Texture analysis of X-ray radiographs is correlated with bone histomorphometry

Three-dimensional (3D) alteration of trabecular microarchitecture is a risk factor for vertebral fractures. Histomorphometry allows microarchitectural analysis of bone, but the necessity to perform a transiliac bone biopsy limits its use in large series of patients. X-Ray films are commonly used in routine practice and constitute a 2D projection of the trabecular architecture. In this study, blocks of trabecular dried bone were prepared from calf bone. They were selected from different parts of the femoral condyle to provide various patterns of trabecular disposition. All blocks (25x15x8 mm) were radiographed on a numeric X-ray system, with the same acquisition parameters. Texture analysis was carried out by several methods: (skeletonization, run lengths, and fractal techniques). Histological sections of the blocks were obtained and analyzed by 2D histomorphometric methods: trabecular bone volume (BV/TV), trabecular characteristics, and 2D descriptors of architecture (star volumes, strut analysis, fractal dimensions). Significant correlations were obtained for BV/TV with run length parameters measured on the X-ray image. The trabecular characteristics were found to be highly correlated with texture parameters describing the X-ray image (e.g., trabecular number [Tb.N]/axis, r=-0.82;/short run emphasis [SRE], r=-0.87; trabecular separation [Tb.Sp]/gray level nonuniformity [GLN], r=-0.82). Several histomorphometric parameters, independent of the plate-and-rod model, were also well correlated with texture descriptors. Although the relationships between the 2D and 3D trabecular architecture are not fully elucidated, the texture analysis of X-ray films might be a suitable approach to investigate the disorganization of bone in osteoporosis.