Cardiac Time-of-flight PET for Evaluating Myocardial Perfusion with <sup>13</sup>N-ammonia

Abstract

Background: Cardiac 13 N-ammonia ( 13 N-NH3) positron emission tomography (PET) is approved by Japanese Ministry of Health, Labour and Welfare for diagnosis of ischemic heart disease. New PET camera recently has three-dimensionalmode acquisition and ordered subset expectation maximization (OSEM) reconstruction with time-of-flight (TOF) and point spread function (PSF) correction technology. The aim of the phantom study was to evaluate the usefulness of this novel technology using 13 N-NH3 and 18 F-fluorodeoxyglucose ( 18 F-FDG). Method: PET imaging was performed using a lung-heart torso phantom with myocardial perfusion defects. The indices of defect contrast, the coefficient of variation (CV) and the index of homogeneity were analyzed by using four reconstruction schemes, including OSEM, OSEM+TOF, OSEM+PSF, and TOF+PSF correction methods. Results: The phantom study showed that TOF resulted in improvements of defect lesion detectability with low statisticalnoise. The defect contrast index of TOF +PSF was significantly larger than that of OSEM only (p= 0.048). The cardiac percent root mean square uncertainty (RMSU) with PSF was 25.9 %i n OSEM+PSF and 20.9 %i n TOF+PSF. In contrast cardiac % RMSU without PSF correction was 14.8% in OSEM and 15.3 %i n TOF, which was lower than that with PSF correction. The average wall counts were homogeneous in four reconstruction methods in 13 N-NH3. The value of % CV on the profile curve of 13 N-NH3 images was confirmed to be smaller than 5% in all reconstruction methods. Conclusions: The new PET technology with TOF and PSF correction may extend the possibility of precise analysis of abnormal perfusion defects, and clinical applications are expected.