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. Author manuscript; available in PMC: 2023 Aug 1.
Published in final edited form as: Surg Oncol. 2022 Mar 18:101739. doi: 10.1016/j.suronc.2022.101739

Table 2.

T2W coronal plane to anal canal and different levels of anal involvement.

T2W coronal plane to anal canal Level of anal involvement
Tumor extends to the level of the internal sphincter but the muscularis propria of the rectal wall is intact with a fully preserved hypointense outer muscle coat. (MERCURY II; LEVEL 1)
Tumor also invades internal anal sphincter but interrupts the hypointense muscle coat without extension into the intersphincteric plane. (MERCURY II; LEVEL 2)
Tumor invades the intersphincteric space without involvement of the external anal sphincter/levator/puborectalis. (MERCURY II; LEVEL 3)
Tumor also invades the external anal sphincter and levator ani muscles. (MERCURY II; LEVEL 4)