Oral Presentation The Annual Scientific Meeting of the Endocrine Society of Australia and the Society for Reproductive Biology 2014

Standardised cooling improves the detection of Brown Adipose Tissue by 18FDG-PET without significant seasonal variation (#63)

Moe Thuzar 1 2 , Phillip W Law 2 3 , Christina Jang 1 2 , Susanne Jeavons 2 3 , Ken KY Ho 1 2
  1. Department of Endocrinology & Diabetes, Princess Alexandra Hospital, Brisbane, Queensland, Australia
  2. School of Medicine, University of Queensland, Brisbane, Queensland, Australia
  3. Department of Molecular Imaging, Princess Alexandra Hospital, Brisbane, Queensland, Australia

Background: Brown adipose tissue (BAT) is highly prevalent in adult humans. Its detection by 18FDG-PET-CT is low in non-temperate regions, being markedly affected by seasonal temperature.

Aim: To determine whether a standardised cooling protocol improves detection of BAT in humans.

Methods: 18 (12 men, 6 women) healthy subjects were placed in an air-conditioned room cooled to 190C for 3 hours before undergoing 18FDG-PET-CT. 11 subjects were studied twice 2-3 weeks apart to ascertain reproducibility, giving a total of 29 scans. The 18FDG dose was 75MBq, four times lower than that for diagnostic scanning. The data were compared to 450 scans of patients who underwent diagnostic 18FDG-PET-CT for various medical indications at room temperature. BAT-positivity was defined by SUVmax ≥ 2 in supraclavicular and cervical areas localising to fat attenuation on CT. The rates were seasonally analysed when the mean daily temperatures for Brisbane were 24-260C in summer, 18-200C in spring and 15-160C in winter respectively.

Results: Under standardised cooling, BAT was detected in 76% (22 of 29). Among those studied twice, the scans were concordant in 82%. In diagnostic scans, BAT was detected in 2% (9 of 450) and the prevalence was significantly greater (p=0.01) in winter (4.7%) than in summer (0.66%) or spring (0.66%). With standardised cooling, the seasonal differences were not significant (p=0.34) between winter (85.7% of 14), spring (80% of 5) and summer (60% of 10).

Summary: BAT prevalence under standardised cooling was 35 fold higher than the background prevalence despite employing a much lower FDG dose. Standardised cooling confers high reproducibility with detection rates that do not vary significantly between seasons.

Conclusion: A standardised cooling protocol markedly improves BAT detection without significant seasonal variation.

Acknowledgement: Supported by a Princess Alexandra Hospital Clinical Research Fellowship.