CT and MR imaging after placement of the GliaSite radiation therapy system to treat brain tumor: Initial experience

BACKGROUND AND PURPOSE: The GliaSite system delivers local, high radiation after brain tumor resection. We describe the imaging appearance of the device and the changes it causes. METHODS: Eight patients with brain tumors were treated with this system. After surgery, all underwent MR imaging, and one underwent CT. Five were examined 1 month after radioactive unloading and every 2 months thereafter (total, 6-9 months). Initial studies were assessed for balloon appearance and complications; subsequent studies, for signal intensity and enhancement. Three patients underwent multivoxel proton MR spectroscopy, and one underwent MR perfusion study. Spectra were reviewed for metabolites suggesting tumor; perfusion studies were reviewed for increased relative cerebral blood volume and flow. RESULTS: CT showed the hyperattenuating balloon with considerable artifact. All MR images showed the device and adjacent brain. Follow-up studies showed enhancement and T2 hyperintensity in five patients. In one, enhancement progressively disappeared with no evidence of tumor recurrence. Another patient had progressive enhancement and low relative cerebral blood volume and flow; biopsy showed necrosis and inflammation. One patient had progressive enhancement and high choline levels (proved anaplastic astrocytoma). In another, T2 signal intensity and contrast enhancement progressed owing to tumor and bacterial infection. The last patient had a high choline level (proved radionecrosis); enhancement progressed over 5 months. In three, the device was removed early because of bleeding, mass effect, and therapeutic changes (no follow-up). CONCLUSION. Good balloon visualization was possible with MR imaging. After brachytherapy, all patients developed T2 hyperintensity; stable or progressive enhancement occurred with tumor recurrence and radionecrosis. High choline levels were suggestive of, but not necessarily diagnostic of, tumor.