MRI evaluation of rectal carcinoma

MR imaging plays a key role in the initial staging of rectal cancer as well as in the assessment of tumor response to preoperative chemoradiotherapy. The excellent spatial and temporal resolution of MRI helps to evaluate the various key structures such as the mesorectal fascia, peritoneal reflection, and pelvic viscera that may be involved by the tumor. Although MRI is limited in nodal assessment, certain morphological characteristics on T1- and T2-weighted images may be useful for predicting nodal involvement. Diffusion weighted imaging is a useful functional imaging technique and may be helpful in evaluating tumor response following chemoradiotherapy.