Use of Synchrotron Radiation Microangiography to Assess Development of Small Collateral Arteries in a Rat Model of Hindlimb Ischemia

Abstract

Background Current methods of angiography cannot provide images of arteries measuring <200 μm in diameter. We have recently developed a new angiography system that uses monochromatic synchrotron radiation and a high-definition video system with a spatial resolution of 30 μm. In the present study, we applied this microangiography system to visualize small arteries in normal and ischemic rat limbs and investigated the development of collateral arteries. Methods and Results Microangiography was performed in the normal and the ischemic limb 4 weeks after the excision of the femoral artery. In the normal limb, up to the fourth branches of the iliac and/or femoral arteries (diameter <100 μm) were readily identified. Some of these branches were found to perfuse the distal thigh area. In the ischemic limb, an extensive structural remodeling of the vascular network was observed. Numerous small arteries had developed from the branches of the iliac artery to constitute a fine arterial network, the so-called “midzone,” which was composed of linear, normal-appearing arteries and those with an undulating, unbranched appearance. Conclusions The small collateral artery network was angiographically visualized with a resolution limit <100 μm. The linear collaterals appeared to result from an opening of preexisting vessels. The undulating, unbranched vessels were not observed in the normal limbs and seemed to be vessels that were newly formed after limb ischemia. Synchrotron radiation microangiography appears to be a powerful means of assessing the development of small collateral arteries, which may help to provide a basis for understanding of the collateral circulation.