IMPLEMENTATION OF QUALITY ASSURANCE PROGRAM IN RADIOGRAPHY—2-YEAR EXPERIENCE OF COLLABORATION WITH PUBLIC HEALTH INSTITUTIONS IN WEST REGION OF CROATIA

IMPLEMENTATION OF QUALITY ASSURANCE PROGRAM IN RADIOGRAPHY—2-YEAR EXPERIENCE OF COLLABORATION... Abstract Quality Assurance program on using ionizing radiation is mandatory in all EU member states but this is still not implemented in most facilities in Croatia mostly because of a lack of medical physicists in diagnostic radiology. Since public health institutions in Croatia do not employ medical physicists in diagnostic radiology, collaboration between these institutions in west region of Croatia with Clinical Hospital Center Rijeka (CHC) was initiated during the year 2015. Physicists from CHC Rijeka performed periodical Quality Control (QC) tests and were included in optimization process. Results of QC tests during the period of 2 years showed a lot of improvements—equipment is maintained more frequently, some old units were replaced with new ones and all institutions acquired QC equipment so radiographers could perform daily and monthly QC tests. All these activities showed that medical physics support in radiology departments is necessary and can improve clinical practice. INTRODUCTION According to the data from the UNSCEAR Report 2008, diagnostic radiology represents majority of population exposure to man-made radiation and there is even a trend for further increase of exposure(1). Even though the rise in number of diagnostic procedures raises exposure to ionizing radiation, there are means to reduce it. Quality Assurance (QA) program in radiology should ensure diagnostic images of sufficient quality with the least possible radiation dose to the patient and with lowest possible cost(2). Producing of optimal results requires all staff within the radiology department to take an active part in achieving QA objectives. QA program is mandatory in all EU member states(3). The absence of such program can lead to poor quality radiograms that can impair diagnosis, increase operating costs and contribute to unnecessary radiation exposure. Terms on use of ionizing radiation for medical purposes are defined by the Croatian regulatory body, but this is still not implemented in most diagnostic and interventional radiology facilities. Although the need for medical physicists in diagnostic radiology has been recognized by international organizations and professional societies(4–6), there is a lack of medical physicists in diagnostic radiology departments in Croatia, even at large clinical hospitals. At this moment, in Croatia, six medical physicists are involved in diagnostic and interventional radiology. MATERIALS AND METHODS A medical physicist at the radiology department of Clinical Hospital Centre Rijeka (CHC Rijeka) is full-time employed since 2012. QA program has been evolving ever since and is fully implemented now. Medical Physics Department strongly worked on public presentations of the results achieved in optimized, responsible and safe use of ionizing radiation in medicine at CHC Rijeka. This made other health institutions in west Croatian region strongly interested on developing and implementing their own QA program. West region of Croatia consists of two counties covering 6401 km2 (11.3% of Croatia’s total area) and counting 504 250 inhabitants (11.7% of Croatia’s population). None of the health institutions in this region employs a medical physicist, so collaboration with CHC Rijeka was initiated during 2015. It was agreed that medical physicists from CHC Rijeka would periodically perform Quality Control (QC) procedures of higher complexity (four times per year) and provide education of radiographers for daily and monthly QC tests. This cooperation included public health institutions in this region—one general hospital, one special hospital and two public health institutions with 13 facilities. Documented QA program was developed for all institutions. First QC procedures were carried out during 2015 and 2016 and included a total of 50 X-ray units—17 radiography units, 4 mobile radiography units, 13 mammography units, 2 computed tomography units, 1 fluoroscopy unit, 3 C-arm units, 8 intraoral dental units, 1 panoramic dental unit and 1 dual-energy X-ray absorptiometry DXA unit. This article refers to the results of QC procedures performed on stationary radiography units only. QC measurements on radiography units included generator performance tests, image quality assessment, image receptor tests and evaluation of viewing conditions. Tests were performed on six film-screen (FS) radiography units, six computed radiography (CR) units and five digital radiography (DR) units. For each radiography unit using film-screen, dark room and image processor were also verified. Firstly, a visual inspection of all X-ray rooms was performed. Inspected parameters were door handles and inability to enter the X-ray room from the outside, indication of ionizing radiation, alerts for pregnant patients, accessibility of lead aprons and visual checks of the unit. Generator performance measurements were performed using Black Piranha multimeter and Dose probe (RTI Electronics, Sweden). Image quality and field size alignment were evaluated using Flu/Rad phantom (PEHA med. Geräte GmbH, Sulzbach, Germany) with 25 mm of aluminum (PEHA med. Geräte GmbH, Sulzbach, Germany) as an attenuating material. Automatic exposure control (AEC) system tests were performed using polymethyl methacrylate (PMMA) blocks of dimensions 24 × 24 cm2 and total thickness of 20 cm. Half value layer (HVL) was tested with aluminum sheets with thicknesses ranging from 0.1 to 2.0 mm (PEHA med. Geräte GmbH, Sulzbach, Germany). For film processing test Densonorm 21 ECO (PEHA med. Geräte GmbH, Sulzbach, Germany) device was used. For viewing conditions measurements; viewing boxes, monitors and ambient light, Light Probe (RTI Electronics, Sweden) was used. All tested parameters on radiography units along with acceptability criteria from Croatian legislation(3) and from European Commission—Radiation Protection 162 (RP162)(7) are listed in Table 1. Results were compared with criteria given in Croatian legislation except beam quality (HVL) since it is not defined separately for units CE marked pre-2012 as it is in RP162. For tests that are not defined in Croatian legislation, RP162 criteria were used. At the time of finalizing this article, the criteria for diagnostic monitors were not given in Croatian legislation nor RP162 so the results were compared to the AAPM task group 18 publication(8) and the values are given in Table 2. Table 1. Tested parameters and acceptability criteria. Parameter  Croatian legislation (NN 41/13)  EC RP162  kV accuracy  <10%  ≤10% or ≤10 kV  kV reproducibility  <5%  N/A  kV variation with mAs  <10%  N/A  Accuracy of exposure time  10% for times >100 ms  ≤20% for times ≥100 ms      ≤30% for times <100 ms  Tube output (80 kV @ 1 m from the focus)  >25 μGy/mAs  25–80 μGy/mAs @ 80 kV and total filtration of 2.5 mm Al  Repeatability of output for a fixed setting  N/A  ≤20% from mean value  Consistency of output in mGy/mAs for a range of mAs values  <20%  ≤20% from mean value  HVL at 80 kV actual beam  >2.9 mm Al  ≥2.9 mm Al      ≥2.3 mm Al for equipment CE marked pre-2012  Correspondence light field and actual X-ray field  <3% of focus-image receptor distance  ≤3% of focus-image receptor distance  X-ray beam perpendicularity to the image receptor  <1.5°  N/A  Image quality  For all:  FS:   High contrast resolution  >2.4 lp/mm at 80 kV  >1.6 lp/mm spatial resolution as indicator of focal spot integrity   Low contrast  7 steps visible  CR and DR:      >2.8 lp/mm for dose ≤10 μGy      >2.4 lp/mm for dose ≤5 μGy      7 steps visible  Grid artefacts  Unacceptable  Unacceptable  Grid movement  Grid not visible  Grid not visible  AEC—FS   Repeatability of the dose  <10%  N/A   Verification of AEC optical density (OD) under reference conditions and repeatability of mAs  1–1.5 OD  0.9–1.4 OD    ±10% from annual testing     Verification of AEC sensors  <0.2 OD from mean value  Film density for each sensor >±0.5 OD from mean value   Thickness compensation  <0.3 OD from mean value  ≤±0.3 OD from mean value for all thicknesses   kV compensation  Step 20 kV for 20 cm PMMA, <0.2 OD from mean value  N/A  AEC—CR and DDR   Verification of receptor-air kerma for CR and DDR under AEC  N/A  <10 μGy   AEC device repeatability with DDI measurements  N/A  DDI or measured kerma differs by ≤40% from mean value   Verification of AEC sensors  N/A  N/A   Thickness compensation  N/A  DDI or measured kerma for given phantom thickness differs by ≤40% from mean value for all thicknesses  Dark room and image processor   Dmin  OD < 0.3  N/A   Speed index  1.2 ± 0.3  N/A   Contrast index  1 ± 0.3  N/A  Viewing conditions   Viewing box luminance  >1000 cd/m2  N/A   Viewing box uniformity  <30%  N/A   Ambient light (viewing box room)  <150 lux  N/A  Parameter  Croatian legislation (NN 41/13)  EC RP162  kV accuracy  <10%  ≤10% or ≤10 kV  kV reproducibility  <5%  N/A  kV variation with mAs  <10%  N/A  Accuracy of exposure time  10% for times >100 ms  ≤20% for times ≥100 ms      ≤30% for times <100 ms  Tube output (80 kV @ 1 m from the focus)  >25 μGy/mAs  25–80 μGy/mAs @ 80 kV and total filtration of 2.5 mm Al  Repeatability of output for a fixed setting  N/A  ≤20% from mean value  Consistency of output in mGy/mAs for a range of mAs values  <20%  ≤20% from mean value  HVL at 80 kV actual beam  >2.9 mm Al  ≥2.9 mm Al      ≥2.3 mm Al for equipment CE marked pre-2012  Correspondence light field and actual X-ray field  <3% of focus-image receptor distance  ≤3% of focus-image receptor distance  X-ray beam perpendicularity to the image receptor  <1.5°  N/A  Image quality  For all:  FS:   High contrast resolution  >2.4 lp/mm at 80 kV  >1.6 lp/mm spatial resolution as indicator of focal spot integrity   Low contrast  7 steps visible  CR and DR:      >2.8 lp/mm for dose ≤10 μGy      >2.4 lp/mm for dose ≤5 μGy      7 steps visible  Grid artefacts  Unacceptable  Unacceptable  Grid movement  Grid not visible  Grid not visible  AEC—FS   Repeatability of the dose  <10%  N/A   Verification of AEC optical density (OD) under reference conditions and repeatability of mAs  1–1.5 OD  0.9–1.4 OD    ±10% from annual testing     Verification of AEC sensors  <0.2 OD from mean value  Film density for each sensor >±0.5 OD from mean value   Thickness compensation  <0.3 OD from mean value  ≤±0.3 OD from mean value for all thicknesses   kV compensation  Step 20 kV for 20 cm PMMA, <0.2 OD from mean value  N/A  AEC—CR and DDR   Verification of receptor-air kerma for CR and DDR under AEC  N/A  <10 μGy   AEC device repeatability with DDI measurements  N/A  DDI or measured kerma differs by ≤40% from mean value   Verification of AEC sensors  N/A  N/A   Thickness compensation  N/A  DDI or measured kerma for given phantom thickness differs by ≤40% from mean value for all thicknesses  Dark room and image processor   Dmin  OD < 0.3  N/A   Speed index  1.2 ± 0.3  N/A   Contrast index  1 ± 0.3  N/A  Viewing conditions   Viewing box luminance  >1000 cd/m2  N/A   Viewing box uniformity  <30%  N/A   Ambient light (viewing box room)  <150 lux  N/A  Table 1. Tested parameters and acceptability criteria. Parameter  Croatian legislation (NN 41/13)  EC RP162  kV accuracy  <10%  ≤10% or ≤10 kV  kV reproducibility  <5%  N/A  kV variation with mAs  <10%  N/A  Accuracy of exposure time  10% for times >100 ms  ≤20% for times ≥100 ms      ≤30% for times <100 ms  Tube output (80 kV @ 1 m from the focus)  >25 μGy/mAs  25–80 μGy/mAs @ 80 kV and total filtration of 2.5 mm Al  Repeatability of output for a fixed setting  N/A  ≤20% from mean value  Consistency of output in mGy/mAs for a range of mAs values  <20%  ≤20% from mean value  HVL at 80 kV actual beam  >2.9 mm Al  ≥2.9 mm Al      ≥2.3 mm Al for equipment CE marked pre-2012  Correspondence light field and actual X-ray field  <3% of focus-image receptor distance  ≤3% of focus-image receptor distance  X-ray beam perpendicularity to the image receptor  <1.5°  N/A  Image quality  For all:  FS:   High contrast resolution  >2.4 lp/mm at 80 kV  >1.6 lp/mm spatial resolution as indicator of focal spot integrity   Low contrast  7 steps visible  CR and DR:      >2.8 lp/mm for dose ≤10 μGy      >2.4 lp/mm for dose ≤5 μGy      7 steps visible  Grid artefacts  Unacceptable  Unacceptable  Grid movement  Grid not visible  Grid not visible  AEC—FS   Repeatability of the dose  <10%  N/A   Verification of AEC optical density (OD) under reference conditions and repeatability of mAs  1–1.5 OD  0.9–1.4 OD    ±10% from annual testing     Verification of AEC sensors  <0.2 OD from mean value  Film density for each sensor >±0.5 OD from mean value   Thickness compensation  <0.3 OD from mean value  ≤±0.3 OD from mean value for all thicknesses   kV compensation  Step 20 kV for 20 cm PMMA, <0.2 OD from mean value  N/A  AEC—CR and DDR   Verification of receptor-air kerma for CR and DDR under AEC  N/A  <10 μGy   AEC device repeatability with DDI measurements  N/A  DDI or measured kerma differs by ≤40% from mean value   Verification of AEC sensors  N/A  N/A   Thickness compensation  N/A  DDI or measured kerma for given phantom thickness differs by ≤40% from mean value for all thicknesses  Dark room and image processor   Dmin  OD < 0.3  N/A   Speed index  1.2 ± 0.3  N/A   Contrast index  1 ± 0.3  N/A  Viewing conditions   Viewing box luminance  >1000 cd/m2  N/A   Viewing box uniformity  <30%  N/A   Ambient light (viewing box room)  <150 lux  N/A  Parameter  Croatian legislation (NN 41/13)  EC RP162  kV accuracy  <10%  ≤10% or ≤10 kV  kV reproducibility  <5%  N/A  kV variation with mAs  <10%  N/A  Accuracy of exposure time  10% for times >100 ms  ≤20% for times ≥100 ms      ≤30% for times <100 ms  Tube output (80 kV @ 1 m from the focus)  >25 μGy/mAs  25–80 μGy/mAs @ 80 kV and total filtration of 2.5 mm Al  Repeatability of output for a fixed setting  N/A  ≤20% from mean value  Consistency of output in mGy/mAs for a range of mAs values  <20%  ≤20% from mean value  HVL at 80 kV actual beam  >2.9 mm Al  ≥2.9 mm Al      ≥2.3 mm Al for equipment CE marked pre-2012  Correspondence light field and actual X-ray field  <3% of focus-image receptor distance  ≤3% of focus-image receptor distance  X-ray beam perpendicularity to the image receptor  <1.5°  N/A  Image quality  For all:  FS:   High contrast resolution  >2.4 lp/mm at 80 kV  >1.6 lp/mm spatial resolution as indicator of focal spot integrity   Low contrast  7 steps visible  CR and DR:      >2.8 lp/mm for dose ≤10 μGy      >2.4 lp/mm for dose ≤5 μGy      7 steps visible  Grid artefacts  Unacceptable  Unacceptable  Grid movement  Grid not visible  Grid not visible  AEC—FS   Repeatability of the dose  <10%  N/A   Verification of AEC optical density (OD) under reference conditions and repeatability of mAs  1–1.5 OD  0.9–1.4 OD    ±10% from annual testing     Verification of AEC sensors  <0.2 OD from mean value  Film density for each sensor >±0.5 OD from mean value   Thickness compensation  <0.3 OD from mean value  ≤±0.3 OD from mean value for all thicknesses   kV compensation  Step 20 kV for 20 cm PMMA, <0.2 OD from mean value  N/A  AEC—CR and DDR   Verification of receptor-air kerma for CR and DDR under AEC  N/A  <10 μGy   AEC device repeatability with DDI measurements  N/A  DDI or measured kerma differs by ≤40% from mean value   Verification of AEC sensors  N/A  N/A   Thickness compensation  N/A  DDI or measured kerma for given phantom thickness differs by ≤40% from mean value for all thicknesses  Dark room and image processor   Dmin  OD < 0.3  N/A   Speed index  1.2 ± 0.3  N/A   Contrast index  1 ± 0.3  N/A  Viewing conditions   Viewing box luminance  >1000 cd/m2  N/A   Viewing box uniformity  <30%  N/A   Ambient light (viewing box room)  <150 lux  N/A  Table 2. Acceptability criteria for diagnostic monitors. Parameter  AAPM Task group 18  Visual evaluation of TG18-QC  -Visibility of the 16 luminance steps  -Continuity of the continuous luminance bars at the right and left  Artefacts  None  Monitor uniformity  ≤30%  Ambient light (monitor room)  2–10 lux  Parameter  AAPM Task group 18  Visual evaluation of TG18-QC  -Visibility of the 16 luminance steps  -Continuity of the continuous luminance bars at the right and left  Artefacts  None  Monitor uniformity  ≤30%  Ambient light (monitor room)  2–10 lux  Table 2. Acceptability criteria for diagnostic monitors. Parameter  AAPM Task group 18  Visual evaluation of TG18-QC  -Visibility of the 16 luminance steps  -Continuity of the continuous luminance bars at the right and left  Artefacts  None  Monitor uniformity  ≤30%  Ambient light (monitor room)  2–10 lux  Parameter  AAPM Task group 18  Visual evaluation of TG18-QC  -Visibility of the 16 luminance steps  -Continuity of the continuous luminance bars at the right and left  Artefacts  None  Monitor uniformity  ≤30%  Ambient light (monitor room)  2–10 lux  Tube voltage accuracy was verified for nominal values ranging from 60 to 120 kV, in steps of 10 kV. This range is typical for clinical radiological practice. Tube voltage reproducibility and accuracy, and reproducibility of exposure time were assessed from five measurements, each under the same conditions in order to determine coefficients of variation of the measurement results. Linearity of tube output was assessed at 80 kV and various mAs values (2.5, 5, 10, 25, 50 and 100) by measuring air kerma in the central beam axis using solid state detector RTI Piranha. Reproducibility of radiation output was assessed from five successive measurements under the same conditions (80 kV, 25 mAs, FDD 100 cm). HVL was determined by adding aluminum filters to a collimated X-ray beam, measuring dose and plotting percentage transmission values versus the thickness of aluminum(9). Alignment of light field with X-ray field and image quality assessment (high contrast resolution and low contrast) was performed using Flu/Rad phantom. Automatic exposure control sensors uniformity was tested using 25 mm Al as an attenuating material at the collimator by measuring detector dose indicator (DDI) variation for CR and DR and optical density (OD) for film-screen. AEC thickness compensation was tested using 10, 15 and 20 cm of PMMA. Verification of receptor air kerma for CR and DR was measured with RTI Dose probe positioned on CR plate in the bucky and on digital detector for DR systems. Sensitometry and densitometry were performed for FS systems. For all institutions, viewing conditions were also tested which includes viewing boxes, monitors and ambient light in the radiological rooms. For viewing boxes, maximum luminance and uniformity was assessed. On diagnostic monitors, resolution, luminance, distortion, artefacts and uniformity were checked using AAPM TG18-QC and TQ18-UNL80 patterns(8). RESULTS Some X-ray rooms had problems with inappropriate door handles and patients or non-authorized personnel could easily enter the room from the hall. Some X-ray rooms did not have adequate signage for ionizing radiation nor alerts for pregnant women. Around 12% of the units had mechanical damage on hardware. Results of the visual inspection are given in Table 3. Table 3. Results of the visual inspection. Test  Passed (%)  2015  2017  Doors are closing properly  76.5  94.1  Alert for ionizing radiation is on the door  76.5  100  Alert for pregnant patients is on the door  70.6  100  Lead aprons are available in the room  100  100  No damage on the console  88.2  88.2  No damage on X-ray unit  100  100  No damage of the patient bed  100  100  No damage on cables and wire ropes  88.2  94.1  Test  Passed (%)  2015  2017  Doors are closing properly  76.5  94.1  Alert for ionizing radiation is on the door  76.5  100  Alert for pregnant patients is on the door  70.6  100  Lead aprons are available in the room  100  100  No damage on the console  88.2  88.2  No damage on X-ray unit  100  100  No damage of the patient bed  100  100  No damage on cables and wire ropes  88.2  94.1  Table 3. Results of the visual inspection. Test  Passed (%)  2015  2017  Doors are closing properly  76.5  94.1  Alert for ionizing radiation is on the door  76.5  100  Alert for pregnant patients is on the door  70.6  100  Lead aprons are available in the room  100  100  No damage on the console  88.2  88.2  No damage on X-ray unit  100  100  No damage of the patient bed  100  100  No damage on cables and wire ropes  88.2  94.1  Test  Passed (%)  2015  2017  Doors are closing properly  76.5  94.1  Alert for ionizing radiation is on the door  76.5  100  Alert for pregnant patients is on the door  70.6  100  Lead aprons are available in the room  100  100  No damage on the console  88.2  88.2  No damage on X-ray unit  100  100  No damage of the patient bed  100  100  No damage on cables and wire ropes  88.2  94.1  Verification of the X-ray generator revealed unsatisfactory performance regarding kV accuracy (12% failed), accuracy of exposure time (12% failed) and the consistency of output (6% failed). Determined HVL values met required criteria from RP162 for almost all except one old unit. For HVL measurements RP162 criteria was taken over Croatia’s legislation, since in our legislation the criteria for equipment CE marked pre-2012 is not given separately. All units had good alignment of X-ray field and light field except one unit. Disfunction of the scatter attenuating grid was recognized in 12% of the tested units. All of the FS units equipped with AEC showed out of tolerance results of the verification of AEC OD values under reference conditions. However, the ability of AEC systems to compensate for varying AEC sensors, thicknesses or kV values was 100% acceptable. On the other hand, CR and DR systems’ verification of receptor-air kerma met the criteria, but the compensation tests failed in 22% of the cases. All other tests concerning X-ray unit met the criteria. Results of viewing conditions showed that 17% of the viewing boxes had luminance below tolerance. However, uniformity test failed in 67% of the measurements. Majority of the radiological rooms had ambient light much higher than recommended; 67% of the viewing box rooms and 62% of monitor rooms. All monitors met the recommendations. After the first year of collaboration overall three conventional FS units were replaced with new DR systems. Since most parameters on the remaining units that did not meet the criteria were easily adjustable by service engineers, recommendations for urgent service were given in the reports. Most of the problems were fixed during the first year and improvements can be seen in the follow-up results. Comparison of the results from 2015 and 2017 is given in Tables 3 and 4. Table 4. Comparison of the QC results from 2015 and 2017. Test  Passed (%)  2015  2017  kV accuracy  88.2  94.1  kV reproducibility  100  100  Accuracy of exposure time  88.2  100  Tube output (80 kV @ 1 m)  100  100  Repeatability of output for fixed settings  100  100  Consistency of output in mGy/mAs  94.1  100  HVL at 80 kV  94.1  100  Correspondence light field and actual X-ray field  94.1  100  X-ray beam perpendicularity to the image receptor  100  100  Image quality  100  100   High contrast resolution  100  100   Low contrast  100  100  Grid artefacts  88.2  88.2  AEC—FS   Verification of AEC optical density (OD)  0  50   Verification of AEC sensors  100  100   AEC kV compensation  100  100   AEC thickness compensation  100  100  AEC—CR and DR   Verification of receptor-air kerma  100  100   Verification of AEC sensors  77.8  77.8   AEC thickness compensation  77.8  77.8  Viewing conditions   Viewing box luminance  83.3  100   Viewing box uniformity  33  66.7   Ambient light (viewing box room)  33.3  83.3   TG18 QC test  100  100   Artefacts  100  100   Monitor uniformity  100  100   Ambient light (monitor room)  37.5  75  Test  Passed (%)  2015  2017  kV accuracy  88.2  94.1  kV reproducibility  100  100  Accuracy of exposure time  88.2  100  Tube output (80 kV @ 1 m)  100  100  Repeatability of output for fixed settings  100  100  Consistency of output in mGy/mAs  94.1  100  HVL at 80 kV  94.1  100  Correspondence light field and actual X-ray field  94.1  100  X-ray beam perpendicularity to the image receptor  100  100  Image quality  100  100   High contrast resolution  100  100   Low contrast  100  100  Grid artefacts  88.2  88.2  AEC—FS   Verification of AEC optical density (OD)  0  50   Verification of AEC sensors  100  100   AEC kV compensation  100  100   AEC thickness compensation  100  100  AEC—CR and DR   Verification of receptor-air kerma  100  100   Verification of AEC sensors  77.8  77.8   AEC thickness compensation  77.8  77.8  Viewing conditions   Viewing box luminance  83.3  100   Viewing box uniformity  33  66.7   Ambient light (viewing box room)  33.3  83.3   TG18 QC test  100  100   Artefacts  100  100   Monitor uniformity  100  100   Ambient light (monitor room)  37.5  75  Table 4. Comparison of the QC results from 2015 and 2017. Test  Passed (%)  2015  2017  kV accuracy  88.2  94.1  kV reproducibility  100  100  Accuracy of exposure time  88.2  100  Tube output (80 kV @ 1 m)  100  100  Repeatability of output for fixed settings  100  100  Consistency of output in mGy/mAs  94.1  100  HVL at 80 kV  94.1  100  Correspondence light field and actual X-ray field  94.1  100  X-ray beam perpendicularity to the image receptor  100  100  Image quality  100  100   High contrast resolution  100  100   Low contrast  100  100  Grid artefacts  88.2  88.2  AEC—FS   Verification of AEC optical density (OD)  0  50   Verification of AEC sensors  100  100   AEC kV compensation  100  100   AEC thickness compensation  100  100  AEC—CR and DR   Verification of receptor-air kerma  100  100   Verification of AEC sensors  77.8  77.8   AEC thickness compensation  77.8  77.8  Viewing conditions   Viewing box luminance  83.3  100   Viewing box uniformity  33  66.7   Ambient light (viewing box room)  33.3  83.3   TG18 QC test  100  100   Artefacts  100  100   Monitor uniformity  100  100   Ambient light (monitor room)  37.5  75  Test  Passed (%)  2015  2017  kV accuracy  88.2  94.1  kV reproducibility  100  100  Accuracy of exposure time  88.2  100  Tube output (80 kV @ 1 m)  100  100  Repeatability of output for fixed settings  100  100  Consistency of output in mGy/mAs  94.1  100  HVL at 80 kV  94.1  100  Correspondence light field and actual X-ray field  94.1  100  X-ray beam perpendicularity to the image receptor  100  100  Image quality  100  100   High contrast resolution  100  100   Low contrast  100  100  Grid artefacts  88.2  88.2  AEC—FS   Verification of AEC optical density (OD)  0  50   Verification of AEC sensors  100  100   AEC kV compensation  100  100   AEC thickness compensation  100  100  AEC—CR and DR   Verification of receptor-air kerma  100  100   Verification of AEC sensors  77.8  77.8   AEC thickness compensation  77.8  77.8  Viewing conditions   Viewing box luminance  83.3  100   Viewing box uniformity  33  66.7   Ambient light (viewing box room)  33.3  83.3   TG18 QC test  100  100   Artefacts  100  100   Monitor uniformity  100  100   Ambient light (monitor room)  37.5  75  Facilities were advised to appropriately mark all entrance doors and to disable non-authorized entrance to the X-ray rooms with proper one-way door locks. Almost all doors are now closing properly, and all of the X-ray rooms have a proper signage for ionizing radiation and alerts for pregnant women. However, none of the damaged consoles were repaired. Follow-up results of the X-ray generator performance showed that kV accuracy failure percentage was lowered (from 12 to 6% of the units) and accuracy of exposure time and the consistency of output now met criteria for all units. The HVL value and field alignment discrepancies were improved to an acceptable level. However, no improvement was made regarding scatter attenuating grid. Half of the FS units that showed out of tolerance results of the verification of AEC OD under reference conditions were fixed. In contrast, no improvement was recorded in the performance of the compensation segment of AEC systems for CR and DR units. Most of the radiological rooms that were too bright were darkened and unacceptable viewing box was replaced. On viewing boxes that failed in uniformity, lamps were replaced and boxes were cleaned so now 34% do not meet criteria. DISCUSSION First results showed few problems with technical parameters mainly because of poorly maintained equipment. The institutions did not have any tools to perform QC procedures which could give them the quantitative information. X-ray units that showed issues with the generator performance were adjusted by the service engineer immediately upon the recommendations given by medical physicists. This clearly shows that the quantification of the problem led to a better argumentation to the management for financial investment in the maintenance of the equipment. QC results from the first year revealed mainly problems with automatic exposure control system. The purpose of AEC is to deliver consistent and reproducible exposures to the image receptor across a wide range of anatomical thicknesses and tube potentials(10). Since it terminates the exposure when a predetermined amount of radiation to the image receptor has been reached, it can tailor the dose delivered to the patient but only when it is properly used and well calibrated. All the FS units and 22% of the CR/DR units were not calibrated properly, so radiographers had to use manual exposures on units equipped with AEC system. It is visible that in some facilities with AEC problems manufacturer engineers did not repair the compensation issues. Hopefully, the implementation of the new directive to national legislation will motivate these facilities to revise their investment policies regarding maintenance.(2) Improvements regarding viewing conditions gave excellent results in clinical application. Low-cost repairing within this segment significantly upgraded possibilities to provide an adequate diagnostic information(11). Comparison of the results from initial and follow-up QC tests showed a lot of improvement—equipment is maintained more frequently, and some old units were replaced. Another three CR units will be replaced with DR units in the beginning of 2018. It is expected that during 2018 and the beginning of 2019 all units that are using FS cassettes will be replaced by CR plates at least and all units without AEC system with new digital ones. Besides the recommendations for regular maintenance of the units, institutions were advised to acquire their own equipment for daily and monthly QC testing. Every facility purchased PMMA blocks, image quality phantom and sensitometer and densitometer—for facilities using FS systems. QC manuals with baseline values and frequencies for every test were developed. Education and training for daily and monthly testing was performed for radiographers. Daily tests that are performed in radiography are visibility of the grid and grid artefacts, repeatability of AEC system in terms of mAs and DDI values for CR and DR and mAs and OD value for FS system using 15 cm of PMMA. Dark room and film developer QC testing is performed daily for facilities that use FS system and this allows them to monitor parameters of the developing device to achieve optimal performance(12). Monthly tests performed are alignment of the light field with actual X-ray field, image quality—high contrast resolution, visibility of the grid and grid artefacts, repeatability of AEC system in terms of mAs and DDI values for CR and DR and mAs and OD value for FS system for 15 cm of PMMA and AEC thickness compensation for 10, 15 and 20 cm of PMMA. The standard operative procedure is that procedures with out of tolerance results are repeated to avoid human error. If the results are still not acceptable, a medical physicist from CHC Rijeka is to be informed in order to perform more detailed tests of respective parameter and advice for solution. Daily and monthly checks that are performed by radiographers enhanced their practice in many ways—they can react more promptly if something is out of tolerance and now they have measurable parameters to present to management and ask for urgent adjustment of the X-ray unit. CONCLUSION These collaborations showed that implementing a full QA program which, apart from QC includes optimization, is necessary and improves radiological practice. Radiologists receive images with higher quality while radiation exposure to patient is kept as low as reasonably achievable. After periodical QC implementation, next task was the establishment of DRL’s and optimization of the radiological practice which is an ongoing process. With this collaboration all institutions became aware that they need medical physics support in their everyday practice. Besides the testing of the equipment, which is fundamental, medical physicists are involved in optimizing and improving clinical practice. They measure radiation dose and examine image quality that directly affects the patient. Medical physicist is in charge for training radiographers and other staff members on quality assurance and radiation protection issues. Above mentioned makes a medical physicist, along with the radiologist and the radiographer, an important part of the radiology team with the aim of providing responsible, justified and safe use of ionizing radiation. REFERENCES 1 United Nations Scientific Committee on the Effects of Atomic Radiation Sources and effects of ionizing radiation: UNSCEAR 2008 report to the General Assembly with scientific annexes ( 2010), New York. 2 European Council Directive 2013/59/Euratom on basic safety standards for protection against the dangers arising from exposure to ionizing radiation and repealing Directives 89/618/Euratom, 90/641/Euratom, 96/29/Euratom, 97/43/Euratom and 2003/122/Euratom. OJ of the EU. L13; 57: 1–73 ( 2014). 3 Law on Radiation Protection and Safety. Regulation on the conditions and radiation protection measures for performing activities with electrical devices that produce ionizing radiation. Official gazette, April 8 ( 2013). 4 International Atomic Energy Agency. Roles and responsibilities, and education and training requirements for clinically qualified medical physicists. IAEA human health reports No. 25 ( 2013), Vienna. 5 American Association of Physicists in Medicine. The role of the clinical medical physicist in diagnostic radiology. AAPM report 42 ( 1994), New York. 6 International Atomic Energy Agency. Radiation protection and safety of radiation sources: international basic safety standards. General safety requirements part 3 ( 2014), Vienna. 7 European Commission—Radiation Protection No. 162. Criteria for acceptability of medical radiological equipment used in diagnostic radiology, nuclear medicine and radiotherapy. Directorate-General for Energy Directorate D—Nuclear Safety & Fuel Cycle Unit D4—Radiation Protection ( 2012). 8 Samei, E. et al.  . Assessment of display performance for medical imaging systems. Report of the American Association of Physicists in Medicine (AAPM) Task Group 18, Medical Physics Publishing, Madison, WI, AAPM On-Line Report No. 03, April 2005. 9 Institution of Physics and Engineering in Medicine and Biology. Measurement of the performance characteristics of diagnostic X-ray systems used in medicine, Part I: X-ray tubes and generators. IPEM Report No. 32, York ( 1995). 10 Automatic exposure control devices. IAEA Human Health Campus, Retrieved 16 December 2016. 11 Moshfeghi, M., Shahbazian, M., Sajadi, S. S., Sajadi, S. and Ansari, H. Effects of different viewing conditions on radiographic interpretation. J. Dent. (Tehran, Iran)  12( 11), 853– 858 ( 2015). 12 Wolfgang, L. The role of the darkroom in radiograph quality control. N. Y. State Dent. J.  64( 6), 26– 29 ( 1998). Google Scholar PubMed  © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiation Protection Dosimetry Oxford University Press

IMPLEMENTATION OF QUALITY ASSURANCE PROGRAM IN RADIOGRAPHY—2-YEAR EXPERIENCE OF COLLABORATION WITH PUBLIC HEALTH INSTITUTIONS IN WEST REGION OF CROATIA

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Abstract

Abstract Quality Assurance program on using ionizing radiation is mandatory in all EU member states but this is still not implemented in most facilities in Croatia mostly because of a lack of medical physicists in diagnostic radiology. Since public health institutions in Croatia do not employ medical physicists in diagnostic radiology, collaboration between these institutions in west region of Croatia with Clinical Hospital Center Rijeka (CHC) was initiated during the year 2015. Physicists from CHC Rijeka performed periodical Quality Control (QC) tests and were included in optimization process. Results of QC tests during the period of 2 years showed a lot of improvements—equipment is maintained more frequently, some old units were replaced with new ones and all institutions acquired QC equipment so radiographers could perform daily and monthly QC tests. All these activities showed that medical physics support in radiology departments is necessary and can improve clinical practice. INTRODUCTION According to the data from the UNSCEAR Report 2008, diagnostic radiology represents majority of population exposure to man-made radiation and there is even a trend for further increase of exposure(1). Even though the rise in number of diagnostic procedures raises exposure to ionizing radiation, there are means to reduce it. Quality Assurance (QA) program in radiology should ensure diagnostic images of sufficient quality with the least possible radiation dose to the patient and with lowest possible cost(2). Producing of optimal results requires all staff within the radiology department to take an active part in achieving QA objectives. QA program is mandatory in all EU member states(3). The absence of such program can lead to poor quality radiograms that can impair diagnosis, increase operating costs and contribute to unnecessary radiation exposure. Terms on use of ionizing radiation for medical purposes are defined by the Croatian regulatory body, but this is still not implemented in most diagnostic and interventional radiology facilities. Although the need for medical physicists in diagnostic radiology has been recognized by international organizations and professional societies(4–6), there is a lack of medical physicists in diagnostic radiology departments in Croatia, even at large clinical hospitals. At this moment, in Croatia, six medical physicists are involved in diagnostic and interventional radiology. MATERIALS AND METHODS A medical physicist at the radiology department of Clinical Hospital Centre Rijeka (CHC Rijeka) is full-time employed since 2012. QA program has been evolving ever since and is fully implemented now. Medical Physics Department strongly worked on public presentations of the results achieved in optimized, responsible and safe use of ionizing radiation in medicine at CHC Rijeka. This made other health institutions in west Croatian region strongly interested on developing and implementing their own QA program. West region of Croatia consists of two counties covering 6401 km2 (11.3% of Croatia’s total area) and counting 504 250 inhabitants (11.7% of Croatia’s population). None of the health institutions in this region employs a medical physicist, so collaboration with CHC Rijeka was initiated during 2015. It was agreed that medical physicists from CHC Rijeka would periodically perform Quality Control (QC) procedures of higher complexity (four times per year) and provide education of radiographers for daily and monthly QC tests. This cooperation included public health institutions in this region—one general hospital, one special hospital and two public health institutions with 13 facilities. Documented QA program was developed for all institutions. First QC procedures were carried out during 2015 and 2016 and included a total of 50 X-ray units—17 radiography units, 4 mobile radiography units, 13 mammography units, 2 computed tomography units, 1 fluoroscopy unit, 3 C-arm units, 8 intraoral dental units, 1 panoramic dental unit and 1 dual-energy X-ray absorptiometry DXA unit. This article refers to the results of QC procedures performed on stationary radiography units only. QC measurements on radiography units included generator performance tests, image quality assessment, image receptor tests and evaluation of viewing conditions. Tests were performed on six film-screen (FS) radiography units, six computed radiography (CR) units and five digital radiography (DR) units. For each radiography unit using film-screen, dark room and image processor were also verified. Firstly, a visual inspection of all X-ray rooms was performed. Inspected parameters were door handles and inability to enter the X-ray room from the outside, indication of ionizing radiation, alerts for pregnant patients, accessibility of lead aprons and visual checks of the unit. Generator performance measurements were performed using Black Piranha multimeter and Dose probe (RTI Electronics, Sweden). Image quality and field size alignment were evaluated using Flu/Rad phantom (PEHA med. Geräte GmbH, Sulzbach, Germany) with 25 mm of aluminum (PEHA med. Geräte GmbH, Sulzbach, Germany) as an attenuating material. Automatic exposure control (AEC) system tests were performed using polymethyl methacrylate (PMMA) blocks of dimensions 24 × 24 cm2 and total thickness of 20 cm. Half value layer (HVL) was tested with aluminum sheets with thicknesses ranging from 0.1 to 2.0 mm (PEHA med. Geräte GmbH, Sulzbach, Germany). For film processing test Densonorm 21 ECO (PEHA med. Geräte GmbH, Sulzbach, Germany) device was used. For viewing conditions measurements; viewing boxes, monitors and ambient light, Light Probe (RTI Electronics, Sweden) was used. All tested parameters on radiography units along with acceptability criteria from Croatian legislation(3) and from European Commission—Radiation Protection 162 (RP162)(7) are listed in Table 1. Results were compared with criteria given in Croatian legislation except beam quality (HVL) since it is not defined separately for units CE marked pre-2012 as it is in RP162. For tests that are not defined in Croatian legislation, RP162 criteria were used. At the time of finalizing this article, the criteria for diagnostic monitors were not given in Croatian legislation nor RP162 so the results were compared to the AAPM task group 18 publication(8) and the values are given in Table 2. Table 1. Tested parameters and acceptability criteria. Parameter  Croatian legislation (NN 41/13)  EC RP162  kV accuracy  <10%  ≤10% or ≤10 kV  kV reproducibility  <5%  N/A  kV variation with mAs  <10%  N/A  Accuracy of exposure time  10% for times >100 ms  ≤20% for times ≥100 ms      ≤30% for times <100 ms  Tube output (80 kV @ 1 m from the focus)  >25 μGy/mAs  25–80 μGy/mAs @ 80 kV and total filtration of 2.5 mm Al  Repeatability of output for a fixed setting  N/A  ≤20% from mean value  Consistency of output in mGy/mAs for a range of mAs values  <20%  ≤20% from mean value  HVL at 80 kV actual beam  >2.9 mm Al  ≥2.9 mm Al      ≥2.3 mm Al for equipment CE marked pre-2012  Correspondence light field and actual X-ray field  <3% of focus-image receptor distance  ≤3% of focus-image receptor distance  X-ray beam perpendicularity to the image receptor  <1.5°  N/A  Image quality  For all:  FS:   High contrast resolution  >2.4 lp/mm at 80 kV  >1.6 lp/mm spatial resolution as indicator of focal spot integrity   Low contrast  7 steps visible  CR and DR:      >2.8 lp/mm for dose ≤10 μGy      >2.4 lp/mm for dose ≤5 μGy      7 steps visible  Grid artefacts  Unacceptable  Unacceptable  Grid movement  Grid not visible  Grid not visible  AEC—FS   Repeatability of the dose  <10%  N/A   Verification of AEC optical density (OD) under reference conditions and repeatability of mAs  1–1.5 OD  0.9–1.4 OD    ±10% from annual testing     Verification of AEC sensors  <0.2 OD from mean value  Film density for each sensor >±0.5 OD from mean value   Thickness compensation  <0.3 OD from mean value  ≤±0.3 OD from mean value for all thicknesses   kV compensation  Step 20 kV for 20 cm PMMA, <0.2 OD from mean value  N/A  AEC—CR and DDR   Verification of receptor-air kerma for CR and DDR under AEC  N/A  <10 μGy   AEC device repeatability with DDI measurements  N/A  DDI or measured kerma differs by ≤40% from mean value   Verification of AEC sensors  N/A  N/A   Thickness compensation  N/A  DDI or measured kerma for given phantom thickness differs by ≤40% from mean value for all thicknesses  Dark room and image processor   Dmin  OD < 0.3  N/A   Speed index  1.2 ± 0.3  N/A   Contrast index  1 ± 0.3  N/A  Viewing conditions   Viewing box luminance  >1000 cd/m2  N/A   Viewing box uniformity  <30%  N/A   Ambient light (viewing box room)  <150 lux  N/A  Parameter  Croatian legislation (NN 41/13)  EC RP162  kV accuracy  <10%  ≤10% or ≤10 kV  kV reproducibility  <5%  N/A  kV variation with mAs  <10%  N/A  Accuracy of exposure time  10% for times >100 ms  ≤20% for times ≥100 ms      ≤30% for times <100 ms  Tube output (80 kV @ 1 m from the focus)  >25 μGy/mAs  25–80 μGy/mAs @ 80 kV and total filtration of 2.5 mm Al  Repeatability of output for a fixed setting  N/A  ≤20% from mean value  Consistency of output in mGy/mAs for a range of mAs values  <20%  ≤20% from mean value  HVL at 80 kV actual beam  >2.9 mm Al  ≥2.9 mm Al      ≥2.3 mm Al for equipment CE marked pre-2012  Correspondence light field and actual X-ray field  <3% of focus-image receptor distance  ≤3% of focus-image receptor distance  X-ray beam perpendicularity to the image receptor  <1.5°  N/A  Image quality  For all:  FS:   High contrast resolution  >2.4 lp/mm at 80 kV  >1.6 lp/mm spatial resolution as indicator of focal spot integrity   Low contrast  7 steps visible  CR and DR:      >2.8 lp/mm for dose ≤10 μGy      >2.4 lp/mm for dose ≤5 μGy      7 steps visible  Grid artefacts  Unacceptable  Unacceptable  Grid movement  Grid not visible  Grid not visible  AEC—FS   Repeatability of the dose  <10%  N/A   Verification of AEC optical density (OD) under reference conditions and repeatability of mAs  1–1.5 OD  0.9–1.4 OD    ±10% from annual testing     Verification of AEC sensors  <0.2 OD from mean value  Film density for each sensor >±0.5 OD from mean value   Thickness compensation  <0.3 OD from mean value  ≤±0.3 OD from mean value for all thicknesses   kV compensation  Step 20 kV for 20 cm PMMA, <0.2 OD from mean value  N/A  AEC—CR and DDR   Verification of receptor-air kerma for CR and DDR under AEC  N/A  <10 μGy   AEC device repeatability with DDI measurements  N/A  DDI or measured kerma differs by ≤40% from mean value   Verification of AEC sensors  N/A  N/A   Thickness compensation  N/A  DDI or measured kerma for given phantom thickness differs by ≤40% from mean value for all thicknesses  Dark room and image processor   Dmin  OD < 0.3  N/A   Speed index  1.2 ± 0.3  N/A   Contrast index  1 ± 0.3  N/A  Viewing conditions   Viewing box luminance  >1000 cd/m2  N/A   Viewing box uniformity  <30%  N/A   Ambient light (viewing box room)  <150 lux  N/A  Table 1. Tested parameters and acceptability criteria. Parameter  Croatian legislation (NN 41/13)  EC RP162  kV accuracy  <10%  ≤10% or ≤10 kV  kV reproducibility  <5%  N/A  kV variation with mAs  <10%  N/A  Accuracy of exposure time  10% for times >100 ms  ≤20% for times ≥100 ms      ≤30% for times <100 ms  Tube output (80 kV @ 1 m from the focus)  >25 μGy/mAs  25–80 μGy/mAs @ 80 kV and total filtration of 2.5 mm Al  Repeatability of output for a fixed setting  N/A  ≤20% from mean value  Consistency of output in mGy/mAs for a range of mAs values  <20%  ≤20% from mean value  HVL at 80 kV actual beam  >2.9 mm Al  ≥2.9 mm Al      ≥2.3 mm Al for equipment CE marked pre-2012  Correspondence light field and actual X-ray field  <3% of focus-image receptor distance  ≤3% of focus-image receptor distance  X-ray beam perpendicularity to the image receptor  <1.5°  N/A  Image quality  For all:  FS:   High contrast resolution  >2.4 lp/mm at 80 kV  >1.6 lp/mm spatial resolution as indicator of focal spot integrity   Low contrast  7 steps visible  CR and DR:      >2.8 lp/mm for dose ≤10 μGy      >2.4 lp/mm for dose ≤5 μGy      7 steps visible  Grid artefacts  Unacceptable  Unacceptable  Grid movement  Grid not visible  Grid not visible  AEC—FS   Repeatability of the dose  <10%  N/A   Verification of AEC optical density (OD) under reference conditions and repeatability of mAs  1–1.5 OD  0.9–1.4 OD    ±10% from annual testing     Verification of AEC sensors  <0.2 OD from mean value  Film density for each sensor >±0.5 OD from mean value   Thickness compensation  <0.3 OD from mean value  ≤±0.3 OD from mean value for all thicknesses   kV compensation  Step 20 kV for 20 cm PMMA, <0.2 OD from mean value  N/A  AEC—CR and DDR   Verification of receptor-air kerma for CR and DDR under AEC  N/A  <10 μGy   AEC device repeatability with DDI measurements  N/A  DDI or measured kerma differs by ≤40% from mean value   Verification of AEC sensors  N/A  N/A   Thickness compensation  N/A  DDI or measured kerma for given phantom thickness differs by ≤40% from mean value for all thicknesses  Dark room and image processor   Dmin  OD < 0.3  N/A   Speed index  1.2 ± 0.3  N/A   Contrast index  1 ± 0.3  N/A  Viewing conditions   Viewing box luminance  >1000 cd/m2  N/A   Viewing box uniformity  <30%  N/A   Ambient light (viewing box room)  <150 lux  N/A  Parameter  Croatian legislation (NN 41/13)  EC RP162  kV accuracy  <10%  ≤10% or ≤10 kV  kV reproducibility  <5%  N/A  kV variation with mAs  <10%  N/A  Accuracy of exposure time  10% for times >100 ms  ≤20% for times ≥100 ms      ≤30% for times <100 ms  Tube output (80 kV @ 1 m from the focus)  >25 μGy/mAs  25–80 μGy/mAs @ 80 kV and total filtration of 2.5 mm Al  Repeatability of output for a fixed setting  N/A  ≤20% from mean value  Consistency of output in mGy/mAs for a range of mAs values  <20%  ≤20% from mean value  HVL at 80 kV actual beam  >2.9 mm Al  ≥2.9 mm Al      ≥2.3 mm Al for equipment CE marked pre-2012  Correspondence light field and actual X-ray field  <3% of focus-image receptor distance  ≤3% of focus-image receptor distance  X-ray beam perpendicularity to the image receptor  <1.5°  N/A  Image quality  For all:  FS:   High contrast resolution  >2.4 lp/mm at 80 kV  >1.6 lp/mm spatial resolution as indicator of focal spot integrity   Low contrast  7 steps visible  CR and DR:      >2.8 lp/mm for dose ≤10 μGy      >2.4 lp/mm for dose ≤5 μGy      7 steps visible  Grid artefacts  Unacceptable  Unacceptable  Grid movement  Grid not visible  Grid not visible  AEC—FS   Repeatability of the dose  <10%  N/A   Verification of AEC optical density (OD) under reference conditions and repeatability of mAs  1–1.5 OD  0.9–1.4 OD    ±10% from annual testing     Verification of AEC sensors  <0.2 OD from mean value  Film density for each sensor >±0.5 OD from mean value   Thickness compensation  <0.3 OD from mean value  ≤±0.3 OD from mean value for all thicknesses   kV compensation  Step 20 kV for 20 cm PMMA, <0.2 OD from mean value  N/A  AEC—CR and DDR   Verification of receptor-air kerma for CR and DDR under AEC  N/A  <10 μGy   AEC device repeatability with DDI measurements  N/A  DDI or measured kerma differs by ≤40% from mean value   Verification of AEC sensors  N/A  N/A   Thickness compensation  N/A  DDI or measured kerma for given phantom thickness differs by ≤40% from mean value for all thicknesses  Dark room and image processor   Dmin  OD < 0.3  N/A   Speed index  1.2 ± 0.3  N/A   Contrast index  1 ± 0.3  N/A  Viewing conditions   Viewing box luminance  >1000 cd/m2  N/A   Viewing box uniformity  <30%  N/A   Ambient light (viewing box room)  <150 lux  N/A  Table 2. Acceptability criteria for diagnostic monitors. Parameter  AAPM Task group 18  Visual evaluation of TG18-QC  -Visibility of the 16 luminance steps  -Continuity of the continuous luminance bars at the right and left  Artefacts  None  Monitor uniformity  ≤30%  Ambient light (monitor room)  2–10 lux  Parameter  AAPM Task group 18  Visual evaluation of TG18-QC  -Visibility of the 16 luminance steps  -Continuity of the continuous luminance bars at the right and left  Artefacts  None  Monitor uniformity  ≤30%  Ambient light (monitor room)  2–10 lux  Table 2. Acceptability criteria for diagnostic monitors. Parameter  AAPM Task group 18  Visual evaluation of TG18-QC  -Visibility of the 16 luminance steps  -Continuity of the continuous luminance bars at the right and left  Artefacts  None  Monitor uniformity  ≤30%  Ambient light (monitor room)  2–10 lux  Parameter  AAPM Task group 18  Visual evaluation of TG18-QC  -Visibility of the 16 luminance steps  -Continuity of the continuous luminance bars at the right and left  Artefacts  None  Monitor uniformity  ≤30%  Ambient light (monitor room)  2–10 lux  Tube voltage accuracy was verified for nominal values ranging from 60 to 120 kV, in steps of 10 kV. This range is typical for clinical radiological practice. Tube voltage reproducibility and accuracy, and reproducibility of exposure time were assessed from five measurements, each under the same conditions in order to determine coefficients of variation of the measurement results. Linearity of tube output was assessed at 80 kV and various mAs values (2.5, 5, 10, 25, 50 and 100) by measuring air kerma in the central beam axis using solid state detector RTI Piranha. Reproducibility of radiation output was assessed from five successive measurements under the same conditions (80 kV, 25 mAs, FDD 100 cm). HVL was determined by adding aluminum filters to a collimated X-ray beam, measuring dose and plotting percentage transmission values versus the thickness of aluminum(9). Alignment of light field with X-ray field and image quality assessment (high contrast resolution and low contrast) was performed using Flu/Rad phantom. Automatic exposure control sensors uniformity was tested using 25 mm Al as an attenuating material at the collimator by measuring detector dose indicator (DDI) variation for CR and DR and optical density (OD) for film-screen. AEC thickness compensation was tested using 10, 15 and 20 cm of PMMA. Verification of receptor air kerma for CR and DR was measured with RTI Dose probe positioned on CR plate in the bucky and on digital detector for DR systems. Sensitometry and densitometry were performed for FS systems. For all institutions, viewing conditions were also tested which includes viewing boxes, monitors and ambient light in the radiological rooms. For viewing boxes, maximum luminance and uniformity was assessed. On diagnostic monitors, resolution, luminance, distortion, artefacts and uniformity were checked using AAPM TG18-QC and TQ18-UNL80 patterns(8). RESULTS Some X-ray rooms had problems with inappropriate door handles and patients or non-authorized personnel could easily enter the room from the hall. Some X-ray rooms did not have adequate signage for ionizing radiation nor alerts for pregnant women. Around 12% of the units had mechanical damage on hardware. Results of the visual inspection are given in Table 3. Table 3. Results of the visual inspection. Test  Passed (%)  2015  2017  Doors are closing properly  76.5  94.1  Alert for ionizing radiation is on the door  76.5  100  Alert for pregnant patients is on the door  70.6  100  Lead aprons are available in the room  100  100  No damage on the console  88.2  88.2  No damage on X-ray unit  100  100  No damage of the patient bed  100  100  No damage on cables and wire ropes  88.2  94.1  Test  Passed (%)  2015  2017  Doors are closing properly  76.5  94.1  Alert for ionizing radiation is on the door  76.5  100  Alert for pregnant patients is on the door  70.6  100  Lead aprons are available in the room  100  100  No damage on the console  88.2  88.2  No damage on X-ray unit  100  100  No damage of the patient bed  100  100  No damage on cables and wire ropes  88.2  94.1  Table 3. Results of the visual inspection. Test  Passed (%)  2015  2017  Doors are closing properly  76.5  94.1  Alert for ionizing radiation is on the door  76.5  100  Alert for pregnant patients is on the door  70.6  100  Lead aprons are available in the room  100  100  No damage on the console  88.2  88.2  No damage on X-ray unit  100  100  No damage of the patient bed  100  100  No damage on cables and wire ropes  88.2  94.1  Test  Passed (%)  2015  2017  Doors are closing properly  76.5  94.1  Alert for ionizing radiation is on the door  76.5  100  Alert for pregnant patients is on the door  70.6  100  Lead aprons are available in the room  100  100  No damage on the console  88.2  88.2  No damage on X-ray unit  100  100  No damage of the patient bed  100  100  No damage on cables and wire ropes  88.2  94.1  Verification of the X-ray generator revealed unsatisfactory performance regarding kV accuracy (12% failed), accuracy of exposure time (12% failed) and the consistency of output (6% failed). Determined HVL values met required criteria from RP162 for almost all except one old unit. For HVL measurements RP162 criteria was taken over Croatia’s legislation, since in our legislation the criteria for equipment CE marked pre-2012 is not given separately. All units had good alignment of X-ray field and light field except one unit. Disfunction of the scatter attenuating grid was recognized in 12% of the tested units. All of the FS units equipped with AEC showed out of tolerance results of the verification of AEC OD values under reference conditions. However, the ability of AEC systems to compensate for varying AEC sensors, thicknesses or kV values was 100% acceptable. On the other hand, CR and DR systems’ verification of receptor-air kerma met the criteria, but the compensation tests failed in 22% of the cases. All other tests concerning X-ray unit met the criteria. Results of viewing conditions showed that 17% of the viewing boxes had luminance below tolerance. However, uniformity test failed in 67% of the measurements. Majority of the radiological rooms had ambient light much higher than recommended; 67% of the viewing box rooms and 62% of monitor rooms. All monitors met the recommendations. After the first year of collaboration overall three conventional FS units were replaced with new DR systems. Since most parameters on the remaining units that did not meet the criteria were easily adjustable by service engineers, recommendations for urgent service were given in the reports. Most of the problems were fixed during the first year and improvements can be seen in the follow-up results. Comparison of the results from 2015 and 2017 is given in Tables 3 and 4. Table 4. Comparison of the QC results from 2015 and 2017. Test  Passed (%)  2015  2017  kV accuracy  88.2  94.1  kV reproducibility  100  100  Accuracy of exposure time  88.2  100  Tube output (80 kV @ 1 m)  100  100  Repeatability of output for fixed settings  100  100  Consistency of output in mGy/mAs  94.1  100  HVL at 80 kV  94.1  100  Correspondence light field and actual X-ray field  94.1  100  X-ray beam perpendicularity to the image receptor  100  100  Image quality  100  100   High contrast resolution  100  100   Low contrast  100  100  Grid artefacts  88.2  88.2  AEC—FS   Verification of AEC optical density (OD)  0  50   Verification of AEC sensors  100  100   AEC kV compensation  100  100   AEC thickness compensation  100  100  AEC—CR and DR   Verification of receptor-air kerma  100  100   Verification of AEC sensors  77.8  77.8   AEC thickness compensation  77.8  77.8  Viewing conditions   Viewing box luminance  83.3  100   Viewing box uniformity  33  66.7   Ambient light (viewing box room)  33.3  83.3   TG18 QC test  100  100   Artefacts  100  100   Monitor uniformity  100  100   Ambient light (monitor room)  37.5  75  Test  Passed (%)  2015  2017  kV accuracy  88.2  94.1  kV reproducibility  100  100  Accuracy of exposure time  88.2  100  Tube output (80 kV @ 1 m)  100  100  Repeatability of output for fixed settings  100  100  Consistency of output in mGy/mAs  94.1  100  HVL at 80 kV  94.1  100  Correspondence light field and actual X-ray field  94.1  100  X-ray beam perpendicularity to the image receptor  100  100  Image quality  100  100   High contrast resolution  100  100   Low contrast  100  100  Grid artefacts  88.2  88.2  AEC—FS   Verification of AEC optical density (OD)  0  50   Verification of AEC sensors  100  100   AEC kV compensation  100  100   AEC thickness compensation  100  100  AEC—CR and DR   Verification of receptor-air kerma  100  100   Verification of AEC sensors  77.8  77.8   AEC thickness compensation  77.8  77.8  Viewing conditions   Viewing box luminance  83.3  100   Viewing box uniformity  33  66.7   Ambient light (viewing box room)  33.3  83.3   TG18 QC test  100  100   Artefacts  100  100   Monitor uniformity  100  100   Ambient light (monitor room)  37.5  75  Table 4. Comparison of the QC results from 2015 and 2017. Test  Passed (%)  2015  2017  kV accuracy  88.2  94.1  kV reproducibility  100  100  Accuracy of exposure time  88.2  100  Tube output (80 kV @ 1 m)  100  100  Repeatability of output for fixed settings  100  100  Consistency of output in mGy/mAs  94.1  100  HVL at 80 kV  94.1  100  Correspondence light field and actual X-ray field  94.1  100  X-ray beam perpendicularity to the image receptor  100  100  Image quality  100  100   High contrast resolution  100  100   Low contrast  100  100  Grid artefacts  88.2  88.2  AEC—FS   Verification of AEC optical density (OD)  0  50   Verification of AEC sensors  100  100   AEC kV compensation  100  100   AEC thickness compensation  100  100  AEC—CR and DR   Verification of receptor-air kerma  100  100   Verification of AEC sensors  77.8  77.8   AEC thickness compensation  77.8  77.8  Viewing conditions   Viewing box luminance  83.3  100   Viewing box uniformity  33  66.7   Ambient light (viewing box room)  33.3  83.3   TG18 QC test  100  100   Artefacts  100  100   Monitor uniformity  100  100   Ambient light (monitor room)  37.5  75  Test  Passed (%)  2015  2017  kV accuracy  88.2  94.1  kV reproducibility  100  100  Accuracy of exposure time  88.2  100  Tube output (80 kV @ 1 m)  100  100  Repeatability of output for fixed settings  100  100  Consistency of output in mGy/mAs  94.1  100  HVL at 80 kV  94.1  100  Correspondence light field and actual X-ray field  94.1  100  X-ray beam perpendicularity to the image receptor  100  100  Image quality  100  100   High contrast resolution  100  100   Low contrast  100  100  Grid artefacts  88.2  88.2  AEC—FS   Verification of AEC optical density (OD)  0  50   Verification of AEC sensors  100  100   AEC kV compensation  100  100   AEC thickness compensation  100  100  AEC—CR and DR   Verification of receptor-air kerma  100  100   Verification of AEC sensors  77.8  77.8   AEC thickness compensation  77.8  77.8  Viewing conditions   Viewing box luminance  83.3  100   Viewing box uniformity  33  66.7   Ambient light (viewing box room)  33.3  83.3   TG18 QC test  100  100   Artefacts  100  100   Monitor uniformity  100  100   Ambient light (monitor room)  37.5  75  Facilities were advised to appropriately mark all entrance doors and to disable non-authorized entrance to the X-ray rooms with proper one-way door locks. Almost all doors are now closing properly, and all of the X-ray rooms have a proper signage for ionizing radiation and alerts for pregnant women. However, none of the damaged consoles were repaired. Follow-up results of the X-ray generator performance showed that kV accuracy failure percentage was lowered (from 12 to 6% of the units) and accuracy of exposure time and the consistency of output now met criteria for all units. The HVL value and field alignment discrepancies were improved to an acceptable level. However, no improvement was made regarding scatter attenuating grid. Half of the FS units that showed out of tolerance results of the verification of AEC OD under reference conditions were fixed. In contrast, no improvement was recorded in the performance of the compensation segment of AEC systems for CR and DR units. Most of the radiological rooms that were too bright were darkened and unacceptable viewing box was replaced. On viewing boxes that failed in uniformity, lamps were replaced and boxes were cleaned so now 34% do not meet criteria. DISCUSSION First results showed few problems with technical parameters mainly because of poorly maintained equipment. The institutions did not have any tools to perform QC procedures which could give them the quantitative information. X-ray units that showed issues with the generator performance were adjusted by the service engineer immediately upon the recommendations given by medical physicists. This clearly shows that the quantification of the problem led to a better argumentation to the management for financial investment in the maintenance of the equipment. QC results from the first year revealed mainly problems with automatic exposure control system. The purpose of AEC is to deliver consistent and reproducible exposures to the image receptor across a wide range of anatomical thicknesses and tube potentials(10). Since it terminates the exposure when a predetermined amount of radiation to the image receptor has been reached, it can tailor the dose delivered to the patient but only when it is properly used and well calibrated. All the FS units and 22% of the CR/DR units were not calibrated properly, so radiographers had to use manual exposures on units equipped with AEC system. It is visible that in some facilities with AEC problems manufacturer engineers did not repair the compensation issues. Hopefully, the implementation of the new directive to national legislation will motivate these facilities to revise their investment policies regarding maintenance.(2) Improvements regarding viewing conditions gave excellent results in clinical application. Low-cost repairing within this segment significantly upgraded possibilities to provide an adequate diagnostic information(11). Comparison of the results from initial and follow-up QC tests showed a lot of improvement—equipment is maintained more frequently, and some old units were replaced. Another three CR units will be replaced with DR units in the beginning of 2018. It is expected that during 2018 and the beginning of 2019 all units that are using FS cassettes will be replaced by CR plates at least and all units without AEC system with new digital ones. Besides the recommendations for regular maintenance of the units, institutions were advised to acquire their own equipment for daily and monthly QC testing. Every facility purchased PMMA blocks, image quality phantom and sensitometer and densitometer—for facilities using FS systems. QC manuals with baseline values and frequencies for every test were developed. Education and training for daily and monthly testing was performed for radiographers. Daily tests that are performed in radiography are visibility of the grid and grid artefacts, repeatability of AEC system in terms of mAs and DDI values for CR and DR and mAs and OD value for FS system using 15 cm of PMMA. Dark room and film developer QC testing is performed daily for facilities that use FS system and this allows them to monitor parameters of the developing device to achieve optimal performance(12). Monthly tests performed are alignment of the light field with actual X-ray field, image quality—high contrast resolution, visibility of the grid and grid artefacts, repeatability of AEC system in terms of mAs and DDI values for CR and DR and mAs and OD value for FS system for 15 cm of PMMA and AEC thickness compensation for 10, 15 and 20 cm of PMMA. The standard operative procedure is that procedures with out of tolerance results are repeated to avoid human error. If the results are still not acceptable, a medical physicist from CHC Rijeka is to be informed in order to perform more detailed tests of respective parameter and advice for solution. Daily and monthly checks that are performed by radiographers enhanced their practice in many ways—they can react more promptly if something is out of tolerance and now they have measurable parameters to present to management and ask for urgent adjustment of the X-ray unit. CONCLUSION These collaborations showed that implementing a full QA program which, apart from QC includes optimization, is necessary and improves radiological practice. Radiologists receive images with higher quality while radiation exposure to patient is kept as low as reasonably achievable. After periodical QC implementation, next task was the establishment of DRL’s and optimization of the radiological practice which is an ongoing process. With this collaboration all institutions became aware that they need medical physics support in their everyday practice. Besides the testing of the equipment, which is fundamental, medical physicists are involved in optimizing and improving clinical practice. They measure radiation dose and examine image quality that directly affects the patient. Medical physicist is in charge for training radiographers and other staff members on quality assurance and radiation protection issues. Above mentioned makes a medical physicist, along with the radiologist and the radiographer, an important part of the radiology team with the aim of providing responsible, justified and safe use of ionizing radiation. REFERENCES 1 United Nations Scientific Committee on the Effects of Atomic Radiation Sources and effects of ionizing radiation: UNSCEAR 2008 report to the General Assembly with scientific annexes ( 2010), New York. 2 European Council Directive 2013/59/Euratom on basic safety standards for protection against the dangers arising from exposure to ionizing radiation and repealing Directives 89/618/Euratom, 90/641/Euratom, 96/29/Euratom, 97/43/Euratom and 2003/122/Euratom. OJ of the EU. L13; 57: 1–73 ( 2014). 3 Law on Radiation Protection and Safety. Regulation on the conditions and radiation protection measures for performing activities with electrical devices that produce ionizing radiation. Official gazette, April 8 ( 2013). 4 International Atomic Energy Agency. Roles and responsibilities, and education and training requirements for clinically qualified medical physicists. IAEA human health reports No. 25 ( 2013), Vienna. 5 American Association of Physicists in Medicine. The role of the clinical medical physicist in diagnostic radiology. AAPM report 42 ( 1994), New York. 6 International Atomic Energy Agency. Radiation protection and safety of radiation sources: international basic safety standards. General safety requirements part 3 ( 2014), Vienna. 7 European Commission—Radiation Protection No. 162. Criteria for acceptability of medical radiological equipment used in diagnostic radiology, nuclear medicine and radiotherapy. Directorate-General for Energy Directorate D—Nuclear Safety & Fuel Cycle Unit D4—Radiation Protection ( 2012). 8 Samei, E. et al.  . Assessment of display performance for medical imaging systems. Report of the American Association of Physicists in Medicine (AAPM) Task Group 18, Medical Physics Publishing, Madison, WI, AAPM On-Line Report No. 03, April 2005. 9 Institution of Physics and Engineering in Medicine and Biology. Measurement of the performance characteristics of diagnostic X-ray systems used in medicine, Part I: X-ray tubes and generators. IPEM Report No. 32, York ( 1995). 10 Automatic exposure control devices. IAEA Human Health Campus, Retrieved 16 December 2016. 11 Moshfeghi, M., Shahbazian, M., Sajadi, S. S., Sajadi, S. and Ansari, H. Effects of different viewing conditions on radiographic interpretation. J. Dent. (Tehran, Iran)  12( 11), 853– 858 ( 2015). 12 Wolfgang, L. The role of the darkroom in radiograph quality control. N. Y. State Dent. J.  64( 6), 26– 29 ( 1998). Google Scholar PubMed  © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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Radiation Protection DosimetryOxford University Press

Published: May 4, 2018

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