title: Dual-energy X-ray absorptiometry: analysis of pediatric fat estimate errors due to tissue hydration effects.
abstract: Dual-energy X-ray absorptiometry (DXA) percent (%) fat estimates may be inaccurate in young children, who typically have high tissue hydration levels. This study was designed to provide a comprehensive analysis of pediatric tissue hydration effects on DXA %fat estimates. Phase 1 was experimental and included three in vitro studies to establish the physical basis of DXA %fat-estimation models. Phase 2 extended phase 1 models and consisted of theoretical calculations to estimate the %fat errors emanating from previously reported pediatric hydration effects. Phase 1 experiments supported the two-compartment DXA soft tissue model and established that pixel ratio of low to high energy (R values) are a predictable function of tissue elemental content. In phase 2, modeling of reference body composition values from birth to age 120 mo revealed that %fat errors will arise if a "constant" adult lean soft tissue R value is applied to the pediatric population; the maximum %fat error, approximately 0.8%, would be present at birth. High tissue hydration, as observed in infants and young children, leads to errors in DXA %fat estimates. The magnitude of these errors based on theoretical calculations is small and may not be of clinical or research significance.
authors.affiliation: Department of Pediatrics, San Raffaele Hospital, 20132 Milano, Italy.
authors.forename: C G
authors.initials: CG
authors.lastname: Testolin
authors.forename: R
authors.initials: R
authors.lastname: Gore
authors.forename: T
authors.initials: T
authors.lastname: Rivkin
authors.forename: M
authors.initials: M
authors.lastname: Horlick
authors.forename: J
authors.initials: J
authors.lastname: Arbo
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: G
authors.initials: G
authors.lastname: Chiumello
authors.forename: S B
authors.initials: SB
authors.lastname: Heymsfield
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000000981:diagnostic imaging* / Q000378:metabolism*; D001823:Body Composition; D001834:Body Water / Q000378:metabolism*; D002675:Child, Preschool; D006801:Humans; D008954:Models, Biological; D010372:Pediatrics / Q000379:methods*; D019047:Phantoms, Imaging