Introduction
Imaging criterion | Key points |
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Extramural tumour spread (Fig. 1a) | For both colon and rectal cancer, extend of tumour spread beyond the muscularis propria should be measured (in mm) at the level of advanced invasion border and staged as <1 mm (T3a), 1–5 mm (T3b), 5–15 mm (T3c) and >15 mm (T3d). |
mrCRM (Fig. 1b) | Minimal tumour distance to the TME plane (mrCRM) should be measured; if clearance is less than 1 mm then the potential TME plane CRM is considered involved. |
Lymph nodes/vascular deposits (Fig. 1c) | Seems to be of no prognostic importance for local recurrence; N1c (tumour/vascular deposits) is of more concern and linked with extramural vascular invasion. |
mrEMVI (Fig. 1c) | Large vein extramural vascular invasion should be reported on both pre- and post-CRT scans and feedback to pathologists to aid their assessment of the specimen. |
Mucinous tumours (Fig. 1d) | Mucin component is readily identified on high-resolution MRIs. MR evidence of mucin within the tumour should be reported. |
Tumour response assessment (Fig. 1e, f) | No uniform threshold for MR RECIST and volumetric analysis. mrTRG is proven to be an independent prognostic factor. It is reproducible and enables to identify complete responders. No validated data concerning the added value of DWI or PET/CT. |
Early rectal cancer (Fig. 1g) | High-resolution MRI is accurate in staging early rectal cancer and allows identifying patients eligible for local excision. |
Low rectal cancers (Fig. 1h) | Tumour distance from the anal verge and intersphincteric plane status should always be reported. |
Beyond TME (Fig. 1i) | High-resolution MRI defines the safe surgical planes. Every pelvic compartment should be assessed for tumour spread. |