Normal brain irradiation during stereotactic brain implants using radioactive iodine-125.

Stereotactic interstitial brain implants deliver locally high radiation doses to treat malignant gliomas. Dose to the surrounding normal brain from an 125I implant has been compared with the dose from an external irradiation technique. Results show that an implant offers a higher dose gradient around the tumor and hence a lower dose to the normal brain. Moreover, some irregular-shaped tumors, while ideal for a stereotactic implant, may be very difficult to treat with external beams without delivering a significant radiation dose to the normal brain. An implant seems to be dosimetrically superior to external irradiation for delivering large tumor doses.