Objective: The purpose of this study was to determine whether use of a high-fat, very-low-carbohydrate protocol for preparing patients for PET decreases the frequency of (18)F-FDG uptake by hypermetabolic brown adipose tissue (BAT) on PET scans.
Materials and methods: In this HIPAA-compliant retrospective study, 741 FDG PET/CT scans obtained during the winter months (October 1-April 30) for patients who prepared with a high-fat, very-low-carbohydrate, protein-permitted protocol were compared with 1,229 FDG PET scans obtained during the winter months for patients who prepared by fasting. FDG uptake on PET scans co-localized with regions of fat identified on the CT scans was assumed to represent hypermetabolic BAT. The categoric variables frequency of occurrence of hypermetabolic BAT (present or not) and the sex ratios of the groups before and after the change in preparation were compared by use of a chi-square test. The continuous variables of age and blood glucose level were compared by use of a two-tailed Student's t test.
Results: In this intention-to-treat analysis, there was no difference between the fasting (n = 1,229) and the high-fat, very-low-carbohydrate, protein-permitted diet (n = 741) groups in terms of age and sex. Patients who prepared with the high-fat diet had a significantly lower frequency of hypermetabolic BAT uptake on FDG PET scans during the winter months (p<0.0002) and had lower blood glucose levels (p<<0.001).
Conclusion: In this intention-to-treat analysis, use of a high-fat preparation protocol significantly lowered the frequency of uptake of FDG by hypermetabolic BAT on FDG PET studies. Use of this protocol has the potential to decrease the rate of false-positive findings on oncologic FDG PET scans.