Figure 1:

Oblique axial view anatomy. (A) Illustration and (B) high-resolution axial oblique T2WI demonstrate the mesorectal fascia, mesorectum and rectal wall layers. On MRI (B) 3 layers are mostly visible: mucosa, as the innermost thin hypointense layer, submucosa, as a middle hyperintense layer and muscularis propria, as the outer hypointense layer. (C) Illustration demonstrating the T-category. T1 - tumor up to submucosa; T2 - tumor up to muscularis propria; T3 - tumor beyond muscularis propria (T3a < 1 mm, T3b: 1–5 mm, T3c: 5–15 mm, and T4d > 15 mm); T4 - tumor infiltrates the peritoneal reflection (T4a) or other pelvic organs and structures (T4b).