Multi-pinhole (MP) SPECT allows simultaneous rest/stress myocardial perfusion imaging (MPI) with low doses of Tc-99m and Tl-201

601 Objectives MP-SPECT is a high sensitivity MPI modality that reduces the level of radiation exposure to patients without increased acquisition time. We investigated variations in diagnostic accuracy between a high and low dose MPI protocol. Methods Sixteen men with stable coronary disease underwent simultaneous rest/stress MPI utilizing dosages reduced to 5 mCi of technetium for rest and 2 mCi of thallium for stress. (RBE comparable to 20 mCi of Tc-99m alone.) All patients had undergone previous MPI within the preceding 18 months using a higher dose protocol of 7 mCi of Tc-99m and 4 mCi of Tl-201 (RBE comparable to 40 mCi of Tc-99m alone). All patients were clinically stable, weighed Results The initial higher dose study showed 6 men with infarction, 4 with flow differences, 2 with flow differences in an area of infarction and 4 with normal images. The second lower dose study showed identical findings. The extent of exercise, the dosing stages of dobutamine and the heart rate and blood pressure response to stress were comparable for the two studies. Image quality, LVEF, segmental function and the confidence of the interpretator were comparable for both studies. Conclusions This study validates that MP-SPECT allows simultaneous stress-rest MPI along with left ventricular contractile performance to be performed using low isotope doses without compromising diagnostic accuracy or prolonging image acquisition time. It was also confirmed that improved system modeling, reconstruction and analytic methodologies will allow further reductions in the required dosage