Assessment and control of medical exposure in Pakistan

Abstract

Medical procedures, such as diagnostic x-rays, computed tomography, nuclear medicine, and radiation therapy are by far the most significant and largest source of human-made radiation exposure to the general public. Diagnostic radiology constitutes approximately 95 percent in number of all medical procedures involving the ionizing radiation. Several technical factor contributes to the wide variations in patient dose and it has been evident from various international dose surveys. Reference dose levels provide a framework to reduce this variability and aid in the optimization of radiation protection. The main purpose of this study was to survey image quality and the entrance surface doses for patients in radiographic examinations in Pakistan for the first time and to perform comparisons with diagnostic reference levels of European Commission. And to establish, a baseline for national reference dose levels for six of the most common x-ray examinations (eight projections): chest, abdomen, pelvis, skull, KUB and lumbar spine and CT examination. A collaborative survey was conducted in 10 randomly selected public hospitals for x-ray diagnostic examination and 2605 patients exposed during different x-ray procedures were included in this survey. For the first time three different Monte Carlo base software PCXMC, Dosecal and CALDose_X were used for calculating the entrance surface doses (ESD). The difference between maximum and minimum individual patient dose values varied up to a factor of 9 for chest, 19 for abdomen, 17 for skull AP, 14 for skull LAT, 12 for pelvis, 38 for KUB, 10 for lumbar spine AP, and 6 for lumbar spine LAT x-ray examinations. The mean ESD were then compared with diagnostic reference levels of European Commission and it was found that mean ESD of Pakistani hospitals were higher up to 1.2 times to 7 times in different x-ray examinations. Water phantom with TLDs were used in next phase of survey to verify the results obtained from above said three softwares.<br />Five hospitals were selected and measurements were made on skull, abdomen, pelvis and lumbar spine examination using the daily routine exposure parameters. Effective doses were also calculated from the ESD values by using the Dosecal software. The mean effective doses for chest, skull, pelvis, abdomen and lumbar spine examinations were compared with mean effective doses of all these examinations in England calculated by NRPB. It was found that effective doses were 1.5 to 12 times higher in different diagnostic examination as compared with effective doses in England for the same procedure. In this survey x-ray film rejection rates were also measured in all ten hospitals and it was found that film rejection rates are higher than internationally recommended film rejection rates. Wide dose differences may emerge from complex causes, but in general, low peak kilovoltage and high mAs, insufficient filtration, low sensitivity of screen/films in correct FFD setting, lack of proper training and absence of DRLs are associated with higher doses. A survey for computed tomography examination in Pakistan was also conducted in six hospitals. CTDI, DLP and effective dose values obtained from this survey were then compared with EU guide lines and other countries. CTDI and DLP values were less then EU guide lines but higher then England. The results of this work can be used as the base for the formulation of national diagnostic reference levels (DRLs) for x-rays and CT in Pakistan.