Catheter-based 32P beta-radiation after stent implantation in porcine coronary arteries: role of source-centering and geographical miss.

The present study examined the role of source-centering and geographical miss in vascular brachytherapy. After implantation of 13 mm long stents, 38 coronary arteries in 13 pigs were randomly assigned to centered brachytherapy (n = 13), eccentric brachytherapy (n = 13), or no radiation (n = 12). Geographical miss was avoided by careful placement of a 27 mm (32)P beta-radiation source. Restenosis was quantified by angiography, histomorphometry, and intravascular ultrasound at 28 days. Source-centering led to a significant (P < 0.001) reduction of in-stent area stenosis (centered radiation, 12% +/- 5%; eccentric radiation, 37% +/- 21%; control arteries, 41% +/- 13%). Despite 7 mm coverage of the edge segments, radiation was found to induce edge stenosis due to neointima formation and constrictive vascular remodeling. We conclude that centered radiation was superior to eccentric radiation in reducing in-stent luminal narrowing while radiation-induced edge stenosis was still observed despite extension of the radiation zone to 7 mm beyond the stent edges.