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Liquid-Filled Balloon Brachytherapy Using 68Ga Is Effective and Safe Because of the Short 68-Minute Half-Life: Results of a Feasibility Study in the Porcine Coronary Overstretch Model

BackgroundLiquid-filled balloons for coronary brachytherapy provide significant advantages over solid sources in dose homogeneity but carry the risk of life-threatening radiointoxication after balloon rupture and laboratory contamination in case of a spill. We hypothesized that the positron emitter 68Ga, with a half-life of only 68 minutes, was well suited to overcome these safety obstacles while providing full therapeutic efficacy. Methods and ResultsThe feasibility, efficacy, and safety of 68Ga liquid-filled balloon brachytherapy were investigated in the porcine coronary overstretch model. Four groups of 5 balloon-induced coronary lesions were irradiated with 8, 12, 16, and 24 Gy targeted to the adventitia. Ten unirradiated lesions served as controls. Segments treated with 16 or 24 Gy exhibited marked suppression of neointimal proliferation at 28-day follow-up, with quantitative parameters of intraluminal proliferation reduced to <20%. This beneficial effect was not compromised by untoward edge effects. Uninjured but irradiated vessels did not show histological signs of radiation damage. The 68Ga whole-body dose due to balloon rupture was estimated to be 5 rem/50 mCi treatment activity and compared favorably with that of 188Re (78 rem/50 mCi). Conclusions68Ga positron radiation suppresses neointimal proliferation at doses of 16 and 24 Gy. This biological efficacy, coupled with the attractive safety profile, suggests the selection of 68Ga as an attractive isotope for liquid-filled balloon brachytherapy.