MRI stands for magnetic resonance imaging. As with ultrasounds, there is no radiation given with this test. A powerful magnet is used to align the atomic nuclei in the body, typically focusing on water and fat content in the various tissues. Like a CT scan, the MRI is typically used to provide detailed images of the abdominal and pelvic organs and structures. It can be of particular use in staging of rectal cancers and in some institutions has replaced the rectal ultrasound for staging. In rare cases it is also used to look for recurrence of rectal cancers after initial treatment. Patients with claustrophobia need to discuss this with the doctor before the test is scheduled.