This award will provide supplementary support to enable Dr. Robert Close of the University of California, Los Angeles, to conduct collaborative research with Dr. Shinichi Tamura for 12 months at the Biomedical Research Center, Osaka University Medical School, in Japan. In order to develop a technique to measure vascular autoregulatory response by combining digital subtraction angiography (DSA) data with pressure measurements, the collaborative project will utilize several novel algorithms for extraction of vascular volume, flow, and perfusion diameters which were developed by Dr. Close. The vascular autoregulatory response may be measured by relating variations in diameter and flow rates of a blood vessel with pressure variations. Dr. Tamura is an expert in the field of DSA and the Osaka University Hospital is developing a new picture archival and communications system (PACS) for handling digital images and radiological data. Utilizing DSA images, digital algorithms developed by Dr. Close will be used to measure vessel size and flow rate. Measurement of the vascular autoregulatory response may be clinically useful as an indicator of atherosclerosis or in evaluating the effects of arteriovenous malformations.