Alikhani B, et al. - The link between the size-dependent conversion factor (f_size) and the body mass index (BMI) in patients who underwent CT examinations of the torso, head, or knee. It was also determined if BMI could be substituted for the anterior-posterior (AP) and lateral (LAT) dimensions for the estimation of f_size. It was possible to estimate f_size based on BMI for the torso and head and knee CT, which facilitated calculation of the probable size-specific dose estimates (SSDE) before image acquisition according to the presumed volumetric computed tomography dose index (CTDI_vol) provided by the scanner. This approach was shown to be advantageous over the traditional calculation of f_size by the AP and LAT dimensions by offering data on the expected patient dose prior to image acquisition.