Quantitative Evaluation of Myocardial Blood Flow and Ejection Fraction with a Single Dose of NH3 and Gated PET

To evaluate myocardial blood flow (MBF) and cardiac function with a single dose of NH3, electrocardiographically (ECG) gated PET acquisition was performed after a dynamic PET scan was obtained. Gated blood-pool (GBP) imaging with C15O PET was also performed to compare the left ventricular ejection fraction (LVEF) obtained using the 2 methods. Methods: Six healthy volunteers and 34 patients with cardiovascular disease were studied. Each subject underwent dynamic PET scanning after a slow intravenous injection of approximately 740 MBq NH3, followed by ECG gated PET scanning. MBF images were calculated by the Patlak plot method. Before obtaining the NH3 scan, the GBP image was obtained with a bolus inhalation of C15O. Twenty patients also underwent left ventriculography (LVG) to compare the value of the LVEF obtained using this technique with that determined using the gated PET method. Results: The mean regional value of MBF calculated for healthy volunteers in the resting condition was 0.61 0.10 mL/min/g. The LVEF obtained using GBP PET (EFCO) was consistent with that obtained using LVG. The LVEF calculated from gated NH3 scans (EFNH3) correlated well with EFCO, although EFNH3 slightly underestimated the LVEF (EFNH3 0.97 . EFCO 2.94; r 0.87). EFNH3 was significantly different from EFCO in patients with a perfusion defect in the cardiac wall (EFNH3 39% 11% vs. EFCO 45% 11%; n 19; P 0.001), whereas no significant difference was found between them in subjects with no defect (EFNH3 58% 13% vs. EFCO 61% 10%; n 21). Conclusion: Gated PET acquisition accompanied by obtaining a dynamic PET scan with a single dose of NH3 is a promising method for the simultaneous clinical evaluation of MBF and cardiac function. However, in patients with a defect in the cardiac wall, EFNH3 showed a tendency to underestimate the EF compared with EFCO.