Magnetic resonance imaging in rectal cancer.

MR imaging plays a key role in staging evaluation of rectal cancer. The cornerstone of staging MR involves high-resolution T2 imaging orthogonal to the rectal lumen. The goals of MR staging are identification of patients who will benefit from neoadjuvant therapy prior to surgery to minimize postoperative recurrence and planning of optimal surgical approach. MR provides excellent anatomic visualization of the rectum and mesorectal fascia, allowing for accurate prediction of circumferential resection margin status and tumor stage. MR has an evolving role for the evaluation of neoadjuvant treatment response, further triaging optimal patient treatment and surgical approach.