title: Measurement of brown adipose tissue mass using a novel dual-echo magnetic resonance imaging approach: a validation study.
abstract: OBJECTIVE
  The aim of this study was to evaluate and validate magnetic resonance imaging (MRI) for the visualization and quantification of brown adipose tissue (BAT) in vivo in a rat model. We hypothesized that, based on differences in tissue water and lipid content, MRI could reliably differentiate between BAT and white adipose tissue (WAT) and could therefore be a possible alternative for (18)F-Fluorodeoxyglucose Positron Emission Tomography ((18)FDG-PET), the current gold standard for non-invasive BAT quantification.
  
  
  METHODS
  Eleven rats were studied using both (18)FDG-PET/CT and MRI (1.5 T). A dual echo (in-and-out-of-phase) sequence was used, both with and without spectral presaturation inversion recovery (SPIR) fat suppression (DUAL-SPIR) to visualize BAT, after which all BAT was surgically excised. The BAT volume measurements obtained via (18)FDG-PET/CT and DUAL-SPIR MR were quantitatively compared with the histological findings. All study protocols were reviewed and approved by the local ethics committee.
  
  
  RESULTS
  The BAT mass measurements that were obtained using DUAL-SPIR MR subtraction images correlated better with the histological findings (P=0.017, R=0.89) than did the measurements obtained using (18)FDG-PET/CT (P=0.78, R=0.15), regardless of the BAT metabolic activation state. Additionally, the basic feasibility of the DUAL-SPIR method was demonstrated in three human pilot subjects.
  
  
  CONCLUSIONS
  This study demonstrates the potential for MRI to reliably detect and quantify BAT in vivo. MRI can provide information beyond that provided by (18)FDG-PET imaging, and its ability to detect BAT is independent of its metabolic activation state. Additionally, MRI is a low-cost alternative that does not require radiation.
authors.affiliation: Medical Imaging Centre of Southwest Finland, Turku University Hospital, Turku, Finland.
authors.forename: Milja
authors.initials: M
authors.lastname: Holstila
authors.forename: Kirsi A
authors.initials: KA
authors.lastname: Virtanen
authors.forename: Tove J
authors.initials: TJ
authors.lastname: Grönroos
authors.forename: Jukka
authors.initials: J
authors.lastname: Laine
authors.forename: Virva
authors.initials: V
authors.lastname: Lepomäki
authors.forename: Jani
authors.initials: J
authors.lastname: Saunavaara
authors.forename: Irina
authors.initials: I
authors.lastname: Lisinen
authors.forename: Markku
authors.initials: M
authors.lastname: Komu
authors.forename: Jarna C
authors.initials: JC
authors.lastname: Hannukainen
authors.forename: Pirjo
authors.initials: P
authors.lastname: Nuutila
authors.forename: Riitta
authors.initials: R
authors.lastname: Parkkola
authors.forename: Ronald J H
authors.initials: RJ
authors.lastname: Borra
mesh_terms: D002001:Adipose Tissue, Brown / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D052436:Adipose Tissue, White / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D000818:Animals; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010865:Pilot Projects; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: (18)F-Fluorodeoxyglucose positron emission tomography; (18)FDG-PET; BAT; CT; Cold exposure; FDG; MRI; Rat; SPIR; WAT; brown adipose tissue; computed tomography; fluorodeoxyglucose; magnetic resonance imaging; spectral presaturation inversion recovery; white adipose tissue