Objectives: In this educational exhibit, we study quantitative approaches to assess adequate metabolic priming of the myocardium prior to 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) to detect cardiac sarcoidosis.

Introduction: The most common standardized protocol for FDG PET imaging of cardiac sarcoidosis is with the high fat, low carbohydrate diet modification. It has been shown to best prepare the myocardium metabolically for assessment of abnormal activity related to sarcoid involvement. This can be further accentuated with the use of low-dose Heparin prior to FDG injection. Careful analysis of these images can provide valuable information regarding the adequate priming of the heart which in turn can improve the diagnostic accuracy of these studies. Methods/Results/Observation: Metabolically priming the myocardium with the aforementioned protocol by virtue of switching the caloric consumption of myocardium from glucose to fatty acids is supposed to cancel out background FDG uptake otherwise seen in the myocardium. This in turn, improves the sensitivity and possibly the specificity of the FDG pet study by increasing the signal contrast and delineation of sarcoid lesions in the affected myocardial regions. Ideally, these images should demonstrate a clear demarcation of the involves areas with an improved the signal to background ratio, primarily by virtue of adequate muting of uptake in the background. We can use the following metrics to quantify the adequate metabolic priming of the myocardium for suitable lesion detection:1. Absence of baseline FDG myocardial uptake (measured using SUV max)2. Lesion to background ratio (measured using SUV max, subtraction analysis)3. Focality of abnormal uptake (measuring through lesional SUVpeak).Conclusion: These metrics can prove to be a useful part of the visual criteria for satisfactory quality assurance in cardiac FDG PET imaging for the purposes of sarcoidosis assessment.