Design and dosimetry of a novel 90Y beta source to prevent restenosis after angioplasty.

Abstract

Post-dilatation irradiation of the vessel wall is currently under investigation for prevention of restenosis after balloon dilatation. For the irradiation, special sources were designed for animal experiments which would give equivalent irradiation conditions and doses to the vessel wall that would later be employed for human application. For the planned irradiations, a specially designed yttrium-wire of 0.45-mm diameter coated with a thin shrink tube to prevent contamination was deployed. Several leakage tests applied before and after application proved that the irradiation source was leakproof. Dosimetry was performed by using 0.1-mm-thick thermoluminescent dosimeters (TLD-100) calibrated against a primary standard. A shielding transport and application container was designed to facilitate the handling of the source during use, while reducing exposure of the medical personnel. The designed source proves to be flexible for the insertion into proximal coronary vessels, and positioning at the site of stenosis. It provides an optimum protection of the animal and requires little radiation protection efforts on behalf of the medical staff. Dosimetric calculations and measurements showed that a centering of the source inside the vessel could be achieved with a maximum deviation of 50% between maximum and average dose levels. A yttrium-90 beta brachytherapy source was designed which provides high flexibility within proximal coronary arteries, ensures an adequate centering inside the artery, and provides irradiation conditions to the vessel wall of the experimental animal comparable to the application inside a human artery.