Abstract
Objectives This study is aimed at investigating the impact of frame numbers in preclinical electrocardiogram- (ECG-) gated 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) on systolic and diastolic left ventricular (LV) parameters in rats. Methods 18F-FDG PET imaging using a dedicated small animal PET system with list mode data acquisition and continuous ECG recording was performed in diabetic and control rats. The list-mode data was sorted and reconstructed with different numbers of frames (4, 8, 12, and 16) per cardiac cycle into tomographic images. Using an automatic ventricular edge detection software, left ventricular (LV) functional parameters, including ejection fraction (EF), end-diastolic (EDV), and end-systolic volume (ESV), were calculated. Diastolic variables (time to peak filling (TPF), first third mean filling rate (1/3 FR), and peak filling rate (PFR)) were also assessed. Results Significant differences in multiple parameters were observed among the reconstructions with different frames per cardiac cycle. EDV significantly increased by numbers of frames (353.8 ± 57.7 μl∗, 380.8 ± 57.2 μl∗, 398.0 ± 63.1 μl∗, and 444.8 ± 75.3 μl at 4, 8, 12, and 16 frames, respectively; ∗P < 0.0001 vs. 16 frames), while systolic (EF) and diastolic (TPF, 1/3 FR and PFR) parameters were not significantly different between 12 and 16 frames. In addition, significant differences between diabetic and control animals in 1/3 FR and PFR in 16 frames per cardiac cycle were observed (P < 0.005), but not for 4, 8, and 12 frames. Conclusions Using ECG-gated PET in rats, measurements of cardiac function are significantly affected by the frames per cardiac cycle. Therefore, if you are going to compare those functional parameters, a consistent number of frames should be used.
Highlights
Positron emission tomography (PET) can provide a reliable read-out of the myocardial glucose metabolism on a cellular level along with a concomitant assessment of cardiac systolic and diastolic function [1]
ECG-gated 18F-FDG PET has been established for the assessment of left ventricular (LV) volumes and LV ejection fraction (EF) in clinical [10,11,12] and preclinical PET studies [1, 13, 14], the influence of the chosen gating mode on the diastolic and systolic functional parameters in small animals has not been investigated yet
In ECG-gated 18F-FDG PET studies, it has been demonstrated that reliable LV volumes and EF could be obtained by using 16 [18] and 8 frames [12] per cycle when compared to cardiac magnetic resonance imaging (MRI)
Summary
Positron emission tomography (PET) can provide a reliable read-out of the myocardial glucose metabolism on a cellular level along with a concomitant assessment of cardiac systolic and diastolic function [1]. Even though there have been studies investigating the impact of frame numbers in ECG-gated single photon emission computed tomography (SPECT) on the EF and LV volumes in humans [8, 9], data for small animals are still lacking. Given their smaller heart size and higher heart rate relative to humans, small animal PET studies may require an increased number of frames per cardiac cycle to generate the required temporal resolution. ECG-gated 18F-FDG PET has been established for the assessment of LV volumes and LV ejection fraction (EF) in clinical [10,11,12] and preclinical PET studies [1, 13, 14], the influence of the chosen gating mode on the diastolic and systolic functional parameters in small animals has not been investigated yet
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