Estimation of organ doses based on patient-specific characteristics undergoing chest-abdomen-pelvis CT examinations of tube current modulation

Abstract This study aimed to investigate the strength of the correlation between organ doses and four computed tomography (CT) dose metrics, and to explore a method for rapidly estimating organ doses in patients undergoing chest-abdominal-pelvic (CAP) CT examinations. We retrospectively collected DICOM images of 43 patients who underwent CAP CT examinations. These images were imported into Archer-CT for organ segmentation and dose calculation. Then, regarding the six radiosensitive organs (spinal cord, lung, oesophagus, stomach, liver, and bladder) that were included in the study, various radiation dose metrics were calculated based on size-specific dose estimate (SSDE) derived from equivalent water diameters ( Dw ), i.e. SSDE centre based on D w in the centre of the scan range, the SSDE mean based on the mean SSDEs of all slices, and the organ-specific SSDE organ for various organs, as prescribed in American Association of Physicists in Medicine Report 220. Subsequently, correlation analyses were applied to evaluate the relationship between the organ doses and each radiation dose metric and to derive conversion factors for rapid estimation of organ doses. The ranked linear correlations of the four dose metrics with each organ dose were as follows, in descending order: SSDE organ , SSDE mean , CTDI vol , and SSDE centre . The strongest and weakest correlations were found between organ dose to liver and SSDE Liver ( R 2 = 0.88),and between organ dose to the bladder and SSDE Bladder ( R 2 = 0.62) respectively, while the R 2 of the rest of the organ doses to SSDE organ was around 0.8. The conversion coefficients for estimating organ doses based on SSDE organ for the spinal cord, lung, oesophagus, liver, stomach, and bladder were 0.75, 1.24, 0.89, 1.17, 1.18, and 0.83, respectively. Higher correlations were observed between organ doses and SSDE organ for organs involved in this study during CAP CT examinations. Thus, SSDE organ can be used to simplify and estimate the individualised organ dose for CAP CT examinations.