Brown Adipose Tissue Uptake Research Articles

A Diurnal Rhythm in Glucose Uptake in Brown Adipose Tissue Revealed by In Vivo PET‐FDG Imaging

Using a micro-PET/CT scanner, we have measured 18F-fluorodeoxyglucose uptake in interscapular brown adipose tissue (iBAT) in C57Bl/6 mice at intervals across a 24-hour light-dark cycle. Our data reveals a strong 24-hour profile of glucose uptake of iBAT, peaking at approximately 9 hours into the light phase of the 12 hour light, 12 hour dark day. BAT is increasingly gaining attention as being involved in metabolic phenotypes and obesity, where BAT, as observed by PET analysis, negatively correlates with obesity and age. Conversely, animals that show perturbations in circadian clocks, behavior and physiology show metabolic phenotypes. The observation of a 24-hour rhythm in glucose uptake in iBAT makes this tissue a candidate site of interaction between metabolic and circadian systems.

Ex Vivo and In Vivo Evaluation of the Norepinephrine Transporter Ligand [11C]MRB for Brown Adipose Tissue Imaging

It has been suggested that brown adipose tissue (BAT) in humans may play a role in energy balance and obesity. We conducted ex vivo and in vivo evaluation using [(11)C]MRB, a highly selective NET (norepinephrine transporter) ligand for BAT imaging at room temperature, which is not achievable with [(18)F]FDG. PET images of male Sprague-Dawley rats with [(18)F]FDG and [(11)C]MRB were compared. Relative [(18)F]FDG or [(11)C]MRB retention at 20, 40 and 60 min post-injection was quantified on awake rats after exposing to cold (4°C for 4h) or remaining at room temperature. Rats pretreated with unlabeled MRB or nisoxetine 30 min before [(11)C]MRB injection were also assessed. The [(11)C]MRB metabolite profile in BAT was evaluated. PET imaging demonstrated intense [(11)C]MRB uptake (SUV of 2.9 to 3.3) in the interscapular BAT of both room temperature and cold-exposed rats and this uptake was significantly diminished by pretreatment with unlabeled MRB; in contrast, [(18)F]FDG in BAT was only detected in rats treated with cold. Ex vivo results were concordant with the imaging findings; i.e. the uptake of [(11)C]MRB in BAT was 3 times higher than that of [(18)F]FDG at room temperature (P=0.009), and the significant cold-stimulated uptake in BAT with [(18)F]FDG (10-fold, P=0.001) was not observed with [(11)C]MRB (P=0.082). HPLC analysis revealed 94%-99% of total radioactivity in BAT represented unchanged [(11)C]MRB. Our study demonstrates that BAT could be specifically labeled with [(11)C]MRB at room temperature and under cold conditions, supporting a NET-PET strategy for imaging BAT in humans under basal conditions.

Intervention to Lower Anxiety of 18F-FDG PET/CT Patients by Use of Audiovisual Imagery During the Uptake Phase Before Imaging

Many patients referred for PET suffer from anxiety, possibly affecting the workflow and patient experience. In addition, patient anxiety may affect image quality through uptake of (18)F-FDG in muscles or brown adipose tissue (BAT).This study investigated the effects of a nonpharmacologic intervention-the use of audiovisual imagery in the PET uptake room-on patient anxiety and false-positive uptake of (18)F-FDG (in muscles and BAT). A 2-stage study was conducted on 101 patients. The cohort undergoing the intervention included 51 patients. The first stage (n = 35) included physiologic measurements (cardiovascular activity, muscular activity, skin conductance, and cortisol), a state anxiety questionnaire, and visual evaluation of (18)F-FDG uptake in muscles and BAT; the second stage (n = 66) included only the state anxiety questionnaire and the (18)F-FDG uptake evaluation. Throughout the stay in the uptake room, a significant decrease in overall anxiety was found, together with several other significant changes in patient physiology. In the cohort with audiovisual intervention, however, the decrease in patient anxiety was significantly larger. The cohort with intervention also showed significantly lower (18)F-FDG uptake in BAT but not in muscles. The investigated audiovisual intervention helps to lower patient anxiety in the PET uptake room and can lower false-positive (18)F-FDG uptake in BAT.

Unexpected Visitor on FDG PET/CT—Brown Adipose Tissue (BAT) in Mesentery in a Case of Retroperitoneal Extra-Adrenal Pheochromocytoma

Fused positron emission tomography-computed tomography (PET/CT) technology has enabled the determination that nonmalignant fluorodeoxyglucose (FDG) uptake is observed in brown adipose tissue (BAT). FDG uptake in BAT is a known potential source of false-positive interpretations for PET. The typical locations of BAT include neck, supraclavicular area, mediastinum, and paravertebral intercostal spaces. Examples of atypical locations for BAT include posterior neck, left paratracheal area, axillae, perirenal area, and retrocrural area. We report PET/CT findings in a young male patient with malignant retroperitoneal extra-adrenal pheochromocytoma, who demonstrated FDG uptake in BAT at multiple locations including mesenteric BAT. We also propose catecholamine-secreting pheochromocytoma as a possible cause of BAT activation in our case.

Assessment of Oxidative Metabolism in Brown Fat Using PET Imaging

Objective: Although it has been believed that brown adipose tissue (BAT) depots disappear shortly after the perinatal period in humans, positron emission tomography (PET) imaging using the glucose analog 18F-deoxy-d-glucose (FDG) has shown unequivocally the existence of functional BAT in humans, suggesting that most humans have some functional BAT. The objective of this study was to determine, using dynamic oxygen-15 (15O) PET imaging, to what extent BAT thermogenesis is activated in adults during cold stress and to establish the relationship between BAT oxidative metabolism and FDG tracer uptake. Methods: Fourteen adult normal subjects (9F/5M, 30 ± 7 years) underwent triple oxygen scans (H215O, C15O, 15O2) as well as indirect calorimetric measurements at both rest and following exposure to mild cold (16°C). Subjects were divided into two groups (BAT+ and BAT−) based on the presence or absence of FDG tracer uptake (SUV > 2) in cervical–supraclavicular BAT. Blood flow and oxygen extraction fraction (OEF) was calculated from dynamic PET scans at the location of BAT, muscle, and white adipose tissue (WAT). The metabolic rate of oxygen (MRO2) in BAT was determined and used to calculate the contribution of activated BAT to daily energy expenditure (DEE). Results: The median mass of activated BAT in the BAT+ group (5F, age 31 ± 8) was 52.4 g (range 14–68 g) and was 1.7 g (range 0–6.3 g) in the BAT − group (5M/4F, age 29 ± 6). Corresponding SUV values were significantly higher in the BAT+ as compared to the BAT− group (7.4 ± 3.7 vs. 1.9 ± 0.9; p = 0.03). Blood flow values in BAT were significantly higher in the BAT+ group as compared to the BAT− group (13.1 ± 4.4 vs. 5.7 ± 1.1 ml/100 g/min, p = 0.03), but were similar in WAT (4.1 ± 1.6 vs. 4.2 ± 1.8 ml/100 g/min) and muscle (3.7 ± 0.8 vs. 3.3 ± 1.2 ml/100 g/min). Moreover, OEF in BAT was similar in the two groups (0.56 ± 0.18 in BAT+ vs. 0.46 ± 0.19 in BAT−, p = 0.39). Calculated MRO2 values in BAT increased from 0.95 ± 0.74 to 1.62 ± 0.82 ml/100 g/min in the BAT+ group and were significantly higher than those determined in the BAT− group (0.43 ± 0.27 vs. 0.56 ± 0.24, p = 0.67). The DEE associated with BAT oxidative metabolism was highly variable in the BAT+ group, with an average of 5.5 ± 6.4 kcal/day (range 0.57–15.3 kcal/day). Conclusion: BAT thermogenesis in humans accounts for less than 20 kcal/day during moderate cold stress, even in subjects with relatively large BAT depots. Furthermore, due to the large differences in blood flow and glucose metabolic rates in BAT between humans and rodents, the application of rodent data to humans is problematic and needs careful evaluation.

Effects of burn injury, cold stress and cutaneous wound injury on the morphology and energy metabolism of murine brown adipose tissue (BAT) in vivo

AimsCold stress has been shown to produce dramatic increases in 2-fluoro-2-deoxy-D-Glucose (18FDG) accumulation by brown adipose tissue (BAT) in rodents. However, neither the effects of other types of stress on 18FDG accumulation nor the effects of stressors on the accumulation of tracers of other aspects of energy metabolism have been evaluated. In this report we studied the effects of cold stress, burn injury and cutaneous wounds on murine BAT at the macroscopic, microscopic and metabolic level. Main methodsGlucose metabolism was studied with 18FDG, fatty acid accumulation was evaluated with trans-9(RS)-18F-fluoro-3,4(RS,RS)-methyleneheptadecanoic acid (FCPHA) and tricarboxcylic acid cycle (TCA) activity was evaluated with 3H acetate. Key findingsAll three stressors produced dramatic changes in BAT at the macroscopic and microscopic level. Macroscopically, BAT from the stressed animals appeared to be a much darker brown in color. Microscopically BAT of stressed animals demonstrated significantly fewer lipid droplets and an overall decrease in lipid content. Accumulation of 18FDG by BAT was significantly (p<0.01) increased by all 3 treatments (Cold: ~16 fold, burn ~7 Fold and cutaneous wound ~14 fold) whereas uptake of FDG by white fat was unchanged. This effect was also demonstrated non invasively by μPET imaging. Although less prominent than with 18FDG, BAT uptake of FCPHA and acetate were also significantly increased by all three treatments. These findings suggest that in addition to cold stress, burn injury and cutaneous wounds produce BAT activation in mice. SignificanceThis study demonstrates brown fat activated by several stressors leads to increased uptake of various substrates.

18F-Fluorobenzyl Triphenyl Phosphonium: A Noninvasive Sensor of Brown Adipose Tissue Thermogenesis

Recent studies have proposed activation of brown adipose tissue (BAT) thermogenesis as a new strategy to combat obesity. Currently, there is no effective noninvasive imaging agent to directly detect unstimulated BAT and quantify the core mechanism of mitochondrial thermogenesis. We investigated an approach to detect BAT depots and monitor thermogenesis using the mitochondria-targeting voltage sensor radiolabeled fluorobenzyltriphenyl phosphonium (FBnTP). (18)F-FBnTP, (14)C-FBnTP, (18)F-FDG, and (99m)Tc-sestamibi uptake in BAT at room temperature (n = 8) and cold-treated (n = 8) Lewis rats was assayed. The effect of the cold condition on (18)F-FBnTP retention in BAT was assessed in 8 treated and 16 control rats. The effect of the noradrenergic inhibitor propranolol on (14)C-FBnTP response to cold stimulation was investigated in an additional 8 treated and 8 control mice. At room temperature, (18)F-FBnTP accumulated in BAT to an extent similar to that in the heart, second only to the kidney and twice as much as (99m)Tc-sestamibi. Prior exposure to cold (4°C) for 4 h resulted in an 82% decrease of (14)C-FBnTP uptake and an 813% increase of (18)F-FDG uptake in BAT. (99m)Tc-sestamibi uptake was not affected by cold. Administration of (18)F-FBnTP at room temperature 60 min before 120 and 240 min of exposure to cold resulted in marked washout of the tracer from BAT. Propranolol significantly diminished the effect of cold on (14)C-FBnTP and (18)F-FDG uptake into BAT. The intense uptake of (18)F-FBnTP into BAT at room temperature and the response to cold stimulation suggest the unique potential advantage of (18)F-FBnTP not only in detecting unstimulated BAT at high contrast but also in quantifying the mitochondrial thermogenic activity. (18)F-FBnTP PET may serve as a useful technique to assess BAT volume and function.

Pharmacological Targeting of Glucagon and Glucagon-Like Peptide 1 Receptors Has Different Effects on Energy State and Glucose Homeostasis in Diet-Induced Obese Mice

Pharmacologic contributions of directly agonizing glucagon-like peptide 1 (GLP-1) receptor or antagonizing glucagon receptor (GCGR) on energy state and glucose homeostasis were assessed in diet-induced obese (DIO) mice. Metabolic rate and respiratory quotient (RQ), hyperglycemic clamp, stable isotope-based dynamic metabolic profiling (SiDMAP) studies of (13)C-labeled glucose during glucose tolerance test (GTT) and gene expression were assessed in cohorts of DIO mice after a single administration of GLP-1 analog [GLP-1-(23)] or anti-GCGR antibody (Ab). GLP-1-(23) and GCGR Ab similarly improved GTT. GLP-1-(23) decreased food intake and body weight trended lower. GCGR Ab modestly decreased food intake without significant effect on body weight. GLP-1-(23) and GCGR Ab decreased RQ with GLP-1, causing a greater effect. In a hyperglycemic clamp, GLP-1-(23) reduced hepatic glucose production (HGP), increased glucose infusion rate (GIR), increased glucose uptake in brown adipose tissue, and increased whole-body glucose turnover, glycolysis, and rate of glycogen synthesis. GCGR Ab slightly decreased HGP, increased GIR, and increased glucose uptake in the heart. SiDMAP showed that GLP-1-(23) and GCGR Ab increased (13)C lactate labeling from glucose, indicating that liver, muscle, and other organs were involved in the rapid disposal of glucose from plasma. GCGR Ab and GLP-1-(23) caused different changes in mRNA expression levels of glucose- and lipid metabolism-associated genes. The effect of GLP-1-(23) on energy state and glucose homeostasis was greater than GCGR Ab. Although GCGR antagonism is associated with increased circulating levels of GLP-1, most GLP-1-(23)-associated pharmacologic effects are more pronounced than GCGR Ab.

Brown adipose tissue 18F-FDG uptake in pediatric PET/CT imaging

Positron emission tomography (PET) using [F-18]2-fluoro-2-deoxyglucose (FDG) fused with CT ((18)F-FDG PET/CT) has been widely adopted in oncological imaging. However, it is known that benign lesions and other metabolically active tissues, such as brown adipose tissue (BAT), can accumulate (18)F-FDG, potentially resulting in false-positive interpretation. Previous studies have reported that (18)F-FDG uptake in BAT is more common in children than in adults. We illustrate BAT FDG uptake in various anatomical locations in children and adolescents. We also review what is known about the effects of patient-related physical attributes and environmental temperatures on BAT FDG uptake, and discuss methods used to reduce BAT FDG uptake on (18)F-FDG PET.

The Relationship between Patients’ Serum Glucose Levels and Metabolically Active Brown Adipose Tissue Detected by PET/CT

To compare blood glucose levels in patients with or without "detectable" brown adipose tissue (BAT) using 2-deoxy-2-[(18)F]fluoro-D-glucose positron emission tomography/computed tomography (FDG PET/CT). Nine hundred eight patients had PET/CT scans and were previously identified as having, or not having, FDG uptake in BAT. The original database was retrospectively reviewed for blood glucose level and body mass index (BMI) at the time of imaging. Blood glucose levels were compared between patients with or without FDG uptake in BAT, adjusting for age, sex, and BMI. Fifty-six patients (6.2%) had FDG uptake in BAT. In the univariate analysis, patients without FDG uptake in BAT had a higher risk of glucose ≥100 mg/dL (odds ratio 3.4, 95% CI = 1.6-7.3; P = 0.0007). After adjustment for age, sex, BMI, and significant interaction of sex and BMI, patients without BAT tended to have a higher risk of glucose ≥100 mg/dL, although not statistically significant (odds ratio = 1.6, 95% CI = 0.7-3.6; P = 0.268). Although causal relationships are not specified, the data suggest that BAT uptake, glucose levels, BMI, sex, and age are inter-related and the possibility that presence of "detectable" BAT is protective against diabetes and obesity. FDG PET/CT may be a vital tool for further investigations of diabetes and obesity.

Determinants of Physiologic 18F-FDG Uptake in Brown Adipose Tissue in Sequential PET/CT Examinations

The aim of this study was to assess independent predictors of 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)F-FDG) uptake in brown adipose tissue (BAT) in patients undergoing repeated positron emission tomography (PET)/computed tomography (CT) scans. Eight hundred forty-eight (mean age 50.9 ± 16 years) patients in whom PET/CT scan was repeated (mean interval 5 ± 1.5 months) constituted the study group. (18)F-FDG uptake in characteristic areas of BAT, with CT density of adipose tissue, greater than background soft-tissue activity was considered as evidence of BAT uptake. Both distribution and maximum standardized uptake values (SUVmax) were registered. Clinical and anamnestic data were collected for each patient. (18)F-FDG uptake in BAT was present in 8.6% patients at first scan. Independent predictors of presence of uptake were age (younger), gender (female), body mass index (lower), and maximum outdoor temperature (lower). Age was the only independent predictor of BAT (18)F-FDG uptake distribution, while SUVmax was related to both age and outdoor temperature. Independent determinants of persistence of BAT (18)F-FDG uptake at second PET/CT were outdoor temperature at time of second scan and extension of metabolically active BAT at first scan. Age, body mass index, and outdoor temperature are significant determinants of BAT evidence at (18)F-FDG PET/CT. Moreover, extension of BAT and outdoor temperature are the strongest determinants of persistence of BAT evidence on (18)F-FDG PET/CT in repeated scan.

FDG uptake in brown adipose tissue—A brief report on brown fat with FDG uptake mechanisms and quantitative analysis using dual-time-point FDG PET/CT

Aims Brown adipose tissue (BAT) is a potential source of false-positive findings on [ 18F] FDG PET. In this report, we have discussed the 18F-FDG uptake mechanisms in BAT and have aimed to determine if dual time point PET imaging helps to differentiate BAT from malignant lesions. Methods Patients with dual-time-point PET/CT scans were reviewed retrospectively and 31 cases (11 males, 20 females, age: 28.6±9.7) having hypermetabolic BAT were included for this study. 18F-FDG uptake in BAT was quantitatively analyzed by maximum standardized uptake values (SUVmax), and average percent change in SUVmax of BAT between early and delayed images was calculated. Results Compared to the initial scans, 18F-FDG uptakes in BAT in delayed images were higher in 26 of the patients, and lower in one patient. In terms of body regions, 18F-FDG uptake increased in 80.6%, remained unchanged in 5.5% and decreased in 13.9% of the body regions. Mean percent change in SUVmax, including all BAT regions, was 19.8±19.1% while the mean percent increase was calculated as 69±25% in regions where progressive accumulation was observed. The increase in SUVmax correlated with the time interval between the two scans. Conclusion Physiologic 18F-FDG uptake in BAT increases over time and may mimic the behavior of malignant lesions on dual time point PET imaging. Without the exact anatomic definition of the CT scan, false positive interpretation of PET data may be possible in cases with atypical BAT.

Prevention of Brown Adipose Tissue Activation in 18F-FDG PET/CT of Breast Cancer Patients Receiving Neoadjuvant Systemic Therapy

(18)F-FDG uptake in brown adipose tissue (BAT) can complicate interpretation and quantification of PET images, especially in regions of possible lymph node metastases such as the axilla and the mediastinum. The aim of this study was to prospectively evaluate the effect of patient preparation using a single oral dose of diazepam and controlled indoor temperature to prevent (18)F-FDG uptake in BAT in breast cancer patients referred for monitoring of therapy response with (18)F-FDG PET. During the fall and winter months, 53 patients referred for (18)F-FDG PET/CT of breast cancer were included. A cohort of 25 patients was imaged without an intervention, and a second cohort of 28 patients was prepared according to a new protocol that included 10 mg of diazepam and adequate indoor temperature. The generated images were visually assessed for the presence of (18)F-FDG at the location of fat-density tissue on CT images using a 4-point scale. In the cohort without intervention, relevant (18)F-FDG uptake in BAT was identified in 4 patients (16%); in the cohort prepared according to the proposed protocol, in only 1 patient (4%). The mean score of BAT (18)F-FDG uptake evaluated with the 4-point system was 0.04 in the group treated according to the new protocol and 0.16 in the group treated according to the previous protocol. In the clinically relevant group of breast cancer patients, (18)F-FDG uptake in BAT can be reduced by a single oral administration of diazepam combined with controlled room temperature in resting rooms.

Identifying Ga-67 Uptake in Brown Adipose Tissue WithSPECT/CT

Identifying Ga-67 Uptake in Brown Adipose Tissue WithSPECT/CT

Thyroid Hormone Induced Brown Adipose Tissue and Amelioration of Diabetes in a Patient with Extreme Insulin Resistance

Brown adipose tissue (BAT) found by positron emission/computed tomography (PET-CT) using flouro-deoxyglucose (FDG) is inducible by cold exposure in men. Factors leading to increased BAT are of great interest for its potential role in the treatment of diabetes and obesity. We tested whether thyroid hormone (TH) levels are related to the volume and activity of BAT in a patient with a mutation in the insulin receptor gene. DESIGN/SETTING/INTERVENTION: Our work was based on the case report of a patient in an observational study at the National Institutes of Health. The patient discontinued insulin and oral antidiabetics after thyroidectomy and suppressive-dose levothyroxine therapy for thyroid cancer. PET-CT uptake in BAT was confirmed by histology and molecular analysis. PET-CT studies were performed, and we measured hemoglobin A1c and resting energy expenditure before and after levothyroxine discontinuation for thyroid cancer testing. Molecular studies of BAT and white adipose samples are presented. Supraclavicular and periumbilical sc adipose tissue demonstrated molecular features of BAT including uncoupling protein-1, type 2 deiodinase, and PR domain containing 16 by quantitative PCR. Activity of type 2 deiodinase activity was increased. The discontinuation of levothyroxine resulted in decreased FDG uptake and diminished volume of BAT depots accompanied by worsening of diabetic control. This case demonstrates the TH effect on BAT activity and volume in this patient and an association between BAT activity and glucose levels in this patient. Because the contribution of TH on skeletal muscle energy expenditure and fuel metabolism was not assessed, an association between BAT activity and glucose homeostasis can only be suggested.

Asymmetric 18F-FDG Uptake in the Infradiaphragmatic Brown Adipose Tissue (BAT) Mimicking Adrenal Metastasis: A Relatively Rare Site of Brown Fat and a Potential Source for False Positive FDG-PET Study

FDG uptake in the metabolically active brown adipose tissue (BAT) is a source of significant concern while interpreting FDG-PET studies. It is also of great interest due to its potential implications for obesity research. In this communication, we describe hitherto unreported asymmetric BAT uptake in the abdomen, persisting after diazepam intervention in the repeat PET study on a separate day. The patient did not have any evidence of disease even at 24 months' follow up. The present case is a useful addition to the current body of literature of false positive FDG-PET due to BAT uptake in unusual location and underscores the importance of high index of suspicion and careful correlation, whenever one comes across an unusual PET finding in a given clinical situation. This assumes important diagnostic value particularly when it coexists in the setting of malignancy where the disease can be falsely upstaged by misinterpretation. The literature relevant to the report is discussed and a schema is suggested for correct interpretation.

Distinct Effects of Leptin and a Melanocortin Receptor Agonist Injected Into Medial Hypothalamic Nuclei on Glucose Uptake in Peripheral Tissues

OBJECTIVEThe medial hypothalamus mediates leptin-induced glucose uptake in peripheral tissues, and brain melanocortin receptors (MCRs) mediate certain central effects of leptin. However, the contributions of the leptin receptor and MCRs in individual medial hypothalamic nuclei to regulation of peripheral glucose uptake have remained unclear. We examined the effects of an injection of leptin and the MCR agonist MT-II into medial hypothalamic nuclei on glucose uptake in peripheral tissues.RESEARCH DESIGN AND METHODSLeptin or MT-II was injected into the ventromedial (VMH), dorsomedial (DMH), arcuate nucleus (ARC), or paraventricular (PVH) hypothalamus or the lateral ventricle (intracerebroventricularly) in freely moving mice. The MCR antagonist SHU9119 was injected intracerebroventricularly. Glucose uptake was measured by the 2-[3H]deoxy-d-glucose method.RESULTSLeptin injection into the VMH increased glucose uptake in skeletal muscle, brown adipose tissue (BAT), and heart, whereas that into the ARC increased glucose uptake in BAT, and that into the DMH or PVH had no effect. SHU9119 abolished these effects of leptin injected into the VMH. Injection of MT-II either into the VMH or intracerebroventricularly increased glucose uptake in skeletal muscle, BAT, and heart, whereas that into the PVH increased glucose uptake in BAT, and that into the DMH or ARC had no effect.CONCLUSIONSThe VMH mediates leptin- and MT-II–induced glucose uptake in skeletal muscle, BAT, and heart. These effects of leptin are dependent on MCR activation. The leptin receptor in the ARC and MCR in the PVH regulate glucose uptake in BAT. Medial hypothalamic nuclei thus play distinct roles in leptin- and MT-II–induced glucose uptake in peripheral tissues.

A novel approach for reduction of brown fat uptake on FDG PET

The aim of this study was to determine whether or not a single dose of a beta-blocker, such as propranolol 40 mg, administered 60 min prior to (18)F-fluorodeoxyglucose ((18)F-FDG) injection would help reduce brown fat uptake of (18)F-FDG. Patients who were referred for either a pre-treatment or a post-treatment evaluation positron emission tomography (PET) scan and who showed (18)F-FDG uptake in brown adipose tissue (BAT) were included in this study. The total number of patients who showed uptake in BAT and in whom a repeat study was carried out after propranolol injection was 40. A repeat PET scan was carried out after an interval of at least 48 h. Propranolol at a dose of 40 mg was given orally 60 min prior to the (18)F-FDG injection. A whole-body PET scan was performed on a dedicated whole-body PET scanner (ADVANCE, GE Medical Systems, Milwaukee, WI), using attenuation correction with 68-Ge external pin sources. We observed that (18)F-FDG uptake in BAT was absent in 36 (90%) patients post propranolol. We conclude that propranolol reduces the uptake of (18)F-FDG in BAT, and thus improves the accuracy of PET imaging.

Preliminary PET/CT study of 18F-FDG uptake in cervical and supraclavicular brown adipose tissue

OBJECTIVE The clinical use of PET/CT in oncology has led to the realization that 18F-FDG uptake in brown adipose tissue (BAT) can be a common cause of potentially misleading false-positive PET scans. The goal of this study was to study 18F-FDG uptake in cervical and supraclavicular regions and its characteristics with PET/CT. METHODS All the PET/CT scans obtained at our institution from July 2007 to January 2008 were retrospectively reviewed for increased 18F-FDG uptake in BAT. The cases in which increased 18F-FDG in cervical and supraclavicular regions was not localized to a soĞ -tissue mass or lymph node or muscle on the CT images, were included in this study. The following features were recorded: body weight, body mass index (BMI) and maximal standardized uptake value (SUVmax). In these selected patients, the BAT uptake in other area of UIF body was also recorded. RESULTS PET/CT scans were obtained in 457 patients (259 males and 198 females). In all of the scans, cervical and supraclavicular BAT uptake was observed in 12 patients (2 males and 10 females) and was typically bilateral, symmetric and intense. The range of the SUVmax was 3.6~12.82 (mean 6.9 ± 2.6). BAT uptake was more common in females than in males, showing a significant difference ( P = 0.004). Although 18F-FDG uptake in BAT occurred more often in underweight patients with low BMI, there was no di ff erence in the body weight ( P = 0.607) or BMI ( P = 0.491) of these patients with hypermetabolic BAT compared with controls. CONCLUSION Hypermetabolic BAT uptake can be localized in cervical and supraclavicular regions with it occurring more commonly in females compared to males. Knowledge of this potential pitfall with PET/CT is important in improving diagnostic interpretation and accurate staging.

Potential False Positive Tc-99m Sestamibi Parathyroid Study Due to Uptake in Brown Adipose Tissue

We report on a 55-year-old woman with suspected primary hyperparathyroidism who underwent dual phase Tc-99m sestamibi parathyroid imaging. Symmetric, patchy activity in the neck and shoulders was localized to low attenuation areas on integrated SPECT/CT and attributed to uptake in brown adipose tissue (BAT). Focal uptake in the anterior thorax on SPECT images, which potentially may have been misinterpreted as ectopic parathyroid tissue, was demonstrated on SPECT/CT as uptake in BAT. Recognition of this pattern on parathyroid SPECT/CT scintigraphy may avoid false positive reports. Our case provides further evidence that in addition to F-18 FDG, I-123 MIBG, and Tc-99m tetrofosmin, Tc-99m sestamibi may also accumulate in BAT.