The objective of this project is the demonstration of the efficacy of a new spectroscopic technique for accurate intraoperative and postoperative on- line monitoring of liver perfusion and oxygenation and the development of a prototype system appropriate for clinical trials. This novel technology employs laser induced fluorescence attenuation spectroscopy (LIFAS) to derive reliable measurements of tissue ischemia on-line. Preliminary in- vivo experimental results have demonstrated the feasibility of this approach. The specific aims of the Phase I project are: a) determine the fluorescence attenuation spectrum of hepatic tissue in-vivo, b) determine the effects of reduced blood perfusion on the fluorescence attenuation spectrum of hepatic tissue. In Phase II, we will develop a multivariate model for the reliable detection of hepatic ischernia from measured attenuation spectra, and we will demonstrate its efficacy in-vivo through extensive animal experiments. Through proper adaptation, the technique can be applied for monitoring ischemia in other organs and tissues. The proposed technique will enable the continuous bedside monitoring of the perfusion and viability of hepatic tissue during and after liver surgery. Currently, the measurement of liver enzymes (transaminases) and clotting factors (prothrombin) in the blood is the only reliable means for detecting perfusion-related hepatic dysfunction, but only after significant liver damage has already occurred. PROPOSED COMMERCIAL APPLICATION: The fully developed and tested system for on-line monitoring of hepatic perfusion will be valuable for intraoperative and postoperative monitoring in liver surgery and transplantation. The same monitoring system can be adapted for other organs (e.g. kidney and heart).