Study: Controlling temp prior to PET scan reduces brown fat FDG uptake

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Brown fat 18F-FDG uptake on PET scan may limit the ability to assess for cancer, and the controlled environmental tempature could affect this limitation, according to research published March 16 in Molecular imaging and Biology.

Carlos A. Garcia, MD, attending physician in the department of nuclear medicine at Washington Hospital Center in Washington, D.C., and colleagues validated the effectiveness of controlled environmental temperature (CET) to reduce physiologic brown fat FDG uptake on a PET scan in a larger series.

The researchers performed a retrospective review from January 2002 to October 2007 of patients who had either a pattern of FDG uptake on PET scan consistent with brown fat or had no evidence of cancer by CT or repeat scan with CET within four months of the first PET scan, and had not used drugs reported to reduce brown fat FDG uptake (e.g., benzodiazepine, beta-blockers and reserpine).

The non-CET and CET-PET images were randomized and three physicians assessed three regions (right neck, left neck, and paraspinal area) semiquantitatively using the following scale: zero (background), 1+ (greater than background but less than liver), 2+ (equal to liver), 3+ (greater than liver), wrote Garcia and colleagues.

Of 8,640 FDG-PET scans performed, 30 patients (26 females) met the above criteria. The median age was 36 years (range, 12-60 years).

According to Garcia and colleagues, the mean of differences in the scores between the two studies for right neck, left neck, and paraspinal regions, respectively, for reader one were: 2.1, 1.95 and 1.85; reader two: 2.3, 1.70 and 1.77; reader three: 2.17, 2.20 and 0.50; maximum standard uptake value scores were 3.4, 3.3 and 1.77.

In this larger series, CET effectively reduced the false-positive 18F-FDG uptake in brown fat on PET scans without the use of drugs, concluded the researchers.