Gifford Aliya, Towse Theodore F, Walker Ronald C, Avison Malcolm J, Welch E Brian
Vanderbilt University Institute of Imaging Science, Nashville, Tennessee; Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee;
Vanderbilt University Institute of Imaging Science, Nashville, Tennessee; Department of Physical Medicine and Rehabilitation, Vanderbilt University School of Medicine, Nashville, Tennessee;
Am J Physiol Endocrinol Metab. 2016 Jul 1;311(1):E95-E104. doi: 10.1152/ajpendo.00482.2015. Epub 2016 May 10.
Activated brown adipose tissue (BAT) plays an important role in thermogenesis and whole body metabolism in mammals. Positron emission tomography (PET)-computed tomography (CT) imaging has identified depots of BAT in adult humans, igniting scientific interest. The purpose of this study is to characterize both active and inactive supraclavicular BAT in adults and compare the values to those of subcutaneous white adipose tissue (WAT). We obtained [(18)F]fluorodeoxyglucose ([(18)F]FDG) PET-CT and magnetic resonance imaging (MRI) scans of 25 healthy adults. Unlike [(18)F]FDG PET, which can detect only active BAT, MRI is capable of detecting both active and inactive BAT. The MRI-derived fat signal fraction (FSF) of active BAT was significantly lower than that of inactive BAT (means ± SD; 60.2 ± 7.6 vs. 62.4 ± 6.8%, respectively). This change in tissue morphology was also reflected as a significant increase in Hounsfield units (HU; -69.4 ± 11.5 vs. -74.5 ± 9.7 HU, respectively). Additionally, the CT HU, MRI FSF, and MRI R2* values are significantly different between BAT and WAT, regardless of the activation status of BAT. To the best of our knowledge, this is the first study to quantify PET-CT and MRI FSF measurements and utilize a semiautomated algorithm to identify inactive and active BAT in the same adult subjects. Our findings support the use of these metrics to characterize and distinguish between BAT and WAT and lay the foundation for future MRI analysis with the hope that some day MRI-based delineation of BAT can stand on its own.
活化的棕色脂肪组织（BAT）在哺乳动物的产热和全身代谢中起着重要作用。正电子发射断层扫描（PET）-计算机断层扫描（CT）成像已在成年人体内发现了BAT的储存部位，引发了科学兴趣。本研究的目的是对成年人中活跃和不活跃的锁骨上BAT进行特征描述，并将这些值与皮下白色脂肪组织（WAT）的值进行比较。我们对25名健康成年人进行了[（18）F]氟脱氧葡萄糖（[（18）F]FDG）PET-CT和磁共振成像（MRI）扫描。与只能检测活跃BAT的[（18）F]FDG PET不同，MRI能够检测活跃和不活跃的BAT。活跃BAT的MRI衍生脂肪信号分数（FSF）显著低于不活跃BAT（均值±标准差；分别为60.2±7.6%和62.4±6.8%）。这种组织形态学变化也表现为亨氏单位（HU）的显著增加（分别为-69.4±11.5和-74.5±9.7 HU）。此外，无论BAT的激活状态如何，BAT和WAT之间的CT HU、MRI FSF和MRI R2*值均存在显著差异。据我们所知，这是第一项对PET-CT和MRI FSF测量进行量化并利用半自动算法在同一成年受试者中识别不活跃和活跃BAT的研究。我们的研究结果支持使用这些指标来表征和区分BAT和WAT，并为未来的MRI分析奠定基础，希望有一天基于MRI的BAT描绘能够独立存在。
