Current methods for quantitating blood flow in the myocardium are limiting by inadequate dead time and random corrections, and errors in attenuation corrections inherent in thoracic imaging. Methods for improving the accuracy of these corrections will be studied. Notably, bank to bank singles will be measured in order to more accurately assess single count rates for cardiac studies. Also the effect of motion on thoracic attenuation corrections will be studied, to determine whether theoretical alteration correction (involving smaller doses and shorter imaging time) may be employed. Preliminary data has been presented in June, 1990 meeting of Society of Nuclear Medicine (2 oral presentations are on deadtime effects in cardiac studies another on attenuation correction). A manuscript is in preparation for the making attenuation correction. In addition, a technique for alignment of PET and MRI cardiac data has been accepted for publication for Computers in Cardiology (1990).