Brief ReportPerformance of 8- vs 16 ECG-gated reconstructions in assessing myocardial function using Rubidium-82 myocardial perfusion imaging: Findings in a young, healthy population
Introduction
Quantification of myocardial perfusion and function using Rubidium-82 (82Rb) has become a central element in the clinical assessments of suspected myocardial disease.1, 2, 3 Left ventricular ejection fraction (LVEF) and its reserve (stress LVEF–rest LVEF) have been reported as predictors of coronary artery disease, with better outcomes if LVEF ≥ 50% and LVEF reserve > 5%.4, 5, 6 Despite the predictive value, several key aspects of ECG gating of 82Rb myocardial perfusion imaging (MPI) are still not fully understood, hereunder impact of the number of ECG gates employed.
Current guidelines from ASNC/SNMMI recommend 8 ECG-gated reconstructions to retrain the best noise characteristics, while 16 ECG gates provide better tracing of the cardiac contraction.2,3,7 Especially the noise in the images is of concern for 82Rb MPI, which is driven by the count statistics employed for the ECG-gated reconstructions.7 The count statistics are affected by factors, such as the injected doses,8 the short half-life of 82Rb (76.2 s), and the patient body mass index (BMI). This study aimed to evaluate the quantitative differences in the assessment of volumetric analyses and their repeatability measures when employing 8 or 16 ECG gates for 82Rb MPI studies. Further, this study addresses the dynamics of left ventricular (LV) emptying and filling by reporting the left ventricle peak emptying rate (PER), peak filling rate (PFR), and time-to-peak filling (TTPF) for the two gating protocols.
Section snippets
Study population
The current study comprised 25 young, healthy volunteers (11 females) (median age = 23 years (interquartile range (IQR) = [22; 25])) recruited for rest/adenosine stress myocardial perfusion 82Rb-PET/CT. Median volunteer weight was 70.0 kg [IQR = 62; 79.5 kg], with corresponding median BMI on 21.8 [IQR = 20.5; 23.8]. The volunteers underwent repeat PET/CT imaging sessions within 27 days [IQR = 17; 36]. Inclusion criteria were age > 18 years, no regular consumption of medicine, no known medical
Quantitative measures
Similar stress EDV, ESV, and SV measures were observed for the two reconstruction protocols using the guideline-recommended reconstruction window (Figure 1). Employment of 16 ECG gates resulted in slightly elevated LVEF for both rest and stress MPI studies, although not significant (P = 0.18) (Figure 1), and no significant difference in LVEF reserve was observed for the 8- vs. 16 ECG-gated reconstructions (P = 0.78) (Figure 1).
Comparisons of PER revealed significantly increased emptying rates
Discussion
This 82Rb-PET-study evaluated the impact of using either 8- or 16 ECG-gated protocols for volumetric assessments. The main finding of this study was that, quantitatively, no differences in the EDV, ESV, SV, LVEF, and LVEF reserve exist for the two reconstruction protocols. Further, 16 ECG-gated reconstructions may permit reliable measures of PER, PFR, and TTPF in cohorts with sinus rhythm and heart rate of around 60 beats per minute.
Similar EDV, ESV, SV, LVEF, and LVEF reserve measures were
New Knowledge Gained
This study evaluated the quantitative differences in using 8- and 16 ECG-gated reconstructions obtained for adenosine stress 82Rb MPI studies. The main finding of this study was that quantitative volumetric measures were comparable for the two gating protocols. Using 16 ECG gates may permit assessments of the peak filling and emptying rates, as well as the time-to-peak filling assessments.
Conclusion
In healthy subjects, we report that 8 and 16 ECG gates can be used intertwined if only volumetric assessments are desired. The test–retest repeatability measures in this study do, however, not permit recommendations of using either 8- or 16 ECG-gated reconstructions nor in the assessment of patients with potential arrhythmias.
Acknowledgements
This project received funding from the European Union’s Horizon 2020 research and innovation program under grant agreements no. 670261 (ERC Advanced Grant) and 668532 (Click-It), the Lundbeck Foundation, the Novo Nordisk Foundation, the Innovation Fund Denmark, the Danish Cancer Society, Arvid Nilsson Foundation, the Neye Foundation, the Research Foundation of Rigshospitalet, the Danish National Research Foundation (grant 126), the Research Council of the Capital Region of Denmark, the Danish
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