An indwelling brachytherapy balloon catheter: potential use as an intracranial light applicator for photodynamic therapy.

An indwelling balloon applicator developed for postoperative intracavity afterloading brachytherapy was evaluated for photodynamic therapy (PDT). Following tumor resection, the applicator is positioned in the center of the resultant cavity and the balloon is inflated with a scattering solution. The liquid-filled balloon stabilizes the resection cavity ensuring a constant and simple geometric shape during treatment. The catheter is brought out through the skin and adjusted so that 1-2 cm projects above the scalp surface. Measurements of light distribution in a phantom model surrounding the balloon catheter, show that it may be used to deliver sufficiently uniform light doses during PDT. The light distribution is uniform to within 5% when the balloon is filled with a scattering medium. Based on simple assumptions, it is shown that the applicator can be used to deliver a sufficient optical dose to brain tissue at a depth of 1 cm in less than 1 h. The applicator has already been used for brachytherapy in 72 patients with few complications. A new treatment protocol employing the combination of both fractionated intracavity brachytherapy and PDT is currently being planned.