Purpose: Besides its application in oncology, 18F-FDG PET-CT imaging is also useful in the diagnosis of certain lung infections, inflammatory diseases, and atherosclerotic plaques. Myocardial uptake of 18F-FDG may hamper visualization of the lesions caused by these diseases. Two approaches have been proposed for reducing myocardial uptake in preclinical studies, namely, calcium channel blockers (verapamil) and high-fat diets such as commercial ketogenic diets and sunflower seed diets. The objective of this study was to compare the efficacy of these approaches in reducing myocardial uptake of 18F-FDG in mice.
Methods: We performed two experiments. In experiment A, each animal underwent four 18F-FDG PET/CT scans in the following order: baseline, after administration of verapamil, after two days on ketogenic diet and after two days on sunflower seeds. PET scans were performed 60 minutes after injection of 18.5 MBq of 18F-FDG. In experiment B, the best protocol of the three (ketogenic diet) was evaluated in a lung inflammation model to assess the efficacy of reducing myocardial uptake of 18F-FDG.
Results: Compared with baseline (SUV 2.03 ± 1.21); the greatest reduction in uptake of 18F-FDG was with ketogenic diet (SUV 0.79 ± 0.16; p = 0.008), followed by sunflower seeds (SUV 0.91 ± 0.13; p = 0.015); the reduction in myocardial uptake produced by verapamil was not statistically significant (SUV 1.78 ± 0.79; p = NS). In experiment B, complete suppression of myocardial uptake noticeably improved the visualization of inflamed areas near the heart, while in the case of null or partial myocardial suppression, it was much harder to distinguish lung inflammation from myocardial spillover.
Conclusion: A high-fat diet appeared to be the most effective method for decreasing myocardial uptake of 18F-FDG in healthy mice, outperforming verapamil. Our findings also demonstrate that ketogenic diet actually improves visualization of inflammatory lesions near the heart.