title: Inter-scanner differences in in vivo QCT measurements of the density and strength of the proximal femur remain after correction with anthropomorphic standardization phantoms.
abstract: In multicenter studies and longitudinal studies that use two or more different quantitative computed tomography (QCT) imaging systems, anthropomorphic standardization phantoms (ASPs) are used to correct inter-scanner differences and allow pooling of data. In this study, in vivo imaging of 20 women on two imaging systems was used to evaluate inter-scanner differences in hip integral BMD (iBMD), trabecular BMD (tBMD), cortical BMD (cBMD), femoral neck yield moment (My) and yield force (Fy), and finite-element derived strength of the femur under stance (FEstance) and fall (FEfall) loading. Six different ASPs were used to derive inter-scanner correction equations. Significant (p<0.05) inter-scanner differences were detected in all measurements except My and FEfall, and no ASP-based correction was able to reduce inter-scanner variability to corresponding levels of intra-scanner precision. Inter-scanner variability was considerably higher than intra-scanner precision, even in cases where the mean inter-scanner difference was statistically insignificant. A significant (p<0.01) effect of body size on inter-scanner differences in BMD was detected, demonstrating a need to address the effects of body size on QCT measurements. The results of this study show that significant inter-scanner differences in QCT-based measurements of BMD and bone strength can remain even when using an ASP.
authors.affiliation: Department of Mechanical Engineering, University of Colorado Denver, Denver, CO, United States. Electronic address: dana.carpenter@ucdenver.edu.
authors.forename: R Dana
authors.initials: RD
authors.lastname: Carpenter
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States.
authors.forename: Isra
authors.initials: I
authors.lastname: Saeed
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States.
authors.forename: Serena
authors.initials: S
authors.lastname: Bonaretti
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States.
authors.forename: Carole
authors.initials: C
authors.lastname: Schreck
authors.affiliation: Department of Radiological Sciences, University of California, Irvine, CA, United States.
authors.forename: Joyce H
authors.initials: JH
authors.lastname: Keyak
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States.
authors.forename: Timothy
authors.initials: T
authors.lastname: Streeper
authors.affiliation: Intramural Research Program, National Institute on Aging, Bethesda, MD, United States.
authors.forename: Tamara B
authors.initials: TB
authors.lastname: Harris
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Lang
mesh_terms: D000368:Aged; D049628:Body Size; D015519:Bone Density; D005260:Female; D005272:Femur Neck / Q000000981:diagnostic imaging* / Q000502:physiology*; D020342:Finite Element Analysis; D006801:Humans; D008875:Middle Aged; D019047:Phantoms, Imaging / Q000592:standards*; D011187:Posture / Q000502:physiology; D012015:Reference Standards; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
keywords: Biomechanics; Bone mineral density; Hip; Quantitative computed tomography