Intracoronary Radiation for Prevention of Restenosis

Abstract

Background —Intravascular irradiation with β-emitters has been proposed for inhibition of restenosis in coronary arteries after balloon angioplasty or stent implantation. Previous studies have shown the effectiveness of γ-radiation to prevent recurrent restenosis, even in the presence of an implanted stent. The limited range of β-particles compared with γ-radiation, however, opens the question of whether absorption and scattering of β-particles by stent struts will cause significant perturbations in the uniformity and magnitude of the radiation dose, which may in turn compromise treatment. Methods and Results —Nine different stents were deployed with a balloon filled with a β-emitting radioactive liquid. Dose distributions were measured with Gafchromic film. Stents varied significantly in their absorption of β-particles. Some stents, constructed of fine meshed wires, produced minimal dose perturbations. Others, with thicker, high-atomic-number struts, induced cold spots in the dose distribution adjacent to the wires of ≤35%. Average dose reduction varied from 4% to 14% in the presence of various stents. Conclusions —Radiation strategy may have to be tailored to stent design. Stents that minimally perturb the dose distribution may be deployed before irradiation. Those that significantly alter the radiation dose might be better deployed after irradiation. Dose prescriptions may require modification if such perturbations prove clinically significant. Observed dose perturbations, however, decreased rapidly with increasing distance from the stent, which may mitigate the clinical impact of these findings. This, as well as the effects of stents on γ-dose distributions, requires further investigation.