A Trimodality Comparison of Volumetric Bone Imaging Technologies. Part III: SD, SEE, LSC Association With Fragility Fractures.

Part II of this 3-part series demonstrated 1-yr precision, standard error of the estimate, and 1-yr least significant change for volumetric bone outcomes determined using peripheral (p) quantitative computed tomography (QCT) and peripheral magnetic resonance imaging (pMRI) modalities in vivo. However, no clinically relevant outcomes have been linked to these measures of change. This study examined 97 women with mean age of 75 ± 9 yr and body mass index of 26.84 ± 4.77 kg/m(2), demonstrating a lack of association between fragility fractures and standard deviation, least significant change and standard error of the estimate-based unit differences in volumetric bone outcomes derived from both pMRI and pQCT. Only cortical volumetric bone mineral density and cortical thickness derived from high-resolution pQCT images were associated with an increased odds for fractures. The same measures obtained by pQCT erred toward significance. Despite the smaller 1-yr and short-term precision error for measures at the tibia vs the radius, the associations with fractures observed at the radius were larger than at the tibia for high-resolution pQCT. Unit differences in cortical thickness and cortical volumetric bone mineral density able to yield a 50% increase in odds for fractures were quantified here and suggested as a reference for future power computations.

A trimodality comparison of volumetric bone imaging technologies. Part I: Short-term precision and validity.

In vivo peripheral quantitative computed tomography (pQCT) and peripheral magnetic resonance imaging (pMRI) modalities can measure apparent bone microstructure at resolutions 200 µm or higher. However, validity and in vivo test-retest reproducibility of apparent bone microstructure have yet to be determined on 1.0 T pMRI (196 µm) and pQCT (200 µm). This study examined 67 women with a mean age of 74±9 yr and body mass index of 27.65±5.74 kg/m2, demonstrating validity for trabecular separation from pMRI, cortical thickness, and bone volume fraction from pQCT images compared with high-resolution pQCT (hr-pQCT), with slopes close to unity. However, because of partial volume effects, cortical and trabecular thickness of bone derived from pMRI and pQCT images matched hr-pQCT more only when values were small. Short-term reproducibility of bone outcomes was highest for bone volume fraction (BV/TV) and densitometric variables and lowest for trabecular outcomes measuring microstructure. Measurements at the tibia for pQCT images were more precise than at the radius. In part I of this 3-part series focused on trimodality comparisons of precision and validity, it is shown that pQCT images can yield valid and reproducible apparent bone structural outcomes, but because of longer scan time and potential for more motion, the pMRI protocol examined here remains limited in achieving reliable values.

A Trimodality Comparison of Volumetric Bone Imaging Technologies. Part II: 1-Yr Change, Long-Term Precision, and Least Significant Change.

The previous article in this 3-part series demonstrated short-term precision and validity for volumetric bone outcome quantification using in vivo peripheral (p) quantitative computed tomography (pQCT) and magnetic resonance imaging (MRI) modalities at resolutions 200 µm or higher. However, 1-yr precision error and clinically significant references are yet to be reported for these modalities. This study examined 59 women with mean age of 75 ± 9 yr and body mass index of 26.84 ± 4.77 kg/m², demonstrating the lowest 1-yr precision error, standard errors of the estimate, and least significant change values for high-resolution (hr) pQCT followed by pQCT, and 1.0-T pMRI for all volumetric bone outcomes except trabecular number. Like short-term precision, 1-yr statistics for trabecular separation were similar across modalities. Excluding individuals with a previous history of fragility fractures, or who were current users of antiresorptives reduced 1-yr change for bone outcomes derived from pQCT and pMR images, but not hr-pQCT images. In Part II of this 3-part series focused on trimodality comparisons of 1-yr changes, hr-pQCT was recommended to be the prime candidate for quantifying change where smaller effect sizes are expected, but pQCT was identified as a feasible alternative for studies expecting larger changes.