Alkhawaldeh Khaled, Alavi Abass
Department of Radiology, Division of Nuclear Medicine, King Hussein Hospital, Amman, Jordan.
Clin Nucl Med. 2008 Oct;33(10):663-7. doi: 10.1097/RLU.0b013e318184b3de.
Brown fat is a potential source of false-positive findings on FDG PET. The purpose of this study was to show the variability in body distribution of brown fat, the degree of FDG uptake, the changes on dual-time-point scanning, and determine if dual-time-point scanning can help in differentiating brown fat from malignant lesions.
Thirty-two patients were included in this retrospective study (14 male, 18 female, age range: 8-72 years). All patients had hypermetabolic brown fat activity on FDG PET imaging confirmed by computed tomography (CT) scanning. All patients underwent 2 sequential FDG PET scanning (dual-time-point imaging). The average percent change in maximum standardized uptake value (SUVmax) for 120 brown fat spots between time point 1 and time point 2 was calculated.
Body distribution of hypermetabolic brown fat in the 32 patients included supraclavicular area (n = 7); cervical and supraclavicular (n = 5); cervical, supraclavicular, and axillae (n = 5); cervical area, supraclavicular, axillae, and paravertebral (n = 8); supraclavicular, cervical, axillae, paravertebral, and mediastinum (n = 4); supraclavicular, cervical, axillae, paravertebral, and upper abdomen (n = 2); and supraclavicular, cervical, axillae, paravertebral, mediastinum, and intercostals (n = 1). SUVmax for brown fat spots ranged from 0.8 to 12.4 and mean SUV was 4.6 + 1.6. On dual-time-point imaging, 91 (76%) of the brown fat spots demonstrated an increase in SUVmax that ranged from 12% to 192% and mean value of 42%, whereas 16 (13%) brown fat spots did not show any change and 11 (11%) spots underwent a drop in SUVmax by 4% to 12%. There was an increase in the number of active brown fat spots in 3 patients on the second time images.
Brown fat is a potential source of false positives, which has wide variability in distribution and degree of FDG uptake. On dual-time-point scanning, there is a progressive increase in FDG uptake within most of the hypermetabolic brown fat areas that mimic malignant lesions.
棕色脂肪是FDG PET检查中假阳性结果的潜在来源。本研究的目的是展示棕色脂肪在体内分布的变异性、FDG摄取程度、双时相扫描的变化，并确定双时相扫描是否有助于区分棕色脂肪和恶性病变。
本回顾性研究纳入了32例患者（男性14例，女性18例，年龄范围：8 - 72岁）。所有患者在FDG PET成像上均有经计算机断层扫描（CT）证实的棕色脂肪代谢活跃。所有患者均接受了2次连续的FDG PET扫描（双时相成像）。计算了120个棕色脂肪部位在时间点1和时间点2之间最大标准化摄取值（SUVmax）的平均变化百分比。
32例患者中棕色脂肪代谢活跃的身体分布包括锁骨上区域（n = 7）；颈部和锁骨上（n = 5）；颈部、锁骨上和腋窝（n = 5）；颈部区域、锁骨上、腋窝和椎旁（n = 8）；锁骨上、颈部、腋窝、椎旁和纵隔（n = 4）；锁骨上、颈部、腋窝、椎旁和上腹部（n = 2）；以及锁骨上、颈部、腋窝、椎旁、纵隔和肋间（n = 1）。棕色脂肪部位的SUVmax范围为0.8至12.4，平均SUV为4.6 ± 1.6。在双时相成像中，91个（76%）棕色脂肪部位的SUVmax增加，范围为12%至192%，平均值为42%，而16个（13%）棕色脂肪部位没有变化，11个（11%）部位的SUVmax下降了4%至12%。在第二次扫描图像上，3例患者的活跃棕色脂肪部位数量增加。
棕色脂肪是假阳性的潜在来源，其在分布和FDG摄取程度上具有很大变异性。在双时相扫描中，大多数代谢活跃的棕色脂肪区域内的FDG摄取呈渐进性增加，类似恶性病变。
