title: A DXA Whole Body Composition Cross-Calibration Experience: Evaluation With Humans, Spine, and Whole Body Phantoms.
abstract: New densitometer installation requires cross-calibration for accurate longitudinal assessment. When replacing a unit with the same model, the International Society for Clinical Densitometry recommends cross-calibrating by scanning phantoms 10 times on each instrument and states that spine bone mineral density (BMD) should be within 1%, whereas total body lean, fat, and %fat mass should be within 2% of the prior instrument. However, there is limited validation that these recommendations provide adequate total body cross-calibration. Here, we report a total body cross-calibration experience with phantoms and humans. Cross-calibration between an existing and new Lunar iDXA was performed using 3 encapsulated spine phantoms (GE [GE Lunar, Madison, WI], BioClinica [BioClinica Inc, Princeton, NJ], and Hologic [Hologic Inc, Bedford, MA]), 1 total body composition phantom (BioClinica), and 30 human volunteers. Thirty scans of each phantom and a total body scan of human volunteers were obtained on each instrument. All spine phantom BMD means were similar (within 1%; <-0.010 g/cm2 bias) between the existing and new dual-energy X-ray absorptiometry unit. The BioClinica body composition phantom (BBCP) BMD and bone mineral content (BMC) values were within 2% with biases of 0.005 g/cm2 and -3.4 g. However, lean and fat mass and %fat differed by 4.6%-7.7% with biases of +463 g, -496 g, and -2.8%, respectively. In vivo comparison supported BBCP data; BMD and BMC were within ∼2%, but lean and fat mass and %fat differed from 1.6% to 4.9% with biases of +833 g, -860 g, and -1.1%. As all body composition comparisons exceeded the recommended 2%, the new densitometer was recalibrated. After recalibration, in vivo bias was lower (<0.05%) for lean and fat; -23 and -5 g, respectively. Similarly, BBCP lean and fat agreement improved. In conclusion, the BBCP behaves similarly, but not identical, to human in vivo measurements for densitometer cross-calibration. Spine phantoms, despite good BMD and BMC agreement, did not detect substantial lean and fat differences observed using BBCP and in vivo assessments. Consequently, spine phantoms are inadequate for dual-energy X-ray absorptiometry whole body composition cross-calibration.
authors.affiliation: Osteoporosis Clinical Research Program, University of Wisconsin, Madison, WI, USA. Electronic address: dckruege@wisc.edu.
authors.forename: Diane
authors.initials: D
authors.lastname: Krueger
authors.affiliation: Osteoporosis Clinical Research Program, University of Wisconsin, Madison, WI, USA.
authors.forename: Jessie
authors.initials: J
authors.lastname: Libber
authors.affiliation: Intercollegiate Athletics University of Wisconsin, Madison, WI, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Sanfilippo
authors.affiliation: BioClinica, Princeton, NJ, USA.
authors.forename: Hui Jing
authors.initials: HJ
authors.lastname: Yu
authors.affiliation: BioClinica, Princeton, NJ, USA.
authors.forename: Blaine
authors.initials: B
authors.lastname: Horvath
authors.affiliation: BioClinica, Princeton, NJ, USA; Alacrita LLC, Cambridge, MA, USA.
authors.forename: Colin G
authors.initials: CG
authors.lastname: Miller
authors.affiliation: Osteoporosis Clinical Research Program, University of Wisconsin, Madison, WI, USA.
authors.forename: Neil
authors.initials: N
authors.lastname: Binkley
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods / Q000592:standards; D000328:Adult; D001823:Body Composition; D015519:Bone Density; D002138:Calibration; D005260:Female; D006801:Humans; D008297:Male; D019047:Phantoms, Imaging; D013131:Spine / Q000000981:diagnostic imaging; D051598:Whole Body Imaging / Q000295:instrumentation / Q000379:methods
keywords: Cross-calibration; dual-energy X-ray absorptiometry; in vivo; spine phantom; whole body phantom