Distribution of accuracy values for each coregistration method across the
study sample. Coregistration accuracy was assessed for our linearized
iterative boundary reconstruction (LIBR) method, the rigid point-based
registration (PBR) method, and the multiscale spectral embedding
registration (MSERg) method using the Dice similarity coefficient (DSC),
the modified Hausdorff distance (MHD), and the target registration error
(TRE). The LIBR method produced lower TRE, DSC, and MHD than the rigid
PBR method across all features evaluated (external rectal contour,
internal rectal contour, and tumor bed) and also produced lower TRE,
DSC, and MHD than MSERg along the internal rectal wall.