Quantitative Gated PET for the Assessment of Left Ventricular Function in Small Animals

Abstract

¹⁸F-FDG PET can identify areas of myocardial viability and necrosis and provide useful information on the effectiveness of experimental techniques designed to improve contractile function and myocardial vascularization in small animals. The left ventricular volume (LVV) and left ventricular ejection fraction (LVEF) in normal and diseased rats were measured in vivo using the high-resolution avalanche photodiode (APD) small-animal PET scanner of the Université de Sherbrooke. The measurements obtained by PET were compared with those obtained by high-resolution echocardiography and with known values obtained from a small, variable-volume cardiac phantom. Methods: List-mode gated ¹⁸F-FDG PET studies were performed using the APD PET scanner on 30 rats: 11 healthy, 4 under septic shock, and 15 with heart failure induced by ligature of the left coronary artery. PET images were resized to match human-scale pixels and analyzed using a standard clinical cardiac software program. The LVV and LVEF from the same animals were also evaluated by echocardiography. Results: Agreement was excellent between the endocardial volumes determined by PET and the actual volumes of the cardiac phantom (r² = 0.96). Agreement between PET and echocardiography for LVV ranged from good in healthy rats (r² = 0.89) to fair in diseased rats (r² = 0.49). Agreement was fair between LVEF values measured by the 2 methods (r² = 0.56). Normal rats had an average LVEF of 83.2% ± 8.0% using PET and 81.6% ± 6.0% using echocardiography. In rats with heart failure, LVEF was 54.6% ± 15.9% using PET and 54.2% ± 13.3% using echocardiography. Conclusion: Both PET and echocardiography clearly differentiated normal rats from rats with heart failure. Echocardiography is fast and convenient, whereas list-mode PET is also able to assess defect size, myocardial viability, and metabolism.