Evaluation of the population exposure from X-ray uses in medical field

Abstract

This study was undertaken to evaluate the population exposure ITomthe X-ray uses in medical field. The entrance skin dose (ESD) was measured directly by placing LiF TLOs on the patients skin during the radiological examination in one Govl. hospital and in two private clinics. These were readout using Harshaw 3000A TLO reader system. The following types of examination were considered for the evaluation of ESD as well as organ dose: Abdominal; Chest; femur; Full spine; Hip; Humerus; IVP; Pelvis; Lumbo sacral spine; Cervical spine; Scapula; Shoulder; Skull; Barium swallow; Mammography; CT brain & CT abdominal. Different parameters such as kVp, mAs, half value layer (HVL) were also collected and evaluated for each type of examination in this study. The mean ESO values measured: are for abdomina! examination 0.19 mGy, chest examination 0.25 mGy, femur examination 0.37 mGy, full spine examination 0.27 mGy, hip examination 0.17 mGy, humerus examination 0,20 mGy, lVP (Intra Venus Pylogram) examination 0.62 mGy, pelvis examination 0.53 mGy, Jumbo sacral spine examination 4.14 mGy, cervical spine examination 0.35 mGy, scapula examination 0.39 mGy, shoulder examination 0.43 mGy, skull(head) examination 0.82 mGy, barium swallow examination 3.9 mGy, mammograpby examination 337.67 mGy, CT (abdomen) examination 18.28 mGy, CT (brain), examination 98,97 mGy. The ESO values for chest, hip, pelvis, lumbo sacral spine, skull (head), mammography, CT brain and abdominal examination are compared with the values world wide. Most of these values were in reasonably good agreement with the doses of other countries. The values for rest could not be compared due to the unavailability of sufficient data. For mammography and CT brain examination the dose value found is much higher than other countries. The comparison was made using the mean dose and spread in dose, It was also seen that the dose for #- .-- -- - lumbo sacral spine examination IS much higher than other radiographic examinations. Three computer software such as X-DOSE, PRE.PARE (Prediction of Patients Doses in Radiological Examination) and CT-DOSE were used to calculate the organ doses. X-DOSE and PRE-PARE uses kVp, mAs, ESD value and HVL as input and returns organ doses as output. These software calculate organ dose using Monte Carlo technique. From the calculated organ doses it is observed that Jumbo sacral spine examination is the greatest contributor to the organ doses for most of the examination types. The other big contributors are chest, pelvis and barium swallow (fluoroscopy) examinations. For testes and ovaries dose hip and pelvis examination were found to be the largest contributor. The comparison between effective doses and EDE for different types of examinations indicates that lumbo sacral spine examination and CT (both type) examinations are the major contributor to the effective dose and also the EDE (effective dose equivalent). The results presented in this work would partly serve as base line data on patient skin dose as well as organ dose distribution for different types of radiological examination in Bangladesh. Moreover the data can be used for evaluation of radiation risk factor of patients undergoing various types of radiological examination.