Radioactive 133-Xenon gas-filled balloon to prevent restenosis: Dosimetry, efficacy, and safety considerations

Background - Ionizing radiation administered intraluminally via catheter-based systems using solid β and γ sources or liquid-filled balloons has shown reduction in the neointima formation after injury in the porcine model. We propose a novel system that uses a 133-Xenon (¹³³Xe) radioactive gas-filled balloon catheter system. Methods and Results - Overstretch balloon injury was performed in the coronary arteries of 33 domestic pigs. A novel ¹³³Xe radioactive gas-filled balloon (3.5/45 mm) was positioned to overlap the injured segment with margins. After vacuum was obtained in the balloon catheter, ≈2.5 cc of ¹³³Xe gas was injected to fill the balloon. Doses of 0, 7.5, 15, and 30 Gy were delivered to a distance of 0.25 mm from the balloon surface. The dwell time ranged from 1.0 to 4.0 minutes, depending on the dose. Localization of ¹³³Xe in the balloon was verified by a γ camera. The average activity in a 3.5/45-mm balloon was measured at 67.7±12.1 mCi, and the total diffusion loss of the injected dose was 0.26% per minute of the injected dose. Bedside radiation exposure measured between 2 and 6 mR/h, and the shallow dose equivalent was calculated as 0.037 mrem per treatment. Histomorphometric analysis at 2 weeks showed inhibition of the intimal area (intimal area corrected for medial fracture length [IA/FL]) in the irradiated segments of 0.26±0.08 with 30 Gy, 0.07±0.24 with 15 Gy, and 0.12±0.89 with 7.5 Gy versus 0.76±0.08 with control P<0.001. Conclusions - ¹³³Xe gas-filled balloon is feasible and effective in the reduction of neointima formation in the porcine model and safe for use in coronary arteries.