title: Operator variability in scan positioning is a major component of HR-pQCT precision error and is reduced by standardized training.
abstract: In this study, we determined that operator positioning precision contributes significant measurement error in high-resolution peripheral quantitative computed tomography (HR-pQCT). Moreover, we developed software to quantify intra- and inter-operator variability and demonstrated that standard positioning training (now available as a web-based application) can significantly reduce inter-operator variability.
  
  
  
  HR-pQCT is increasingly used to assess bone quality, fracture risk, and anti-fracture interventions. The contribution of the operator has not been adequately accounted in measurement precision. Operators acquire a 2D projection ("scout view image") and define the region to be scanned by positioning a "reference line" on a standard anatomical landmark. In this study, we (i) evaluated the contribution of positioning variability to in vivo measurement precision, (ii) measured intra- and inter-operator positioning variability, and (iii) tested if custom training software led to superior reproducibility in new operators compared to experienced operators.
  
  
  
  To evaluate the operator in vivo measurement precision, we compared precision errors calculated in 64 co-registered and non-co-registered scan-rescan images. To quantify operator variability, we developed software that simulates the positioning process of the scanner's software. Eight experienced operators positioned reference lines on scout view images designed to test intra- and inter-operator reproducibility. Finally, we developed modules for training and evaluation of reference line positioning. We enrolled six new operators to participate in a common training, followed by the same reproducibility experiments performed by the experienced group.
  
  
  
  In vivo precision errors were up to threefold greater (Tt.BMD and Ct.Th) when variability in scan positioning was included. The inter-operator precision errors were significantly greater than the short-term intra-operator precision (p < 0.001). New trained operators achieved comparable intra-operator reproducibility to experienced operators and lower inter-operator reproducibility (p < 0.001). Precision errors were significantly greater for the radius than for the tibia.
  
  
  
  Operator reference line positioning contributes significantly to in vivo measurement precision and is significantly greater for multi-operator datasets. Inter-operator variability can be significantly reduced using a systematic training platform, now available online ( http://webapps.radiology.ucsf.edu/refline/ ).
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA. serena.bonaretti@stanford.edu.|Department of Radiology, Stanford University, Stanford, CA, USA. serena.bonaretti@stanford.edu.
authors.forename: S
authors.initials: S
authors.lastname: Bonaretti
authors.affiliation: Scanco Medical AG, Brüttisellen, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: Vilayphiou
authors.affiliation: University of California Berkeley, Berkeley, CA, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Chan
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.
authors.forename: A
authors.initials: A
authors.lastname: Yu
authors.affiliation: Division of Endocrinology, Department of Medicine, Columbia University Medical Center, New York, NY, USA.
authors.forename: K
authors.initials: K
authors.lastname: Nishiyama
authors.affiliation: University of British Columbia, Vancouver, BC, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Liu
authors.affiliation: INSERM UMR 1033, Université de Lyon, Lyon, France.
authors.forename: S
authors.initials: S
authors.lastname: Boutroy
authors.affiliation: Department of Medicine, Austin Health, University of Melbourne, Melbourne, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Ghasem-Zadeh
authors.affiliation: Department of Radiology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: S K
authors.initials: SK
authors.lastname: Boyd
authors.affiliation: INSERM UMR 1033, Université de Lyon, Lyon, France.
authors.forename: R
authors.initials: R
authors.lastname: Chapurlat
authors.affiliation: University of British Columbia, Vancouver, BC, Canada.
authors.forename: H
authors.initials: H
authors.lastname: McKay
authors.affiliation: Division of Endocrinology, Department of Medicine, Columbia University Medical Center, New York, NY, USA.
authors.forename: E
authors.initials: E
authors.lastname: Shane
authors.affiliation: Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Boston, MA, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Bouxsein
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Black
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Majumdar
authors.affiliation: Division of Endocrinology, Bone and Mineral Unit, Oregon Health & Science University, Portland, OR, USA.
authors.forename: E S
authors.initials: ES
authors.lastname: Orwoll
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.
authors.forename: T F
authors.initials: TF
authors.lastname: Lang
authors.affiliation: Division of Endocrinology, Metabolism and Nutrition, Department of Internal Medicine, College of Medicine, Mayo Clinic, Rochester, MN, USA.
authors.forename: S
authors.initials: S
authors.lastname: Khosla
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Burghardt
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks; D002983:Clinical Competence; D005260:Female; D006801:Humans; D007318:Inservice Training / Q000379:methods; D008297:Male; D010024:Osteoporosis / Q000000981:diagnostic imaging*; D011884:Radius / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D012985:Software Design; D013977:Tibia / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards*
keywords: HR-pQCT; Multicenter studies; Operator reproducibility; Precision; Standardization