A size-specific effective dose for patients undergoing CT examinations

Abstract

This study aims to develop a simple method for estimating the size-specific effective dose using the ImPACT software. The size-specific effective dose was calculated from the images of patients who underwent CT examinations of the thorax and abdomen regions. Volume computed tomography dose index (CTDIvol) and mAs data were obtained from the dose report. The average of mAs and CTDIvol were used to determine the normalized CTDIvol (nCTDIvol). Patient size was expressed in effective diameter (Deff), and was measured at nine slices along the z-axis. The normalized size-specific dose estimate (nSSDE) was then calculated. The normalized size-specific effective dose was obtained in the "effective dose" text-box by inputting an arbitrary value in the "CTDI (air)" text-box so that the "CTDIvol" text-box showed a similar value to the nSSDE. The results show that the normalized size-specific effective dose decreases exponentially with increasing patient size. The results are consistent with results of Sahbaee formula to within 20%.