Liquid Embolization Material Reduces the Delivered Radiation Dose: Clinical Myth or Reality?

BACKGROUND AND PURPOSE: To be radiopaque, BAVM embolization products must contain high-atomic-number materials, which may also attenuate photon beams delivered with radiosurgery. This "shielding effect" has been invoked to explain why radiation therapy may be less effective for previously embolized BAVMs. To evaluate the impact of embolization material on radiation dose, we measured and compared the dose delivered to the center of an AVM model, before and following embolization with various materials in a LINAC. MATERIALS AND METHODS: Two in vitro AVM models were constructed by drilling interconnected tubular perforations in plastic water phantoms to simulate nidal vessels. Phantoms were designed to allow the positioning of a radiation detector at their center. One model was embolized with Onyx 18 and a second model, with a combination of Indermil, Lipiodol, tungsten powder, and Onyx 18. The radiation delivered was compared between embolized and nonembolized controls following irradiation with a standard 250-cGy dose. RESULTS: The mean dose of radiation delivered to the model embolized with Onyx alone was 244 +/- 5 cGy before and 246 +/- 5 cGy following embolization. The mean dose of radiation delivered to the model embolized with various agents was 242 +/- 5 cGy before, and 254 +/- 5 cGy after embolization. CONCLUSIONS: Embolic material did not reduce the radiation dose delivered by a LINAC to the center of our experimental BAVM models. The shielding effect may be compensated by scattered and reflected radiation.