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Varying definitions of rectum in RT studies and practice
Superior:
Rectosigmoid junction
12 cm from the anus
Top of acetabula
At the level of
S3
Inferior level of sacroiliac joints
1 cm above the PTV
Inferior:
Anal verge
Ano-rectal junction
1cm below PTV
Ischial tuberosities
Ischial tuberosities + 2 cm
Circumferential:
Rectum + contents
Rectal wall
Anorectum