Postirradiation changes in the rectum assessed at CT

This paper evaluates the postirradiation changes in the rectum and perirectal tissue with CT. In 54 patients who had undergone pelvic irradiation, the authors retrospectively evaluated the CT tissue changes in the early acute, acute, subacute, and chronic postirradiation period. CT findings in the rectum, perirectal fascia, perirectal fat, and presacral space were compared with calculated organ dosimetry. MR images were available in 27 patients. No postirradiation changes were observed in any tissue in patients receiving a total radiation dose of under 40 Gy. In patients receiving 40 Gy and above, thickening of the rectal wall was seen in 15%, thickening of perirectal fascia and increasing attenuation of perirectal fat in 65%, and widening of presacral space in 20%. Increasing attenuation of perirectal fat showed high signal intensity in 40% and low signal intensity in 60% on T2-weighted images. CT rectal changes were seen above 40 Gy after irradiation. Evaluation of CT findings after irradiation may assist in differentiating recurrent or residual tumor from postirradiation changes