MR imaging of the pelvis after radiation therapy

In 50 patients who had undergone pelvic irradiation, the authors have retrospectively evaluated the MR imaging tissue changes in the early acute (n=6), acute (n=15), subacute (n=17), and chronic (n=12) postradiation period. MR findings were compared with total radiation dose, calculated organ dosimetry, and clinical symptoms; histologic correlation was available in 14 cases. The frequency of severe bladder or rectal tissue changes rose from 2% in patients receiving less than 4,000 cGy to 38% and 30%, respectively, in those receiving greater than 4,000 cGy. In patients with no clinical symptoms, MR imaging demonstrated minor bladder changes in 47% and rectal changes in 10%. In patients with moderate or severe bladder or rectal symptoms, MR imaging demonstrated no changes in two whose total radiation dose was under 2,000 cGy. Extensive MR changes were recorded in the remaining patients. In the early acute phase, the only change detected was edema of the trigone or rectal mucosa