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Figure 1: (a) Sagittal plane presenting the rectal contours of the initial and followup simulation computed tomography. (b) Examples of maximal radial distance and CAR in midaxis. After the most different area between yellow (initial computed tomography) and green (followup computed tomography) contours was indicated, a necessary radius from the isocenter of the yellow to cover the green (blue line) was defined as maximal radial distance. The rate of red intersection area of the yellow and the green was defined as common area rate 
