CT slice. Slice of a CT scan. The manual contours of (red) the prostate and (green) the rectum, as well as (brown) the ROI defined as the prostate gland extended with a margin of 8 mm are drawn. The rectal distension occurred between the CT and the CBCT scans was estimated by calculating the value of F as defined in Equation 2. Ī
) was calculated within the red region on the CT (CBCT after bony rigid alignment) scan. Ī
) was calculated within the intersection of the green and the brown regions on the CT (CBCT after bony rigid alignment) scan.