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Estimation of Radiation Risk and Establishment of Diagnostic Reference Levels for Patients Undergoing Computed Tomography Chest–Abdomen–Pelvic Examinations in Sudan

Estimation of Radiation Risk and Establishment of Diagnostic Reference Levels for Patients... Abstract Establishment of diagnostic reference levels (DRLs) is an essential radiation optimization tool used to indicate optimum practice and radiation protection. This study aimed to report the current computed tomography (CT) of the chest–abdomen–pelvis radiation practice in Sudan as a part of the DRL establishment effort and dose optimization. CT radiation doses were collected from 530 patients of age ranging between 28 and 85 y and body weight ranging between 65 and 120 kg. DRLs were calculated based on the 75th percentile of dose length product (DLP) and CT dose index volume (CTDIvol). Effective and organ doses were calculated using the National Cancer Institute dosimetry system for the CT programme. The proposed DRLs are CTDIvol, 6 mGy, and DLP, 970 mGy.cm, and an effective dose of 9.9 mSv. Organ dose estimation showed that the thyroid received the highest dose during the scan. INTRODUCTION Computed tomography (CT) is reported as the main source of radiation in diagnostic medical imaging, which contributes up to 60% of the total collective dose(1). Multi-slice CT expansion made diagnostic fast, accurate and valued in routine and emergency patients. However, the availability and widespread use of CT examinations results in a potential increase in unnecessary radiation exposure(2). Implementation of ‘as low as reasonably achievable’ (ALARA) and optimization of CT radiation dose should be encouraged to reduce the potential of stochastic and deterministic effects(3). CT dose optimization and dose-reduction strategies are continuous efforts by radiology workers, including radiologists, radiographers and referring physicians. The goal of dose optimization is to reduce the radiation dose while obtaining a high diagnostic image quality. Estimation of radiation dose for specific imaging modality and protocol as a part of diagnostic reference levels (DRLs) establishment is considered to be the first step of optimization. The International Commission on Radiological Protection (ICRP) has described DRL establishment as a method for identifying the increment of radiation dose(4, 5). DRLs are used to improve radiation protection knowledge and awareness among radiologists and referring physicians and are used to encourage radiation dose reduction. The optimization of patient protection in CT procedures requires tailoring protocol according to the patient characteristics, age or size, and it is of interest and clinical indication to achieve the ALARA principles(6). Protocol and dose standardization without compromising image quality promotes radiation protection and improves health care. As part of this effort, the Sudan Atomic Agency, in collaboration with other health organizations and academic institutes, is working closely to establish DRLs for various imaging and procedures. Several surveys were carried out in Sudan regarding the establishment of DRLs. The aim of was to improve radiation protection awareness and dose optimization and to establish standard practice(7–9). This study aimed to report the current CT chest–abdomen–pelvis (CAP) radiation practice in Sudan as a part of the DRL establishment effort and dose optimization. We believe that the number of CT CAP examinations has increased and that request justification and radiation dose optimization are necessary as a result. METHOD This study evaluated the radiation dose for non-contrast CT CAP protocols. The data were collected from three scanners over a period of 3 months in 2020. The survey collected data from CT CAP procedures for patients sized ranging between 65 and 120 kg. The data collection form included instructions and guidelines to ensure that the data collected were representative of standard examinations and patients. CT machines The examination was performed using a single CT instrument manufactured by Toshiba Aquilion Prime CT scanner 160 slice (TSX-303A) (Toshiba Medical Systems, Otawara, Japan) installed in 2016. The machine had a 0.78-m gantry bore, an X-ray couch loading capacity of 300 kg, 50 frames/s reconstruction speed, provided for by 80 rows of detectors of 0.5 mm spacing to give 160 slices per rotation and 50 cm field of view. The machine had the capability for low dose reduction through adaptive iterative dose reduction using an iterative reconstruction algorithm. A quality control measurement of the CT machine was performed regularly to ensure consistency of the radiation output, exposure and protocol parameters. Radiation dosimetry The patient’s radiation dose was determined using DLP (mGy.cm) and CTDIvol (mGy) for the scan and the required dose per sequence, respectively. Estimation of effective and organ dose was conducted using the National Cancer Institute dosimetry system for CT (NCICT). The software was used to estimate organ, effective and size-specific dose estimate (SSDE) doses. The programme is based on a comprehensive library of computational human phantoms combined with Monte Carlo radiation simulation of reference CT scanners(10). Table 1 CTDIvol per sequence and total DLP per examination. CT Protocol . Median values of CTDIvol per sequence . Median values of DLP per sequence . . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . CAP 3–7.9 5.4 (0.9) 4.5 5.4 6 661.3–999.8 952.1 (39.7) 947.5 958.5 970 CT Protocol . Median values of CTDIvol per sequence . Median values of DLP per sequence . . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . CAP 3–7.9 5.4 (0.9) 4.5 5.4 6 661.3–999.8 952.1 (39.7) 947.5 958.5 970 SD = Standard Deviation Min = Minmum Max = Maximum Open in new tab Table 1 CTDIvol per sequence and total DLP per examination. CT Protocol . Median values of CTDIvol per sequence . Median values of DLP per sequence . . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . CAP 3–7.9 5.4 (0.9) 4.5 5.4 6 661.3–999.8 952.1 (39.7) 947.5 958.5 970 CT Protocol . Median values of CTDIvol per sequence . Median values of DLP per sequence . . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . CAP 3–7.9 5.4 (0.9) 4.5 5.4 6 661.3–999.8 952.1 (39.7) 947.5 958.5 970 SD = Standard Deviation Min = Minmum Max = Maximum Open in new tab CT CAP examination protocols The scan ranges from the lung apices to the lesser trochanter, with the patients lie supine, arms above their heads and feet down. Scout images in anteroposterior and lateral projection were obtained to determine the area of interest and ensure the accurate patient position. The kVp were fixed at 120, and auto mAs were used for quality reference according to patient size and scan protocol. The patients were instructed to hold their breath during the scan to ensure elimination of motion artefacts. DRL calculation Microsoft Excel was used to organize data, including patient gender, weight, kVp, mAs, CTDIvol, DLP and effective dose. Descriptive data analysis was conducted, including minimum, maximum and standard deviation, first quartile (25th percentile), second quartile (median, 50th percentile) and third quartile (75th percentile). For the typical dose value, the mode was calculated, and the achievable dose was proposed based on the median value. To establish the DRLs, the third quartile was rounded and compared with available national, regional and international data(11, 12). RESULTS Data were collected from 530 patients during the study period; 267 were males and 263 were females. The patient age ranged between 28 and 85 y with a mean of 55.9 y and standard deviation of 11.6. The patients’ body parameters were: weight ranging between 65 and 120 kg and BMI of 19.6–30.2 kg/m2. The weight and BMI variation were compared with the radiation dose using Pearson’s correlation coefficient and were found to be insignificant with p-value < 0.01. The scan protocol parameters were as follows: tube voltage (kVp) used was fixed at 120, tube current time (mAs) ranged between 140 and 210, pitch was 0.8–1, rotation time was 0.5–0.75 and the scan length was 64–73 cm. CTDIvol and DLP were used to establish the DRLs. The calculation was based on the values per exam, including range, mean, median and first and third quartile values. For the typical practice, the median values were suggested as the local DRL (Table 1). Effective and organ doses were calculated using the NCICT programme. The results are based on the scanner manufacturer, model and input scan protocol. The mean results showed CTDIvol of 5.7 mGy, DLP of 684.8 mGy-cm and effective dose of 9.9 mSv. The mean of SSDE was 11.2 mGy used to estimate radiation dose that takes a patient’s size into account(13). Figure 1 shows that the organ dose values ranged from 0.15 ± 0.1 to 17.8 ± 2.1 mSv. The lowest dose was noted at the lens with a value of 0.1 mSv, whereas the highest value of 17.8 mSv was found in the thyroid. This dose is lower than the suggested dose to induce stochastic effects and should be considered(14, 15). Figure 1 Open in new tabDownload slide graph shows organ dose (mGy) for patients underwent CT CAP examination. Figure 1 Open in new tabDownload slide graph shows organ dose (mGy) for patients underwent CT CAP examination. DISCUSSION The utilization of DRLs as a tool for identification of practice errors and as alerts for the radiology department to observe radiation doses was examined. When the radiation dose exceeds the DRLs, it is important to run the necessary investigation to identify the error and take corrective actions. This study is considered to be the first study in Sudan to describe radiation dose during CT CAP procedures as a part of an emergency protocol. The study was able to achieve the main objective, which is to propose DRLs for CT CAP practice in Sudan. The CT CAP without contrast media examination in this study focused on trauma and emergency patients who arrived with multiple body injuries. Figure 2 shows the DLP results in comparison with similar studies in other countries. The CAP-DLP was lower than most of the previously reported doses except for values reported in Australia in 2014(16–21). The reason for this lower dose compared to those of other countries could be due to the relatively new CT CAP practice in Sudan, the high awareness and education of the radiographers, as well as the designed protocol used with the mA modulation. The radiographers’ understanding of the factors affecting the radiation dose in CT has a great impact on dose optimization. Figure 2 Open in new tabDownload slide comparison of DLP values in this study and similar studies in other countries. Figure 2 Open in new tabDownload slide comparison of DLP values in this study and similar studies in other countries. The proposed DRLs based on the 75th percentile in this study were estimated as CTDIvol (6 mGy) and DLP (970 mGy-cm) when compared with those of two large studies in the USA with similar parameters, which obtained relatively low CTDIvol of 16 and 19 mGy and DLP of 1263 and 1193 mGY-cm(19, 20). The organ dose and radiation risk were estimated from radiation exposure using the NCICT computational method. As shown in Figure 1, the organ dose ranged between 0.15 and 17.81 mSv. The abdominal organ and the thyroid obviously received the highest organ doses, which is due to their location and thickness. The average effective dose from the CT CAP examination was 11.76 ± 9 mSv. This average dose can result in radiation cancer risk between 1 in 2000, although the maximum risk is 1 per 200 cancer risk per procedure(14). Although some studies reported that a 7.5 mSv can produce potential damage to the DNA, it is important not to underestimate the radiation dose(22). Focusing on the production of good image quality should consider radiation dose optimization. In practice, image quality and radiation dose should be balanced; radiation should produce the highest diagnostic image quality while staying below permissible limits. Therefore, dose monitoring is a critical component of dose optimization. The ICRP introduced the DRL concept as a tool for dosage optimization. The findings demonstrated the significance of dose optimization utilizing DRLs. LIMITATIONS Further study to include other states in the country will improve the dose variation and established national DRL values. CONCLUSION CT CAP examinations have become an acceptable method for diagnostics of patients who arrive at the emergency department with multiple traumas. However, the potential radiation risk resulting from the high radiation dose during the scan should be taken into consideration. This study showed the importance of protocol standardization and radiation dose optimization using DRLs at a national level. The use of organ and effective doses is necessary to estimate cancer risk and to increase radiation awareness among radiology and referral professionals. Patient protection is a continuous and shared effort and using a thyroid shield as a protection tool during CT CAP is essential. Radiographers’ knowledge, awareness and practice should be improved and monitored to ensure the production of high image quality while protecting the patient. Improving operators’ awareness and the proper use of dose-reduction methodologies will decrease unnecessary radiation exposure. AUTHORS’ CONTRIBUTIONS All authors participated in the project development, data collection and manuscript writing. All authors read and approved the final manuscript. ACKNOWLEDGEMENTS This research was funded by the Deanship of Scientific Research at Princess Nourah bint Abdulrahman University through the Fast-track Research Funding Program. CONFLICT OF INTEREST The authors declare no conflict of interest. References 1. Martin , C. J. and Vano , E. Diagnostic reference levels and optimisation in radiology: Where do we go from here? J. Radiol. Prot. 38 ( 1 ), E1 – E4 ( 2018 ). Google Scholar Crossref Search ADS PubMed WorldCat 2. Lin , C. J. , Mok , G. S. P., Tsai , M. F., Tsai , W. T., Yang , B. H., Tu , C. Y. National survey of radiation dose and image quality in adult CT head scans in Taiwan . PLoS One 10 ( 6 ), 1 – 12 ( 2015 ). Google Scholar OpenURL Placeholder Text WorldCat 3. Abuzaid , M. M. , Elshami , W. and Steelman , C. Measurements of radiation exposure of radiography students during their clinical training using thermoluminescent dosimetry . Radiat. Prot. Dosimetry 179 ( 3 ), 1 – 4 ( 2018 ). Google Scholar Crossref Search ADS PubMed WorldCat 4. Vano , E. et al. Diagnostic reference levels in medical imaging . Ann. ICRP 44 , 1–131 (ICRP) ( 2015 ). Google Scholar OpenURL Placeholder Text WorldCat 5. ICRP . The 2007 Recommendations of the International Commission on Radiological Protection . Vol. 37 . ICRP, 2007. ICRP Publication 103. (Ottawa, Ontario, Canada: ICRP) (2007). Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 6. Leithner , R. and Homolka , P. A quantitative comparison of data evaluation methods to derive diagnostic reference levels for CT from a dosimetric survey: correlation analysis compared to simple evaluation strategies . Phys. Med. 29 ( 5 ), 470 – 477 ( 2013 ). Google Scholar Crossref Search ADS PubMed WorldCat 7. Elmahdi , A. , Abuzaid , M. M., Babikir , E. and Sulieman , A. Radiation dose associated with multi-detector 64-slice computed tomography brain examinations in Khartoum state . Sudan. Polish J Radiol. 82 , 603 – 606 ( 2017 ). Google Scholar Crossref Search ADS WorldCat 8. Suliman , I. I. , Khamis , H. M., Ombada , T. H., Alzimami , K., Alkhorayef , M. and Sulieman , A. Radiation exposure during paediatric CT in Sudan: CT dose, organ and effective doses . Radiat. Prot. Dosimetry 167 ( 4 ), 513 – 518 ( 2015 ). Google Scholar Crossref Search ADS PubMed WorldCat 9. Salama , D. , Vassileva , J., Mahdaly , G., Shawki , M., Salama , A., Gilley , D., Rehani M. Establishing national diagnostic reference levels (DRLs) for computed tomography in Egypt . Phys. Med. 39 , 16 – 24 ( 2017 ). Google Scholar Crossref Search ADS PubMed WorldCat 10. Lee , C. , Kim , K. P., Bolch , W. E., Moroz , B. E. and Folio , L. NCICT: a computational solution to estimate organ doses for pediatric and adult patients undergoing CT scans . J. Radiol. Prot. 35 ( 4 ), 891 – 909 ( 2015 ). Google Scholar Crossref Search ADS PubMed WorldCat 11. Abuzaid , M. M. , Elshami , W., Tekin , H. O., Ghonim , H., Shawki , M. and Salama , D. H. Computed tomography radiation doses for common computed tomography examinations: a nationwide dose survey in United Arab Emirates . Insights Imaging 11 ( 1 ), 0 – 5 ( 2020 ). Google Scholar Crossref Search ADS WorldCat 12. Abuzaid , M. M. , Elshami , W., El Serafi , A., Hussien , T., McConnell , J. R. and Tekin , H. O. Toward national Ct diagnostic reference levels in the United Arab Emirates: a multicenter review of Ct dose index and dose area product . Radiat. Prot. Dosimetry 190 ( 3 ), 243 – 249 ( 2020 ). Google Scholar Crossref Search ADS PubMed WorldCat 13. Report of AAPM Task Group 204 . Size-Specific Dose Esitmates (SSDE) in Pediatric and Adult Body CT Examinations . (MD: American Association of physicists in Medicine) ( 2011 ). 14. Alkhorayef , M. , Babikir , E., Alrushoud , A., Al-Mohammed , H. and Sulieman , A. Patient radiation biological risk in computed tomography angiography procedure . Saudi J. Biol. Sci. 24 ( 2 ), 235 – 240 ( 2017 ). Google Scholar Crossref Search ADS PubMed WorldCat 15. Karim , M. K. A. , Hashim , S., Sabarudin , A., Bradley , D. A. and Bahruddin , N. A. Evaluating organ dose and radiation risk of routine CT examinations in Johor Malaysia . Sains Malaysiana 45 ( 4 ), 567 – 573 ( 2016 ). Google Scholar OpenURL Placeholder Text WorldCat 16. Sutton , D. G. , McVey , S., Gentle , D., Hince , A. J., MacDonald , N. and McCallum , S. CT chest abdomen pelvis doses in Scotland: has the DRL had its day? Br. J. Radiol. 87 , 20140157 ( 2014 ). Google Scholar OpenURL Placeholder Text WorldCat 17. Bolowia , N. Establishment of computed tomography diagnostic reference levels in Tobruk . J. Med. Diagn. Meth. 7 , 274 ( 2018 ). Google Scholar OpenURL Placeholder Text WorldCat 18. Qurashi , A. A. , Rainford , L. A. and Foley , S. J. Establishmentof diagnostic reference levels for CT trunk examinations in thewestern region of Saudi Arabia . Radiat. Prot. Dosimetry 167 ( 4 ), 569 – 575 ( 2015 ). Google Scholar Crossref Search ADS PubMed WorldCat 19. Israel , G. M. , Cicchiello , L., Brink , J. and Huda , W. Patient size and radiation exposure in thoracic, pelvic, and abdominal CT examinations performed with automatic exposure control . Am. J. Roentgenol. 195 ( 6 ), 1342 – 1346 ( 2010 ). Google Scholar Crossref Search ADS WorldCat 20. Lee , K. L. , Beveridge , T., Sanagou , M. and Thomas , P. Updated Australian diagnostic reference levels for adult CT . J. Med. Radiat. Sci. 67 ( 1 ), 5 – 15 ( 2020 ). Google Scholar Crossref Search ADS PubMed WorldCat 21. Manssor , E. , Abuderman , A., Osman , S., Alenezi , S. B., Almehemeid , S., Babikir , E. Radiation doses in chest, abdomen and pelvis CT procedures . Radiat. Prot. Dosimetry 165 ( (1–4) ), 194 – 198 ( 2015 ). Google Scholar PubMed OpenURL Placeholder Text WorldCat 22. Davies , R. M. , Scrimshire , A. B., Sweetman , L., Anderton , M. J. and Holt , E. M. A decision tool for whole-body CT in major trauma that safely reduces unnecessary scanning and associated radiation risks: an initial exploratory analysis . Injury 47 ( 1 ), 43 – 49 ( 2016 ). Google Scholar Crossref Search ADS PubMed WorldCat © The Author(s) 2021. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected] This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiation Protection Dosimetry Oxford University Press

Estimation of Radiation Risk and Establishment of Diagnostic Reference Levels for Patients Undergoing Computed Tomography Chest–Abdomen–Pelvic Examinations in Sudan

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Oxford University Press
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0144-8420
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10.1093/rpd/ncab136
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Abstract

Abstract Establishment of diagnostic reference levels (DRLs) is an essential radiation optimization tool used to indicate optimum practice and radiation protection. This study aimed to report the current computed tomography (CT) of the chest–abdomen–pelvis radiation practice in Sudan as a part of the DRL establishment effort and dose optimization. CT radiation doses were collected from 530 patients of age ranging between 28 and 85 y and body weight ranging between 65 and 120 kg. DRLs were calculated based on the 75th percentile of dose length product (DLP) and CT dose index volume (CTDIvol). Effective and organ doses were calculated using the National Cancer Institute dosimetry system for the CT programme. The proposed DRLs are CTDIvol, 6 mGy, and DLP, 970 mGy.cm, and an effective dose of 9.9 mSv. Organ dose estimation showed that the thyroid received the highest dose during the scan. INTRODUCTION Computed tomography (CT) is reported as the main source of radiation in diagnostic medical imaging, which contributes up to 60% of the total collective dose(1). Multi-slice CT expansion made diagnostic fast, accurate and valued in routine and emergency patients. However, the availability and widespread use of CT examinations results in a potential increase in unnecessary radiation exposure(2). Implementation of ‘as low as reasonably achievable’ (ALARA) and optimization of CT radiation dose should be encouraged to reduce the potential of stochastic and deterministic effects(3). CT dose optimization and dose-reduction strategies are continuous efforts by radiology workers, including radiologists, radiographers and referring physicians. The goal of dose optimization is to reduce the radiation dose while obtaining a high diagnostic image quality. Estimation of radiation dose for specific imaging modality and protocol as a part of diagnostic reference levels (DRLs) establishment is considered to be the first step of optimization. The International Commission on Radiological Protection (ICRP) has described DRL establishment as a method for identifying the increment of radiation dose(4, 5). DRLs are used to improve radiation protection knowledge and awareness among radiologists and referring physicians and are used to encourage radiation dose reduction. The optimization of patient protection in CT procedures requires tailoring protocol according to the patient characteristics, age or size, and it is of interest and clinical indication to achieve the ALARA principles(6). Protocol and dose standardization without compromising image quality promotes radiation protection and improves health care. As part of this effort, the Sudan Atomic Agency, in collaboration with other health organizations and academic institutes, is working closely to establish DRLs for various imaging and procedures. Several surveys were carried out in Sudan regarding the establishment of DRLs. The aim of was to improve radiation protection awareness and dose optimization and to establish standard practice(7–9). This study aimed to report the current CT chest–abdomen–pelvis (CAP) radiation practice in Sudan as a part of the DRL establishment effort and dose optimization. We believe that the number of CT CAP examinations has increased and that request justification and radiation dose optimization are necessary as a result. METHOD This study evaluated the radiation dose for non-contrast CT CAP protocols. The data were collected from three scanners over a period of 3 months in 2020. The survey collected data from CT CAP procedures for patients sized ranging between 65 and 120 kg. The data collection form included instructions and guidelines to ensure that the data collected were representative of standard examinations and patients. CT machines The examination was performed using a single CT instrument manufactured by Toshiba Aquilion Prime CT scanner 160 slice (TSX-303A) (Toshiba Medical Systems, Otawara, Japan) installed in 2016. The machine had a 0.78-m gantry bore, an X-ray couch loading capacity of 300 kg, 50 frames/s reconstruction speed, provided for by 80 rows of detectors of 0.5 mm spacing to give 160 slices per rotation and 50 cm field of view. The machine had the capability for low dose reduction through adaptive iterative dose reduction using an iterative reconstruction algorithm. A quality control measurement of the CT machine was performed regularly to ensure consistency of the radiation output, exposure and protocol parameters. Radiation dosimetry The patient’s radiation dose was determined using DLP (mGy.cm) and CTDIvol (mGy) for the scan and the required dose per sequence, respectively. Estimation of effective and organ dose was conducted using the National Cancer Institute dosimetry system for CT (NCICT). The software was used to estimate organ, effective and size-specific dose estimate (SSDE) doses. The programme is based on a comprehensive library of computational human phantoms combined with Monte Carlo radiation simulation of reference CT scanners(10). Table 1 CTDIvol per sequence and total DLP per examination. CT Protocol . Median values of CTDIvol per sequence . Median values of DLP per sequence . . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . CAP 3–7.9 5.4 (0.9) 4.5 5.4 6 661.3–999.8 952.1 (39.7) 947.5 958.5 970 CT Protocol . Median values of CTDIvol per sequence . Median values of DLP per sequence . . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . CAP 3–7.9 5.4 (0.9) 4.5 5.4 6 661.3–999.8 952.1 (39.7) 947.5 958.5 970 SD = Standard Deviation Min = Minmum Max = Maximum Open in new tab Table 1 CTDIvol per sequence and total DLP per examination. CT Protocol . Median values of CTDIvol per sequence . Median values of DLP per sequence . . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . CAP 3–7.9 5.4 (0.9) 4.5 5.4 6 661.3–999.8 952.1 (39.7) 947.5 958.5 970 CT Protocol . Median values of CTDIvol per sequence . Median values of DLP per sequence . . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . Range (Min–Max) . Mean (SD) . First quartile (25%) . Median (50%) . Third quartile (75%) . CAP 3–7.9 5.4 (0.9) 4.5 5.4 6 661.3–999.8 952.1 (39.7) 947.5 958.5 970 SD = Standard Deviation Min = Minmum Max = Maximum Open in new tab CT CAP examination protocols The scan ranges from the lung apices to the lesser trochanter, with the patients lie supine, arms above their heads and feet down. Scout images in anteroposterior and lateral projection were obtained to determine the area of interest and ensure the accurate patient position. The kVp were fixed at 120, and auto mAs were used for quality reference according to patient size and scan protocol. The patients were instructed to hold their breath during the scan to ensure elimination of motion artefacts. DRL calculation Microsoft Excel was used to organize data, including patient gender, weight, kVp, mAs, CTDIvol, DLP and effective dose. Descriptive data analysis was conducted, including minimum, maximum and standard deviation, first quartile (25th percentile), second quartile (median, 50th percentile) and third quartile (75th percentile). For the typical dose value, the mode was calculated, and the achievable dose was proposed based on the median value. To establish the DRLs, the third quartile was rounded and compared with available national, regional and international data(11, 12). RESULTS Data were collected from 530 patients during the study period; 267 were males and 263 were females. The patient age ranged between 28 and 85 y with a mean of 55.9 y and standard deviation of 11.6. The patients’ body parameters were: weight ranging between 65 and 120 kg and BMI of 19.6–30.2 kg/m2. The weight and BMI variation were compared with the radiation dose using Pearson’s correlation coefficient and were found to be insignificant with p-value < 0.01. The scan protocol parameters were as follows: tube voltage (kVp) used was fixed at 120, tube current time (mAs) ranged between 140 and 210, pitch was 0.8–1, rotation time was 0.5–0.75 and the scan length was 64–73 cm. CTDIvol and DLP were used to establish the DRLs. The calculation was based on the values per exam, including range, mean, median and first and third quartile values. For the typical practice, the median values were suggested as the local DRL (Table 1). Effective and organ doses were calculated using the NCICT programme. The results are based on the scanner manufacturer, model and input scan protocol. The mean results showed CTDIvol of 5.7 mGy, DLP of 684.8 mGy-cm and effective dose of 9.9 mSv. The mean of SSDE was 11.2 mGy used to estimate radiation dose that takes a patient’s size into account(13). Figure 1 shows that the organ dose values ranged from 0.15 ± 0.1 to 17.8 ± 2.1 mSv. The lowest dose was noted at the lens with a value of 0.1 mSv, whereas the highest value of 17.8 mSv was found in the thyroid. This dose is lower than the suggested dose to induce stochastic effects and should be considered(14, 15). Figure 1 Open in new tabDownload slide graph shows organ dose (mGy) for patients underwent CT CAP examination. Figure 1 Open in new tabDownload slide graph shows organ dose (mGy) for patients underwent CT CAP examination. DISCUSSION The utilization of DRLs as a tool for identification of practice errors and as alerts for the radiology department to observe radiation doses was examined. When the radiation dose exceeds the DRLs, it is important to run the necessary investigation to identify the error and take corrective actions. This study is considered to be the first study in Sudan to describe radiation dose during CT CAP procedures as a part of an emergency protocol. The study was able to achieve the main objective, which is to propose DRLs for CT CAP practice in Sudan. The CT CAP without contrast media examination in this study focused on trauma and emergency patients who arrived with multiple body injuries. Figure 2 shows the DLP results in comparison with similar studies in other countries. The CAP-DLP was lower than most of the previously reported doses except for values reported in Australia in 2014(16–21). The reason for this lower dose compared to those of other countries could be due to the relatively new CT CAP practice in Sudan, the high awareness and education of the radiographers, as well as the designed protocol used with the mA modulation. The radiographers’ understanding of the factors affecting the radiation dose in CT has a great impact on dose optimization. Figure 2 Open in new tabDownload slide comparison of DLP values in this study and similar studies in other countries. Figure 2 Open in new tabDownload slide comparison of DLP values in this study and similar studies in other countries. The proposed DRLs based on the 75th percentile in this study were estimated as CTDIvol (6 mGy) and DLP (970 mGy-cm) when compared with those of two large studies in the USA with similar parameters, which obtained relatively low CTDIvol of 16 and 19 mGy and DLP of 1263 and 1193 mGY-cm(19, 20). The organ dose and radiation risk were estimated from radiation exposure using the NCICT computational method. As shown in Figure 1, the organ dose ranged between 0.15 and 17.81 mSv. The abdominal organ and the thyroid obviously received the highest organ doses, which is due to their location and thickness. The average effective dose from the CT CAP examination was 11.76 ± 9 mSv. This average dose can result in radiation cancer risk between 1 in 2000, although the maximum risk is 1 per 200 cancer risk per procedure(14). Although some studies reported that a 7.5 mSv can produce potential damage to the DNA, it is important not to underestimate the radiation dose(22). Focusing on the production of good image quality should consider radiation dose optimization. In practice, image quality and radiation dose should be balanced; radiation should produce the highest diagnostic image quality while staying below permissible limits. Therefore, dose monitoring is a critical component of dose optimization. The ICRP introduced the DRL concept as a tool for dosage optimization. The findings demonstrated the significance of dose optimization utilizing DRLs. LIMITATIONS Further study to include other states in the country will improve the dose variation and established national DRL values. CONCLUSION CT CAP examinations have become an acceptable method for diagnostics of patients who arrive at the emergency department with multiple traumas. However, the potential radiation risk resulting from the high radiation dose during the scan should be taken into consideration. This study showed the importance of protocol standardization and radiation dose optimization using DRLs at a national level. The use of organ and effective doses is necessary to estimate cancer risk and to increase radiation awareness among radiology and referral professionals. Patient protection is a continuous and shared effort and using a thyroid shield as a protection tool during CT CAP is essential. Radiographers’ knowledge, awareness and practice should be improved and monitored to ensure the production of high image quality while protecting the patient. Improving operators’ awareness and the proper use of dose-reduction methodologies will decrease unnecessary radiation exposure. AUTHORS’ CONTRIBUTIONS All authors participated in the project development, data collection and manuscript writing. All authors read and approved the final manuscript. 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A decision tool for whole-body CT in major trauma that safely reduces unnecessary scanning and associated radiation risks: an initial exploratory analysis . Injury 47 ( 1 ), 43 – 49 ( 2016 ). Google Scholar Crossref Search ADS PubMed WorldCat © The Author(s) 2021. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected] This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

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Published: Sep 15, 2021

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