Automated Segmentation of Fractured Distal Radii by 3D Geodesic Active Contouring ofin vivoHR-pQCT Images

Abstract

Radius fractures are among the most common fracture types; however, there is limited consensus on the standard of care. A better understanding of the fracture healing process could help to shape future treatment protocols and thus improve functional outcomes of patients. High-resolution peripheral quantitative computed tomography (HR-pQCT) allows monitoring and evaluation of the radius on the micro-structural level, which is crucial to our understanding of fracture healing. However, current radius fracture studies using HR-pQCT are limited by the lack of automated contouring routines, hence only including small number of patients due to the prohibitively time-consuming task of manually contouring HR-pQCT images. In the present study, a new method to automatically contour images of distal radius fractures based on 3D morphological geodesic active contours (3D-GAC) is presented. Contours of 60 HR-pQCT images of fractured and conservatively treated radii spanning the healing process up to one year post-fracture are compared to the current gold standard, hand-drawn 2D contours, to assess the accuracy of the algorithm. Furthermore, robustness was established by applying the algorithm to HR-pQCT images of intact radii of 73 patients and comparing the resulting morphometric indices to the gold standard patient evaluation. Reproducibility was evaluated using repeat scans of intact radii of 19 patients. The new 3D-GAC approach offers accurate contours within inter-operator variability for images of fractured distal radii. The generated contours for images of intact radii yielded morphometric indices within in vivo reproducibility limits compared to the current gold standard. Additionally, the 3D-GAC approach shows an improved robustness against failure when dealing with cortical interruptions, fracture fragments, etc. Using the 3D-GAC approach assures consistent results, while reducing the need for time-consuming semi-automatic contouring.

Clinical Observation of Diminished Bone Quality and Quantity through Longitudinal HR-pQCT-derived Remodeling and Mechanoregulation

“…The later of the two images was then rigidly registered and transformed to align with the earlier image using a pyramid-based approach optimized relative to the mean squared error between the two images 51 . Masks of the radius in each image were generated using geodesic active contouring 52 and used to generate cortical and trabecular masks using the scanner manufacturer’s software.…”

Formation Dominates Resorption With Increasing Mineralized Density and Time Postfracture in Cortical but Not Trabecular Bone: A Longitudinal HRpQCT Imaging Study in the Distal Radius

“…The radius of each registered image was then contoured using a geodesic active contouring method. ( 19 ) Within this contour, both cortical and trabecular regions were isolated, as well as the region of the fracture (Supplementary Information S1).…”

Bone Mechanoregulation Allows Subject-Specific Load Estimation Based on Time-Lapsed Micro-CT and HR-pQCT in Vivo

“…Trabecular regions were automatically contoured from binarised images. For the human distal radius images, an approach described by Ohs et al (2020b) was used; for the mouse vertebra images, a method described by Kohler et al (2007) was used. FE meshes were generated by converting all voxels to 8 node hexahedral elements and assigning a Poisson's ratio of 0.3 as well as Young's modulus of 6.8 GPa for the human distal radius (Christen et al, 2013) and 14.8 GPa (Webster et al, 2008) for the mouse vertebra.…”