title: Fat mass measured by DXA varies with scan velocity.
abstract: OBJECTIVE
  To study the influence of scan velocities of DXA on the measured size of fat mass, lean body mass, bone mineral content and density, and total body weight.
  
  
  METHODS
  The subjects were 71 healthy white adults, 38 women and 33 men. The mean age was 41.7 +/- 13.5 years and body mass index was 28.6 +/- 5.6 kg/m(2). The subjects were scanned consecutively in slow, medium, and fast scan mode by a Lunar DPX-IQ DXA scanner.
  
  
  RESULTS
  Throughout the body mass index and sagittal height ranges, scanned lean body mass significantly decreased with higher scan velocity and lean body mass was 2.7% lower in fast than in medium mode (p < 0.0001). In contrast, fat mass, percentage of body fat, and bone mineral contents were higher with increasing scan velocity. Areas not analyzed by the scanner, so called blue spots, increased with scan velocity and sagittal height, and their presence significantly enhanced the error. Body weight estimated by DXA in slow mode was -0.8% lower than scale weight in the women (p < 0.001) and -0.2% in men (not significant), and the difference was greater with increasing scan velocity.
  
  
  CONCLUSIONS
  Scan velocity significantly influences the measured fat mass size, lean body mass, bone mineral content, and body weight. To obtain the most accurate results, slow mode is preferable and fast scans should be avoided. Future studies should report and take scan velocity into consideration.
authors.affiliation: Research Department of Human Nutrition, Centre for Advanced Food Studies, The Royal Veterinary and Agricultural University, Frederiksberg C, Denmark. eva.black@dadlnet.dk
authors.forename: Eva
authors.initials: E
authors.lastname: Black
authors.forename: Liselotte
authors.initials: L
authors.lastname: Petersen
authors.forename: Martin
authors.initials: M
authors.lastname: Kreutzer
authors.forename: Søren
authors.initials: S
authors.lastname: Toubro
authors.forename: Thorkild I A
authors.initials: TI
authors.lastname: Sørensen
authors.forename: Oluf
authors.initials: O
authors.lastname: Pedersen
authors.forename: Arne
authors.initials: A
authors.lastname: Astrup
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods* / Q000592:standards*; D000273:Adipose Tissue; D000328:Adult; D000368:Aged; D001823:Body Composition; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D015519:Bone Density; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity