Estimation of radiation dose and associated cancer risks from computed tomographic scans

Abstract

Absorbed dose of 100 patients during CT imaging procedure in a renowned hospital of Dhaka city were measured using Thermoluminescence (TL) chips. For dose measurement at the scanned region TL chips were sealed in a uniform manner with 10 rows and 5 columns between two polythene sheets. Fifty TL chips were used for each CT scan at the scanned region. These TL chips were readout using the Harshaw TLD Reader (model 3500) of Health Physics Division, Atomic Energy Center, BAEC, Dhaka. The patients were selected randomly based on three different CT types e.g. CT abdomen, CT chest and CT head. Applied voltage, applied current, exposure time, scanning length, dose length product (DLP), age and sex of the patient were recorded for each CT scan. The maximum value of absorbed dose was obtained 79.05 mSv for CT head scanning and the minimum value of it was obtained 1.27 mSv for CT abdomen scanning. The effective dose was calculated by multiplying DLP value obtained from the dose report with the conversion coefficient provided by European Guidelines for multi-slice computed tomography (MSCT). The maximum and minimum value of effective dose was obtained 45.93 mSv for CT abdomen and 1.24 mSv for CT head scanning respectively. The lifetime attributable risk (LAR) of cancer was also estimated using web based calculator X-rayrisk.com. It was observed that the LAR of cancer increases with the decrease of patient age and the increase of the effective dose. Therefore, pediatric patients are in higher radiation risk than adult patients. So it is very important in radiology departments to monitor and control the dose of the patients during CT imaging procedures and the dose should always be as low as reasonably achievable.