Feasibility of rigid 3D image registration of high-resolution peripheral quantitative computed tomography images of healing distal radius fractures

Abstract

For accurate analysis of bone formation and resorption during fracture healing, correct registration of follow-up onto baseline image is required. A per-fragment approach could improve alignment compared to standard registration based on the whole fractured region. In this exploratory study, we tested the effect of fragment size and displacement on a per-fragment registration, and compared the results of this per-fragment registration to the results of the standard registration in two stable fractures and one unstable fracture.To test the effect of fragment size and displacement, high-resolution peripheral quantitative computed tomography (HR-pQCT) scans of three unfractured radii were divided into subvolumes. Different displacements in x-, y, or z-direction or rotations around each axis were applied, and each subvolume was registered onto the initial volume to realign it. Next, registration of follow-up onto baseline scan was performed in two stable and one unstable fracture. After coarsely aligning the follow-up onto the baseline scan, a more accurate registration was performed of the whole fracture, i.e. the standard registration, and of each fracture fragment separately, i.e. per-fragment registration. Alignment was checked using overlay images showing baseline, follow-up and overlap between these scans, and by comparing correlation coefficients between the standard and per-fragment registration.Generally, subvolumes as small as 300 mm3 that were displaced up to 0.82 mm in x- or y-, or up to 1.64 mm in z-direction could be realigned correctly. For the fragments of all fractures, correlation coefficients were higher after per-fragment registration compared to standard registration. Most improvement was found in the unstable fracture and one fragment of the unstable fracture did not align correctly.This exploratory study showed that image registration of individual subvolumes, such as fracture fragments, is feasible in both stable and unstable fractures, and leads to better alignment of these fragments compared to an approach that is based on registration using the whole fractured region. This result is promising for additional analysis of bone formation and resorption in HR-pQCT studies on fracture healing.

Virtual mechanical tests out‐perform morphometric measures for assessment of mechanical stability of fracture healing in vivo

“…Finite element analysis (FEA) with models derived from computed tomography (CT) scans is increasing in prevalence as a research and clinical diagnostic tool in orthopedics. [1][2][3][4][5][6][7][8] This technique is able to accurately capture both the complex geometries and localized material acquired by the CT scan to build representative animalspecific or patient-specific models. 9,10 FEA can then be used to simulate different loading scenarios and assess the structural biomechanics of the anatomy of interest.…”

Improvements in radiographic and clinical assessment of distal radius fracture healing by FE-estimated bone stiffness

“…We also recommend that future work focuses on improving the precision of the μFE models by reducing repositioning error through image registration. We were unable to apply whole bone 3D image registration due to large differences in bone structure across follow-up scans; however, new image registration techniques have been developed to register individual bone fragments accounting for inter-fragmentary displacement ( de Jong et al, 2017 ).…”

The utility of multi-stack alignment and 3D longitudinal image registration to assess bone remodeling in rheumatoid arthritis patients from second generation HR-pQCT scans

“…Slight errors in registration and/or motion artifact may lead to inaccuracies in the global bone remodeling analysis. Previous studies using microCT in animal models have demonstrated that longitudinal analyses of bone remodeling produces better accuracy and precision when performed on a local region of interest rather than the whole bone [26][27][28]. It is likely that future studies using this bone remodeling analysis in the context of rheumatoid arthritis will be primarily concerned with bone changes around the region of an erosion, rather than the global changes throughout the bone.…”