Establishment of CT diagnostic reference levels in select procedures in South India

Background: To suggest South India CT diagnostic reference levels (DRLs) by collecting radiation doses for the most commonly performed CT examinations. Materials and Methods: A pilot study investigated the most frequent CT examinations. 110 CT sites were asked to complete a survey booklet to allow the recording of CT parameters for each of 3 CT examinations during a 1 year time period. Dose data such Volumetric Computed Tomography Dose Index (CTDIv) and Dose length product (DLP) on a minimum of 50 average-sized patients in each category were recorded to calculate a mean site CTDIvol and DLP value. The rounded 75th percentile was used to calculate a DRL for each site and the region by compiling all results. Results are compared with international DRL data. Results: Data were collected for 16,500 patients. All equipment had multislice capability (2-256 slices). DRLs are proposed using CTDIvol (mGy) and DLP (mGy.cm) for CT head (47 and 1041 respectively), CT chest (10 and 445 respectively), and CT abdomen (12 and 550 respectively). These values are lower than current DRLs and comparable to other international studies. Wide variations in mean doses are noted across the region. Conclusion: Baseline figures for South India CT DRLs are provided on the most frequently performed CT examinations. It was noted that there was a wide variation in mean doses among the CT scanners used during diagnosis. The differences in CT doses between CT scanner departments as well as identical scanners suggest a large potential for optimization of examinations.