885  892  Entire body (T-D0010)  2  306  61.7  19.39  48  55  62  69  75  1779.9  217.16  1626  1703  1780  1857  1934  Pelvis (T-D6000)  11  667  19.9  14.01  8  13  15  21  57  854.9  379.42  335  637  740  1031  1514  Lumbar spine (T-11503)  7  988  20.4  8.39  10  17  19  20  37  641.8  67.45  529  611  655  673  740  Spine (T-D0146)  1  35  7.6  0  8  8  8  8  8  346.6  0  347  347  347  347  347  Extremity (T-D0300)  10  1093  12.8  7.16  7  8  11  12  29  544.7  172.83  144  488  542  685  722  Arm (T-D8200)  2  49  17.9  4.95  14  16  18  20  21  602.4  118.05  519  561  602  644  686  Shoulder (T-D2220)  8  776  18.3  7.25  5  16  21  23  26  439.1  175.34  126  348  538  558  581  Leg (T-D9400)  5  183  22.2  25.15  4  9  10  22  66  692.5  448.17  228  529  553  724  1428  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)  DLP (mGy cm)  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  Head (T-D1100)b, Brain (T-A0100)b  13  26 128  68.9  11.26  47  62  67  78  88  1170.7  268.81  655  1059  1174  1292  1684  Circle of Willis (T-45526)b  1  9  29.2  0  29  29  29  29  29  558.3  0  558  558  558  558  558  Eye region (T-D0801)b  4  1979  35.0  11.52  20  29  37  44  45  624.3  205.52  344  563  658  720  836  Orbit region (T-D0801)b  5  542  39.9  19.15  19  29  36  46  69  719.2  636.24  293  351  520  596  1836  Neck (T-D1600)  13  3757  20.1  12.85  9  12  18  24  58  566.3  376.04  236  392  513  553  1741  Heart (T-32000)  3  279  41.6  27.12  18  27  36  54  71  983.6  292.97  653  871  1089  1149  1210  Chest (T-D3000)  13  52 318  16.3  14.66  8  11  12  15  63  721.5  337.52  290  587  659  689  1660  Abdomen (T-D4000)  13  33 890  15.4  15.03  8  10  11  12  65  641.3  344.54  351  485  549  640  1706  Chest and abdomen (R-FAB55)  2  7329  36.4  41.28  7  22  36  51  66  1039.3  963.45  358  699  1039  1380  1721  Chest, abdomen and pelvis (R-FAB56)  2  3083  17.0  0.73  17  17  17  17  18  877.3  20.63  863  870  877  885  892  Entire body (T-D0010)  2  306  61.7  19.39  48  55  62  69  75  1779.9  217.16  1626  1703  1780  1857  1934  Pelvis (T-D6000)  11  667  19.9  14.01  8  13  15  21  57  854.9  379.42  335  637  740  1031  1514  Lumbar spine (T-11503)  7  988  20.4  8.39  10  17  19  20  37  641.8  67.45  529  611  655  673  740  Spine (T-D0146)  1  35  7.6  0  8  8  8  8  8  346.6  0  347  347  347  347  347  Extremity (T-D0300)  10  1093  12.8  7.16  7  8  11  12  29  544.7  172.83  144  488  542  685  722  Arm (T-D8200)  2  49  17.9  4.95  14  16  18  20  21  602.4  118.05  519  561  602  644  686  Shoulder (T-D2220)  8  776  18.3  7.25  5  16  21  23  26  439.1  175.34  126  348  538  558  581  Leg (T-D9400)  5  183  22.2  25.15  4  9  10  22  66  692.5  448.17  228  529  553  724  1428  aSRT is structured reporting templates. bCTDIvol and DLP values adjusted to 16-cm PMMA phantom. Table 3. CTDIvol and DLP for single scan of each anatomical region for adult. Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)  DLP (mGy cm)  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  Head (T-D1100)b, Brain (T-A0100)b  13  26 128  68.9  11.26  47  62  67  78  88  1170.7  268.81  655  1059  1174  1292  1684  Circle of Willis (T-45526)b  1  9  29.2  0  29  29  29  29  29  558.3  0  558  558  558  558  558  Eye region (T-D0801)b  4  1979  35.0  11.52  20  29  37  44  45  624.3  205.52  344  563  658  720  836  Orbit region (T-D0801)b  5  542  39.9  19.15  19  29  36  46  69  719.2  636.24  293  351  520  596  1836  Neck (T-D1600)  13  3757  20.1  12.85  9  12  18  24  58  566.3  376.04  236  392  513  553  1741  Heart (T-32000)  3  279  41.6  27.12  18  27  36  54  71  983.6  292.97  653  871  1089  1149  1210  Chest (T-D3000)  13  52 318  16.3  14.66  8  11  12  15  63  721.5  337.52  290  587  659  689  1660  Abdomen (T-D4000)  13  33 890  15.4  15.03  8  10  11  12  65  641.3  344.54  351  485  549  640  1706  Chest and abdomen (R-FAB55)  2  7329  36.4  41.28  7  22  36  51  66  1039.3  963.45  358  699  1039  1380  1721  Chest, abdomen and pelvis (R-FAB56)  2  3083  17.0  0.73  17  17  17  17  18  877.3  20.63  863  870  877  885  892  Entire body (T-D0010)  2  306  61.7  19.39  48  55  62  69  75  1779.9  217.16  1626  1703  1780  1857  1934  Pelvis (T-D6000)  11  667  19.9  14.01  8  13  15  21  57  854.9  379.42  335  637  740  1031  1514  Lumbar spine (T-11503)  7  988  20.4  8.39  10  17  19  20  37  641.8  67.45  529  611  655  673  740  Spine (T-D0146)  1  35  7.6  0  8  8  8  8  8  346.6  0  347  347  347  347  347  Extremity (T-D0300)  10  1093  12.8  7.16  7  8  11  12  29  544.7  172.83  144  488  542  685  722  Arm (T-D8200)  2  49  17.9  4.95  14  16  18  20  21  602.4  118.05  519  561  602  644  686  Shoulder (T-D2220)  8  776  18.3  7.25  5  16  21  23  26  439.1  175.34  126  348  538  558  581  Leg (T-D9400)  5  183  22.2  25.15  4  9  10  22  66  692.5  448.17  228  529  553  724  1428  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)  DLP (mGy cm)  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  Head (T-D1100)b, Brain (T-A0100)b  13  26 128  68.9  11.26  47  62  67  78  88  1170.7  268.81  655  1059  1174  1292  1684  Circle of Willis (T-45526)b  1  9  29.2  0  29  29  29  29  29  558.3  0  558  558  558  558  558  Eye region (T-D0801)b  4  1979  35.0  11.52  20  29  37  44  45  624.3  205.52  344  563  658  720  836  Orbit region (T-D0801)b  5  542  39.9  19.15  19  29  36  46  69  719.2  636.24  293  351  520  596  1836  Neck (T-D1600)  13  3757  20.1  12.85  9  12  18  24  58  566.3  376.04  236  392  513  553  1741  Heart (T-32000)  3  279  41.6  27.12  18  27  36  54  71  983.6  292.97  653  871  1089  1149  1210  Chest (T-D3000)  13  52 318  16.3  14.66  8  11  12  15  63  721.5  337.52  290  587  659  689  1660  Abdomen (T-D4000)  13  33 890  15.4  15.03  8  10  11  12  65  641.3  344.54  351  485  549  640  1706  Chest and abdomen (R-FAB55)  2  7329  36.4  41.28  7  22  36  51  66  1039.3  963.45  358  699  1039  1380  1721  Chest, abdomen and pelvis (R-FAB56)  2  3083  17.0  0.73  17  17  17  17  18  877.3  20.63  863  870  877  885  892  Entire body (T-D0010)  2  306  61.7  19.39  48  55  62  69  75  1779.9  217.16  1626  1703  1780  1857  1934  Pelvis (T-D6000)  11  667  19.9  14.01  8  13  15  21  57  854.9  379.42  335  637  740  1031  1514  Lumbar spine (T-11503)  7  988  20.4  8.39  10  17  19  20  37  641.8  67.45  529  611  655  673  740  Spine (T-D0146)  1  35  7.6  0  8  8  8  8  8  346.6  0  347  347  347  347  347  Extremity (T-D0300)  10  1093  12.8  7.16  7  8  11  12  29  544.7  172.83  144  488  542  685  722  Arm (T-D8200)  2  49  17.9  4.95  14  16  18  20  21  602.4  118.05  519  561  602  644  686  Shoulder (T-D2220)  8  776  18.3  7.25  5  16  21  23  26  439.1  175.34  126  348  538  558  581  Leg (T-D9400)  5  183  22.2  25.15  4  9  10  22  66  692.5  448.17  228  529  553  724  1428  aSRT is structured reporting templates. bCTDIvol and DLP values adjusted to 16-cm PMMA phantom. Table 4. CTDIvol and DLP for single scan of each anatomical region for pediatric. Age group (years)  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)b  DLP (mGy cm)b  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  0 to <1  Head (T-D1100), brain (T-A0100)  11  85  35.0  13.92  14  27  35  43  60  529.1  261.03  180  351  509  739  928  Neck (T-D1600)  3  5  8.8  3.06  5  8  10  11  11  119.8  59.72  70  87  103  145  186  Chest (T-D3000)  9  49  9.2  8.87  1  4  9  10  31  117.5  125.02  2  51  79  123  406  Abdomen (T-D4000)  6  18  5.2  3.50  1  3  4  7  11  105.6  76.39  18  60  81  161  213  Chest and abdomen (R-FAB55)  2  13  31.0  34.19  7  19  31  43  55  384.5  445.91  69  227  385  542  700  1 to <6  Head (T-D1100), brain (T-A0100)  11  239  42.1  20.76  6  32  39  56  82  708.5  295.03  242  577  667  863  1320  Neck (T-D1600)  6  19  11.4  4.63  6  8  11  14  18  128.5  69.53  70  80  104  153  251  Chest (T-D3000)  9  104  15.1  18.33  4  6  9  13  63  180.0  145.15  69  83  117  236  507  Abdomen (T-D4000)  7  48  14.4  23.23  2  4  7  8  67  211.5  236.66  37  108  126  184  734  Chest and abdomen (R-FAB55)  2  19  25.4  27.38  6  16  25  35  45  343.7  331.91  109  226  344  461  578  6 to <11  Head (T-D1100), brain (T-A0100)  13  311  59.9  22.10  26  48  59  67  103  950.8  417.27  226  692  911  1249  1706  Neck (T-D1600)  8  22  19.7  11.13  7  11  17  27  36  300.6  250.77  62  146  187  433  725  Chest (T-D3000)  9  87  16.3  19.03  4  5  8  12  57  328.5  400.11  70  94  157  215  1192  Abdomen (T-D4000)  10  51  12.9  15.82  3  5  8  12  57  196.7  188.33  30  99  125  242  683  Chest and abdomen (R-FAB55)  2  27  41.8  48.17  8  25  42  59  76  467.5  514.75  104  286  467  649  831  11 to <15  Head (T-D1100), brain (T-A0100)  13  274  59.8  23.31  1  52  64  71  92  1090.0  398.56  436  799  1056  1278  1733  Neck (T-D1600)  5  27  38.4  19.27  19  23  33  57  60  704.6  350.26  180  508  901  967  967  Chest (T-D3000)  10  98  31.3  33.76  8  12  17  25  103  530.1  343.12  226  282  376  702  1117  Abdomen (T-D4000)  13  73  15.9  8.72  4  10  13  22  32  396.1  246.51  10  198  439  622  780  Chest and abdomen (R-FAB55)  2  32  40.3  43.42  10  25  40  56  71  730.7  395.64  274  617  959  959  959  Age group (years)  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)b  DLP (mGy cm)b  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  0 to <1  Head (T-D1100), brain (T-A0100)  11  85  35.0  13.92  14  27  35  43  60  529.1  261.03  180  351  509  739  928  Neck (T-D1600)  3  5  8.8  3.06  5  8  10  11  11  119.8  59.72  70  87  103  145  186  Chest (T-D3000)  9  49  9.2  8.87  1  4  9  10  31  117.5  125.02  2  51  79  123  406  Abdomen (T-D4000)  6  18  5.2  3.50  1  3  4  7  11  105.6  76.39  18  60  81  161  213  Chest and abdomen (R-FAB55)  2  13  31.0  34.19  7  19  31  43  55  384.5  445.91  69  227  385  542  700  1 to <6  Head (T-D1100), brain (T-A0100)  11  239  42.1  20.76  6  32  39  56  82  708.5  295.03  242  577  667  863  1320  Neck (T-D1600)  6  19  11.4  4.63  6  8  11  14  18  128.5  69.53  70  80  104  153  251  Chest (T-D3000)  9  104  15.1  18.33  4  6  9  13  63  180.0  145.15  69  83  117  236  507  Abdomen (T-D4000)  7  48  14.4  23.23  2  4  7  8  67  211.5  236.66  37  108  126  184  734  Chest and abdomen (R-FAB55)  2  19  25.4  27.38  6  16  25  35  45  343.7  331.91  109  226  344  461  578  6 to <11  Head (T-D1100), brain (T-A0100)  13  311  59.9  22.10  26  48  59  67  103  950.8  417.27  226  692  911  1249  1706  Neck (T-D1600)  8  22  19.7  11.13  7  11  17  27  36  300.6  250.77  62  146  187  433  725  Chest (T-D3000)  9  87  16.3  19.03  4  5  8  12  57  328.5  400.11  70  94  157  215  1192  Abdomen (T-D4000)  10  51  12.9  15.82  3  5  8  12  57  196.7  188.33  30  99  125  242  683  Chest and abdomen (R-FAB55)  2  27  41.8  48.17  8  25  42  59  76  467.5  514.75  104  286  467  649  831  11 to <15  Head (T-D1100), brain (T-A0100)  13  274  59.8  23.31  1  52  64  71  92  1090.0  398.56  436  799  1056  1278  1733  Neck (T-D1600)  5  27  38.4  19.27  19  23  33  57  60  704.6  350.26  180  508  901  967  967  Chest (T-D3000)  10  98  31.3  33.76  8  12  17  25  103  530.1  343.12  226  282  376  702  1117  Abdomen (T-D4000)  13  73  15.9  8.72  4  10  13  22  32  396.1  246.51  10  198  439  622  780  Chest and abdomen (R-FAB55)  2  32  40.3  43.42  10  25  40  56  71  730.7  395.64  274  617  959  959  959  aSRT is structured reporting templates. bThe values adjusted to 16-cm PMMA phantom. Table 4. CTDIvol and DLP for single scan of each anatomical region for pediatric. Age group (years)  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)b  DLP (mGy cm)b  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  0 to <1  Head (T-D1100), brain (T-A0100)  11  85  35.0  13.92  14  27  35  43  60  529.1  261.03  180  351  509  739  928  Neck (T-D1600)  3  5  8.8  3.06  5  8  10  11  11  119.8  59.72  70  87  103  145  186  Chest (T-D3000)  9  49  9.2  8.87  1  4  9  10  31  117.5  125.02  2  51  79  123  406  Abdomen (T-D4000)  6  18  5.2  3.50  1  3  4  7  11  105.6  76.39  18  60  81  161  213  Chest and abdomen (R-FAB55)  2  13  31.0  34.19  7  19  31  43  55  384.5  445.91  69  227  385  542  700  1 to <6  Head (T-D1100), brain (T-A0100)  11  239  42.1  20.76  6  32  39  56  82  708.5  295.03  242  577  667  863  1320  Neck (T-D1600)  6  19  11.4  4.63  6  8  11  14  18  128.5  69.53  70  80  104  153  251  Chest (T-D3000)  9  104  15.1  18.33  4  6  9  13  63  180.0  145.15  69  83  117  236  507  Abdomen (T-D4000)  7  48  14.4  23.23  2  4  7  8  67  211.5  236.66  37  108  126  184  734  Chest and abdomen (R-FAB55)  2  19  25.4  27.38  6  16  25  35  45  343.7  331.91  109  226  344  461  578  6 to <11  Head (T-D1100), brain (T-A0100)  13  311  59.9  22.10  26  48  59  67  103  950.8  417.27  226  692  911  1249  1706  Neck (T-D1600)  8  22  19.7  11.13  7  11  17  27  36  300.6  250.77  62  146  187  433  725  Chest (T-D3000)  9  87  16.3  19.03  4  5  8  12  57  328.5  400.11  70  94  157  215  1192  Abdomen (T-D4000)  10  51  12.9  15.82  3  5  8  12  57  196.7  188.33  30  99  125  242  683  Chest and abdomen (R-FAB55)  2  27  41.8  48.17  8  25  42  59  76  467.5  514.75  104  286  467  649  831  11 to <15  Head (T-D1100), brain (T-A0100)  13  274  59.8  23.31  1  52  64  71  92  1090.0  398.56  436  799  1056  1278  1733  Neck (T-D1600)  5  27  38.4  19.27  19  23  33  57  60  704.6  350.26  180  508  901  967  967  Chest (T-D3000)  10  98  31.3  33.76  8  12  17  25  103  530.1  343.12  226  282  376  702  1117  Abdomen (T-D4000)  13  73  15.9  8.72  4  10  13  22  32  396.1  246.51  10  198  439  622  780  Chest and abdomen (R-FAB55)  2  32  40.3  43.42  10  25  40  56  71  730.7  395.64  274  617  959  959  959  Age group (years)  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)b  DLP (mGy cm)b  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  0 to <1  Head (T-D1100), brain (T-A0100)  11  85  35.0  13.92  14  27  35  43  60  529.1  261.03  180  351  509  739  928  Neck (T-D1600)  3  5  8.8  3.06  5  8  10  11  11  119.8  59.72  70  87  103  145  186  Chest (T-D3000)  9  49  9.2  8.87  1  4  9  10  31  117.5  125.02  2  51  79  123  406  Abdomen (T-D4000)  6  18  5.2  3.50  1  3  4  7  11  105.6  76.39  18  60  81  161  213  Chest and abdomen (R-FAB55)  2  13  31.0  34.19  7  19  31  43  55  384.5  445.91  69  227  385  542  700  1 to <6  Head (T-D1100), brain (T-A0100)  11  239  42.1  20.76  6  32  39  56  82  708.5  295.03  242  577  667  863  1320  Neck (T-D1600)  6  19  11.4  4.63  6  8  11  14  18  128.5  69.53  70  80  104  153  251  Chest (T-D3000)  9  104  15.1  18.33  4  6  9  13  63  180.0  145.15  69  83  117  236  507  Abdomen (T-D4000)  7  48  14.4  23.23  2  4  7  8  67  211.5  236.66  37  108  126  184  734  Chest and abdomen (R-FAB55)  2  19  25.4  27.38  6  16  25  35  45  343.7  331.91  109  226  344  461  578  6 to <11  Head (T-D1100), brain (T-A0100)  13  311  59.9  22.10  26  48  59  67  103  950.8  417.27  226  692  911  1249  1706  Neck (T-D1600)  8  22  19.7  11.13  7  11  17  27  36  300.6  250.77  62  146  187  433  725  Chest (T-D3000)  9  87  16.3  19.03  4  5  8  12  57  328.5  400.11  70  94  157  215  1192  Abdomen (T-D4000)  10  51  12.9  15.82  3  5  8  12  57  196.7  188.33  30  99  125  242  683  Chest and abdomen (R-FAB55)  2  27  41.8  48.17  8  25  42  59  76  467.5  514.75  104  286  467  649  831  11 to <15  Head (T-D1100), brain (T-A0100)  13  274  59.8  23.31  1  52  64  71  92  1090.0  398.56  436  799  1056  1278  1733  Neck (T-D1600)  5  27  38.4  19.27  19  23  33  57  60  704.6  350.26  180  508  901  967  967  Chest (T-D3000)  10  98  31.3  33.76  8  12  17  25  103  530.1  343.12  226  282  376  702  1117  Abdomen (T-D4000)  13  73  15.9  8.72  4  10  13  22  32  396.1  246.51  10  198  439  622  780  Chest and abdomen (R-FAB55)  2  32  40.3  43.42  10  25  40  56  71  730.7  395.64  274  617  959  959  959  aSRT is structured reporting templates. bThe values adjusted to 16-cm PMMA phantom. Table 5 compares the 75th percentiles of adult head, chest, abdomen and heart CTs of this study with DRLs published from 10 countries and their mean values. Table 6 compares the 75th percentiles in the head, chest and abdomen of pediatric cases with the DRLs of seven countries with their mean values. Table 5. Comparison of CTDIvol and DLP for adult in each anatomical region with other countries. Anatomical region  Dose index  This study  EU  UK  Norway  Switzerland  Germany  Kenya  Ireland  Italy  Finland  Japan  Mean ± SDa  2004 [5]  2005 [6]  2009 [7]  2010 [8]  2010 [9]  2012 [10]  2012 [11]  2014 [12]  2015 [13]  2015 [18]  Headb  CTDIvol  78  60  65  75  65  65  65  66  69  55  85  67.0 ± 8.2  DLP  1292  990  930  1000  1000  950  760  940  1312  800  1350  1003 ± 191.0  DLP/CTDI  16.6  16.5  14.3  13.3  15.4  14.6  11.7  14.2  19.0  14.5  15.9  15.0 ± 1.95  Chestc  CTDIvol  15  12  13  15  10  12  13  9  15  9  15  12.3 ± 2.36  DLP  689  430  580  400  400  400  580  390  569  290  550  459 ± 102.3  DLP/CTDI  45.9  35.8  44.6  26.7  40.0  33.3  44.6  43.3  37.9  32.2  36.7  37.3 ± 5.85  Abdomenc  CTDIvol  12  16  14  15  15  20  14  12  18  12  20  15.6 ± 2.91  DLP  640  726  560  710  650  900  470  600  920  560  1000  710 ± 177.3  DLP/CTDI  53  45  40  47  43  45  34  50  51  47  50  45.5 ± 5.31  Heartc  CTDIvol  54  —  —  —  50  —  —  —  61  —  90  67.0 ± 20.66  DLP  1149  —  —  —  1000  —  —  —  1208  —  1400  1203 ± 200.1  DLP/CTDI  21.3  —  —  —  20.0  —  —  —  19.8  —  15.6  18.0 ± 2.51  Anatomical region  Dose index  This study  EU  UK  Norway  Switzerland  Germany  Kenya  Ireland  Italy  Finland  Japan  Mean ± SDa  2004 [5]  2005 [6]  2009 [7]  2010 [8]  2010 [9]  2012 [10]  2012 [11]  2014 [12]  2015 [13]  2015 [18]  Headb  CTDIvol  78  60  65  75  65  65  65  66  69  55  85  67.0 ± 8.2  DLP  1292  990  930  1000  1000  950  760  940  1312  800  1350  1003 ± 191.0  DLP/CTDI  16.6  16.5  14.3  13.3  15.4  14.6  11.7  14.2  19.0  14.5  15.9  15.0 ± 1.95  Chestc  CTDIvol  15  12  13  15  10  12  13  9  15  9  15  12.3 ± 2.36  DLP  689  430  580  400  400  400  580  390  569  290  550  459 ± 102.3  DLP/CTDI  45.9  35.8  44.6  26.7  40.0  33.3  44.6  43.3  37.9  32.2  36.7  37.3 ± 5.85  Abdomenc  CTDIvol  12  16  14  15  15  20  14  12  18  12  20  15.6 ± 2.91  DLP  640  726  560  710  650  900  470  600  920  560  1000  710 ± 177.3  DLP/CTDI  53  45  40  47  43  45  34  50  51  47  50  45.5 ± 5.31  Heartc  CTDIvol  54  —  —  —  50  —  —  —  61  —  90  67.0 ± 20.66  DLP  1149  —  —  —  1000  —  —  —  1208  —  1400  1203 ± 200.1  DLP/CTDI  21.3  —  —  —  20.0  —  —  —  19.8  —  15.6  18.0 ± 2.51  aThe values were calculated at DRL which excluded this study. bThe values adjusted to 16-cm PMMA phantom. cThe values adjusted to 32-cm PMMA phantom. Table 5. Comparison of CTDIvol and DLP for adult in each anatomical region with other countries. Anatomical region  Dose index  This study  EU  UK  Norway  Switzerland  Germany  Kenya  Ireland  Italy  Finland  Japan  Mean ± SDa  2004 [5]  2005 [6]  2009 [7]  2010 [8]  2010 [9]  2012 [10]  2012 [11]  2014 [12]  2015 [13]  2015 [18]  Headb  CTDIvol  78  60  65  75  65  65  65  66  69  55  85  67.0 ± 8.2  DLP  1292  990  930  1000  1000  950  760  940  1312  800  1350  1003 ± 191.0  DLP/CTDI  16.6  16.5  14.3  13.3  15.4  14.6  11.7  14.2  19.0  14.5  15.9  15.0 ± 1.95  Chestc  CTDIvol  15  12  13  15  10  12  13  9  15  9  15  12.3 ± 2.36  DLP  689  430  580  400  400  400  580  390  569  290  550  459 ± 102.3  DLP/CTDI  45.9  35.8  44.6  26.7  40.0  33.3  44.6  43.3  37.9  32.2  36.7  37.3 ± 5.85  Abdomenc  CTDIvol  12  16  14  15  15  20  14  12  18  12  20  15.6 ± 2.91  DLP  640  726  560  710  650  900  470  600  920  560  1000  710 ± 177.3  DLP/CTDI  53  45  40  47  43  45  34  50  51  47  50  45.5 ± 5.31  Heartc  CTDIvol  54  —  —  —  50  —  —  —  61  —  90  67.0 ± 20.66  DLP  1149  —  —  —  1000  —  —  —  1208  —  1400  1203 ± 200.1  DLP/CTDI  21.3  —  —  —  20.0  —  —  —  19.8  —  15.6  18.0 ± 2.51  Anatomical region  Dose index  This study  EU  UK  Norway  Switzerland  Germany  Kenya  Ireland  Italy  Finland  Japan  Mean ± SDa  2004 [5]  2005 [6]  2009 [7]  2010 [8]  2010 [9]  2012 [10]  2012 [11]  2014 [12]  2015 [13]  2015 [18]  Headb  CTDIvol  78  60  65  75  65  65  65  66  69  55  85  67.0 ± 8.2  DLP  1292  990  930  1000  1000  950  760  940  1312  800  1350  1003 ± 191.0  DLP/CTDI  16.6  16.5  14.3  13.3  15.4  14.6  11.7  14.2  19.0  14.5  15.9  15.0 ± 1.95  Chestc  CTDIvol  15  12  13  15  10  12  13  9  15  9  15  12.3 ± 2.36  DLP  689  430  580  400  400  400  580  390  569  290  550  459 ± 102.3  DLP/CTDI  45.9  35.8  44.6  26.7  40.0  33.3  44.6  43.3  37.9  32.2  36.7  37.3 ± 5.85  Abdomenc  CTDIvol  12  16  14  15  15  20  14  12  18  12  20  15.6 ± 2.91  DLP  640  726  560  710  650  900  470  600  920  560  1000  710 ± 177.3  DLP/CTDI  53  45  40  47  43  45  34  50  51  47  50  45.5 ± 5.31  Heartc  CTDIvol  54  —  —  —  50  —  —  —  61  —  90  67.0 ± 20.66  DLP  1149  —  —  —  1000  —  —  —  1208  —  1400  1203 ± 200.1  DLP/CTDI  21.3  —  —  —  20.0  —  —  —  19.8  —  15.6  18.0 ± 2.51  aThe values were calculated at DRL which excluded this study. bThe values adjusted to 16-cm PMMA phantom. cThe values adjusted to 32-cm PMMA phantom. Table 6. Comparison of CTDIvol and DLP for pediatric in each anatomical region with other countries. Anatomical region  Age group (years)  Dose index  This study  UK  Germany  Switzerland  France  Thai  Japan  Japan  Mean ± SDa  2005 [6]  2007 [14]  2008 [15]  2009 [16]  2012 [17]  2015 [22]  2015 [18]  Headb  0 to <1  CTDIvol  43  30  33  20  30  25  30  38  29.4 ± 5.71  DLP  739  270  390  270  420  400  404  500  379 ± 82.9  DLP/CTDI  17.2  9.0  11.8  13.5  14.0  16.0  13.5  13.2  12.9 ± 2.16  1 to <6  CTDIvol  56  45  40  30  40  30  40  47  38.9 ± 6.64  DLP  863  470  520  420  600  570  624  660  552 ± 86.3  DLP/CTDI  15.4  10.4  13.0  14.0  15.0  19.0  15.6  14.0  14.2 ± 2.61  6 to <11  CTDIvol  67  50  50  40  50  40  45  60  47.9 ± 6.99  DLP  1249  620  710  560  900  610  734  850  712 ± 127.0  DLP/CTDI  18.6  12.4  14.2  14.0  18.0  15.3  16.3  14.2  14.9 ± 1.82  11 to <15  CTDIvol  71  65  60  60  —  45  53  —  56.6 ± 7.77  DLP  1278  930  920  1000  —  800  869  —  904 ± 74.5  DLP/CTDI  18.0  14.3  15.3  16.7  —  17.8  16.4  —  16.0 ± 1.33  Chestb  0 to <1  CTDIvol  10  12  3.5  5  6  4.5  5  11  6.7 ± 3.36  DLP  123  200  55  110  60  80  104  210  117 ± 63.5  DLP/CTDI  12.3  16.7  15.7  22.0  10.0  17.8  20.8  19.1  17.4 ± 3.96  1 to <6  CTDIvol  13  13  5.5  8  7  5.7  5  14  8.3 ± 3.69  DLP  236  230  110  200  126  140  127  300  176 ± 70.0  DLP/CTDI  18.2  17.7  20.0  25.0  18.0  24.6  25.4  21.4  21.2 ± 3.30  6 to <11  CTDIvol  12  20  8.5  10  11  10  5  15  11.4 ± 4.84  DLP  215  370  210  220  274  305  137  410  275 ± 95.3  DLP/CTDI  17.9  18.5  24.7  22.0  24.9  30.5  27.4  27.3  24.2 ± 3.93  11 to <15  CTDIvol  25  14  14  12  —  15.6  11  —  13.3 ± 1.82  DLP  702  580  205  460  —  470  359  —  415 ± 141.0  DLP/CTDI  28.1  41.4  14.6  38.3  —  30.1  32.6  —  31.4 ± 10.40  Abdomenb  0 to <1  CTDIvol  7  20  5  7  8  7.7  7  11  9.4 ± 5.01  DLP  161  170  145  130  160  220  126  220  167 ± 39.2  DLP/CTDI  23.0  8.5  29.0  18.6  20.0  28.6  18.0  20.0  17.8 ± 6.97  1 to <6  CTDIvol  8  25  8  9  9  9  7  16  11.9 ± 6.49  DLP  184  250  255  300  242  275  209  400  276 ± 61.5  DLP/CTDI  23.0  10.0  31.9  33.3  26.9  30.6  29.9  25.0  23.3 ± 7.93  6 to <11  CTDIvol  12  30  13  13  14  14  7  17  15.4 ± 7.09  DLP  242  500  475  380  490  560  346  530  469 ± 78.0  DLP/CTDI  20.2  16.7  36.5  29.2  35.0  40.0  49.4  31.2  30.4 ± 10.1  11 to <15  CTDIvol  22  14  20  16  —  17  13  —  16.0 ± 2.74  DLP  622  560  1000  500  —  765  549  —  675 ± 208.2  DLP/CTDI  28.3  40.0  50.0  31.3  —  45.0  42.2  —  42.2 ± 6.93  Anatomical region  Age group (years)  Dose index  This study  UK  Germany  Switzerland  France  Thai  Japan  Japan  Mean ± SDa  2005 [6]  2007 [14]  2008 [15]  2009 [16]  2012 [17]  2015 [22]  2015 [18]  Headb  0 to <1  CTDIvol  43  30  33  20  30  25  30  38  29.4 ± 5.71  DLP  739  270  390  270  420  400  404  500  379 ± 82.9  DLP/CTDI  17.2  9.0  11.8  13.5  14.0  16.0  13.5  13.2  12.9 ± 2.16  1 to <6  CTDIvol  56  45  40  30  40  30  40  47  38.9 ± 6.64  DLP  863  470  520  420  600  570  624  660  552 ± 86.3  DLP/CTDI  15.4  10.4  13.0  14.0  15.0  19.0  15.6  14.0  14.2 ± 2.61  6 to <11  CTDIvol  67  50  50  40  50  40  45  60  47.9 ± 6.99  DLP  1249  620  710  560  900  610  734  850  712 ± 127.0  DLP/CTDI  18.6  12.4  14.2  14.0  18.0  15.3  16.3  14.2  14.9 ± 1.82  11 to <15  CTDIvol  71  65  60  60  —  45  53  —  56.6 ± 7.77  DLP  1278  930  920  1000  —  800  869  —  904 ± 74.5  DLP/CTDI  18.0  14.3  15.3  16.7  —  17.8  16.4  —  16.0 ± 1.33  Chestb  0 to <1  CTDIvol  10  12  3.5  5  6  4.5  5  11  6.7 ± 3.36  DLP  123  200  55  110  60  80  104  210  117 ± 63.5  DLP/CTDI  12.3  16.7  15.7  22.0  10.0  17.8  20.8  19.1  17.4 ± 3.96  1 to <6  CTDIvol  13  13  5.5  8  7  5.7  5  14  8.3 ± 3.69  DLP  236  230  110  200  126  140  127  300  176 ± 70.0  DLP/CTDI  18.2  17.7  20.0  25.0  18.0  24.6  25.4  21.4  21.2 ± 3.30  6 to <11  CTDIvol  12  20  8.5  10  11  10  5  15  11.4 ± 4.84  DLP  215  370  210  220  274  305  137  410  275 ± 95.3  DLP/CTDI  17.9  18.5  24.7  22.0  24.9  30.5  27.4  27.3  24.2 ± 3.93  11 to <15  CTDIvol  25  14  14  12  —  15.6  11  —  13.3 ± 1.82  DLP  702  580  205  460  —  470  359  —  415 ± 141.0  DLP/CTDI  28.1  41.4  14.6  38.3  —  30.1  32.6  —  31.4 ± 10.40  Abdomenb  0 to <1  CTDIvol  7  20  5  7  8  7.7  7  11  9.4 ± 5.01  DLP  161  170  145  130  160  220  126  220  167 ± 39.2  DLP/CTDI  23.0  8.5  29.0  18.6  20.0  28.6  18.0  20.0  17.8 ± 6.97  1 to <6  CTDIvol  8  25  8  9  9  9  7  16  11.9 ± 6.49  DLP  184  250  255  300  242  275  209  400  276 ± 61.5  DLP/CTDI  23.0  10.0  31.9  33.3  26.9  30.6  29.9  25.0  23.3 ± 7.93  6 to <11  CTDIvol  12  30  13  13  14  14  7  17  15.4 ± 7.09  DLP  242  500  475  380  490  560  346  530  469 ± 78.0  DLP/CTDI  20.2  16.7  36.5  29.2  35.0  40.0  49.4  31.2  30.4 ± 10.1  11 to <15  CTDIvol  22  14  20  16  —  17  13  —  16.0 ± 2.74  DLP  622  560  1000  500  —  765  549  —  675 ± 208.2  DLP/CTDI  28.3  40.0  50.0  31.3  —  45.0  42.2  —  42.2 ± 6.93  aThe values were calculated at DRL which excluded this study. bThe values adjusted to 16-cm PMMA phantom. Table 6. Comparison of CTDIvol and DLP for pediatric in each anatomical region with other countries. Anatomical region  Age group (years)  Dose index  This study  UK  Germany  Switzerland  France  Thai  Japan  Japan  Mean ± SDa  2005 [6]  2007 [14]  2008 [15]  2009 [16]  2012 [17]  2015 [22]  2015 [18]  Headb  0 to <1  CTDIvol  43  30  33  20  30  25  30  38  29.4 ± 5.71  DLP  739  270  390  270  420  400  404  500  379 ± 82.9  DLP/CTDI  17.2  9.0  11.8  13.5  14.0  16.0  13.5  13.2  12.9 ± 2.16  1 to <6  CTDIvol  56  45  40  30  40  30  40  47  38.9 ± 6.64  DLP  863  470  520  420  600  570  624  660  552 ± 86.3  DLP/CTDI  15.4  10.4  13.0  14.0  15.0  19.0  15.6  14.0  14.2 ± 2.61  6 to <11  CTDIvol  67  50  50  40  50  40  45  60  47.9 ± 6.99  DLP  1249  620  710  560  900  610  734  850  712 ± 127.0  DLP/CTDI  18.6  12.4  14.2  14.0  18.0  15.3  16.3  14.2  14.9 ± 1.82  11 to <15  CTDIvol  71  65  60  60  —  45  53  —  56.6 ± 7.77  DLP  1278  930  920  1000  —  800  869  —  904 ± 74.5  DLP/CTDI  18.0  14.3  15.3  16.7  —  17.8  16.4  —  16.0 ± 1.33  Chestb  0 to <1  CTDIvol  10  12  3.5  5  6  4.5  5  11  6.7 ± 3.36  DLP  123  200  55  110  60  80  104  210  117 ± 63.5  DLP/CTDI  12.3  16.7  15.7  22.0  10.0  17.8  20.8  19.1  17.4 ± 3.96  1 to <6  CTDIvol  13  13  5.5  8  7  5.7  5  14  8.3 ± 3.69  DLP  236  230  110  200  126  140  127  300  176 ± 70.0  DLP/CTDI  18.2  17.7  20.0  25.0  18.0  24.6  25.4  21.4  21.2 ± 3.30  6 to <11  CTDIvol  12  20  8.5  10  11  10  5  15  11.4 ± 4.84  DLP  215  370  210  220  274  305  137  410  275 ± 95.3  DLP/CTDI  17.9  18.5  24.7  22.0  24.9  30.5  27.4  27.3  24.2 ± 3.93  11 to <15  CTDIvol  25  14  14  12  —  15.6  11  —  13.3 ± 1.82  DLP  702  580  205  460  —  470  359  —  415 ± 141.0  DLP/CTDI  28.1  41.4  14.6  38.3  —  30.1  32.6  —  31.4 ± 10.40  Abdomenb  0 to <1  CTDIvol  7  20  5  7  8  7.7  7  11  9.4 ± 5.01  DLP  161  170  145  130  160  220  126  220  167 ± 39.2  DLP/CTDI  23.0  8.5  29.0  18.6  20.0  28.6  18.0  20.0  17.8 ± 6.97  1 to <6  CTDIvol  8  25  8  9  9  9  7  16  11.9 ± 6.49  DLP  184  250  255  300  242  275  209  400  276 ± 61.5  DLP/CTDI  23.0  10.0  31.9  33.3  26.9  30.6  29.9  25.0  23.3 ± 7.93  6 to <11  CTDIvol  12  30  13  13  14  14  7  17  15.4 ± 7.09  DLP  242  500  475  380  490  560  346  530  469 ± 78.0  DLP/CTDI  20.2  16.7  36.5  29.2  35.0  40.0  49.4  31.2  30.4 ± 10.1  11 to <15  CTDIvol  22  14  20  16  —  17  13  —  16.0 ± 2.74  DLP  622  560  1000  500  —  765  549  —  675 ± 208.2  DLP/CTDI  28.3  40.0  50.0  31.3  —  45.0  42.2  —  42.2 ± 6.93  Anatomical region  Age group (years)  Dose index  This study  UK  Germany  Switzerland  France  Thai  Japan  Japan  Mean ± SDa  2005 [6]  2007 [14]  2008 [15]  2009 [16]  2012 [17]  2015 [22]  2015 [18]  Headb  0 to <1  CTDIvol  43  30  33  20  30  25  30  38  29.4 ± 5.71  DLP  739  270  390  270  420  400  404  500  379 ± 82.9  DLP/CTDI  17.2  9.0  11.8  13.5  14.0  16.0  13.5  13.2  12.9 ± 2.16  1 to <6  CTDIvol  56  45  40  30  40  30  40  47  38.9 ± 6.64  DLP  863  470  520  420  600  570  624  660  552 ± 86.3  DLP/CTDI  15.4  10.4  13.0  14.0  15.0  19.0  15.6  14.0  14.2 ± 2.61  6 to <11  CTDIvol  67  50  50  40  50  40  45  60  47.9 ± 6.99  DLP  1249  620  710  560  900  610  734  850  712 ± 127.0  DLP/CTDI  18.6  12.4  14.2  14.0  18.0  15.3  16.3  14.2  14.9 ± 1.82  11 to <15  CTDIvol  71  65  60  60  —  45  53  —  56.6 ± 7.77  DLP  1278  930  920  1000  —  800  869  —  904 ± 74.5  DLP/CTDI  18.0  14.3  15.3  16.7  —  17.8  16.4  —  16.0 ± 1.33  Chestb  0 to <1  CTDIvol  10  12  3.5  5  6  4.5  5  11  6.7 ± 3.36  DLP  123  200  55  110  60  80  104  210  117 ± 63.5  DLP/CTDI  12.3  16.7  15.7  22.0  10.0  17.8  20.8  19.1  17.4 ± 3.96  1 to <6  CTDIvol  13  13  5.5  8  7  5.7  5  14  8.3 ± 3.69  DLP  236  230  110  200  126  140  127  300  176 ± 70.0  DLP/CTDI  18.2  17.7  20.0  25.0  18.0  24.6  25.4  21.4  21.2 ± 3.30  6 to <11  CTDIvol  12  20  8.5  10  11  10  5  15  11.4 ± 4.84  DLP  215  370  210  220  274  305  137  410  275 ± 95.3  DLP/CTDI  17.9  18.5  24.7  22.0  24.9  30.5  27.4  27.3  24.2 ± 3.93  11 to <15  CTDIvol  25  14  14  12  —  15.6  11  —  13.3 ± 1.82  DLP  702  580  205  460  —  470  359  —  415 ± 141.0  DLP/CTDI  28.1  41.4  14.6  38.3  —  30.1  32.6  —  31.4 ± 10.40  Abdomenb  0 to <1  CTDIvol  7  20  5  7  8  7.7  7  11  9.4 ± 5.01  DLP  161  170  145  130  160  220  126  220  167 ± 39.2  DLP/CTDI  23.0  8.5  29.0  18.6  20.0  28.6  18.0  20.0  17.8 ± 6.97  1 to <6  CTDIvol  8  25  8  9  9  9  7  16  11.9 ± 6.49  DLP  184  250  255  300  242  275  209  400  276 ± 61.5  DLP/CTDI  23.0  10.0  31.9  33.3  26.9  30.6  29.9  25.0  23.3 ± 7.93  6 to <11  CTDIvol  12  30  13  13  14  14  7  17  15.4 ± 7.09  DLP  242  500  475  380  490  560  346  530  469 ± 78.0  DLP/CTDI  20.2  16.7  36.5  29.2  35.0  40.0  49.4  31.2  30.4 ± 10.1  11 to <15  CTDIvol  22  14  20  16  —  17  13  —  16.0 ± 2.74  DLP  622  560  1000  500  —  765  549  —  675 ± 208.2  DLP/CTDI  28.3  40.0  50.0  31.3  —  45.0  42.2  —  42.2 ± 6.93  aThe values were calculated at DRL which excluded this study. bThe values adjusted to 16-cm PMMA phantom. DISCUSSION In this study, we introduced a series of systems that automatically collect RDSR or dose sheet output from CT, and summarized scan parameters and scan dose. The output formats of RDSR are unified, making it possible to collect information on recorded dose indices and imaging conditions(30). However, the equipment compatible with the output of RDSR is limited to the latest models. The IEC issued the 2012 Dose SR Standard for CT apparatus in IEC 60601-2-44, recommending collection of dose data from CT scans(28). In addition, it has been reported that the accuracy of reading text is 95% because information is collected only by the method of image capture of dose sheets, and each manufacturer has various display formats(31). For more detailed scan parameters, it is a disadvantage that it cannot be captured only from the dose sheet. In Table 2, the targets from the RDSR collection were 20 regions, but in reality, each center was conducting daily inspections using a more specific detailed protocol, e.g. in the case of multiphase scanning of the abdomen (T-D4000, SRT). Furthermore, because RDSR and dose sheet cannot directly obtain information on body type such as body weight and height of patients, and the AEC automatically adjusts for habitus, various ages and body types, are considered to be the cause of differences between centers. Although it has also been reported that the patients undergoing abdominal CT with body mass index (BMI) < 30 that the CTDIvol and DLP of patients who exceeded NDRL was under 0.5% and under 0.8%, respectively(20). DRL is based on standard patients in each country, making it desirable to collect body type information, such as the height and weight. From Table 3, it is conceivable that the CTDIvol of the adult chest–abdominal CT is higher than that of the abdomen–pelvis CT, because some CT scanners include devices that calculate the CTDI value from the maximum, and not the mean, tube current. In addition, CT angiography was included in the chest and abdomen studies, and there is a difference in the dose index due to angiography’s lower pitch setting. From Table 5, in comparison with the DRL of each Japanese study, the CTDIvol and DLP of the head and chest were both higher than those of the other countries, and the values in the abdomen and heart were all lower than the mean values of each country. In automatic collection of data, there are possibilities that local protocols unique to various centers may be included, and that is considered one aspect which cannot be compared with the NDRL of each country. From Table 6, in pediatric DRL, head and chest CT showed higher results than in the other countries. This may be due to the scan range in head CT being set wider in Japan than in other countries by up to ~4 cm, in order to maintain the head within the field of view. As children are more radiosensitive than adults, we should actively adopt methods that can calculate tube current for each age recommended by the Image Gently Program of the American Society of Pediatric Radiology (SPR)(32). The National Radiology Data Registry (NRDR) of the American College of Radiology (ACR) has been collecting large-scale RDSRs throughout North America as a Dose Index Registration (DIR) since 2011(33). The collected dose information is divided into detailed scan regions by a Radlex playbook ID (RPID) code, transmitted anonymously to ACR, and the results of comparative evaluation with the whole are fed back to each center. The size-specific dose estimates (SSDE) taking into consideration the body shape is beginning to be introduced in addition to CTDI and DLP in the dose index, we think that dose optimization is possible in the future(34). Even in Japan, the JJ 1017 code, which codes modality and scan region, is under development. This should lead to higher precision(35). We plan to continue to collect dosage data and to periodically compare, discover and investigate specific causes, and review protocols with the goal of dose optimization. Currently, we are sharing data with a limited collection of equipment. Constructing a cloud-based collection will allow sampling from more centers in the future. We hope this will eliminate disparities among centers and facilitate the optimization of dosimetry. REFERENCES 1 Brenner, D. J. and Hall, E. J. Computed tomography—an increasing source of radiation exposure. N. Engl. J. Med.  357( 22), 2277– 2284 ( 2007) 10.1056/NEJMra072149. Google Scholar CrossRef Search ADS PubMed  2 Harding, K., and Thomson, W. H.. International Commission on Radiological Protection. Radiological Protection and Safety in Medicine ICRP Publication 73. Ann. ICRP  26( 2) ( 1996). 3 International Commission on Radiological Protection. The 2007 Recommendations of the ICRP. ICRP Publication 103. Ann. ICRP  37( 2–4), 1– 332 ( 2007) 10.1016/j.icrp.2007.10.003. 4 International Commission on Radiological Protection. Managing patient dose in computed tomography. Ann. ICRP  30( 4), 7– 45 ( 2000). CrossRef Search ADS   5 Jessen, K. et al.  . European Guidelines on Quality Criteria for Computed Tomography, EUR 16262EN. Official Publication of the European Communities 2000. Available on http://www.drs.dk/guidelines/ct/quality/htmlindex.htm. Accessed on 22 August 2016. 6 Shrimpton, P. C., Hiller, M. C., Lewis, M. A. and Dunn, M. National survey of doses from CT in the UK: 2003. Br. J. Radiol.  79( 948), 968– 980 ( 2006) 10.1259/bjr/93277434. Google Scholar CrossRef Search ADS PubMed  7 Friberg, E. G., Widmark, A. and Ryste Hauge, I. H. National Collection of Local Diagnostic Reference Levels in Norway and Their Role in Optimization of X-Ray Examinations  ( Østerås, Norway: Norwegian Radiation Protection Authority) ( 2009). 8 Treier, R., Aroua, A., Verdun, F. R., Samara, E., Stuessi, A. and Trueb, P. R. Patient doses in CT examinations in Switzerland: implementation of national diagnostic reference levels. Radiat. Prot. Dosim.  142( 2–4), 244– 254 ( 2010) 10.1093/rpd/ncq279. Google Scholar CrossRef Search ADS   9 German Federal Office for Radiation Protection. Publication of Updated Diagnostic Reference Levels for Diagnostic and Interventional X-ray Examinations ( 2010). Available on http://www.bfs.de/DE/themen/ion/anwendungmedizin/diagnostik/referenzwerte/referenzwerte.html [in German]. Accessed on 11 November 2015. 10 Korir, G. K., Wambani, J. S. and Korir, I. K. Patient doses using multidetector computed tomography scanners in Kenya. Radiat. Prot. Dosim.  151( 2), 267– 271 ( 2012) 10.1093/rpd/ncr484. Google Scholar CrossRef Search ADS   11 Foley, S. J., McEntee, M. F. and Rainford, L. A. Establishment of CT diagnostic reference levels in Ireland. Br. J. Radiol.  85( 1018), 1390– 1397 ( 2012) 10.1259/bjr/15839549. Google Scholar CrossRef Search ADS PubMed  12 Palorini, F., Origgi, D. and Granata, C. Adult exposures from MDCT including multiphase studies: first Italian nationwide survey. Eur. Radiol.  24( 2), 469– 483 ( 2014) 10.1007/s00330-013-3031-7. Google Scholar CrossRef Search ADS PubMed  13 Lajunen, A. Indication-based diagnostic reference levels for adult CT-examinations in Finland. Radiat. Prot. Dosim.  165( 1–4), 95– 97 ( 2015) 10.1093/rpd/ncv087. Google Scholar CrossRef Search ADS   14 Glanski, M., Nagel, H. D. and Stamm, G. Paediatric CT exposure practice in the Federal Republic of Germany: results of a nationwide survey in 2005–2006. Rofo  179( 11), 1110– 1111 ( 2007). Google Scholar CrossRef Search ADS PubMed  15 Verdun, F. R., Guiterrez, D., Vader, J., Aroua, A., Alamo-Maestre, L. T., Bochud, F. and Gudinchet, F. CT radiation dose in children: a survey to establish age-based diagnostic reference levels in Switzerland. Eur. Radiol.  18( 9), 1980– 1986 ( 2008) 10.1007/s00330-008-0963-4. Google Scholar CrossRef Search ADS PubMed  16 Roch, P. and Aubert, B. French diagnostic reference levels in diagnostic radiology, computed tomography and nuclear medicine: 2004–2008 review. Radiat. Prot. Dosim.  154( 1), 52– 75 ( 2012) 10.1093/rpd/ncs152. Google Scholar CrossRef Search ADS   17 Kritsaneepaiboon, S., Trinavarat, P. and Visrutaratna, P. Survey of pediatric MDCT radiation dose from university hospitals in Thailand: a preliminary for national dose survey. Acta Radiol.  53( 7), 820– 826 ( 2012) 10.1258/ar.2012.110641. Google Scholar CrossRef Search ADS PubMed  18 J-RIME 2015. Diagnostic Reference Levels Based on Latest Surveys in Japan, -JapanDRLs2015-. Available on http://www.radher.jp/J-RIME/report/DRLhoukokusyoEng.pdf. Accessed on 11 October 2016. 19 International Commission on Radiological Protection. ICRP Publication 105. Radiation protection in medicine. Ann. ICRP  37( 6), 1– 63 ( 2007) 10.1016/j.icrp.2008.08.001. CrossRef Search ADS   20 Boos, J., Lanzman, R. S., Meineke, A., Heusch, P., Sawicki, L. M., Antoch, G. and Kröpil, P. Dose monitoring using the DICOM structured report: assessment of the relationship between cumulative radiation exposure and BMI in abdominal CT. Clin. Radiol.  70( 2), 176– 182 ( 2015) 10.1016/j.crad.2014.11.002. Google Scholar CrossRef Search ADS PubMed  21 Vano, E. and Fernandez Soto, J. Patient dose management in digital radiography. Biomed. Imaging Interv. J.  3( 2), e26 ( 2007) 10.2349/biij.3.2.e26. Google Scholar CrossRef Search ADS PubMed  22 Nakada, Y., Fujiwara, M. and Yakami, M. Optimised paediatric CT dose at a tertiary children’s hospital in Japan: a 4-y single-centre analysis. Radiat. Prot. Dosim.  168( 1), 61– 71 ( 2016) 10.1093/rpd/ncv004. Google Scholar CrossRef Search ADS   23 Cook, T. S., Zimmerman, S. L., Steingall, S. R., Maidment, A. D., Kim, W. and Boonn, W. W. RADIANCE: An automated, enterprise-wide solution for archiving and reporting CT radiation dose estimates. Radiographics  31( 7), 1833– 1846 ( 2011) 10.1148/rg.317115048. Google Scholar CrossRef Search ADS PubMed  24 Noumeir, R. Benefits of the DICOM modality performed procedure step. J. Digit. Imaging  18( 4), 260– 269 ( 2005) 10.1007/s10278-005-6702-3. Google Scholar CrossRef Search ADS PubMed  25 Dave, J. K. and Gingold, E. L. Extraction of CT dose information from DICOM metadata: automated Matlab-based approach. AJR Am. J. Roentgenol.  200( 1), 142– 145 ( 2013) 10.2214/AJR.12.8501. Google Scholar CrossRef Search ADS PubMed  26 DICOM diagnostic x-ray radiation dose reporting (Dose SR). 27 DICOM part 16 content mapping resource. 28 International Electrotechnical Commission. Medical electrical equipment, Part 2-44: Particular requirements for the safety of X-ray equipment for computed tomography. Geneva: IEC; ( 2012). IEC 60601-2-44. 29 Data book of medical devices & systems, Iryokiki sytem hakusho 2016, MEshinkoukyokai 2015. 30 DICOM Standards Committee, Working Group 6, Base Standard. Supplement 94: radiation dose report, NEMA 2004. Available on http://dicom.nema.org/dicom/geninfo/strategy.pdf#search=%2728.+DICOM+Standards+Committee%2C+Working+Group+6%2C+Base+Standard.+Supplement+150%27. Accessed on 21 March 2017. 31 Li, X., Zhang, D. and Liu, B. Automated extraction of radiation dose information from CT dose report images. AJR Am. J. Roentgenol.  196( 6), W781– W783 ( 2011) 10.2214/AJR.10.5718. Google Scholar CrossRef Search ADS PubMed  32 Image Gently Homepage Radiology Safety. Protocol for Image Gently. Available on http://www.imagegently.org/Procedures/Computed-Tomography#2018473-technologists. Accessed on 10 March 2016. 33 American College of Radiology (ACR). About Dose Index Registry (DIR). Available on http://www.acr.org/Quality-Safety/National-Radiology-Data-Registry/Dose-Index-Registry/About-DIR. Accessed on 8 February 2014. 34 Moore, B. M., Brady, S. L., Mirro, A. E. and Kaufman, R. A. Size-specific dose estimate (SSDE) provides a simple method to calculate organ dose for pediatric CT examinations. Med. Phys.  41( 7), 071917 ( 2014). Google Scholar CrossRef Search ADS PubMed  35 Medical Information Special Interest Section. JJ1017 ver3.3 ( 2016). Japanese Society of Radiological Technology (JSRT). Available on http://www.jsrt.or.jp/97mi/content/jj1017.html. Accessed on 22 January 2017. © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiation Protection Dosimetry Oxford University Press

Loading next page...
 
/lp/ou_press/automatic-acquisition-of-ct-radiation-dose-data-using-the-diagnostic-9iADudE3Io
Publisher
Oxford University Press
Copyright
© The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com
ISSN
0144-8420
eISSN
1742-3406
D.O.I.
10.1093/rpd/ncy003
Publisher site
See Article on Publisher Site

Abstract

Abstract The present work describes that we try to construct a system that collects dose information that performed CT examination from multiple facilities and unified management. The results of analysis are compared with other National diagnostic reference level (DRL), and the results are fed back to each facility and the cause of the abnormal value is investigated for dose optimization. Medical information collected 139 144 tests from 33 CT devices in 13 facilities. Although the DRL of this study is lower than that of Japan DRL, it was higher than the DRL of each country. When collecting all the examination, it is thought that the variation of the dose due to the error other than the intended imaging site is large. In future, we should continue to collect information in order to DRL renewal and we also think that it is desirable to collect information on physique and detailed scan region as well. INTRODUCTION Computed tomography (CT) is about 40 years old. Japan’s annual medical radiation dose per capita is the world’s largest, and most of the exposure is from CT examinations(1). Diagnostic reference level (DRL) recommendations to restrict exposure to that which is medically necessary have been made by the International Commission on Radiological Protection (ICRP)(2, 3). Regarding the role of DRL, if the typical dose used in the institution exceeds DRL, it is necessary to review to determine whether the dose is optimized unless there is a clinically valid cause is there. In general, investigate the performance and examination protocols (procedures) of the equipment used, find the cause of high dose (low dose), and take countermeasures to use a more appropriate dose. After taking countermeasures, dose optimization is achieved by reassessing the typical dose of the facility and confirming that it is lower than DRL. DRLs of CT examinations are expressed as volume CT dose index (CTDIvol, mGy) and dose-length products (DLP, mGy cm); for pediatrics, limits may be extrapolated from adult values, or set using pediatric phantoms(4–17). DRLs for Japan were published in 2015 using the 75th percentile of dosimetry data collected by questionnaire(18). There are three types of DRL: national DRL (NDRL), set at the national level; regional DRL (RDRL), set at the regional/academic level; and local DRL (LDRL), set at the individual center level(19). Dose indices from many centers are required to establish NDRL and RDRL, but rules on how to determine NDRL and RDRL have not been finalized. Modern radiographic diagnostic equipment records information including patient demographics, scan parameters and dose index. It is important to collect information on radiological examinations from several centers(20), and to build a dose management system capable of calculating RDRL and aggregating and managing dose information. There are several methods of collecting dosimetry data: Digital Imaging and Communications in Medicine (DICOM) headers(21, 22). Reading dose information from an image file containing data from the CT device(23). DICOM modality performed procedure step (MPPS)(24). DICOM structured report (DICOM SR)(25). We can easily read patient information and scan parameter information from a DICOM header, but the information on the dose index is often not recorded. The data recorded in the CT scanner of each manufacturers vary, and the examination information, the patient information, and the dose information are recorded as image data called ‘Dose report’ or ‘Dose sheet’. MPPS is a protocol for managing the information of the examination. The types of tags that can be handled are small in number and insufficient for dose management. DICOM standardized ‘CT Radiation Dose Reporting (Dose SR)’ in 2007 for the purpose of unifying the information output format used for dose management(26). And defined a template structure for the information to be output at DICOM part 16: content mapping resource(27). This template structure was summarizing different exposure doses and related information for each device into a unit called Information Object Definition (IOD) and defined as ‘CT Radiation Dose SR IOD templates’ (Figure 1). Furthermore, the International Electrotechnical Commission (IEC) was recommended outputting dose information according to the Dose SR standard for CT device in 2012(28). Figure 1. View largeDownload slide Fundamental structure of ‘CT radiation dose SRa Information Object Description (IOD) templates’. This is part of the CT dose SR template. The templates have a hierarchical structure, and there are other contents showing X-ray, mammography and fluoroscopy. As the hierarchy progresses, scan parameters other than dose information and patient information are also described. aSR = structured report; bTID = template ID. Figure 1. View largeDownload slide Fundamental structure of ‘CT radiation dose SRa Information Object Description (IOD) templates’. This is part of the CT dose SR template. The templates have a hierarchical structure, and there are other contents showing X-ray, mammography and fluoroscopy. As the hierarchy progresses, scan parameters other than dose information and patient information are also described. aSR = structured report; bTID = template ID. We collected RDSR on dose index for CT examination and attempted to construct an aggregation system that collects dose information and scan parameter of multiple facilities by collecting information by image capture of dose sheet for noncompliant CT devices. For dose optimization, we set regional DRL and the results of analysis were compared with other National DRL, and the results were fed back to each facility and the cause of the abnormal value was investigated. METHODS AND MATERIALS Patients This retrospective study was approved by the National Institute of Radiological Sciences (NIRS) and the ethics committees of the target centers. Target patients were those who underwent CT examination from October 2014 to December 2015. Patients 0 to ≤15 years of age were classified as pediatric, and were subdivided into 0–≤1 year old, 1–≤6 years old, 6–≤11 years old and 11–≤15 years old groups. Patients over 15 years old were classified as adults. Protocols All centers had CT scanners with >16 detectors, adjusted to the most appropriate scan parameters according to age, physique and examination(17). About protocol name, in the case of RDSR we referred to ‘Target region’ mentioned in CT irradiation event data of TID10013 and the case of Dose sheet we referred to ‘Body part examination’ of DICOM header. For the dose index, the collected data included contrast-enhanced examinations when a patient underwent an examination with >2 scans (i.e. three-phase contrast examination) both CTDIvol and DLP were calculated from the mean dose. Data acquisition Two types of collection tools were used, corresponding to Japan Dose Index Registry (J-DIR). One is the National Institute of Radiological Sciences Tool ‘NIRS Tool’ (Carestream Health, Tokyo, Japan) that we developed originally. It corresponds to collection of RDSR and information collection by image capture of CT Dose sheet. The other is a commercially available ‘Dose Manager’ (Cure Hope, Osaka, Japan), which supports collection of only RDSR. Both tools collect RDSR for a certain period and output, there is no difference in accuracy. For facilities that use models that cannot output RDSR from CT, we used the image capture version of NIRS Tool. The collection tool connected to each center’s network and acquires information in real time by collecting the RDSRs or dose sheets outputted from the CT device (Figure 2). We selected 13 centers equipped with CT scanners with different manufacturers roughly representative of the distribution throughout Japan (Figure 3). The collection period of each center varied depending on the permission of the center and the burden on the personnel (Table 1). Figure 2. View largeDownload slide RDSR acquisition system. This is the connection diagram of the Tool used in this study. We collected SR data from CT or PACS in real time. CT scanners not equipped to issue SRs were handled by image capture of the dose sheet. The acquisition data was compressed and anonymized the current day between 0 o’clock and 3 o’clock every day. In addition, we made anonymization that data cannot be concatenated. The technician uploads the anonymized data on SafeSync. NIRS aggregates the SR data from each facility to the server and uploads the analysis data again. Figure 2. View largeDownload slide RDSR acquisition system. This is the connection diagram of the Tool used in this study. We collected SR data from CT or PACS in real time. CT scanners not equipped to issue SRs were handled by image capture of the dose sheet. The acquisition data was compressed and anonymized the current day between 0 o’clock and 3 o’clock every day. In addition, we made anonymization that data cannot be concatenated. The technician uploads the anonymized data on SafeSync. NIRS aggregates the SR data from each facility to the server and uploads the analysis data again. Figure 3. View largeDownload slide Distribution of CT venders. (a) Distribution of CT venders in Japan(29), n = 11 349. (b) Distribution of CT venders in this study, n = 33. Figure 3. View largeDownload slide Distribution of CT venders. (a) Distribution of CT venders in Japan(29), n = 11 349. (b) Distribution of CT venders in this study, n = 33. Table 1. Collection period and examination number, age of adult and pediatric patients. Center  Bed  Scanner number  Toola  Acquisition period  Examination number of adult  Nunmber/scanner/dayb  Age (year old)  Examination number of pediatric  Nunmber/scanner/dayb  Age (year old)  Start  End  Male  Female  Total  Mean ± SD  Male  Female  Total  Mean ± SD  A  749  2  N  1/16/15  4/9/15  4575  3415  7990  48  64.07 ± 16.56  96  61  157  0.9  6.66 ± 4.84  B  712  1  N  7/9/15  12/30/15  7138  5335  12 473  72  66.48 ± 17.36  219  118  337  1.9  6.55 ± 4.88  Cc  740  3  N  7/8/15  12/31/15  7572  4588  12 160  23  64.21 ± 15.43  259  145  404  0.8  6.55 ± 4.48  D  676  2  N  8/19/15  9/29/15  902  752  1654  20  66.29 ± 17.61  23  12  35  0.4  6.49 ± 4.94  E  227  1  N  9/15/15  12/30/15  1306  1301  2607  25  68.81 ± 14.65  33  29  62  0.6  5.21 ± 4.54  F  715  2  Ncap  12/18/14  1/30/15  1205  910  2115  25  64.66 ± 15.03  11  17  28  0.3  8.96 ± 4.86  G  580  2  N  1/20/15  12/31/15  26 785  20 806  47 591  69  66.6 ± 15.53  264  144  408  0.6  9.54 ± 3.88  H  388  1  D  4/20/15  7/28/15  1596  1331  2927  30  64.87 ± 17.38  49  25  74  0.7  7.11 ± 4.76  Ic  600  2  D  11/18/15  12/31/15  1040  788  1828  21  61.46 ± 17.02  28  32  60  0.7  8.53 ± 4.49  J  269  2  N  9/29/15  12/31/15  2109  2041  4150  22  71.23 ± 14.57  6  0  6  0.03  11.17 ± 2.93  K  1001  6  N  10/29/15  12/30/15  4412  3526  7938  21  67.47 ± 14.26  28  13  41  0.1  9.07 ± 4.53  Lc  1225  4  N  10/28/14  2/2/15  8648  6958  15 606  40  60.93 ± 16.90  165  125  290  0.7  7.63 ± 4.34  Mc  600  5  N  2/19/15  12/31/15  9164  6673  15 837  10  65.24 ± 14.96  97  135  232  0.1  7.56 ± 4.79  Total  652.5 ± 271.27d  33    10/28/14  12/31/15  76 452  58 424  134 876  32.8 ± 19.15d  65.50 ± 15.92  1278  856  2134  0.62 ± 0.49 d  7.52 ± 0.43  Center  Bed  Scanner number  Toola  Acquisition period  Examination number of adult  Nunmber/scanner/dayb  Age (year old)  Examination number of pediatric  Nunmber/scanner/dayb  Age (year old)  Start  End  Male  Female  Total  Mean ± SD  Male  Female  Total  Mean ± SD  A  749  2  N  1/16/15  4/9/15  4575  3415  7990  48  64.07 ± 16.56  96  61  157  0.9  6.66 ± 4.84  B  712  1  N  7/9/15  12/30/15  7138  5335  12 473  72  66.48 ± 17.36  219  118  337  1.9  6.55 ± 4.88  Cc  740  3  N  7/8/15  12/31/15  7572  4588  12 160  23  64.21 ± 15.43  259  145  404  0.8  6.55 ± 4.48  D  676  2  N  8/19/15  9/29/15  902  752  1654  20  66.29 ± 17.61  23  12  35  0.4  6.49 ± 4.94  E  227  1  N  9/15/15  12/30/15  1306  1301  2607  25  68.81 ± 14.65  33  29  62  0.6  5.21 ± 4.54  F  715  2  Ncap  12/18/14  1/30/15  1205  910  2115  25  64.66 ± 15.03  11  17  28  0.3  8.96 ± 4.86  G  580  2  N  1/20/15  12/31/15  26 785  20 806  47 591  69  66.6 ± 15.53  264  144  408  0.6  9.54 ± 3.88  H  388  1  D  4/20/15  7/28/15  1596  1331  2927  30  64.87 ± 17.38  49  25  74  0.7  7.11 ± 4.76  Ic  600  2  D  11/18/15  12/31/15  1040  788  1828  21  61.46 ± 17.02  28  32  60  0.7  8.53 ± 4.49  J  269  2  N  9/29/15  12/31/15  2109  2041  4150  22  71.23 ± 14.57  6  0  6  0.03  11.17 ± 2.93  K  1001  6  N  10/29/15  12/30/15  4412  3526  7938  21  67.47 ± 14.26  28  13  41  0.1  9.07 ± 4.53  Lc  1225  4  N  10/28/14  2/2/15  8648  6958  15 606  40  60.93 ± 16.90  165  125  290  0.7  7.63 ± 4.34  Mc  600  5  N  2/19/15  12/31/15  9164  6673  15 837  10  65.24 ± 14.96  97  135  232  0.1  7.56 ± 4.79  Total  652.5 ± 271.27d  33    10/28/14  12/31/15  76 452  58 424  134 876  32.8 ± 19.15d  65.50 ± 15.92  1278  856  2134  0.62 ± 0.49 d  7.52 ± 0.43  aN, NIRS Tool; Ncap, NIRS Tool capture version; D, Dose Manager. bThe value is total examination number per acquisition period day and scaner number. cThe center is a university hospital. dThe value is mean value ± SD. View Large Table 1. Collection period and examination number, age of adult and pediatric patients. Center  Bed  Scanner number  Toola  Acquisition period  Examination number of adult  Nunmber/scanner/dayb  Age (year old)  Examination number of pediatric  Nunmber/scanner/dayb  Age (year old)  Start  End  Male  Female  Total  Mean ± SD  Male  Female  Total  Mean ± SD  A  749  2  N  1/16/15  4/9/15  4575  3415  7990  48  64.07 ± 16.56  96  61  157  0.9  6.66 ± 4.84  B  712  1  N  7/9/15  12/30/15  7138  5335  12 473  72  66.48 ± 17.36  219  118  337  1.9  6.55 ± 4.88  Cc  740  3  N  7/8/15  12/31/15  7572  4588  12 160  23  64.21 ± 15.43  259  145  404  0.8  6.55 ± 4.48  D  676  2  N  8/19/15  9/29/15  902  752  1654  20  66.29 ± 17.61  23  12  35  0.4  6.49 ± 4.94  E  227  1  N  9/15/15  12/30/15  1306  1301  2607  25  68.81 ± 14.65  33  29  62  0.6  5.21 ± 4.54  F  715  2  Ncap  12/18/14  1/30/15  1205  910  2115  25  64.66 ± 15.03  11  17  28  0.3  8.96 ± 4.86  G  580  2  N  1/20/15  12/31/15  26 785  20 806  47 591  69  66.6 ± 15.53  264  144  408  0.6  9.54 ± 3.88  H  388  1  D  4/20/15  7/28/15  1596  1331  2927  30  64.87 ± 17.38  49  25  74  0.7  7.11 ± 4.76  Ic  600  2  D  11/18/15  12/31/15  1040  788  1828  21  61.46 ± 17.02  28  32  60  0.7  8.53 ± 4.49  J  269  2  N  9/29/15  12/31/15  2109  2041  4150  22  71.23 ± 14.57  6  0  6  0.03  11.17 ± 2.93  K  1001  6  N  10/29/15  12/30/15  4412  3526  7938  21  67.47 ± 14.26  28  13  41  0.1  9.07 ± 4.53  Lc  1225  4  N  10/28/14  2/2/15  8648  6958  15 606  40  60.93 ± 16.90  165  125  290  0.7  7.63 ± 4.34  Mc  600  5  N  2/19/15  12/31/15  9164  6673  15 837  10  65.24 ± 14.96  97  135  232  0.1  7.56 ± 4.79  Total  652.5 ± 271.27d  33    10/28/14  12/31/15  76 452  58 424  134 876  32.8 ± 19.15d  65.50 ± 15.92  1278  856  2134  0.62 ± 0.49 d  7.52 ± 0.43  Center  Bed  Scanner number  Toola  Acquisition period  Examination number of adult  Nunmber/scanner/dayb  Age (year old)  Examination number of pediatric  Nunmber/scanner/dayb  Age (year old)  Start  End  Male  Female  Total  Mean ± SD  Male  Female  Total  Mean ± SD  A  749  2  N  1/16/15  4/9/15  4575  3415  7990  48  64.07 ± 16.56  96  61  157  0.9  6.66 ± 4.84  B  712  1  N  7/9/15  12/30/15  7138  5335  12 473  72  66.48 ± 17.36  219  118  337  1.9  6.55 ± 4.88  Cc  740  3  N  7/8/15  12/31/15  7572  4588  12 160  23  64.21 ± 15.43  259  145  404  0.8  6.55 ± 4.48  D  676  2  N  8/19/15  9/29/15  902  752  1654  20  66.29 ± 17.61  23  12  35  0.4  6.49 ± 4.94  E  227  1  N  9/15/15  12/30/15  1306  1301  2607  25  68.81 ± 14.65  33  29  62  0.6  5.21 ± 4.54  F  715  2  Ncap  12/18/14  1/30/15  1205  910  2115  25  64.66 ± 15.03  11  17  28  0.3  8.96 ± 4.86  G  580  2  N  1/20/15  12/31/15  26 785  20 806  47 591  69  66.6 ± 15.53  264  144  408  0.6  9.54 ± 3.88  H  388  1  D  4/20/15  7/28/15  1596  1331  2927  30  64.87 ± 17.38  49  25  74  0.7  7.11 ± 4.76  Ic  600  2  D  11/18/15  12/31/15  1040  788  1828  21  61.46 ± 17.02  28  32  60  0.7  8.53 ± 4.49  J  269  2  N  9/29/15  12/31/15  2109  2041  4150  22  71.23 ± 14.57  6  0  6  0.03  11.17 ± 2.93  K  1001  6  N  10/29/15  12/30/15  4412  3526  7938  21  67.47 ± 14.26  28  13  41  0.1  9.07 ± 4.53  Lc  1225  4  N  10/28/14  2/2/15  8648  6958  15 606  40  60.93 ± 16.90  165  125  290  0.7  7.63 ± 4.34  Mc  600  5  N  2/19/15  12/31/15  9164  6673  15 837  10  65.24 ± 14.96  97  135  232  0.1  7.56 ± 4.79  Total  652.5 ± 271.27d  33    10/28/14  12/31/15  76 452  58 424  134 876  32.8 ± 19.15d  65.50 ± 15.92  1278  856  2134  0.62 ± 0.49 d  7.52 ± 0.43  aN, NIRS Tool; Ncap, NIRS Tool capture version; D, Dose Manager. bThe value is total examination number per acquisition period day and scaner number. cThe center is a university hospital. dThe value is mean value ± SD. View Large The NIRS tool compresses and anonymizes the current day’s RDSR between midnight and 3:00 am. Also, performs anonymization that cannot be concatenated. The information acquired from each facilities should be aggregated in the RDSR server in NIRS via the network, but it was impossible to realize because the clinical network did not allow connection with the external network due to facility policy problem. Therefore, as a method of acquiring information collected by each facility, we thought that it was safe to share it with NIRS by another PC connected to the virtual private network (VPN). Sharing is one to one with NIRS and each facility, and facility sharing is not done. In order to realize these sharing we used SafeSync (Trend Micro Incorporated, Tokyo, Japan). The data were aggregated into the RDSR System of a dedicated server. Dose Manager was able to output RDSR collected from CT at all times in anonymous state and shared by SafeSync. Data analysis The data of each center aggregated in the RDSR System were output with comma separated values (csv) and analyzed with spreadsheet software (Excel 2013, Microsoft Office, Redmond WA, USA). Data are expressed as mean ± standard deviation (SD). We used the VPN to summarize each center on a spreadsheet, and examined analytic data from each center. Comparison of dose-related data to DRLs RDSR and dose sheets included CTDIvol and DLP for the dose index, calculated the mean and SD for each anatomical region in adults and children, the representative value of each center. For CTDIvol and DLP of ‘Head and Brain’, ‘Circle of Willis’, ‘Eye region’ and ‘Orbit region’ in adults, the dose index value normalized to a 16-cm phantom standard is shown. For the other anatomical regions, it shows the values normalized to a 32-cm phantom. For the CTDIvol and DLP of pediatric patients, the values derived with the 32-cm phantom were doubled to simulate a 16-cm phantom(17). The mean and SD values, minimum value, 25th percentile, 50th percentile, 75th percentile and maximum value were calculated from the dose indices of each center. The mean value of each center was used as a representative value, and its 75th percentile values were taken as adult and pediatric DRLs in this study. We compared our findings with DRLs of the head, chest, abdomen and heart in adults from data published by 10 countries. The pediatric DRL was compared with DRLs of head, chest and abdominal CT published from six countries. RESULTS The total number of centers participating in the survey was 13, of which four were university hospitals. The number of beds was 227 in the smallest center and 1225 in the largest (Table 1). There were 134 876 examinations of patients over 15 years old (males: 76 452, females: 58 424) with RDSR obtained during the survey period from October 2014 to December 2015, and there were 2134 examinations of patients ≤15 years old (males: 1278, females: 856). There were 84 203 adult (males: 47 213, females: 36 990) and 1316 pediatric (males: 745, females: 571) subjects. The mean value for all centers was 32.8 ± 19.15 cases per day. The mean value for pediatric cases at all centers was 0.6 cases. The mean age of adults was 65.5 ± 15.92 years and the mean age of pediatric subjects was 7.5 ± 0.43 years. Figure 4 shows the age ranges in more detail. Figure 4. View largeDownload slide Distribution of examinations by age and sex. Figure 4. View largeDownload slide Distribution of examinations by age and sex. The total number of CT devices targeted for collection was 33, and all had more than 16 rows of detectors. Figure 3 shows the vendor breakdown and departures from the average. No Hitachi scanners were included. Table 2 shows the 20 target regions acquired from all the centers. ‘Unknown’ cases were excluded from the analysis. Table 2. Acquisition of CT target region and patient number of adult and pediatric patients. Target region (SRTa)  Adult examination number  Pediatric examination number  M  F  Total  M  F  Total  Head (T-D1100), brain (T-A0100)  14 302  11 826  26 128  535  374  909  Circle of Willis (T-45526)  0  9  9  0  0  0  Eye region (T-D0801)  1002  977  1979  83  45  128  Orbit region (T-D0801)  297  245  542  30  21  51  Neck (T-D1600)  2177  1580  3757  49  24  73  Heart (T-32000)  182  97  279  0  0  0  Chest (T-D3000)  29 726  22 592  52 318  193  145  338  Abdomen (T-D4000)  19 745  14 145  33 890  110  80  190  Chest and abdomen (R-FAB55)  3974  3355  7329  50  41  91  Chest, abdomen and pelvis (R-FAB56)  1940  1143  3083  82  33  115  Entire body (T-D0010)  216  90  306  22  16  38  Pelvis (T-D6000)  311  356  667  11  4  15  Lumbar spine (T-11503)  551  437  988  11  8  19  Spine (T-D0146)  13  22  35  2  0  2  Extremity (T-D0300)  537  556  1093  23  13  36  Arm (T-D8200)  26  23  49  4  1  5  Shoulder (T-D2220)  519  257  776  17  8  25  Leg (T-D9400)  116  67  183  12  7  19  Unknown (00001,99GEMS)  818  647  1465  44  36  80  Total examination number  76 452  58 424  134 876  1278  856  2134  Target region (SRTa)  Adult examination number  Pediatric examination number  M  F  Total  M  F  Total  Head (T-D1100), brain (T-A0100)  14 302  11 826  26 128  535  374  909  Circle of Willis (T-45526)  0  9  9  0  0  0  Eye region (T-D0801)  1002  977  1979  83  45  128  Orbit region (T-D0801)  297  245  542  30  21  51  Neck (T-D1600)  2177  1580  3757  49  24  73  Heart (T-32000)  182  97  279  0  0  0  Chest (T-D3000)  29 726  22 592  52 318  193  145  338  Abdomen (T-D4000)  19 745  14 145  33 890  110  80  190  Chest and abdomen (R-FAB55)  3974  3355  7329  50  41  91  Chest, abdomen and pelvis (R-FAB56)  1940  1143  3083  82  33  115  Entire body (T-D0010)  216  90  306  22  16  38  Pelvis (T-D6000)  311  356  667  11  4  15  Lumbar spine (T-11503)  551  437  988  11  8  19  Spine (T-D0146)  13  22  35  2  0  2  Extremity (T-D0300)  537  556  1093  23  13  36  Arm (T-D8200)  26  23  49  4  1  5  Shoulder (T-D2220)  519  257  776  17  8  25  Leg (T-D9400)  116  67  183  12  7  19  Unknown (00001,99GEMS)  818  647  1465  44  36  80  Total examination number  76 452  58 424  134 876  1278  856  2134  aSRT is structured reporting templates. Table 2. Acquisition of CT target region and patient number of adult and pediatric patients. Target region (SRTa)  Adult examination number  Pediatric examination number  M  F  Total  M  F  Total  Head (T-D1100), brain (T-A0100)  14 302  11 826  26 128  535  374  909  Circle of Willis (T-45526)  0  9  9  0  0  0  Eye region (T-D0801)  1002  977  1979  83  45  128  Orbit region (T-D0801)  297  245  542  30  21  51  Neck (T-D1600)  2177  1580  3757  49  24  73  Heart (T-32000)  182  97  279  0  0  0  Chest (T-D3000)  29 726  22 592  52 318  193  145  338  Abdomen (T-D4000)  19 745  14 145  33 890  110  80  190  Chest and abdomen (R-FAB55)  3974  3355  7329  50  41  91  Chest, abdomen and pelvis (R-FAB56)  1940  1143  3083  82  33  115  Entire body (T-D0010)  216  90  306  22  16  38  Pelvis (T-D6000)  311  356  667  11  4  15  Lumbar spine (T-11503)  551  437  988  11  8  19  Spine (T-D0146)  13  22  35  2  0  2  Extremity (T-D0300)  537  556  1093  23  13  36  Arm (T-D8200)  26  23  49  4  1  5  Shoulder (T-D2220)  519  257  776  17  8  25  Leg (T-D9400)  116  67  183  12  7  19  Unknown (00001,99GEMS)  818  647  1465  44  36  80  Total examination number  76 452  58 424  134 876  1278  856  2134  Target region (SRTa)  Adult examination number  Pediatric examination number  M  F  Total  M  F  Total  Head (T-D1100), brain (T-A0100)  14 302  11 826  26 128  535  374  909  Circle of Willis (T-45526)  0  9  9  0  0  0  Eye region (T-D0801)  1002  977  1979  83  45  128  Orbit region (T-D0801)  297  245  542  30  21  51  Neck (T-D1600)  2177  1580  3757  49  24  73  Heart (T-32000)  182  97  279  0  0  0  Chest (T-D3000)  29 726  22 592  52 318  193  145  338  Abdomen (T-D4000)  19 745  14 145  33 890  110  80  190  Chest and abdomen (R-FAB55)  3974  3355  7329  50  41  91  Chest, abdomen and pelvis (R-FAB56)  1940  1143  3083  82  33  115  Entire body (T-D0010)  216  90  306  22  16  38  Pelvis (T-D6000)  311  356  667  11  4  15  Lumbar spine (T-11503)  551  437  988  11  8  19  Spine (T-D0146)  13  22  35  2  0  2  Extremity (T-D0300)  537  556  1093  23  13  36  Arm (T-D8200)  26  23  49  4  1  5  Shoulder (T-D2220)  519  257  776  17  8  25  Leg (T-D9400)  116  67  183  12  7  19  Unknown (00001,99GEMS)  818  647  1465  44  36  80  Total examination number  76 452  58 424  134 876  1278  856  2134  aSRT is structured reporting templates. Table 3 shows the ranges and values of the CTDIvol and DLP of each target region at each center as a representative value in adults. Table 4 shows the pediatric values. Table 3. CTDIvol and DLP for single scan of each anatomical region for adult. Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)  DLP (mGy cm)  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  Head (T-D1100)b, Brain (T-A0100)b  13  26 128  68.9  11.26  47  62  67  78  88  1170.7  268.81  655  1059  1174  1292  1684  Circle of Willis (T-45526)b  1  9  29.2  0  29  29  29  29  29  558.3  0  558  558  558  558  558  Eye region (T-D0801)b  4  1979  35.0  11.52  20  29  37  44  45  624.3  205.52  344  563  658  720  836  Orbit region (T-D0801)b  5  542  39.9  19.15  19  29  36  46  69  719.2  636.24  293  351  520  596  1836  Neck (T-D1600)  13  3757  20.1  12.85  9  12  18  24  58  566.3  376.04  236  392  513  553  1741  Heart (T-32000)  3  279  41.6  27.12  18  27  36  54  71  983.6  292.97  653  871  1089  1149  1210  Chest (T-D3000)  13  52 318  16.3  14.66  8  11  12  15  63  721.5  337.52  290  587  659  689  1660  Abdomen (T-D4000)  13  33 890  15.4  15.03  8  10  11  12  65  641.3  344.54  351  485  549  640  1706  Chest and abdomen (R-FAB55)  2  7329  36.4  41.28  7  22  36  51  66  1039.3  963.45  358  699  1039  1380  1721  Chest, abdomen and pelvis (R-FAB56)  2  3083  17.0  0.73  17  17  17  17  18  877.3  20.63  863  870  877  885  892  Entire body (T-D0010)  2  306  61.7  19.39  48  55  62  69  75  1779.9  217.16  1626  1703  1780  1857  1934  Pelvis (T-D6000)  11  667  19.9  14.01  8  13  15  21  57  854.9  379.42  335  637  740  1031  1514  Lumbar spine (T-11503)  7  988  20.4  8.39  10  17  19  20  37  641.8  67.45  529  611  655  673  740  Spine (T-D0146)  1  35  7.6  0  8  8  8  8  8  346.6  0  347  347  347  347  347  Extremity (T-D0300)  10  1093  12.8  7.16  7  8  11  12  29  544.7  172.83  144  488  542  685  722  Arm (T-D8200)  2  49  17.9  4.95  14  16  18  20  21  602.4  118.05  519  561  602  644  686  Shoulder (T-D2220)  8  776  18.3  7.25  5  16  21  23  26  439.1  175.34  126  348  538  558  581  Leg (T-D9400)  5  183  22.2  25.15  4  9  10  22  66  692.5  448.17  228  529  553  724  1428  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)  DLP (mGy cm)  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  Head (T-D1100)b, Brain (T-A0100)b  13  26 128  68.9  11.26  47  62  67  78  88  1170.7  268.81  655  1059  1174  1292  1684  Circle of Willis (T-45526)b  1  9  29.2  0  29  29  29  29  29  558.3  0  558  558  558  558  558  Eye region (T-D0801)b  4  1979  35.0  11.52  20  29  37  44  45  624.3  205.52  344  563  658  720  836  Orbit region (T-D0801)b  5  542  39.9  19.15  19  29  36  46  69  719.2  636.24  293  351  520  596  1836  Neck (T-D1600)  13  3757  20.1  12.85  9  12  18  24  58  566.3  376.04  236  392  513  553  1741  Heart (T-32000)  3  279  41.6  27.12  18  27  36  54  71  983.6  292.97  653  871  1089  1149  1210  Chest (T-D3000)  13  52 318  16.3  14.66  8  11  12  15  63  721.5  337.52  290  587  659  689  1660  Abdomen (T-D4000)  13  33 890  15.4  15.03  8  10  11  12  65  641.3  344.54  351  485  549  640  1706  Chest and abdomen (R-FAB55)  2  7329  36.4  41.28  7  22  36  51  66  1039.3  963.45  358  699  1039  1380  1721  Chest, abdomen and pelvis (R-FAB56)  2  3083  17.0  0.73  17  17  17  17  18  877.3  20.63  863  870  877  885  892  Entire body (T-D0010)  2  306  61.7  19.39  48  55  62  69  75  1779.9  217.16  1626  1703  1780  1857  1934  Pelvis (T-D6000)  11  667  19.9  14.01  8  13  15  21  57  854.9  379.42  335  637  740  1031  1514  Lumbar spine (T-11503)  7  988  20.4  8.39  10  17  19  20  37  641.8  67.45  529  611  655  673  740  Spine (T-D0146)  1  35  7.6  0  8  8  8  8  8  346.6  0  347  347  347  347  347  Extremity (T-D0300)  10  1093  12.8  7.16  7  8  11  12  29  544.7  172.83  144  488  542  685  722  Arm (T-D8200)  2  49  17.9  4.95  14  16  18  20  21  602.4  118.05  519  561  602  644  686  Shoulder (T-D2220)  8  776  18.3  7.25  5  16  21  23  26  439.1  175.34  126  348  538  558  581  Leg (T-D9400)  5  183  22.2  25.15  4  9  10  22  66  692.5  448.17  228  529  553  724  1428  aSRT is structured reporting templates. bCTDIvol and DLP values adjusted to 16-cm PMMA phantom. Table 3. CTDIvol and DLP for single scan of each anatomical region for adult. Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)  DLP (mGy cm)  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  Head (T-D1100)b, Brain (T-A0100)b  13  26 128  68.9  11.26  47  62  67  78  88  1170.7  268.81  655  1059  1174  1292  1684  Circle of Willis (T-45526)b  1  9  29.2  0  29  29  29  29  29  558.3  0  558  558  558  558  558  Eye region (T-D0801)b  4  1979  35.0  11.52  20  29  37  44  45  624.3  205.52  344  563  658  720  836  Orbit region (T-D0801)b  5  542  39.9  19.15  19  29  36  46  69  719.2  636.24  293  351  520  596  1836  Neck (T-D1600)  13  3757  20.1  12.85  9  12  18  24  58  566.3  376.04  236  392  513  553  1741  Heart (T-32000)  3  279  41.6  27.12  18  27  36  54  71  983.6  292.97  653  871  1089  1149  1210  Chest (T-D3000)  13  52 318  16.3  14.66  8  11  12  15  63  721.5  337.52  290  587  659  689  1660  Abdomen (T-D4000)  13  33 890  15.4  15.03  8  10  11  12  65  641.3  344.54  351  485  549  640  1706  Chest and abdomen (R-FAB55)  2  7329  36.4  41.28  7  22  36  51  66  1039.3  963.45  358  699  1039  1380  1721  Chest, abdomen and pelvis (R-FAB56)  2  3083  17.0  0.73  17  17  17  17  18  877.3  20.63  863  870  877  885  892  Entire body (T-D0010)  2  306  61.7  19.39  48  55  62  69  75  1779.9  217.16  1626  1703  1780  1857  1934  Pelvis (T-D6000)  11  667  19.9  14.01  8  13  15  21  57  854.9  379.42  335  637  740  1031  1514  Lumbar spine (T-11503)  7  988  20.4  8.39  10  17  19  20  37  641.8  67.45  529  611  655  673  740  Spine (T-D0146)  1  35  7.6  0  8  8  8  8  8  346.6  0  347  347  347  347  347  Extremity (T-D0300)  10  1093  12.8  7.16  7  8  11  12  29  544.7  172.83  144  488  542  685  722  Arm (T-D8200)  2  49  17.9  4.95  14  16  18  20  21  602.4  118.05  519  561  602  644  686  Shoulder (T-D2220)  8  776  18.3  7.25  5  16  21  23  26  439.1  175.34  126  348  538  558  581  Leg (T-D9400)  5  183  22.2  25.15  4  9  10  22  66  692.5  448.17  228  529  553  724  1428  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)  DLP (mGy cm)  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  Head (T-D1100)b, Brain (T-A0100)b  13  26 128  68.9  11.26  47  62  67  78  88  1170.7  268.81  655  1059  1174  1292  1684  Circle of Willis (T-45526)b  1  9  29.2  0  29  29  29  29  29  558.3  0  558  558  558  558  558  Eye region (T-D0801)b  4  1979  35.0  11.52  20  29  37  44  45  624.3  205.52  344  563  658  720  836  Orbit region (T-D0801)b  5  542  39.9  19.15  19  29  36  46  69  719.2  636.24  293  351  520  596  1836  Neck (T-D1600)  13  3757  20.1  12.85  9  12  18  24  58  566.3  376.04  236  392  513  553  1741  Heart (T-32000)  3  279  41.6  27.12  18  27  36  54  71  983.6  292.97  653  871  1089  1149  1210  Chest (T-D3000)  13  52 318  16.3  14.66  8  11  12  15  63  721.5  337.52  290  587  659  689  1660  Abdomen (T-D4000)  13  33 890  15.4  15.03  8  10  11  12  65  641.3  344.54  351  485  549  640  1706  Chest and abdomen (R-FAB55)  2  7329  36.4  41.28  7  22  36  51  66  1039.3  963.45  358  699  1039  1380  1721  Chest, abdomen and pelvis (R-FAB56)  2  3083  17.0  0.73  17  17  17  17  18  877.3  20.63  863  870  877  885  892  Entire body (T-D0010)  2  306  61.7  19.39  48  55  62  69  75  1779.9  217.16  1626  1703  1780  1857  1934  Pelvis (T-D6000)  11  667  19.9  14.01  8  13  15  21  57  854.9  379.42  335  637  740  1031  1514  Lumbar spine (T-11503)  7  988  20.4  8.39  10  17  19  20  37  641.8  67.45  529  611  655  673  740  Spine (T-D0146)  1  35  7.6  0  8  8  8  8  8  346.6  0  347  347  347  347  347  Extremity (T-D0300)  10  1093  12.8  7.16  7  8  11  12  29  544.7  172.83  144  488  542  685  722  Arm (T-D8200)  2  49  17.9  4.95  14  16  18  20  21  602.4  118.05  519  561  602  644  686  Shoulder (T-D2220)  8  776  18.3  7.25  5  16  21  23  26  439.1  175.34  126  348  538  558  581  Leg (T-D9400)  5  183  22.2  25.15  4  9  10  22  66  692.5  448.17  228  529  553  724  1428  aSRT is structured reporting templates. bCTDIvol and DLP values adjusted to 16-cm PMMA phantom. Table 4. CTDIvol and DLP for single scan of each anatomical region for pediatric. Age group (years)  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)b  DLP (mGy cm)b  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  0 to <1  Head (T-D1100), brain (T-A0100)  11  85  35.0  13.92  14  27  35  43  60  529.1  261.03  180  351  509  739  928  Neck (T-D1600)  3  5  8.8  3.06  5  8  10  11  11  119.8  59.72  70  87  103  145  186  Chest (T-D3000)  9  49  9.2  8.87  1  4  9  10  31  117.5  125.02  2  51  79  123  406  Abdomen (T-D4000)  6  18  5.2  3.50  1  3  4  7  11  105.6  76.39  18  60  81  161  213  Chest and abdomen (R-FAB55)  2  13  31.0  34.19  7  19  31  43  55  384.5  445.91  69  227  385  542  700  1 to <6  Head (T-D1100), brain (T-A0100)  11  239  42.1  20.76  6  32  39  56  82  708.5  295.03  242  577  667  863  1320  Neck (T-D1600)  6  19  11.4  4.63  6  8  11  14  18  128.5  69.53  70  80  104  153  251  Chest (T-D3000)  9  104  15.1  18.33  4  6  9  13  63  180.0  145.15  69  83  117  236  507  Abdomen (T-D4000)  7  48  14.4  23.23  2  4  7  8  67  211.5  236.66  37  108  126  184  734  Chest and abdomen (R-FAB55)  2  19  25.4  27.38  6  16  25  35  45  343.7  331.91  109  226  344  461  578  6 to <11  Head (T-D1100), brain (T-A0100)  13  311  59.9  22.10  26  48  59  67  103  950.8  417.27  226  692  911  1249  1706  Neck (T-D1600)  8  22  19.7  11.13  7  11  17  27  36  300.6  250.77  62  146  187  433  725  Chest (T-D3000)  9  87  16.3  19.03  4  5  8  12  57  328.5  400.11  70  94  157  215  1192  Abdomen (T-D4000)  10  51  12.9  15.82  3  5  8  12  57  196.7  188.33  30  99  125  242  683  Chest and abdomen (R-FAB55)  2  27  41.8  48.17  8  25  42  59  76  467.5  514.75  104  286  467  649  831  11 to <15  Head (T-D1100), brain (T-A0100)  13  274  59.8  23.31  1  52  64  71  92  1090.0  398.56  436  799  1056  1278  1733  Neck (T-D1600)  5  27  38.4  19.27  19  23  33  57  60  704.6  350.26  180  508  901  967  967  Chest (T-D3000)  10  98  31.3  33.76  8  12  17  25  103  530.1  343.12  226  282  376  702  1117  Abdomen (T-D4000)  13  73  15.9  8.72  4  10  13  22  32  396.1  246.51  10  198  439  622  780  Chest and abdomen (R-FAB55)  2  32  40.3  43.42  10  25  40  56  71  730.7  395.64  274  617  959  959  959  Age group (years)  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)b  DLP (mGy cm)b  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  0 to <1  Head (T-D1100), brain (T-A0100)  11  85  35.0  13.92  14  27  35  43  60  529.1  261.03  180  351  509  739  928  Neck (T-D1600)  3  5  8.8  3.06  5  8  10  11  11  119.8  59.72  70  87  103  145  186  Chest (T-D3000)  9  49  9.2  8.87  1  4  9  10  31  117.5  125.02  2  51  79  123  406  Abdomen (T-D4000)  6  18  5.2  3.50  1  3  4  7  11  105.6  76.39  18  60  81  161  213  Chest and abdomen (R-FAB55)  2  13  31.0  34.19  7  19  31  43  55  384.5  445.91  69  227  385  542  700  1 to <6  Head (T-D1100), brain (T-A0100)  11  239  42.1  20.76  6  32  39  56  82  708.5  295.03  242  577  667  863  1320  Neck (T-D1600)  6  19  11.4  4.63  6  8  11  14  18  128.5  69.53  70  80  104  153  251  Chest (T-D3000)  9  104  15.1  18.33  4  6  9  13  63  180.0  145.15  69  83  117  236  507  Abdomen (T-D4000)  7  48  14.4  23.23  2  4  7  8  67  211.5  236.66  37  108  126  184  734  Chest and abdomen (R-FAB55)  2  19  25.4  27.38  6  16  25  35  45  343.7  331.91  109  226  344  461  578  6 to <11  Head (T-D1100), brain (T-A0100)  13  311  59.9  22.10  26  48  59  67  103  950.8  417.27  226  692  911  1249  1706  Neck (T-D1600)  8  22  19.7  11.13  7  11  17  27  36  300.6  250.77  62  146  187  433  725  Chest (T-D3000)  9  87  16.3  19.03  4  5  8  12  57  328.5  400.11  70  94  157  215  1192  Abdomen (T-D4000)  10  51  12.9  15.82  3  5  8  12  57  196.7  188.33  30  99  125  242  683  Chest and abdomen (R-FAB55)  2  27  41.8  48.17  8  25  42  59  76  467.5  514.75  104  286  467  649  831  11 to <15  Head (T-D1100), brain (T-A0100)  13  274  59.8  23.31  1  52  64  71  92  1090.0  398.56  436  799  1056  1278  1733  Neck (T-D1600)  5  27  38.4  19.27  19  23  33  57  60  704.6  350.26  180  508  901  967  967  Chest (T-D3000)  10  98  31.3  33.76  8  12  17  25  103  530.1  343.12  226  282  376  702  1117  Abdomen (T-D4000)  13  73  15.9  8.72  4  10  13  22  32  396.1  246.51  10  198  439  622  780  Chest and abdomen (R-FAB55)  2  32  40.3  43.42  10  25  40  56  71  730.7  395.64  274  617  959  959  959  aSRT is structured reporting templates. bThe values adjusted to 16-cm PMMA phantom. Table 4. CTDIvol and DLP for single scan of each anatomical region for pediatric. Age group (years)  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)b  DLP (mGy cm)b  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  0 to <1  Head (T-D1100), brain (T-A0100)  11  85  35.0  13.92  14  27  35  43  60  529.1  261.03  180  351  509  739  928  Neck (T-D1600)  3  5  8.8  3.06  5  8  10  11  11  119.8  59.72  70  87  103  145  186  Chest (T-D3000)  9  49  9.2  8.87  1  4  9  10  31  117.5  125.02  2  51  79  123  406  Abdomen (T-D4000)  6  18  5.2  3.50  1  3  4  7  11  105.6  76.39  18  60  81  161  213  Chest and abdomen (R-FAB55)  2  13  31.0  34.19  7  19  31  43  55  384.5  445.91  69  227  385  542  700  1 to <6  Head (T-D1100), brain (T-A0100)  11  239  42.1  20.76  6  32  39  56  82  708.5  295.03  242  577  667  863  1320  Neck (T-D1600)  6  19  11.4  4.63  6  8  11  14  18  128.5  69.53  70  80  104  153  251  Chest (T-D3000)  9  104  15.1  18.33  4  6  9  13  63  180.0  145.15  69  83  117  236  507  Abdomen (T-D4000)  7  48  14.4  23.23  2  4  7  8  67  211.5  236.66  37  108  126  184  734  Chest and abdomen (R-FAB55)  2  19  25.4  27.38  6  16  25  35  45  343.7  331.91  109  226  344  461  578  6 to <11  Head (T-D1100), brain (T-A0100)  13  311  59.9  22.10  26  48  59  67  103  950.8  417.27  226  692  911  1249  1706  Neck (T-D1600)  8  22  19.7  11.13  7  11  17  27  36  300.6  250.77  62  146  187  433  725  Chest (T-D3000)  9  87  16.3  19.03  4  5  8  12  57  328.5  400.11  70  94  157  215  1192  Abdomen (T-D4000)  10  51  12.9  15.82  3  5  8  12  57  196.7  188.33  30  99  125  242  683  Chest and abdomen (R-FAB55)  2  27  41.8  48.17  8  25  42  59  76  467.5  514.75  104  286  467  649  831  11 to <15  Head (T-D1100), brain (T-A0100)  13  274  59.8  23.31  1  52  64  71  92  1090.0  398.56  436  799  1056  1278  1733  Neck (T-D1600)  5  27  38.4  19.27  19  23  33  57  60  704.6  350.26  180  508  901  967  967  Chest (T-D3000)  10  98  31.3  33.76  8  12  17  25  103  530.1  343.12  226  282  376  702  1117  Abdomen (T-D4000)  13  73  15.9  8.72  4  10  13  22  32  396.1  246.51  10  198  439  622  780  Chest and abdomen (R-FAB55)  2  32  40.3  43.42  10  25  40  56  71  730.7  395.64  274  617  959  959  959  Age group (years)  Target region (SRTa)  Center number  Examination number  CTDIvol (mGy)b  DLP (mGy cm)b  Mean  SD  Min  25th  50th  75th  Max  Mean  SD  Min  25th  50th  75th  Max  0 to <1  Head (T-D1100), brain (T-A0100)  11  85  35.0  13.92  14  27  35  43  60  529.1  261.03  180  351  509  739  928  Neck (T-D1600)  3  5  8.8  3.06  5  8  10  11  11  119.8  59.72  70  87  103  145  186  Chest (T-D3000)  9  49  9.2  8.87  1  4  9  10  31  117.5  125.02  2  51  79  123  406  Abdomen (T-D4000)  6  18  5.2  3.50  1  3  4  7  11  105.6  76.39  18  60  81  161  213  Chest and abdomen (R-FAB55)  2  13  31.0  34.19  7  19  31  43  55  384.5  445.91  69  227  385  542  700  1 to <6  Head (T-D1100), brain (T-A0100)  11  239  42.1  20.76  6  32  39  56  82  708.5  295.03  242  577  667  863  1320  Neck (T-D1600)  6  19  11.4  4.63  6  8  11  14  18  128.5  69.53  70  80  104  153  251  Chest (T-D3000)  9  104  15.1  18.33  4  6  9  13  63  180.0  145.15  69  83  117  236  507  Abdomen (T-D4000)  7  48  14.4  23.23  2  4  7  8  67  211.5  236.66  37  108  126  184  734  Chest and abdomen (R-FAB55)  2  19  25.4  27.38  6  16  25  35  45  343.7  331.91  109  226  344  461  578  6 to <11  Head (T-D1100), brain (T-A0100)  13  311  59.9  22.10  26  48  59  67  103  950.8  417.27  226  692  911  1249  1706  Neck (T-D1600)  8  22  19.7  11.13  7  11  17  27  36  300.6  250.77  62  146  187  433  725  Chest (T-D3000)  9  87  16.3  19.03  4  5  8  12  57  328.5  400.11  70  94  157  215  1192  Abdomen (T-D4000)  10  51  12.9  15.82  3  5  8  12  57  196.7  188.33  30  99  125  242  683  Chest and abdomen (R-FAB55)  2  27  41.8  48.17  8  25  42  59  76  467.5  514.75  104  286  467  649  831  11 to <15  Head (T-D1100), brain (T-A0100)  13  274  59.8  23.31  1  52  64  71  92  1090.0  398.56  436  799  1056  1278  1733  Neck (T-D1600)  5  27  38.4  19.27  19  23  33  57  60  704.6  350.26  180  508  901  967  967  Chest (T-D3000)  10  98  31.3  33.76  8  12  17  25  103  530.1  343.12  226  282  376  702  1117  Abdomen (T-D4000)  13  73  15.9  8.72  4  10  13  22  32  396.1  246.51  10  198  439  622  780  Chest and abdomen (R-FAB55)  2  32  40.3  43.42  10  25  40  56  71  730.7  395.64  274  617  959  959  959  aSRT is structured reporting templates. bThe values adjusted to 16-cm PMMA phantom. Table 5 compares the 75th percentiles of adult head, chest, abdomen and heart CTs of this study with DRLs published from 10 countries and their mean values. Table 6 compares the 75th percentiles in the head, chest and abdomen of pediatric cases with the DRLs of seven countries with their mean values. Table 5. Comparison of CTDIvol and DLP for adult in each anatomical region with other countries. Anatomical region  Dose index  This study  EU  UK  Norway  Switzerland  Germany  Kenya  Ireland  Italy  Finland  Japan  Mean ± SDa  2004 [5]  2005 [6]  2009 [7]  2010 [8]  2010 [9]  2012 [10]  2012 [11]  2014 [12]  2015 [13]  2015 [18]  Headb  CTDIvol  78  60  65  75  65  65  65  66  69  55  85  67.0 ± 8.2  DLP  1292  990  930  1000  1000  950  760  940  1312  800  1350  1003 ± 191.0  DLP/CTDI  16.6  16.5  14.3  13.3  15.4  14.6  11.7  14.2  19.0  14.5  15.9  15.0 ± 1.95  Chestc  CTDIvol  15  12  13  15  10  12  13  9  15  9  15  12.3 ± 2.36  DLP  689  430  580  400  400  400  580  390  569  290  550  459 ± 102.3  DLP/CTDI  45.9  35.8  44.6  26.7  40.0  33.3  44.6  43.3  37.9  32.2  36.7  37.3 ± 5.85  Abdomenc  CTDIvol  12  16  14  15  15  20  14  12  18  12  20  15.6 ± 2.91  DLP  640  726  560  710  650  900  470  600  920  560  1000  710 ± 177.3  DLP/CTDI  53  45  40  47  43  45  34  50  51  47  50  45.5 ± 5.31  Heartc  CTDIvol  54  —  —  —  50  —  —  —  61  —  90  67.0 ± 20.66  DLP  1149  —  —  —  1000  —  —  —  1208  —  1400  1203 ± 200.1  DLP/CTDI  21.3  —  —  —  20.0  —  —  —  19.8  —  15.6  18.0 ± 2.51  Anatomical region  Dose index  This study  EU  UK  Norway  Switzerland  Germany  Kenya  Ireland  Italy  Finland  Japan  Mean ± SDa  2004 [5]  2005 [6]  2009 [7]  2010 [8]  2010 [9]  2012 [10]  2012 [11]  2014 [12]  2015 [13]  2015 [18]  Headb  CTDIvol  78  60  65  75  65  65  65  66  69  55  85  67.0 ± 8.2  DLP  1292  990  930  1000  1000  950  760  940  1312  800  1350  1003 ± 191.0  DLP/CTDI  16.6  16.5  14.3  13.3  15.4  14.6  11.7  14.2  19.0  14.5  15.9  15.0 ± 1.95  Chestc  CTDIvol  15  12  13  15  10  12  13  9  15  9  15  12.3 ± 2.36  DLP  689  430  580  400  400  400  580  390  569  290  550  459 ± 102.3  DLP/CTDI  45.9  35.8  44.6  26.7  40.0  33.3  44.6  43.3  37.9  32.2  36.7  37.3 ± 5.85  Abdomenc  CTDIvol  12  16  14  15  15  20  14  12  18  12  20  15.6 ± 2.91  DLP  640  726  560  710  650  900  470  600  920  560  1000  710 ± 177.3  DLP/CTDI  53  45  40  47  43  45  34  50  51  47  50  45.5 ± 5.31  Heartc  CTDIvol  54  —  —  —  50  —  —  —  61  —  90  67.0 ± 20.66  DLP  1149  —  —  —  1000  —  —  —  1208  —  1400  1203 ± 200.1  DLP/CTDI  21.3  —  —  —  20.0  —  —  —  19.8  —  15.6  18.0 ± 2.51  aThe values were calculated at DRL which excluded this study. bThe values adjusted to 16-cm PMMA phantom. cThe values adjusted to 32-cm PMMA phantom. Table 5. Comparison of CTDIvol and DLP for adult in each anatomical region with other countries. Anatomical region  Dose index  This study  EU  UK  Norway  Switzerland  Germany  Kenya  Ireland  Italy  Finland  Japan  Mean ± SDa  2004 [5]  2005 [6]  2009 [7]  2010 [8]  2010 [9]  2012 [10]  2012 [11]  2014 [12]  2015 [13]  2015 [18]  Headb  CTDIvol  78  60  65  75  65  65  65  66  69  55  85  67.0 ± 8.2  DLP  1292  990  930  1000  1000  950  760  940  1312  800  1350  1003 ± 191.0  DLP/CTDI  16.6  16.5  14.3  13.3  15.4  14.6  11.7  14.2  19.0  14.5  15.9  15.0 ± 1.95  Chestc  CTDIvol  15  12  13  15  10  12  13  9  15  9  15  12.3 ± 2.36  DLP  689  430  580  400  400  400  580  390  569  290  550  459 ± 102.3  DLP/CTDI  45.9  35.8  44.6  26.7  40.0  33.3  44.6  43.3  37.9  32.2  36.7  37.3 ± 5.85  Abdomenc  CTDIvol  12  16  14  15  15  20  14  12  18  12  20  15.6 ± 2.91  DLP  640  726  560  710  650  900  470  600  920  560  1000  710 ± 177.3  DLP/CTDI  53  45  40  47  43  45  34  50  51  47  50  45.5 ± 5.31  Heartc  CTDIvol  54  —  —  —  50  —  —  —  61  —  90  67.0 ± 20.66  DLP  1149  —  —  —  1000  —  —  —  1208  —  1400  1203 ± 200.1  DLP/CTDI  21.3  —  —  —  20.0  —  —  —  19.8  —  15.6  18.0 ± 2.51  Anatomical region  Dose index  This study  EU  UK  Norway  Switzerland  Germany  Kenya  Ireland  Italy  Finland  Japan  Mean ± SDa  2004 [5]  2005 [6]  2009 [7]  2010 [8]  2010 [9]  2012 [10]  2012 [11]  2014 [12]  2015 [13]  2015 [18]  Headb  CTDIvol  78  60  65  75  65  65  65  66  69  55  85  67.0 ± 8.2  DLP  1292  990  930  1000  1000  950  760  940  1312  800  1350  1003 ± 191.0  DLP/CTDI  16.6  16.5  14.3  13.3  15.4  14.6  11.7  14.2  19.0  14.5  15.9  15.0 ± 1.95  Chestc  CTDIvol  15  12  13  15  10  12  13  9  15  9  15  12.3 ± 2.36  DLP  689  430  580  400  400  400  580  390  569  290  550  459 ± 102.3  DLP/CTDI  45.9  35.8  44.6  26.7  40.0  33.3  44.6  43.3  37.9  32.2  36.7  37.3 ± 5.85  Abdomenc  CTDIvol  12  16  14  15  15  20  14  12  18  12  20  15.6 ± 2.91  DLP  640  726  560  710  650  900  470  600  920  560  1000  710 ± 177.3  DLP/CTDI  53  45  40  47  43  45  34  50  51  47  50  45.5 ± 5.31  Heartc  CTDIvol  54  —  —  —  50  —  —  —  61  —  90  67.0 ± 20.66  DLP  1149  —  —  —  1000  —  —  —  1208  —  1400  1203 ± 200.1  DLP/CTDI  21.3  —  —  —  20.0  —  —  —  19.8  —  15.6  18.0 ± 2.51  aThe values were calculated at DRL which excluded this study. bThe values adjusted to 16-cm PMMA phantom. cThe values adjusted to 32-cm PMMA phantom. Table 6. Comparison of CTDIvol and DLP for pediatric in each anatomical region with other countries. Anatomical region  Age group (years)  Dose index  This study  UK  Germany  Switzerland  France  Thai  Japan  Japan  Mean ± SDa  2005 [6]  2007 [14]  2008 [15]  2009 [16]  2012 [17]  2015 [22]  2015 [18]  Headb  0 to <1  CTDIvol  43  30  33  20  30  25  30  38  29.4 ± 5.71  DLP  739  270  390  270  420  400  404  500  379 ± 82.9  DLP/CTDI  17.2  9.0  11.8  13.5  14.0  16.0  13.5  13.2  12.9 ± 2.16  1 to <6  CTDIvol  56  45  40  30  40  30  40  47  38.9 ± 6.64  DLP  863  470  520  420  600  570  624  660  552 ± 86.3  DLP/CTDI  15.4  10.4  13.0  14.0  15.0  19.0  15.6  14.0  14.2 ± 2.61  6 to <11  CTDIvol  67  50  50  40  50  40  45  60  47.9 ± 6.99  DLP  1249  620  710  560  900  610  734  850  712 ± 127.0  DLP/CTDI  18.6  12.4  14.2  14.0  18.0  15.3  16.3  14.2  14.9 ± 1.82  11 to <15  CTDIvol  71  65  60  60  —  45  53  —  56.6 ± 7.77  DLP  1278  930  920  1000  —  800  869  —  904 ± 74.5  DLP/CTDI  18.0  14.3  15.3  16.7  —  17.8  16.4  —  16.0 ± 1.33  Chestb  0 to <1  CTDIvol  10  12  3.5  5  6  4.5  5  11  6.7 ± 3.36  DLP  123  200  55  110  60  80  104  210  117 ± 63.5  DLP/CTDI  12.3  16.7  15.7  22.0  10.0  17.8  20.8  19.1  17.4 ± 3.96  1 to <6  CTDIvol  13  13  5.5  8  7  5.7  5  14  8.3 ± 3.69  DLP  236  230  110  200  126  140  127  300  176 ± 70.0  DLP/CTDI  18.2  17.7  20.0  25.0  18.0  24.6  25.4  21.4  21.2 ± 3.30  6 to <11  CTDIvol  12  20  8.5  10  11  10  5  15  11.4 ± 4.84  DLP  215  370  210  220  274  305  137  410  275 ± 95.3  DLP/CTDI  17.9  18.5  24.7  22.0  24.9  30.5  27.4  27.3  24.2 ± 3.93  11 to <15  CTDIvol  25  14  14  12  —  15.6  11  —  13.3 ± 1.82  DLP  702  580  205  460  —  470  359  —  415 ± 141.0  DLP/CTDI  28.1  41.4  14.6  38.3  —  30.1  32.6  —  31.4 ± 10.40  Abdomenb  0 to <1  CTDIvol  7  20  5  7  8  7.7  7  11  9.4 ± 5.01  DLP  161  170  145  130  160  220  126  220  167 ± 39.2  DLP/CTDI  23.0  8.5  29.0  18.6  20.0  28.6  18.0  20.0  17.8 ± 6.97  1 to <6  CTDIvol  8  25  8  9  9  9  7  16  11.9 ± 6.49  DLP  184  250  255  300  242  275  209  400  276 ± 61.5  DLP/CTDI  23.0  10.0  31.9  33.3  26.9  30.6  29.9  25.0  23.3 ± 7.93  6 to <11  CTDIvol  12  30  13  13  14  14  7  17  15.4 ± 7.09  DLP  242  500  475  380  490  560  346  530  469 ± 78.0  DLP/CTDI  20.2  16.7  36.5  29.2  35.0  40.0  49.4  31.2  30.4 ± 10.1  11 to <15  CTDIvol  22  14  20  16  —  17  13  —  16.0 ± 2.74  DLP  622  560  1000  500  —  765  549  —  675 ± 208.2  DLP/CTDI  28.3  40.0  50.0  31.3  —  45.0  42.2  —  42.2 ± 6.93  Anatomical region  Age group (years)  Dose index  This study  UK  Germany  Switzerland  France  Thai  Japan  Japan  Mean ± SDa  2005 [6]  2007 [14]  2008 [15]  2009 [16]  2012 [17]  2015 [22]  2015 [18]  Headb  0 to <1  CTDIvol  43  30  33  20  30  25  30  38  29.4 ± 5.71  DLP  739  270  390  270  420  400  404  500  379 ± 82.9  DLP/CTDI  17.2  9.0  11.8  13.5  14.0  16.0  13.5  13.2  12.9 ± 2.16  1 to <6  CTDIvol  56  45  40  30  40  30  40  47  38.9 ± 6.64  DLP  863  470  520  420  600  570  624  660  552 ± 86.3  DLP/CTDI  15.4  10.4  13.0  14.0  15.0  19.0  15.6  14.0  14.2 ± 2.61  6 to <11  CTDIvol  67  50  50  40  50  40  45  60  47.9 ± 6.99  DLP  1249  620  710  560  900  610  734  850  712 ± 127.0  DLP/CTDI  18.6  12.4  14.2  14.0  18.0  15.3  16.3  14.2  14.9 ± 1.82  11 to <15  CTDIvol  71  65  60  60  —  45  53  —  56.6 ± 7.77  DLP  1278  930  920  1000  —  800  869  —  904 ± 74.5  DLP/CTDI  18.0  14.3  15.3  16.7  —  17.8  16.4  —  16.0 ± 1.33  Chestb  0 to <1  CTDIvol  10  12  3.5  5  6  4.5  5  11  6.7 ± 3.36  DLP  123  200  55  110  60  80  104  210  117 ± 63.5  DLP/CTDI  12.3  16.7  15.7  22.0  10.0  17.8  20.8  19.1  17.4 ± 3.96  1 to <6  CTDIvol  13  13  5.5  8  7  5.7  5  14  8.3 ± 3.69  DLP  236  230  110  200  126  140  127  300  176 ± 70.0  DLP/CTDI  18.2  17.7  20.0  25.0  18.0  24.6  25.4  21.4  21.2 ± 3.30  6 to <11  CTDIvol  12  20  8.5  10  11  10  5  15  11.4 ± 4.84  DLP  215  370  210  220  274  305  137  410  275 ± 95.3  DLP/CTDI  17.9  18.5  24.7  22.0  24.9  30.5  27.4  27.3  24.2 ± 3.93  11 to <15  CTDIvol  25  14  14  12  —  15.6  11  —  13.3 ± 1.82  DLP  702  580  205  460  —  470  359  —  415 ± 141.0  DLP/CTDI  28.1  41.4  14.6  38.3  —  30.1  32.6  —  31.4 ± 10.40  Abdomenb  0 to <1  CTDIvol  7  20  5  7  8  7.7  7  11  9.4 ± 5.01  DLP  161  170  145  130  160  220  126  220  167 ± 39.2  DLP/CTDI  23.0  8.5  29.0  18.6  20.0  28.6  18.0  20.0  17.8 ± 6.97  1 to <6  CTDIvol  8  25  8  9  9  9  7  16  11.9 ± 6.49  DLP  184  250  255  300  242  275  209  400  276 ± 61.5  DLP/CTDI  23.0  10.0  31.9  33.3  26.9  30.6  29.9  25.0  23.3 ± 7.93  6 to <11  CTDIvol  12  30  13  13  14  14  7  17  15.4 ± 7.09  DLP  242  500  475  380  490  560  346  530  469 ± 78.0  DLP/CTDI  20.2  16.7  36.5  29.2  35.0  40.0  49.4  31.2  30.4 ± 10.1  11 to <15  CTDIvol  22  14  20  16  —  17  13  —  16.0 ± 2.74  DLP  622  560  1000  500  —  765  549  —  675 ± 208.2  DLP/CTDI  28.3  40.0  50.0  31.3  —  45.0  42.2  —  42.2 ± 6.93  aThe values were calculated at DRL which excluded this study. bThe values adjusted to 16-cm PMMA phantom. Table 6. Comparison of CTDIvol and DLP for pediatric in each anatomical region with other countries. Anatomical region  Age group (years)  Dose index  This study  UK  Germany  Switzerland  France  Thai  Japan  Japan  Mean ± SDa  2005 [6]  2007 [14]  2008 [15]  2009 [16]  2012 [17]  2015 [22]  2015 [18]  Headb  0 to <1  CTDIvol  43  30  33  20  30  25  30  38  29.4 ± 5.71  DLP  739  270  390  270  420  400  404  500  379 ± 82.9  DLP/CTDI  17.2  9.0  11.8  13.5  14.0  16.0  13.5  13.2  12.9 ± 2.16  1 to <6  CTDIvol  56  45  40  30  40  30  40  47  38.9 ± 6.64  DLP  863  470  520  420  600  570  624  660  552 ± 86.3  DLP/CTDI  15.4  10.4  13.0  14.0  15.0  19.0  15.6  14.0  14.2 ± 2.61  6 to <11  CTDIvol  67  50  50  40  50  40  45  60  47.9 ± 6.99  DLP  1249  620  710  560  900  610  734  850  712 ± 127.0  DLP/CTDI  18.6  12.4  14.2  14.0  18.0  15.3  16.3  14.2  14.9 ± 1.82  11 to <15  CTDIvol  71  65  60  60  —  45  53  —  56.6 ± 7.77  DLP  1278  930  920  1000  —  800  869  —  904 ± 74.5  DLP/CTDI  18.0  14.3  15.3  16.7  —  17.8  16.4  —  16.0 ± 1.33  Chestb  0 to <1  CTDIvol  10  12  3.5  5  6  4.5  5  11  6.7 ± 3.36  DLP  123  200  55  110  60  80  104  210  117 ± 63.5  DLP/CTDI  12.3  16.7  15.7  22.0  10.0  17.8  20.8  19.1  17.4 ± 3.96  1 to <6  CTDIvol  13  13  5.5  8  7  5.7  5  14  8.3 ± 3.69  DLP  236  230  110  200  126  140  127  300  176 ± 70.0  DLP/CTDI  18.2  17.7  20.0  25.0  18.0  24.6  25.4  21.4  21.2 ± 3.30  6 to <11  CTDIvol  12  20  8.5  10  11  10  5  15  11.4 ± 4.84  DLP  215  370  210  220  274  305  137  410  275 ± 95.3  DLP/CTDI  17.9  18.5  24.7  22.0  24.9  30.5  27.4  27.3  24.2 ± 3.93  11 to <15  CTDIvol  25  14  14  12  —  15.6  11  —  13.3 ± 1.82  DLP  702  580  205  460  —  470  359  —  415 ± 141.0  DLP/CTDI  28.1  41.4  14.6  38.3  —  30.1  32.6  —  31.4 ± 10.40  Abdomenb  0 to <1  CTDIvol  7  20  5  7  8  7.7  7  11  9.4 ± 5.01  DLP  161  170  145  130  160  220  126  220  167 ± 39.2  DLP/CTDI  23.0  8.5  29.0  18.6  20.0  28.6  18.0  20.0  17.8 ± 6.97  1 to <6  CTDIvol  8  25  8  9  9  9  7  16  11.9 ± 6.49  DLP  184  250  255  300  242  275  209  400  276 ± 61.5  DLP/CTDI  23.0  10.0  31.9  33.3  26.9  30.6  29.9  25.0  23.3 ± 7.93  6 to <11  CTDIvol  12  30  13  13  14  14  7  17  15.4 ± 7.09  DLP  242  500  475  380  490  560  346  530  469 ± 78.0  DLP/CTDI  20.2  16.7  36.5  29.2  35.0  40.0  49.4  31.2  30.4 ± 10.1  11 to <15  CTDIvol  22  14  20  16  —  17  13  —  16.0 ± 2.74  DLP  622  560  1000  500  —  765  549  —  675 ± 208.2  DLP/CTDI  28.3  40.0  50.0  31.3  —  45.0  42.2  —  42.2 ± 6.93  Anatomical region  Age group (years)  Dose index  This study  UK  Germany  Switzerland  France  Thai  Japan  Japan  Mean ± SDa  2005 [6]  2007 [14]  2008 [15]  2009 [16]  2012 [17]  2015 [22]  2015 [18]  Headb  0 to <1  CTDIvol  43  30  33  20  30  25  30  38  29.4 ± 5.71  DLP  739  270  390  270  420  400  404  500  379 ± 82.9  DLP/CTDI  17.2  9.0  11.8  13.5  14.0  16.0  13.5  13.2  12.9 ± 2.16  1 to <6  CTDIvol  56  45  40  30  40  30  40  47  38.9 ± 6.64  DLP  863  470  520  420  600  570  624  660  552 ± 86.3  DLP/CTDI  15.4  10.4  13.0  14.0  15.0  19.0  15.6  14.0  14.2 ± 2.61  6 to <11  CTDIvol  67  50  50  40  50  40  45  60  47.9 ± 6.99  DLP  1249  620  710  560  900  610  734  850  712 ± 127.0  DLP/CTDI  18.6  12.4  14.2  14.0  18.0  15.3  16.3  14.2  14.9 ± 1.82  11 to <15  CTDIvol  71  65  60  60  —  45  53  —  56.6 ± 7.77  DLP  1278  930  920  1000  —  800  869  —  904 ± 74.5  DLP/CTDI  18.0  14.3  15.3  16.7  —  17.8  16.4  —  16.0 ± 1.33  Chestb  0 to <1  CTDIvol  10  12  3.5  5  6  4.5  5  11  6.7 ± 3.36  DLP  123  200  55  110  60  80  104  210  117 ± 63.5  DLP/CTDI  12.3  16.7  15.7  22.0  10.0  17.8  20.8  19.1  17.4 ± 3.96  1 to <6  CTDIvol  13  13  5.5  8  7  5.7  5  14  8.3 ± 3.69  DLP  236  230  110  200  126  140  127  300  176 ± 70.0  DLP/CTDI  18.2  17.7  20.0  25.0  18.0  24.6  25.4  21.4  21.2 ± 3.30  6 to <11  CTDIvol  12  20  8.5  10  11  10  5  15  11.4 ± 4.84  DLP  215  370  210  220  274  305  137  410  275 ± 95.3  DLP/CTDI  17.9  18.5  24.7  22.0  24.9  30.5  27.4  27.3  24.2 ± 3.93  11 to <15  CTDIvol  25  14  14  12  —  15.6  11  —  13.3 ± 1.82  DLP  702  580  205  460  —  470  359  —  415 ± 141.0  DLP/CTDI  28.1  41.4  14.6  38.3  —  30.1  32.6  —  31.4 ± 10.40  Abdomenb  0 to <1  CTDIvol  7  20  5  7  8  7.7  7  11  9.4 ± 5.01  DLP  161  170  145  130  160  220  126  220  167 ± 39.2  DLP/CTDI  23.0  8.5  29.0  18.6  20.0  28.6  18.0  20.0  17.8 ± 6.97  1 to <6  CTDIvol  8  25  8  9  9  9  7  16  11.9 ± 6.49  DLP  184  250  255  300  242  275  209  400  276 ± 61.5  DLP/CTDI  23.0  10.0  31.9  33.3  26.9  30.6  29.9  25.0  23.3 ± 7.93  6 to <11  CTDIvol  12  30  13  13  14  14  7  17  15.4 ± 7.09  DLP  242  500  475  380  490  560  346  530  469 ± 78.0  DLP/CTDI  20.2  16.7  36.5  29.2  35.0  40.0  49.4  31.2  30.4 ± 10.1  11 to <15  CTDIvol  22  14  20  16  —  17  13  —  16.0 ± 2.74  DLP  622  560  1000  500  —  765  549  —  675 ± 208.2  DLP/CTDI  28.3  40.0  50.0  31.3  —  45.0  42.2  —  42.2 ± 6.93  aThe values were calculated at DRL which excluded this study. bThe values adjusted to 16-cm PMMA phantom. DISCUSSION In this study, we introduced a series of systems that automatically collect RDSR or dose sheet output from CT, and summarized scan parameters and scan dose. The output formats of RDSR are unified, making it possible to collect information on recorded dose indices and imaging conditions(30). However, the equipment compatible with the output of RDSR is limited to the latest models. The IEC issued the 2012 Dose SR Standard for CT apparatus in IEC 60601-2-44, recommending collection of dose data from CT scans(28). In addition, it has been reported that the accuracy of reading text is 95% because information is collected only by the method of image capture of dose sheets, and each manufacturer has various display formats(31). For more detailed scan parameters, it is a disadvantage that it cannot be captured only from the dose sheet. In Table 2, the targets from the RDSR collection were 20 regions, but in reality, each center was conducting daily inspections using a more specific detailed protocol, e.g. in the case of multiphase scanning of the abdomen (T-D4000, SRT). Furthermore, because RDSR and dose sheet cannot directly obtain information on body type such as body weight and height of patients, and the AEC automatically adjusts for habitus, various ages and body types, are considered to be the cause of differences between centers. Although it has also been reported that the patients undergoing abdominal CT with body mass index (BMI) < 30 that the CTDIvol and DLP of patients who exceeded NDRL was under 0.5% and under 0.8%, respectively(20). DRL is based on standard patients in each country, making it desirable to collect body type information, such as the height and weight. From Table 3, it is conceivable that the CTDIvol of the adult chest–abdominal CT is higher than that of the abdomen–pelvis CT, because some CT scanners include devices that calculate the CTDI value from the maximum, and not the mean, tube current. In addition, CT angiography was included in the chest and abdomen studies, and there is a difference in the dose index due to angiography’s lower pitch setting. From Table 5, in comparison with the DRL of each Japanese study, the CTDIvol and DLP of the head and chest were both higher than those of the other countries, and the values in the abdomen and heart were all lower than the mean values of each country. In automatic collection of data, there are possibilities that local protocols unique to various centers may be included, and that is considered one aspect which cannot be compared with the NDRL of each country. From Table 6, in pediatric DRL, head and chest CT showed higher results than in the other countries. This may be due to the scan range in head CT being set wider in Japan than in other countries by up to ~4 cm, in order to maintain the head within the field of view. As children are more radiosensitive than adults, we should actively adopt methods that can calculate tube current for each age recommended by the Image Gently Program of the American Society of Pediatric Radiology (SPR)(32). The National Radiology Data Registry (NRDR) of the American College of Radiology (ACR) has been collecting large-scale RDSRs throughout North America as a Dose Index Registration (DIR) since 2011(33). The collected dose information is divided into detailed scan regions by a Radlex playbook ID (RPID) code, transmitted anonymously to ACR, and the results of comparative evaluation with the whole are fed back to each center. The size-specific dose estimates (SSDE) taking into consideration the body shape is beginning to be introduced in addition to CTDI and DLP in the dose index, we think that dose optimization is possible in the future(34). Even in Japan, the JJ 1017 code, which codes modality and scan region, is under development. This should lead to higher precision(35). We plan to continue to collect dosage data and to periodically compare, discover and investigate specific causes, and review protocols with the goal of dose optimization. Currently, we are sharing data with a limited collection of equipment. Constructing a cloud-based collection will allow sampling from more centers in the future. We hope this will eliminate disparities among centers and facilitate the optimization of dosimetry. REFERENCES 1 Brenner, D. J. and Hall, E. J. Computed tomography—an increasing source of radiation exposure. N. Engl. J. Med.  357( 22), 2277– 2284 ( 2007) 10.1056/NEJMra072149. Google Scholar CrossRef Search ADS PubMed  2 Harding, K., and Thomson, W. H.. International Commission on Radiological Protection. Radiological Protection and Safety in Medicine ICRP Publication 73. Ann. ICRP  26( 2) ( 1996). 3 International Commission on Radiological Protection. The 2007 Recommendations of the ICRP. ICRP Publication 103. Ann. ICRP  37( 2–4), 1– 332 ( 2007) 10.1016/j.icrp.2007.10.003. 4 International Commission on Radiological Protection. Managing patient dose in computed tomography. Ann. ICRP  30( 4), 7– 45 ( 2000). CrossRef Search ADS   5 Jessen, K. et al.  . European Guidelines on Quality Criteria for Computed Tomography, EUR 16262EN. Official Publication of the European Communities 2000. Available on http://www.drs.dk/guidelines/ct/quality/htmlindex.htm. Accessed on 22 August 2016. 6 Shrimpton, P. C., Hiller, M. C., Lewis, M. A. and Dunn, M. National survey of doses from CT in the UK: 2003. Br. J. Radiol.  79( 948), 968– 980 ( 2006) 10.1259/bjr/93277434. Google Scholar CrossRef Search ADS PubMed  7 Friberg, E. G., Widmark, A. and Ryste Hauge, I. H. National Collection of Local Diagnostic Reference Levels in Norway and Their Role in Optimization of X-Ray Examinations  ( Østerås, Norway: Norwegian Radiation Protection Authority) ( 2009). 8 Treier, R., Aroua, A., Verdun, F. R., Samara, E., Stuessi, A. and Trueb, P. R. Patient doses in CT examinations in Switzerland: implementation of national diagnostic reference levels. Radiat. Prot. Dosim.  142( 2–4), 244– 254 ( 2010) 10.1093/rpd/ncq279. Google Scholar CrossRef Search ADS   9 German Federal Office for Radiation Protection. Publication of Updated Diagnostic Reference Levels for Diagnostic and Interventional X-ray Examinations ( 2010). Available on http://www.bfs.de/DE/themen/ion/anwendungmedizin/diagnostik/referenzwerte/referenzwerte.html [in German]. Accessed on 11 November 2015. 10 Korir, G. K., Wambani, J. S. and Korir, I. K. Patient doses using multidetector computed tomography scanners in Kenya. Radiat. Prot. Dosim.  151( 2), 267– 271 ( 2012) 10.1093/rpd/ncr484. Google Scholar CrossRef Search ADS   11 Foley, S. J., McEntee, M. F. and Rainford, L. A. Establishment of CT diagnostic reference levels in Ireland. Br. J. Radiol.  85( 1018), 1390– 1397 ( 2012) 10.1259/bjr/15839549. Google Scholar CrossRef Search ADS PubMed  12 Palorini, F., Origgi, D. and Granata, C. Adult exposures from MDCT including multiphase studies: first Italian nationwide survey. Eur. Radiol.  24( 2), 469– 483 ( 2014) 10.1007/s00330-013-3031-7. Google Scholar CrossRef Search ADS PubMed  13 Lajunen, A. Indication-based diagnostic reference levels for adult CT-examinations in Finland. Radiat. Prot. Dosim.  165( 1–4), 95– 97 ( 2015) 10.1093/rpd/ncv087. Google Scholar CrossRef Search ADS   14 Glanski, M., Nagel, H. D. and Stamm, G. Paediatric CT exposure practice in the Federal Republic of Germany: results of a nationwide survey in 2005–2006. Rofo  179( 11), 1110– 1111 ( 2007). Google Scholar CrossRef Search ADS PubMed  15 Verdun, F. R., Guiterrez, D., Vader, J., Aroua, A., Alamo-Maestre, L. T., Bochud, F. and Gudinchet, F. CT radiation dose in children: a survey to establish age-based diagnostic reference levels in Switzerland. Eur. Radiol.  18( 9), 1980– 1986 ( 2008) 10.1007/s00330-008-0963-4. Google Scholar CrossRef Search ADS PubMed  16 Roch, P. and Aubert, B. French diagnostic reference levels in diagnostic radiology, computed tomography and nuclear medicine: 2004–2008 review. Radiat. Prot. Dosim.  154( 1), 52– 75 ( 2012) 10.1093/rpd/ncs152. Google Scholar CrossRef Search ADS   17 Kritsaneepaiboon, S., Trinavarat, P. and Visrutaratna, P. Survey of pediatric MDCT radiation dose from university hospitals in Thailand: a preliminary for national dose survey. Acta Radiol.  53( 7), 820– 826 ( 2012) 10.1258/ar.2012.110641. Google Scholar CrossRef Search ADS PubMed  18 J-RIME 2015. Diagnostic Reference Levels Based on Latest Surveys in Japan, -JapanDRLs2015-. Available on http://www.radher.jp/J-RIME/report/DRLhoukokusyoEng.pdf. Accessed on 11 October 2016. 19 International Commission on Radiological Protection. ICRP Publication 105. Radiation protection in medicine. Ann. ICRP  37( 6), 1– 63 ( 2007) 10.1016/j.icrp.2008.08.001. CrossRef Search ADS   20 Boos, J., Lanzman, R. S., Meineke, A., Heusch, P., Sawicki, L. M., Antoch, G. and Kröpil, P. Dose monitoring using the DICOM structured report: assessment of the relationship between cumulative radiation exposure and BMI in abdominal CT. Clin. Radiol.  70( 2), 176– 182 ( 2015) 10.1016/j.crad.2014.11.002. Google Scholar CrossRef Search ADS PubMed  21 Vano, E. and Fernandez Soto, J. Patient dose management in digital radiography. Biomed. Imaging Interv. J.  3( 2), e26 ( 2007) 10.2349/biij.3.2.e26. Google Scholar CrossRef Search ADS PubMed  22 Nakada, Y., Fujiwara, M. and Yakami, M. Optimised paediatric CT dose at a tertiary children’s hospital in Japan: a 4-y single-centre analysis. Radiat. Prot. Dosim.  168( 1), 61– 71 ( 2016) 10.1093/rpd/ncv004. Google Scholar CrossRef Search ADS   23 Cook, T. S., Zimmerman, S. L., Steingall, S. R., Maidment, A. D., Kim, W. and Boonn, W. W. RADIANCE: An automated, enterprise-wide solution for archiving and reporting CT radiation dose estimates. Radiographics  31( 7), 1833– 1846 ( 2011) 10.1148/rg.317115048. Google Scholar CrossRef Search ADS PubMed  24 Noumeir, R. Benefits of the DICOM modality performed procedure step. J. Digit. Imaging  18( 4), 260– 269 ( 2005) 10.1007/s10278-005-6702-3. Google Scholar CrossRef Search ADS PubMed  25 Dave, J. K. and Gingold, E. L. Extraction of CT dose information from DICOM metadata: automated Matlab-based approach. AJR Am. J. Roentgenol.  200( 1), 142– 145 ( 2013) 10.2214/AJR.12.8501. Google Scholar CrossRef Search ADS PubMed  26 DICOM diagnostic x-ray radiation dose reporting (Dose SR). 27 DICOM part 16 content mapping resource. 28 International Electrotechnical Commission. Medical electrical equipment, Part 2-44: Particular requirements for the safety of X-ray equipment for computed tomography. Geneva: IEC; ( 2012). IEC 60601-2-44. 29 Data book of medical devices & systems, Iryokiki sytem hakusho 2016, MEshinkoukyokai 2015. 30 DICOM Standards Committee, Working Group 6, Base Standard. Supplement 94: radiation dose report, NEMA 2004. Available on http://dicom.nema.org/dicom/geninfo/strategy.pdf#search=%2728.+DICOM+Standards+Committee%2C+Working+Group+6%2C+Base+Standard.+Supplement+150%27. Accessed on 21 March 2017. 31 Li, X., Zhang, D. and Liu, B. Automated extraction of radiation dose information from CT dose report images. AJR Am. J. Roentgenol.  196( 6), W781– W783 ( 2011) 10.2214/AJR.10.5718. Google Scholar CrossRef Search ADS PubMed  32 Image Gently Homepage Radiology Safety. Protocol for Image Gently. Available on http://www.imagegently.org/Procedures/Computed-Tomography#2018473-technologists. Accessed on 10 March 2016. 33 American College of Radiology (ACR). About Dose Index Registry (DIR). Available on http://www.acr.org/Quality-Safety/National-Radiology-Data-Registry/Dose-Index-Registry/About-DIR. Accessed on 8 February 2014. 34 Moore, B. M., Brady, S. L., Mirro, A. E. and Kaufman, R. A. Size-specific dose estimate (SSDE) provides a simple method to calculate organ dose for pediatric CT examinations. Med. Phys.  41( 7), 071917 ( 2014). Google Scholar CrossRef Search ADS PubMed  35 Medical Information Special Interest Section. JJ1017 ver3.3 ( 2016). Japanese Society of Radiological Technology (JSRT). Available on http://www.jsrt.or.jp/97mi/content/jj1017.html. Accessed on 22 January 2017. © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Journal

Radiation Protection DosimetryOxford University Press

Published: Feb 7, 2018

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off