A new generation whole body computed tomography scanner has been developed capable of continuous, multislice scanning with exposure times of 33, 50 and 100 milliseconds for high temporal resolution and three-dimensional imaging. This type of instrument has the potential to yield improved cardiac diagnosis by providing more accurate and simultaneous measurements of ventricular volumes, mass and regional myocardial function than presently possible using standard techniques including angiography and echocardiography. This proposal will evaluate the first production (IMATRON C-100) millisecond CT scanner for real time three-dimensional cardiac imaging. Quantitation of regional myocardial function will be based upon two CT methods: measurements of myocardial wall thickening and motion, and regional myocardial perfusion evaluation using 3-D Cine densitometry. CT measurements will be validated in animals with radiolabelled microspheres and post mortem measurement of infarct volume. Sequential millisecond multilevel scans will enable reconstruction of the entire left ventricle throughout successive cardiac cycles. The half contour CT density numbers will be used for myocardial wall boundary analysis. Finally, the utility of Cine-CT for identifying and sizing acute myocardial infarction in animals will be compared with post mortem histochemical morphometry. Cine CT will be used for longitudinal measurements of the mass of infarcted and normal myocardium in order to define evolutionary changes in infarct size and compensatory hypertrophy for infarcted myocardium. Previous studies using conventional CT scanners have demonstrated that this may be feasible but until now the slow scanning speed and single slice imaging capability have precluded accurate volume measurements in a clinically realistic manner. Should it indeed be possible to attain the specific aims described in this proposal, the improved speed of a Cine-CT scanner would be a major breakthrough in extending the capabilities of CT scanning for the evaluation of cardiac abnormalities and pathophysiology in patients. It would permit the diagnosis and quantitation of regional myocardial contractile function, mass and myocardial blood flow with greater accuracy than is presently possible. This information, furthermore, could be derived during a single, relatively non-invasive, diagnostic procedure.