Establishment of institutional diagnostic reference level for CT imaging associated with multiple anatomical regions

Advancement of CT technology has increased the frequency of CT scanning in diagnosis. However, the concern on dose increment that related to radiation-associated health risk from CT also improved. The aim of this study was to establish an institutional diagnostic reference level (DRL) for computed tomography (CT) imaging associated with multiple or combined anatomical regions and compared with other international DRLs. CT dose data of 705 subjects were collected retrospectively from January 2015 until December 2017 at AMDI, USM, Malaysia. The most common CT examination of combined anatomical regions were neck-thorax-abdomen-pelvis (NTAP), thorax-abdomen (TA), thorax-abdomen-pelvis (TAP), and abdomen-pelvis (AP). CT dose data such as CTDI_vol, CTDI_w and dose-length product (DLP) were collected including contrast, non-contrast, single-phasic, and multiphasic examinations. The 50th and 75th percentile of dose distribution were calculated and compared with other established DRLs. TAP CT was the most frequently performed examination at AMDI (73%). The local dose values of multiphasic and non-contrast examinations were higher compared to single phasic and contrast study. The results show a weak correlation between different CT sequences and DRLs for AP examination. Local dose values reported for all CT examinations were below any international DRLs except for CT TAP (multiphasic) study. The institutional DRL for combined anatomical regions was established using the third quartile values of dose distribution and is categorized based on CT sequences. (paper)