Early CT findings after interstitial radiation therapy for primary malignant brain tumors.

The CT findings after interstitial radiation therapy for brain tumors have not been extensively described. We evaluated retrospectively the CT scans of 13 patients who were treated with brachytherapy for malignant glioma. We found no typical CT appearance that differentiates recurrent tumor from radiation effect. After undergoing brachytherapy, eight of the 13 patients scanned demonstrated enhancement of brain tissue beyond the margins of the original enhancing tumor mass. In most cases, the pattern of enhancement diminished and extended more peripherally from the central necrotic area with time. We also report a new CT finding of focal calcification developing at the site of the radioactive implant.