EDITORIAL Optimizing interventions for preventing uptake in the brown adipose tissue in FDG-PET Sandip Basu & Abass Alavi Received: 1 January 2008 / Accepted: 4 January 2008 / Published online: 19 March 2008 # Springer-Verlag 2008 Keywords Brown adipose tissue . FDG . PET . Propranolol . Brown fat . Diazepam . Fentanyl . PET-CT With the increasing use of 18-fluoro-deoxy-glucose-positron emission tomography (FDG-PET) in the practice of medi- cine, enhanced glycolysis in brown adipose tissue (BAT) has posed a major concern for accurate interpretation of the images [1, 2]. Brown fat is a sub-type of adipose tissue and regulates body temperature by non-shivering thermogenesis. This has been termed “USA Fat” by some investigators [2]. Histologically, it is characterized by high vascularity, dense mitochondria in the cells, and abundant sympathetic norad- renergic innervation. The usual distribution of BAT includes neck and shoulder region, axillae, mediastinum, retrocrural and paravertebral sites [1–4]. FDG uptake in BAT has been noted to occur more frequently in cold months [5]. Recent data suggests that FDG uptake in BAT occurs more often as a result of acute response to cold weather rather than the prolonged periods of average cold weather [6]. Significant localization of FDG in BAT has been particularly problem- atic for accurate assessment of suspected malignant lymph nodes in the neck region. Also, there have been reports [7, 8] of atypical as well as asymmetrical distribution of BAT. Therefore, it is important to recognize these variants so that they are not misinterpreted as disease sites. In addition, the serendipitous discovery of brown fat by FDG-PET has provided a unique opportunity to study the physiology of this complex adipose tissue [9, 10]. In fact, there has been significant interest in identifying and studying the physiology of active brown adipose tissue in the recent years by in vivo functional imaging techniques [9–14]. It is now clear that a sizeable proportion of adult humans possess active brown adipose tissue [10] and the distribution of BAT in the human is slightly different from those in the rodents, being primarily located in the supraclavicular and the neck regions. Such studies are essential for optimal understanding of its importance in regulating human metabolism and for its potential role in the genesis and treatment of obesity. Hence, we strongly believe the therapeutic interventions that may influence BAT activity will also shed some light on this type of investigation and can provide valuable insights into the antiobesity research. Several types of interventions [15–21] have been proposed to reduce the metabolic activity of BAT, but there has not been any clear consensus or a set protocol to stop FDG uptake in BAT. The methods adopted can be broadly classified into three groups: (a) pharmacological interven- tions such as premedication with benzodiazepine, propran- olol, reserpine, and fentanyl [15–18] and (b) warming maneuvers and temperature control during the PET proce- dure [19, 20]. In addition, (c) precise localization with fusion PET/CT scan [1, 2, 21, 22] has been proposed as a means to reduce misinterpretation of the results generated. Obviously, comparison with the corresponding CT image is of great importance in making the optimal diagnosis in this setting. The initial results with oral diazepam have been reproduced with limited success. In one study [18], FDG Eur J Nucl Med Mol Imaging (2008) 35:1421–1423 DOI 10.1007/s00259-008-0720-6 S. Basu : A. Alavi (*) Division of Nuclear Medicine, Hospital of University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA e-mail: abass.alavi@uphs.upenn.edu S. Basu Radiation Medicine Centre (BARC), Tata Memorial Hospital Annex, Bombay 400012, India