title: Dual-energy X-ray absorptiometry-based body volume measurement for 4-compartment body composition.
abstract: BACKGROUND
  Total body volume (TBV), with the exclusion of internal air voids, is necessary to quantify body composition in Lohman's 4-compartment (4C) model.
  
  
  OBJECTIVE
  This investigation sought to derive a novel, TBV measure with the use of only dual-energy X-ray absorptiometry (DXA) attenuation values for use in Lohman's 4C body composition model.
  
  
  METHODS
  Pixel-specific masses and volumes were calculated from low- and high-energy attenuation values with the use of first principle conversions of mass attenuation coefficients. Pixel masses and volumes were summed to derive body mass and total body volume. As proof of concept, 11 participants were recruited to have 4C measures taken: DXA, air-displacement plethysmography (ADP), and total body water (TBW). TBV measures with the use of only DXA (DXA-volume) and ADP-volume measures were compared for each participant. To see how body composition estimates were affected by these 2 methods, we used Lohman's 4C model to quantify percentage fat measures for each participant and compared them with conventional DXA measures.
  
  
  RESULTS
  DXA-volume and ADP-volume measures were highly correlated (R(2) = 0.99) and showed no statistically significant bias. Percentage fat by DXA volume was highly correlated with ADP-volume percentage fat measures and DXA software-reported percentage fat measures (R(2) = 0.96 and R(2) = 0.98, respectively) but were slightly biased.
  
  
  CONCLUSIONS
  A novel method to calculate TBV with the use of a clinical DXA system was developed, compared against ADP as proof of principle, and used in Lohman's 4C body composition model. The DXA-volume approach eliminates many of the inherent inaccuracies associated with displacement measures for volume and, if validated in larger groups of participants, would simplify the acquisition of 4C body composition to a single DXA scan and TBW measure.
authors.affiliation: University of California, Berkeley-University of California, San Francisco Graduate Program in Bioengineering, USA.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Wilson
authors.forename: Kathleen
authors.initials: K
authors.lastname: Mulligan
authors.forename: Bo
authors.initials: B
authors.lastname: Fan
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Sherman
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Murphy
authors.forename: Viva W
authors.initials: VW
authors.lastname: Tai
authors.forename: Cassidy L
authors.initials: CL
authors.lastname: Powers
authors.forename: Lorena
authors.initials: L
authors.lastname: Marquez
authors.forename: Viviana
authors.initials: V
authors.lastname: Ruiz-Barros
authors.forename: John A
authors.initials: JA
authors.lastname: Shepherd
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods*; D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D000328:Adult; D001823:Body Composition; D049628:Body Size; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009765:Obesity / Q000175:diagnosis / Q000000981:diagnostic imaging*; D010991:Plethysmography / Q000379:methods*; D015203:Reproducibility of Results