The long term goal of this research is to develop a new approach to the evaluation of microregional circulation. This research is based on the working hypothesis that fluorescent microspheres can be spatially located by fluorescence imaging of organ serial sections. The project will develop instrumentation and procedures to evaluate regional flow in an entire organ. During Phase I a computer-controlled imaging system will be assembled and images of fluorescent microspheres embedded in perfused rat hearts will be taken. Data analysis procedures will be developed to determine microregional flow characteristics Phase I studies will demonstrate the feasibility of the working hypothesis and provide design parameters for imaging systems to be constructed during Phase II for use with larger hearts. This project will provide researchers with the instrumentation to rapidly and automatically evaluate microregional flow in tissue using the same procedures involved in radioactive microsphere flow determinations.