Guidelines for the assessment of bone density and microarchitecture in vivo using high-resolution peripheral quantitative computed tomography

Abstract

Introduction: The application of high-resolution peripheral quantitative computed tomography (HR-pQCT) to assess bone microarchitecture has grown rapidly since its introduction in 2005. As the use of HR-pQCT for clinical research continues to grow, there is an urgent need to form a consensus on imaging and analysis methodologies so that studies can be appropriately compared. In addition, with the recent introduction of the second-generation HrpQCT, which differs from the first-generation HR-pQCT in scan region, resolution, and morphological measurement techniques, there is a need for guidelines on appropriate reporting of results and considerations as the field adopts newer systems.

Methods: A joint working group between the International Osteoporosis Foundation, American Society of Bone and Mineral Research, and European Calcified Tissue Society convened in person and by teleconference over several years to produce the guidelines and recommendations presented in this document.

Results: An overview and discussion is provided for (1) standardized protocol for imaging distal radius and tibia sites using HR-pQCT, with the importance of quality control and operator training discussed; (2) standardized terminology and recommendations on reporting results; (3) factors influencing accuracy and precision error, with considerations for longitudinal and multi-center study designs; and finally (4) comparison between scanner generations and other high-resolution CT systems.

Conclusion: This article addresses the need for standardization of HR-pQCT imaging techniques and terminology, provides guidance on interpretation and reporting of results, and discusses unresolved issues in the field.

Keywords: Bone microarchitecture; Guidelines; High-resolution peripheral quantitative computed tomography; Imaging protocol.

Figure 1:

Scout view from a first-generation HR-pQCT showing reference line placement for the fixed offset distance (left) and relative offset distance (right) methods for the radius and tibia [36]. The edge of the radiocarpal joint surface of the distal radius and tibial plafond are marked in red. Scan regions represented here are approximate and illustrate a scenario where the fixed and relative offset are aligned.

Figure 2:

Motion grading guideline as recommended by the manufacturer and presented by Sode et al. [41], with visual examples provided here for second-generation HR-pQCT radius (top row) and tibia (bottom row) scans.

Figure 3:

Example of distal radius scan from a first-generation HR-pQCT and outputs from image processing protocol, where A) is the greyscale slice-wise view with the periosteal contour (green) identified, B) segmented whole bone volume, C) cortical bone region extracted using the standard analysis protocol, and D) cortical bone region extracted using the dual-threshold technique.

Figure 4:

Example a segmented second-generation HR-pQCT tibia scan converted into an FE mesh using a voxel-by-voxel conversion approach. The model is composed of millions of hexahedral elements.

Figure 5:

Examples of axial (A) and angular (B) offsets in between scan regions captured at baseline (blue) and follow-up (red).