Anti-restenotic effect of copper-62 liquid-filled balloon in porcine coronary arteries: Novel use of a short half-life positron emitter

Purpose: To determine the efficacy of the use of copper-62, a positron emitter with a half-life of 9.7 minutes, as an intracoronary brachytherapy (IRBT) source in the prevention of neointima formation (NF) following overstretch balloon injury (BI) in the porcine model. Methods and Materials: Sixteen swine were treated after BI to their left anterior descending (LAD), left circumflex (LCX), and/or right coronary artery (RCA). Twelve of the injured arteries received placebo and 10 received 25 Gy, delivered to 0.5 mm from the surface of the treatment balloon filled with liquid ⁶²Cu. Dosimetry was based on Monte Carlo calculations. Two weeks after treatment, the animals were sacrificed, and the treated coronaries were perfusion-fixed and stained. Intimal area (IA) and medial fracture length (FL) were analyzed by computer-aided histomorphometry. Results: The (⁶²Zn/⁶²Cu) generator, together with a rapid concentration process, was successful in delivering the short-lived ⁶²Cu at the high concentration required for intravascular brachytherapy (IVBT). The fracture length in the two groups was similar (2.10 ± 0.57; 2.02 ± 0.77; p = NS). Arteries studied showed significant reduction in NF (IA: 0.23 ± 0.47 mm² vs. 1.08 ± 0.57 mm²; p < 0.01. IA/FL = 0.09 ± 0.17 mm vs. 0.51 ± 0.21 mm; p < 0.01). Conclusions: This study demonstrated that use of liquid ⁶²Cu as an IVBT source is safe and feasible. All 16 swine tolerated the treatment well with no radiation-induced side effects or symptoms throughout the 2-week period. The isotope delivered the dose necessary to inhibit NF in the porcine coronary BI model.