Objective: To detect cardiac hypermetabolic lesions using fluorodeoxyglucose (FDG) with PET/computed tomography (PET/CT), the efficiency of long fasting and temperature condition for lowering physiological myocardial FDG uptake is controversial and may be confounded by other factors. We thus aimed to investigate the impact of fasting duration and ambient temperature on myocardial uptake in diabetic and nondiabetic patients.
Methods: FDG PET/CT scans (n = 666) were reviewed and the myocardial uptake was visually graded on a four-point scale and quantified using standardized uptake value (SUV). The associations between myocardial uptake and fasting duration, diabetes status, ambient temperature parameters, age, gender, and BMI were evaluated.
Results: Intraobserver [κ = 0.94; intraclass correlation coefficient (ICC) = 0.99] and interobserver (κ = 0.91; ICC = 0.99) reliabilities of both visual and SUV measurements were all excellent. Fasting duration and diabetes status were found to be significantly associated with myocardial FDG uptake, but the ambient temperature parameters and other factor were not. Patients with intense (Grade 4) myocardial uptake had a shorter fasting duration (P = 0.011). The SUVmax of myocardium was significantly higher in nondiabetic than diabetic patients (P < 0.001). Fasting duration ≥ 12 h in diabetic and ≥16 h in nondiabetic patients was associated with low prevalence of Grade 4 uptake (4.2%, P = 0.016; 2.3%, P = 0.028).
Conclusion: Fasting for long enough durations but not ambient temperature was associated with decreased physiological myocardial FDG uptake. A fasting duration of more than 12 h for diabetic, 16 h for nondiabetic patients is a simple and valuable recommendation.
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