Dose-length product to effective dose conversion factors for common computed tomography examinations based on Canadian clinical experience

摘要

Modern computed tomography (CT) scanners report the dose-length product (DLP). Although the DLP is related to patient dose and risk, it is unique to CT and is not useful for comparisons with other modalities. The International Commission on Radiation Projection (ICRP) uses the concept of effective dose (E), in units of J/kg or sievert (Sv), to quantify risk [1,2]. The E is a weighted sum of the organ doses, in which the weights represent the relative sensitivity of organs to radiation damage and their contribution to overall determinant from stochastic effects (cancer). Generally, the risk of a fatal cancer for adults is estimated at 5%/Sv [1] and is higher for children. DLP-to-E conversion factors have been derived and are useful in quickly estimating patient risk from the DLP values reported by CT systems [3,4]. Recently, the ICRP updated the tissue-weighting factors [1], which necessitates that the DLP-to-E conversion factors be updated as well. Several articles have proposed new DLP-to-E conversion factors for the case of a single CT scanner model [5,6]. Recently, Huda et al [7] published updated average conversion factors based on ICRP 103 but did not provide scanner-specific results.