RECTAL CANCER MRI

Australian Rectal cancer site

High-resolution MRI

High-resolution MRI of the rectum is the recommended primary staging imaging investigation.[8][9][10][11][1][12]

Protocol

Coverage: L5/S1 to anal verge

The tumour and all mesorectal lymph nodes at and above the level of the tumour should be covered by high-resolution (HR) sequences.

Low tumours within 5 cm of the anal verge need imaging angled to the anal canal to assess the relationship of tumour to the levator ani muscles and anal sphincter complex.

The protocol is set out in Table 7.2.

Notes:

• • Anterior saturation bands should be used. Phase L-R can be useful in the axial images to reduce breathing artefact.

  • An antiperistaltic agent (e.g hyoscine butylbromide) can be given to reduce artefact from adjacent bowel motion.

  • Patients may fast, but there is no other bowel preparation required. The use of per-rectal fluid or gel is not recommended, as it can distort the rectal wall.[1]

    • Table 7.2. Rectal cancer MRI protocol

FOV: field of view; HR: high resolution

† optional but recommended

‡ within 5cm of anal verge

^ calculated using acquired matrix measurements. Interpolated or zipped measurements do not give the required spatial resolution.