FDG uptake in brown fat in Chinese: Description on 18F-FDG PET/CT

Abstract

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Objectives: The purpose of this study was to evaluate this FDG uptake pattern by positron emission tomography (PET) and computer tomography (CT) imaging. Methods: Between August 2005 and June 2006, 2478 patients (1658 female and 820 male), 2528 consecutive FDG whole-body scans were obtained with a PET/CT scanner. Scanning was performed using the Discovery LS PET/CT scanner (General Electric Medical Systems). Patients were fasted at least 6 h before the PET acquisition. Intravenous injection of 55.5MBq/kg of 18F-FDG was followed by a tracer uptake phase of about 60 min, during which the patients sat in a quiet room without talking. Imaging parameters were as follows for an acquisition at 5-7 bed positions: 140 kV, 120mAs, 0.8s per CT rotation, a pitch of 6, a table speed of 22.5 mm/s, 722.5mm coverage, and a 31.9s acquisition time. All PET/CT scans were examined retrospectively by 1 observer on an interactive display using fusion software (Xeleris; General Electric Medical Systems). Results: Twenty-five patients (7 male and 18 female) of the 2528 scans (0.99%) demonstrated brown fat uptake. The incidence rate was 2.20% in scans of female patients and 0.42% in scans of male patients. Patients with brown fat uptake were younger than patients without (35.3±13y vs.53.6±14y, P<0.01). Although there was no significant difference in BMI between patients with brown fat uptake, they tended to be thinner (BMI, 20.4±2 vs. 23.2±5, P>0.05). BMI was 19.6±2 for male patients and 20.8±2 for female patients with brown fat uptake (P>0.05). When comparing the monthly incidence rate from April to October, the incidence was highest from November to March in the whole group of patients (1.68% vs. 0.48%, P<0.01). Conclusions: FDG uptake in brown fat occurs particularly in female, younger patients and those with lower BMI values. The incidence of brown fat is clearly increased during the cooler period of the year.

Research Support (if any): 04BA03. 04JC14044