| This thesis examines the ability of near-infrared spectroscopic imaging (NIRSI) to detect and characterize regional myocardial ischemia with three sets of proof-of-concept experiments. It is hypothesized that NIRSI can not only identify ischemic tissue under surgical conditions, but also quantify the degree of ischemia suffered by the tissue.;In the first study, LAIRS images were acquired throughout an ischemia-reperfusion protocol in arrested pig hearts (n = 4). Following a period of normal perfusion, the left anterior descending (LAD) artery was completely occluded for 2 hrs. LAD flow was then restored for 10 min, followed by global ischemia for 10 min and a final 10 min period of reperfusion.;The second study applied a similar procedure to isolated, beating pig hearts (n = 8), with image acquisition triggered by the ECG to ensure that acquisition was consistently in the same phase of the cardiac cycle. The ability of NIRSI to distinguish between degrees of partial ischemia was investigated by reducing LAD flow stepwise to 50%, 20%, and 0% of baseline. The third study investigated spectroscopic imaging of working pig hearts under conditions mimicking open heart surgery, again triggering image acquisition to the ECG. Following a period of normal perfusion, the LAD was either completely occluded (n = 4) or partially occluded (20% flow: n = 6, 50% flow: n = 4) for 90 min. Hearts were then reperfused for 2 hrs.;These results demonstrate that NIRSI can identify ischemic regions of cardiac tissue rapidly and without probes or exogenous contrast agents. Moreover, identification of ischemia by NIRSI is effective on both isolated and in vivo hearts, showing promise as a diagnostic tool for use in both research and cardiac surgery. (Abstract shortened by UMI.). |
