Abstract
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Objectives Accurate measurement of left ventricular functional parameters like ejection fraction (EF) or volumes potentially enables therapy monitoring in rat models of heart diseases. The present study aimed to estimate (LVEF) acquired by different PET imaging techniques and to compare these against the reference standard cine-MRI.
Methods Seven healthy female Sprague-Dawley rats (220 ± 10 g) underwent a series of ECG-gated microPET examinations under isoflurane anesthesia. ECG-gated [18F]-FDG PET list mode acquisition was performed over 60 minutes beginning with an intravenous injection of 138 ± 8 MBq. The blood pool phase of the first 40 seconds of this dynamic recording (FDGBP) as well as the myocardial tracer accumulation of the last 15 minutes (FDGMyo) were used to calculate LVEF. On the following day, ECG-gated blood pool measurements were obtained during 30 minutes following intravenous administration of 21 ± 2 MBq [68Ga]-Albumin. Finally, each animal was examined with cine-MRI (1.5 T) and LVEF was calculated for each animal.
Results The mean LVEF estimates in the group of healthy anaesthetized rats were 56 ± 3 % based on FDGBP, 55 ± 3 % based on FDGMyo, 57 ± 3 % based on [68Ga]-Albumin, and 57 ± 2 % based on MRI. There were good to excellent correlations found between the LVEF-values as compared to MRI for FDGBP (r=0.71), FDGMyo (r= 0.86) and Albumin (r=0.88). Bland-Altman plots showed all estimates to fall within the limits of agreements.
Conclusions In healthy rats there was good to excellent agreement for LVEF measurements by FDGBP, FDGMyo and [68Ga]-Albumin with the reference standard MRI, where the novel blood pool tracer [68Ga]-Albumin showed the best correlations. ECG-gated image fusion of blood-pool with myocardial uptake techniques is feasible and might help to optimize delineation of the endocardial borders especially in animal models of myocardial infarction