Fig. 7. Limitation of qualitative evaluation based on SI of anatomical T2-weighted imaging for tumor response evaluation.

A. Baseline T2-weighted image (left) shows bulky mass with MRF involvement at 8 o'clock direction (arrow). DWI (right) demonstrates strong diffusion restriction within whole tumor area (arrow). B. On post-CRT T2-weighted image (left), intermixed SI of tumor and fibrosis at initial tumor site (arrow) is noted. Therefore, mrTRG 3 was reported. CRM involvement by treated tumor is still suspected at same direction (arrow) because CRM threatening is determined by whole treated tumor including fibrotic component on post-CRT MRI interpretation. On DWI (right), however, no diffusion restriction is seen in entire tumor area (arrow). Pathologic complete response was confirmed after TME (not shown). CRM = circumferential resection margin, DWI = diffusion-weighted imaging, MRF = mesorectal fascia, TME = total mesorectal excision