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Where rectum looses round shape in axial plane & loops
anteriorly to connect with sigmoid colon Commonly:
close to inferior level of SI joints.
Empty the rectum at EBRT simulatio
Avoid systematic error in PTV coverage
Delineate Rectum + contents
http://www.rtog.org/CoreLab/ContouringAtlases/Anorectal.aspxMichalski 2010 IJROBP
From: RTOG atlas
Use metallic marker at anal verge. Commonly:
bottom of ischial tuberosities
Recto-sigmoid
junction
Ano-rectal sphincter
Gay H, et al. Int J Radiat Oncol Biol Phys 2012;83(3):353-362.
Separate delineation of anus not specified…
EBRT
Anorectum