title: Characterizing active and inactive brown adipose tissue in adult humans using PET-CT and MR imaging.
abstract: 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.
authors.affiliation: Vanderbilt University Institute of Imaging Science, Nashville, Tennessee; Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee;
authors.forename: Aliya
authors.initials: A
authors.lastname: Gifford
authors.affiliation: Vanderbilt University Institute of Imaging Science, Nashville, Tennessee; Department of Physical Medicine and Rehabilitation, Vanderbilt University School of Medicine, Nashville, Tennessee;
authors.forename: Theodore F
authors.initials: TF
authors.lastname: Towse
authors.affiliation: Department of Medical Imaging, Tennessee Valley Veterans Affairs Healthcare, Nashville, Nashville, Tennessee; Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee; and.
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Walker
authors.affiliation: Vanderbilt University Institute of Imaging Science, Nashville, Tennessee; Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee; Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee; and Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Malcolm J
authors.initials: MJ
authors.lastname: Avison
authors.affiliation: Vanderbilt University Institute of Imaging Science, Nashville, Tennessee; Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee; Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee; and brian.welch@vanderbilt.edu.
authors.forename: E Brian
authors.initials: EB
authors.lastname: Welch
mesh_terms: D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging* / Q000378:metabolism; D000328:Adult; D003080:Cold Temperature; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D000072078:Positron Emission Tomography Computed Tomography; D019275:Radiopharmaceuticals; D022722:Thermogenesis; D035441:Thoracic Wall / Q000000981:diagnostic imaging*; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: brown adipose tissue; fat signal fraction; fat water magnetic resonance imaging; tissue segmentation; white adipose tissue