Operator variability in scan positioning is a major component of HR-pQCT precision error and is reduced by standardized training

Bonaretti, Serena; Vilayphiou, Nicolas; Chan, CM; Yu, Aihong; Nishiyama, Kyle K.; Liu, D; Boutroy, Stéphanie; Ghasem‐Zadeh, Ali; Boyd, Steven K.; Chapurlat, Roland; McKay, Heather; Shane, Elizabeth; Bouxsein, Mary L.; Black, DM; Majumdar, Sharmila; Orwoll, E.; Lang, T.F.; Khosla, Sundeep; Burghardt, Andrew J.

doi:10.1007/s00198-016-3705-5

Cited by 36 publications

(30 citation statements)

References 34 publications

(47 reference statements)

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“…Using paired fixed offset and relative offset scans, Shanbhouge and colleagues [16] found similar magnitude differences. These observations are also consistent with recent data that documents high precision errors for the measurement of cortical bone due to variability in operator scan positioning [26]. With RMS differences of 20% and 13% for the radius and tibia respectively, the variability confounding measurement of Ct.Th by not accounting for limb length is comparable to clinically relevant differences observed, for example, in fracture case-control studies [38,39].…”

Section: Discussionsupporting

confidence: 90%

“…This corresponds approximately to one tenth of the error that biological variability in individual limb-length introduces to fixed-offset scan positioning (i.e. 1.14 mm), and less than half the error introduced by the operator positioning the reference line to prescribe the scan (0.38 mm) [26]. Thus, despite moderate imprecision in limb length measurement, the effect on the positioning variability is relatively small.…”

Section: Discussionmentioning

confidence: 99%

“…For the radius, we defined the relative offset as a percentage of ulnar length offset from the proximal margin of the articular surface of the radius (Figure 1c), consistent with other common procedures for measuring bone density at the distal radius (DXA, pQCT), but notably different from previous manufacturer recommendations for HR-pQCT. The position of the alternative reference landmark in the radius was determined retrospectively for each scan using software implemented for a complementary study of operator positioning precision [26]. Briefly, we developed a graphical user interface that reproduces the manufacturer’s acquisition software.…”

Section: Methodsmentioning

confidence: 99%

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The comparability of HR-pQCT bone measurements is improved by scanning anatomically standardized regions

et al. 2017

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Introduction High-resolution peripheral quantitative computed tomography (HR-pQCT) measures of bone do not account for anatomic variability in bone length: a 1-cm volume is acquired at a fixed offset from an anatomic landmark. Our goal was to evaluate HR-pQCT measurement variability introduced by imaging fixed vs. proportional volumes and to propose a standard protocol for relative anatomic positioning. Methods Double-length (2-cm) scans were acquired in 30 adults. We compared measurements from 1-cm subvolumes located at the default fixed offset, and the average %-of-length offset. The average position corresponded to 4.0% ± 1.1 mm for radius, and 7.2% ± 2.2 mm for tibia. We calculated the RMS difference in bone parameters and T-Scores to determine the measurement variability related to differences in limb length. We used anthropometric ratios to estimate the mean limb length for published HR-pQCT reference data, and then calculated mean %-of-length offsets. Results Variability between fixed vs. relative scan positions was highest in the radius, and for cortical bone in general (RMS difference Ct.Th = 19.5%), while individuals had T-score differentials as high as +3.0 SD (radius Ct.BMD). We estimated that average scan position for published HR-pQCT reference data corresponded to 4.0% at the radius, and 7.3% at tibia. Conclusion Variability in limb length introduces significant bias to HR-pQCT measures, confounding cross-sectional analyses and limiting the clinical application for individual assessment of skeletal status. We propose to standardize scan positioning using 4.0% and 7.3% of total bone length for the distal radius and tibia, respectively.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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The comparability of HR-pQCT bone measurements is improved by scanning anatomically standardized regions

et al. 2017

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“…Compared to precision errors for cortical bone parameters obtained by a short-term repositioning study that used S-AUTO [10], the precision errors of S-AUTOmean and AUTO were higher, particularly those of Ct.Po.V and Ct.Po of the distal tibia. In contrast, the error introduced by not correcting the endocortical contour to the precision was comparable to the error introduced by variability in positioning of the reference line for the parameters Ct.BMD and Ct.Th, but not for Ct.Po [22]. Additionally, the precision error of S-AUTOmean and AUTO for Ct.Po and Ct.Po.Dm of the distal radius is comparable to the precision error of a donor specimen that was scanned and evaluated at 9 different sites [23].…”

Section: Discussionmentioning

confidence: 99%

Reliability of HR-pQCT Derived Cortical Bone Structural Parameters When Using Uncorrected Instead of Corrected Automatically Generated Endocortical Contours in a Cross-Sectional Study: The Maastricht Study

et al. 2018

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Most HR-pQCT studies examining cortical bone use an automatically generated endocortical contour (AUTO), which is manually corrected if it visually deviates from the apparent endocortical margin (semi-automatic method, S-AUTO). This technique may be prone to operator-related variability and is time consuming. We examined whether the AUTO instead of the S-AUTO method can be used for cortical bone analysis. Fifty scans of the distal radius and tibia from participants of The Maastricht Study were evaluated with AUTO, and subsequently with S-AUTO by three independent operators. AUTO cortical bone parameters were compared to the average parameters obtained by the three operators (S-AUTOmean). All differences in mean cortical bone parameters between AUTO and S-AUTOmean were < 5%, except for lower AUTO cortical porosity of the radius (− 16%) and tibia (− 6%), and cortical pore volume (Ct.Po.V) of the radius (− 7%). The ICC of S-AUTOmean and AUTO was > 0.90 for all parameters, except for cortical pore diameter of the radius (0.79) and tibia (0.74) and Ct.Po.V of the tibia (0.89), without systematic errors on the Bland–Altman plots. The precision errors (RMS-CV%) of the radius parameters between S-AUTOmean and AUTO were comparable to those between the individual operators, whereas the tibia RMS-CV% between S-AUTOmean and AUTO were higher than those of the individual operators. Comparison of the three operators revealed clear inter-operator variability. This study suggests that the AUTO method can be used for cortical bone analysis in a cross-sectional study, but that the absolute values—particularly of the porosity-related parameters—will be lower.Electronic supplementary materialThe online version of this article (10.1007/s00223-018-0416-2) contains supplementary material, which is available to authorized users.

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“…Finally, we did not consider the motion artefacts occurring during in vivo scans, but accounted for the operator variability via three operators. The influence of both aspects can be minimized (Pauchard et al 2012, Bonaretti et al 2016). …”

Section: Discussionmentioning

confidence: 99%

μCT-based trabecular anisotropy can be reproducibly computed from HR-pQCT scans using the triangulated bone surface

Hosseini

Maquer

Zysset

2017

Bone

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word count: 244 Total word count: 3727 Attachments: 4 figures and 2 tablesArticle in Bone · January 2017 -DOI: 10.1016/j.bone.2017 Highlights  A new method for evaluating the fabric tensor from triangulated bone surfaces was introduced: the mean surface length (MSL)  24 human radii were scanned via low and high resolution HR-pQCT protocols repeated three times and µCT  The performance and reproducibility of MSL, MIL, GST and SCANCO's TRI were compared using 182 regions of interest  MSL derived from HR-pQCT was the best surrogate for the gold standard MIL on µCT  MSL was more reproducible than MIL for capturing the fabric tensor from HR-pQCT Article in Bone · January 2017 -DOI: 10.1016/j.bone.2017.01.016 AbstractThe trabecular structure can be assessed at the wrist or tibia via high-resolution peripheral quantitative computed tomography (HR-pQCT). Yet on this modality, the performance of the existing methods, evaluating trabecular anisotropy is usually overlooked, especially in terms of reproducibility. We thus proposed to compare the TRI routine used by SCANCO Medical AG (Brüttisellen, Switzerland), the classical mean intercept length (MIL), and the grey-level structure tensor (GST) to the mean surface length (MSL), a new method for evaluating a second-order fabric tensor based on the triangulation of the bone surface. The distal radius of 24 fresh-frozen human forearms was scanned three times via HR-pQCT protocols (61µm, 82µm nominal voxel size), dissected, and imaged via micro computed tomography (µCT) at 16µm nominal voxel size. After registering the scans, we compared for each resolution the fabric tensors, determined by the mentioned techniques for 182 trabecular regions of interest.We then evaluated the reproducibility of the fabric information measured by HR-pQCT via precision errors. On µCT, TRI and GST were respectively the best and worst surrogates for MILµCT (MIL computed on µCT) in terms of eigenvalues and main direction of anisotropy. On HR-pQCT, however, MSL provided the best approximation of MILµCT. Surprisingly, surfacebased approaches (TRI, MSL) also proved to be more precise than both MIL and GST. Our findings confirm that MSL can reproducibly estimate MILµCT, the current gold standard. MSL thus enables the direct mapping of the fabric-dependent material properties required in homogenised HR-pQCT-based finite element models.

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Operator variability in scan positioning is a major component of HR-pQCT precision error and is reduced by standardized training

Cited by 36 publications

References 34 publications

The comparability of HR-pQCT bone measurements is improved by scanning anatomically standardized regions

The comparability of HR-pQCT bone measurements is improved by scanning anatomically standardized regions

Reliability of HR-pQCT Derived Cortical Bone Structural Parameters When Using Uncorrected Instead of Corrected Automatically Generated Endocortical Contours in a Cross-Sectional Study: The Maastricht Study

μCT-based trabecular anisotropy can be reproducibly computed from HR-pQCT scans using the triangulated bone surface

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