Effective reduction of brown fat FDG uptake by controlling environmental temperature prior to PET scan: an expanded case series.
BACKGROUND
Brown fat uptake of 2-deoxy-2-[F-18]fluoro-D: -glucose (FDG) on a positron emission tomography (PET) scan may limit the ability to assess for cancer. Previously, Garcia et al. demonstrated in ten patients a significant decrease in brown fat uptake of 2-deoxy-2-[F-18]fluoro-D: -glucose (FDG) after controlling the patient's environmental temperature.


OBJECTIVE
The objective of the current study is to validate the effectiveness of controlled environmental temperature (CET) to reduce physiologic brown fat (BF) FDG uptake on a PET scan in a larger series.


METHODS
A retrospective review was performed from January 2002 to October 2007 of patients who had (1) a pattern of FDG uptake on PET scan consistent with BF, (2) no evidence of cancer by computed tomography in the regions of interest noted below, (3) repeat scan with CET within 4 months of the 1st PET scan, and (4) no use of drugs reported to reduce BF FDG uptake (e.g., benzodiazepine, beta-blockers, reserpine) unless they were used identically prior to and during both studies. The FDG-PET and controlled environmental temperature-positron emission tomography (CET-PET) scans were performed as per protocol. The non-CET and CET-PET images were blinded/randomized, and three physicians assessed three regions (right neck, left neck, and paraspinal area) semiquantitatively using the following scale: "0" (background [bkgd]), 1 + (> bkgd < liver), 2 + (equal to liver), 3 + (> liver). Standard uptake value (SUV) data was recorded. Results were analyzed using a two-tailed t test.


RESULTS
Of 8,640 FDG-PET scans performed, 30 patients (four male, 26 female) met the above criteria. The median age was 36 years (range, 12-60 years). The mean (± 1 standard deviation) of differences in the scores between the two studies for right neck, left neck, and paraspinal regions, respectively, were for reader 1:(2.1 ± 1.37), (1.95 ± 1.43), and (1.85 ± 1.26); reader 2 (2.3 ± 1.40), (1.70 ± 1.13), and (1.77 ± 1.13); reader 3 (2.17 ± 1.17), (2.20 ± 1.18), and (0.50 ± 1.30); for maximum SUV score (3.4 ± 2.9), (3.3 ± 2.9), and (1.77 ± 1.13). All p values were <0.001.


CONCLUSIONS
In this larger series, CET effectively reduced the false-positive (18)FDG uptake in BF on PET scans without the use of drugs.
Garcia
Carlos
C
Division of Nuclear Medicine, Department of Medicine, Washington Hospital Center, 110 Irving St. NW, Washington, DC 20010, USA. carlos.garcia@medstar.net
Bandaru
Varalakshmi
V
Van Nostrand
Douglas
D
Chennupati
Shyam
S
Atkins
Frank
F
Acio
Elmo
E
Kulkarni
Kanchan
K
Majd
Massoud
M
D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D001833:Body Temperature Regulation / Q000502:physiology; D016022:Case-Control Studies; D002648:Child; D004526:Efficiency; D004777:Environment; D005189:False Positive Reactions; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods* / Q000592:standards; D012189:Retrospective Studies; D013696:Temperature; D055815:Young Adult
D019788:Fluorodeoxyglucose F18