Advances in PET Imaging of Sarcoidosis

Purpose of Review: The purpose of this paper is to provide an updated review of recent advances in protocols for positron emission tomography (PET) or PET/computed tomography (PET/CT) imaging in patients with sarcoidosis. Recent Findings: There has been more research focused on developing newer and improved PET imaging modalities to diagnose and follow-up cardiac sarcoidosis (CS). Fluorine-18-fluorodeoxyglucose ( ¹⁸ F- FDG)-PET are widely used to diagnose CS, with or without concurrent rest nuclear myocardial perfusion study. There have been various patient preparation strategies for FDG PET/CT in CS. Interpretation criteria for cardiac FDG PET/CT in diagnosing CS also varies. There are emerging data utilizing new PET radiotracers (i.e., ⁶⁸ Ga-DOTATATE, ¹⁸ F-Flurpiridaz) and PET/MRI imaging for CS diagnosis. Summary: Based on published imaging data, patient preparation with a 72-h high-fat, high-protein, and very-low-carbohydrate diet protocol generates the most promising results in suppression of physiological myocardial FDG uptake in cardiac PET/CT. The “focal-on-diffuse uptake” pattern on myocardial uptake is not convincing and should not be interpreted as active CS. Nuclear myocardial perfusion test might not be needed to diagnose CS if optimal suppression of myocardial background uptake of FDG is achieved. FDG PET/MRI with optimal patient preparation may increase diagnostic confidence. More data will be needed for new tracers to be used for CS diagnosis.