A microangiographic technique using synchrotron radiation to visualize dermal circulation in vivo.

Conventional angiography cannot resolve dermal small vessels with a diameter of 200 microm or less. In vitro microangiography is currently characterized by better spatial resolution than conventional angiography but does not allow visualization of the blood stream in dermal vessels in vivo. In this study, we introduce a novel synchrotron radiation microangiographic system for visualizing the structure of and blood flow in dermal microvessels in vivo repeatedly. We used monochromatic synchrotron radiation with an energy just above the k-edge of iodine (33.3 keV) as an x-ray and a high-definition television camera system with a high-sensitivity image pick-up tube for detection. The 33.3-keV monochromatic synchrotron radiation allows detection of a small amount of iodine, and the high-definition television camera system can resolve small vessels with high-spatial resolution and no loss of sensitivity. We performed synchrotron radiation angiography of superficial inferior epigastric arteries and their branches in nine rats, and of the caudal artery in 14 rats, and compared angiographic images taken by the current system with those taken by a conventional angiographic system in seven rats. With this new microangiographic technique, we could visualize small dermal vessels with a diameter as low as 50 microm. In addition, repeated angiograms at baseline and under increasing body temperature could be obtained. This new microangiographic approach is expected to be very useful for the assessment of dermal circulation in patients.