Optimizing Acquisition Parameters and Interpretive Methods of FDG-PET/CT With Rb-82

Sarcoidosis

In this this investigation, 15 subjects with a high probability of cardiac sarcoidosis based on clinical criteria and abnormal cardiac FDG uptake on initial, clinically indicted FDG PET study will be considered for this study. The study will test the following Aims: Aim 1. Effect of FDG incubation time on visual and quantitative interpretation of FDG uptake. Changes in incubation time can affect imaging target:background ratios and study sensitivity/specificity. For the study-directed exam, all patients will undergo sequential cardiacfocused FDG-PET imaging at 90 and 120 minutes after injection of FDG. Imaging variables will be evaluated as below. Aim 2. Reproducibility of FDG and Rb82 PET findings on sequential imaging. It is unknown whether FDG-positive imaging findings in cardiac sarcoidosis are reproducible. All patients will undergo study-directed FDG-PET/CT with MPI imaging within approximately 2 weeks from initial clinical scan.

Sarcoidosis is a systemic disease of unknown etiology characterized by non-caseating granulomatous inflammation. The pathophysiologic features of cardiac sarcoidosis include macrophage-induced, T-cell mediated non-caseating granulomatous inflammation, followed by myocardial scarring/fibrosis with clinical sequelae including arrhythmias, conduction abnormalities, and contractile dysfunction. These lead to high event rates in patients with cardiac sarcoidosis, with several studies reporting a prevalence of ventricular tachycardia ranging from 23% to 38% and an \ 20% rate of clinical congestive heart failure. FDG-PET/CT with Rb82 myocardial perfusion imaging (FDG-PET with MPI) is becoming the gold standard imaging technique for evaluating the degree of inflammation and the response to immunosuppressive treatment in patients with cardiac sarcoidosis. FDG PET imaging allows for evaluation of inflammatory macrophage infiltration, while Rb82 MPI allows for determination of myocardial scar burden. Despite emerging data from our center and others on the clinical utility of this technique in predicting prognosis, there is little consensus on the reproducibility of this technique or optimal imaging acquisition techniques and interpretative strategies. In this study, patients with a high clinical likelihood of cardiac sarcoidosis will undergo a study-directed FDG PET/CT with Rb82 myocardial perfusion imaging study approximately 2 weeks following an initial clinically-directed examination. The two FDG PET with MPI examinations will be examined for reproducibility of imaging findings, including: SUVmax, SUVmean, distribution of FDG uptake, extra cardiac FDG uptake, SUVvolume, SUVvolume:intensity, perfusion defect size/severity/location, LV ejection fraction, myocardial blood flow. Strict attention will be paid to ensure patients undergo the same metabolic preparation prior to the two examinations.

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