Fig. 1

Schematic representation of ROI selection in the mesorectum for different prognostic statuses (dotted arrow indicates positive CRM, solid arrow indicates positive EMVI). The ROIs of the MAT (solid circle a, b and c) were placed within 5 mm of the tumour, or in the upper or lower slice closest to the outline of the largest cross-section of the tumour if there was no available space. The ROIs of MDT (dotted circle d) were placed on the mesorectum contralateral to the semiperimeter tumour cross-section or at least 10 mm away from the full-perimeter tumour cross-section. The ROIs of both the MAT and MDT were drawn to avoid the tumour infiltration area, the invasion vasculature, and suspicious lymph nodes or dissemination