Endovascular brachytherapy for the prevention of neointimal hyperplasia with ~(90)Sr seeds afterloading system in a rabbit restenosis model

Objective To evaluate the dose effect of intravascular radiation on the smooth muscle cells (SMCs) of arterial wall with an encapsulated 90Sr seeds afterloading system. Methods 18 rabbits were divided into three groups. In 12 rabbits, after endothelial denudation of one of the iliac artery randomly with 2.5 mm-balloon catheter, intravascular irradiation was performed with 90Sr seeds through afterloading using different dosages (16, 50 Gy at 2 mm from central axis of the radiation source). The control group was other 6 rabbits without intravascular irradiation. Then, 28 d after intervention, all of the rabbits were sacrificed and the vessels were excised with morphologic examinations. Results The thrombotic rate in 50 Gy group (3/6) was higher than that of control (0/6) and 16 Gy (1/6) groups. Additionally, in 50 Gy group, the media layer of vessel was covered by endothelium-like cells. Whereas in 16 Gy group, the indexes of stenosis and proliferation, the rate of SMCs proliferating cell nuclear antigen and apoptosis differed significantly from control. The indexes of stenosis, proliferation in 50 Gy group compared with the control and 16 Gy groups also showed significantly different. Conclusion The result demonstrated that neointimal proliferation was markedly depressed after 16 Gy irradiation, and was completely inhibited after 50 Gy irradiation. Aside from the high thrombotic rates, severe complications such as fibrosis, aneurysm formation and necrosis were not revealed.