Comparison of the Effect of Three Different Dietary Modifications on Myocardial Suppression in ¹⁸F-FDG PET/CT Evaluation of Patients for Suspected Cardiac Sarcoidosis

A definitive dietary preparation recommendation is not possible based on literature on the achievement of myocardial suppression for diagnosis of cardiac sarcoidosis (CS) with ¹⁸F-FDG PET/CT. Our goal is to compare 3 different dietary preparations in achievement of the best myocardial suppression and CS diagnosis. Methods: We retrospectively reviewed and compared 3 dietary preparations used at our institution. Three different diets were applied from March 2014 to December 2019: a 24-h ketogenic diet with overnight fasting (n 5 94); 18-h fasting (n 5 44); and 72-h daytime ketogenic diet with 3-d overnight fasting (n 5 98). The interpretation of initial reports was recorded, and an independent radiologist (observer) retrospectively reevaluated each case regarding CS diagnosis (negative, positive, indeterminant) and myocardial suppression (complete, failed, partial). Interobserver agreement was analyzed. We measured SUVmax from blood pool, liver, and the most suppressed normal myocardium. Results: We identified superior myocardial suppression with the 72-h preparation, indicated by higher blood pool-to-myocardium and liver-to-myocardium ratios (P, 0.001). Myocardial suppression rates for the 72-h ketogenic diet, 24-h ketogenic diet, and 18-h fasting preparations were as follows: complete myocardial suppression, 96.9%, 68.1%, and 52.3%, respectively; failed myocardial suppression, 0%, 23.4%, and 25%, respectively; and partial myocardial suppression, 3.1%, 8.5%, and 22.7%, respectively (P, 0.001). The 72-h preparation had significantly fewer indeterminant and positive examinations. CS diagnosis rates for 72-h ketogenic diet, 24-h ketogenic diet, and 18-h fasting preparations were negative, 82.7%, 52.1%, and 27.3%, respectively; indeterminant, 2.0%, 24.5%, and 40.9%, respectively; and positive, 15.3%, 23.4%, and 31.8%, respectively (P, 0.001). A high agreement was present with the observer and the report (k 5 0.88). Conclusion: A 72-h daytime ketogenic diet with 3-d overnight fasting achieved substantially superior myocardial suppression versus a 24-h ketogenic diet with overnight fasting and an 18 h-fasting using ¹⁸F-FDG PET/CT. This 72-h preparation results in significantly fewer indeterminant and potentially false-positive CS results.