title: Human Brown Fat Radiodensity Indicates Underlying Tissue Composition and Systemic Metabolic Health.
abstract: Metabolic imaging studying brown adipose tissue (BAT) physiology has increased, in which computed tomography (CT) is commonly used as an anatomical reference for metabolic positron emission tomography (PET) imaging. However, the capacity of CT to provide metabolic information has been underexploited.
  
  
  
  To evaluate whether CT radiodensity of BAT could noninvasively estimate underlying tissue morphology, regarding amount of stored triglycerides. Furthermore, could the alteration in tissue characteristics due to cold stimulus, as a marker for active BAT, be detected with radiodensity? Can BAT be differentiated from white adipose tissue (WAT) solely using CT-based measurements?
  
  
  
  A cross-sectional study evaluating 66 healthy human subjects with CT, PET, and 1H-magnetic resonance spectroscopy (1H-MRS).
  
  
  
  BAT radiodensity was measured with CT. BAT-stored triglyceride content was measured with 1H-MRS. Arterial blood volume in BAT, as a marker of tissue vascularity, was measured with [15O]H2O, along with glucose or fatty acid uptake using [18F]2-fluoro-2-deoxy-D-glucose or 14(R,S)-[18F]fluoro-6-thia-heptadecanoic acid PET imaging, respectively.
  
  
  
  BAT radiodensity was found to be correlating with tissue-retained blood and triglyceride content. Cold stimulus induced an increase in BAT radiodensity. Active BAT depots had higher radiodensity than both nonactive BAT and WAT. BAT radiodensity associated with systemic metabolic health parameters.
  
  
  
  BAT radiodensity can be used as a marker of underlying tissue morphology. Active BAT can be identified using CT, exploiting tissue composition information. Moreover, BAT radiodensity provides an insight into whole-body systemic metabolic health.
authors.affiliation: Turku PET Centre, Turku University Hospital, 20520 Turku, Finland.|Turku PET Centre, University of Turku, 20520 Turku, Finland.
authors.forename: Mueez
authors.initials: M
authors.lastname: U Din
authors.affiliation: Turku PET Centre, Turku University Hospital, 20520 Turku, Finland.|Turku PET Centre, University of Turku, 20520 Turku, Finland.
authors.forename: Juho
authors.initials: J
authors.lastname: Raiko
authors.affiliation: Turku PET Centre, Turku University Hospital, 20520 Turku, Finland.|Turku PET Centre, University of Turku, 20520 Turku, Finland.
authors.forename: Teemu
authors.initials: T
authors.lastname: Saari
authors.affiliation: Turku PET Centre, Turku University Hospital, 20520 Turku, Finland.
authors.forename: Virva
authors.initials: V
authors.lastname: Saunavaara
authors.affiliation: Department of Medical Physics, Faculty of Medicine, Kagawa University, Kagawa 761-0793, Japan.
authors.forename: Nobu
authors.initials: N
authors.lastname: Kudomi
authors.affiliation: Turku PET Centre, Department of Chemistry, University of Turku and Accelerator Laboratory, Åbo Akademi University, 20520 Turku, Finland.
authors.forename: Olof
authors.initials: O
authors.lastname: Solin
authors.affiliation: Department of Radiology, Turku University Hospital and University of Turku, 20520 Turku, Finland.
authors.forename: Riitta
authors.initials: R
authors.lastname: Parkkola
authors.affiliation: Turku PET Centre, Turku University Hospital, 20520 Turku, Finland.|Turku PET Centre, University of Turku, 20520 Turku, Finland.
authors.forename: Pirjo
authors.initials: P
authors.lastname: Nuutila
authors.affiliation: Turku PET Centre, Turku University Hospital, 20520 Turku, Finland.|Turku PET Centre, University of Turku, 20520 Turku, Finland.
authors.forename: Kirsi A
authors.initials: KA
authors.lastname: Virtanen
mesh_terms: D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging* / Q000378:metabolism; D000328:Adult; D000886:Anthropometry / Q000379:methods; D003080:Cold Temperature; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods; D014280:Triglycerides / Q000378:metabolism
chemical_list: D014280:Triglycerides