Assessment of Cardiac Wall Motion and Ejection Fraction With Gated PET Using N-13 Ammonia

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Abstract
Cardiac gating is not routinely used in cardiac positron emission tomography (PET). The aim of this study was to determine the feasibility of assessing regional wall motion, ejection fraction (EF), cardiac volumes, and mass with nitrogen-13 ammonia (N-13 ammonia) at the time of PET myocardial perfusion imaging. We studied 12 healthy volunteers (mean age, 28 ± 8 years) and 53 patients with documented coronary artery disease (CAD) (mean age, 59 ± 11 years). All subjects received a single administration of approximately 600 MBq (16 mCi) of N-13 ammonia intravenously. A 6-minute dynamic scan was performed for quantitative assessment of myocardial perfusion at rest, followed by a separate, 13-minute static scan acquired in the gated mode (8 equal bins). Gated data was imported into the Emory Toolbox. Wall motion was evaluated by dividing the myocardium into 9 anatomic regions graded semiquantitatively. Healthy volunteers had a normal EF (61 ± 6), end systolic volume (ESV) (37 ± 15 mL), end diastolic volume (EDV) (89 ± 25 mL), and cardiac mass (116 ± 18 g). In contrast, patients with CAD showed reduced EF (32 ± 13%) and increased ESV (129 ± 56 mL), EDV (188 ± 68 mL), and cardiac mass (173 ± 45g) (P < 0.001 for each). In patients with CAD, EF measured by gated PET correlated significantly to independent measurements of EF (P < 0.001). Gating of cardiac perfusion images obtained after administration of N-13 ammonia is feasible and appears to be an accurate means of evaluating regional and global cardiac function. Gating can provide important additional diagnostic and prognostic information.