Anal canal cancer protocol (MRI)

Last revised by Andrew Murphy on 23 Mar 2023

Citation, DOI, disclosures and article data

Citation:

Weerakkody Y, Murphy A, Glick Y, et al. Anal canal cancer protocol (MRI). Reference article, Radiopaedia.org (Accessed on 18 Apr 2024) https://doi.org/10.53347/rID-9439

DOI:

https://doi.org/10.53347/rID-9439

Permalink:

https://radiopaedia.org/articles/9439

rID:

9439

Article created:

19 Apr 2010, Yuranga Weerakkody ◉

Disclosures:

At the time the article was created Yuranga Weerakkody had no recorded disclosures.

View Yuranga Weerakkody's current disclosures

Last revised:

23 Mar 2023, Andrew Murphy ◉

Disclosures:

At the time the article was last revised Andrew Murphy had no financial relationships to ineligible companies to disclose.

View Andrew Murphy's current disclosures

Revisions:

9 times, by 5 contributors - see full revision history and disclosures

Systems:

Gastrointestinal

Tags:

mri protocol, stub, refs

Synonyms:

Pelvic MRI protocol for anal canal cancer assessment
MRI protocol for assessment of anal cancer
MRI protocol: anal canal cancer
MRI protocol: anal cancer

MRI protocol for anal canal cancer is a group of MRI sequences put together to asses extension and stage anal canal tumours.

Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's and referrer's preference, institutional protocols, patient factors (e.g. allergy) and time constraints.

No special patient preparation is usually needed for the anal canal MRI (cf. other bowel MRI protocols). An endorectal coil should not be used as it can be really painful due to friable tumour mucosa ⁵.

Sequences

A good protocol for this purpose would include:

T1 weighted
- plane: axial whole pelvis
- sequence: fast-spin echo (T1 FSE) or gradient (T1 MPRAGE)
- purpose: anatomical overview (some institutions replace this sequence for T2 weighted images of the whole pelvis)
T2 weighted
- plane:
  - axial whole pelvis
  - anal canal centred high-spatial-resolution images (small FOV) on three planes ²
    - axial: perpendicular to the long axis of the anal canal
    - coronal: parallel to the long axis of the anal canal
    - sagittal
- sequence: T2 FSE, high-resolution T2-weighted sequences with the small FOV images
- purpose:
  - whole pelvis: anatomical overview
  - small FOV: delineation of anal canal layers allowing evaluation of tumour depth (hyperintense submucosa, hypointense muscularis propria, and hypointense mesorectal fascia) ²
    - coronal images aid in assessing for extension along with the internal and external sphincters
diffusion-weighted imaging (DWI)
- plane: axial
- sequence: DWI: B=0, B=1000 and ADC
- purpose: evaluation of the tumour cellularity; assessment of tumour recurrence after treatment ⁴
postcontrast sequences
- most institutions do not include post-contrast images on the assessment of anal canal tumours as it is unlikely to give additional information to the high-resolution T2 images ^2-5