[Post radiation changes in the rectum: assessment by MR imaging].

MRI findings of pelvic radiation changes in 42 patients were correlated with the tumor and critical tissue dose, time post treatment, and clinical symptoms. The severity of tissue changes was graded. The ability of MRI to differentiate post radiation tissue changes from residual or recurrent tumor was also correlated. Radiation tissue toxicity increased significantly when the dose exceeded 4,500 cGy, with the incidence of marked rectal changes rising from 8% to 44% with a dose greater than 4,500 cGy. All grades of tissue change were seen in the rectum of time from start of therapy. All patients who exhibited clinical grade 2 or 3 rectal changes showed moderate or severe changes on MRI. Grade 1 MRI changes indicative of mucosal edema were present in 33% of patients with no clinical symptoms. In conclusion, the gradation and sequence of MRI changes following radiation therapy to the pelvis have been documented and correlated with clinical findings. With its potential for distinguishing radiation change from recurrent tumor. MRI should prove to be of value in the assessment of the post-radiation pelvis.