CT-Based Characterization of Transverse and Longitudinal Trabeculae and Its Applications

Abstract

Osteoporosis is a common age-related disease characterized by reduced bone mineral density (BMD), micro-structural deterioration, and enhanced fracture-risk. Although, BMD is clinically used to define osteoporosis, there are compelling evidences that bone micro-structural properties are strong determinants of bone strength and fracture-risk. Reliable measures of effective trabecular bone (Tb) micro-structural features are of paramount clinical significance. Tb consists of transverse and longitudinal micro-structures, and there is a hypothesis that transverse trabeculae improve bone strength by arresting buckling of longitudinal trabeculae. In this paper, we present an emerging clinical CT-based new method for characterizing transverse and longitudinal trabeculae, validate the method, and examine its application in human studies. Specifically, we examine repeat CT scan reproducibility, and evaluate the relationships of these measures with gender and body size using human CT data from the Iowa Bone Development Study (IBDS) (n = 99; 49 female). Based on a cadaveric ankle study (n = 12), both transverse and longitudinal Tb measures are found reproducible (ICC > 0.94). It was observed in the IBDS human data that males have significantly higher trabecular bone measures than females for both inner (p < 0.05) and outer (p < 0.01) regions of interest (ROIs). For weight, Spearman correlations ranged 0.43-0.48 for inner ROI measures and 0.50-0.52 for outer ROI measures for females versus 0.30-0.34 and 0.23-0.25 for males. Correlation with height was lower (0.36-0.39), but still mostly significant for females. No association of trabecular measures with height was found for males.

Keywords: CT imaging; Osteoporosis; longitudinal trabeculae; micro-structure; orientation; topology; trabecular bone; transverse trabeculae.

Figure 1.

Computation of transverse and longitudinal trabeculae in high resolution CT imaging. (a) Three-dimensional reconstruction of the Tb network using CT scan of a cadaveric distal tibia specimen. (b) Results of individual trabecular segmentation on the curve skeleton of (a). Each trabecular segment is shown using a unique color. (c) Volumetric representation of individual trabecular segmentation. (d) A color-coded display of longitudinal (green) and transverse (red) trabecular characterization.

Figure 2.

Illustration of different digital junctions in a curve skeletal. Top row: Examples of conventional topological junctions forming more than two components, or a tunnel or cavity in the neighborhood. Middle row: Examples of junctions involving hidden branches (marked by ‘*’), which do not contribute separate components in the neighborhood. Bottom row: Examples of extended junctions, where multiple voxels together form a junction.