Patient dose resulting from CT examinations in Yazd, Iran

Background: With the introduction of computed tomography in diagnostic radiology a new and fundamentally different imaging modality has become available. Meanwhile, it is clear that the absorbed doses by the patients during CT were relatively high in comparison with those of other diagnostic radiology techniques. The aim of this survey was to determine the average absorbed dose in Yazd province by CT examinations, and to survey the potential risks per year by these examinations. Materials and Methods: This study was conducted in CT centers of Yazd during 2005-2006. The examination frequencies from 3 CT scanners were collected from all types of examinations. Effective dose were determined by CT Dose program (ImPACT CT patient dosimetry calculator). To use of this software, CTDIair, mAs and the thickness and number of slices in each type of CT examinations should have been measured. CTDIair was measured by pencil diode detector. Results: It was estimated that the annual collective dose and caput dose were about 32.48 Person-Sv and 0.038 mSv, respectively for the Yazd population, which is lower than that reported for other countries. The numbers of examinations per 1000 people of Yazd was 18 which were equal to many other countries such as UK and New Zealand. The mean effective dose of each CT examinations was also lower than that of other countries. Conclusion: Using the ICRP risk factors, radiation dose from CT could be induced to about 1 fatal cancer per year in Yazd. Therefore choosing CT imaging must be completely justified.