Computed Tomography Diagnostic Reference Levels in India: Results from the First National Survey

To conduct the first nationwide survey of patient radiation doses from adult computed tomography (CT) examinations for establishing national diagnostic reference levels (DRLs) in India.

The study included data from a total of 6454 patients for five categories of CT examinations selected for the dose survey, collected from 76 CT facilities across the country. Descriptive statistical analysis of the distribution of medians of volume computed tomography dose index (CTDI_vol) and dose length product (DLP) provided the quartile values. The national DRLs for adult CT examinations in India are proposed based on the 75th percentile (third quartile) of distribution of medians.

National DRLs of India in terms of CTDI_vol are 70, 21, 13, 13 and 15 mGy, for head, neck, thorax, abdomen-pelvis routine and abdomen-pelvis multi-phase examinations, respectively. The corresponding DRLs, in terms of DLP, are 1279, 1059, 602, 956 and 2340 mGy-cm, respectively. The results show that the India's national DRLs, in terms of CTDI_vol, are in a similar range to those of other countries, whereas Indian DRLs in terms of DLP are comparatively higher. Large variations were observed in exposure parameters and range of dose delivered in similar examination categories across the facilities which may be due to use of non-optimised scan protocols.

A substantial potential for dose reduction is evident, as higher DLP values across almost all scan categories indicate the use of longer scan lengths than necessary for diagnostic purposes.