TEST-RETEST REPEATABILITY AND INTRA- AND INTER-OPERATOR REPRODUCIBILITY OF [11C]ACETATE PET OXIDATIVE METABOLISM AND MEASUREMENTS OF MYOCARDIAL EFFICIENCY

Noninvasive approaches to investigate myocardial efficiency can help track the progression of diseases such as heart failure, and monitor the benefits of therapeutic interventions that enhance cardiac efficiency. Understanding the reproducibility and repeatability of [11C]acetate PET imaging of oxidative metabolism is essential for both research and clinical applications. Dynamic [11C]acetate PET scans were performed at rest and follow-up (47±22 days apart) in 20 patients with heart failure and reduced ejection fraction (HFrEF). Two observers blinded to patients’ clinical data used FlowQuant® software to evaluate intra- and inter-observer reproducibility and test-retest repeatability of [11C]acetate tracer uptake and clearance rates, to obtain measures of myocardial oxygen consumption (MVO2), myocardial external efficiency (MEE), work-metabolic-index (WMI) and myocardial blood flow (MBF). Reproducibility and repeatability were evaluated using intra-class-correlation (ICC) and Bland-Altman coefficient-of-repeatability (CR) metrics. Test-retest correlations were good for MVO2(kmono) (ICC =0.55) and MVO2(k2) (ICC = 0.64) but were excellent for WMI and MEE (ICC = 0.91 and 0.98, respectively). Repeatability was better for MEE and WMI (CR = 22 and 34%) compared to MVO2 measurements (CR = 30-54%). Corresponding intra- and inter-observer correlations were excellent (ICC = 0.95-0.99) and the CR values were significantly lower (CR = 3%, p < 0.007), suggesting that operator training/experience is a relatively small source of measurement variability. [11C]acetate PET analysis can be performed reliably by different operators, using a highly-automated program. WMI and MEE exhibit excellent reproducibility and repeatability and may provide useful measurements to track disease progression or monitor the effects of therapeutic interventions that affect cardiac efficiency.View Large Image Figure ViewerDownload Hi-res image Download (PPT)