Preliminary diagnostic reference levels for computed tomography examinations in Uttarakhand, India

Computed tomography (CT) is an important imaging modality that is widely employed for patient diagnosis across the globe. However, its increased usage has made it a significant contributor to population exposure from diagnostic X-rays. To optimize radiation exposure in CT, it is recommended to determine diagnostic reference levels (DRLs) in terms of the two measurable dose metrics, namely, computed tomography dose index (CTDI) and dose-length product (DLP). The present study was aimed to carry out an extensive survey of CT doses in Uttarakhand state of India. Radiation dose measurements were conducted on 48 CT scanners for three routine examinations (head, thorax, and abdomen) to obtain CT dose data for establishing preliminary DRLs for CT. Dose measurements were performed using an ion chamber positioned within designated grooves into two concentric water-equivalent head and body phantoms. Significant discrepancies in doses were observed, primarily due to variations in CT scanner types and scanning parameters. The DRL values were found to be lower than the corresponding European DRLs for all types of CT examinations. Additionally, the dose values for conventional, single, and double-slice scanners were relatively smaller compared to those of multi slice CT scanners. The estimated values of effective doses for the considered examination were also found below the corresponding results reported in literature. The findings highlight the need for ongoing monitoring and implementation of DRLs in CT practices to optimize patient doses. (author)