Anisotropy changes in post-menopausal osteoporosis: characterization by a new index applied to trabecular bone radiographic images

Abstract

Bone intrinsic strength is conditioned by several factors, including material property and trabecular micro-architecture. Bone mineral density (BMD) is a good surrogate for material property. Architectural anisotropy is of special interest in mechanics-architecture relations and characterizes the degree of directional organization of a material. We have developed anisotropy indices from the Fast Fourier Transform (FFT) on bone radiographs. We have validated these indices in a cross-sectional uni-center case-control study including 39 postmenopausal women with vertebral fracture and 70 age-matched control cases. BMD was measured at the lumbar spine and femoral neck. A fractal analysis of texture was performed on calcaneus radiographs at three regions of interest (ROIs), and the result was expressed as the H parameter (fractal dimension =H-2). The anisotropy evaluation was based on the FFT spectrum of these three ROIs extracted on calcaneus radiographs. On the FFT spectrum, we have measured the spreading angle of the longitudinal trabeculae called the dispersion longitudinal index (DLI) and the spreading angle of the transversal trabeculae called the dispersion transversal index (DTI). From the measured parameters, an anisotropy index was derived, and the degree of anisotropy (DA) calculated with DLI and DTI. We have compared the results from the vertebral fracture cases and control cases. The best distinction was obtained for the largest ROI located in the great tuberosity of the calcaneus for all parameters ( P <10(-4)).( )The DA parameter showed a higher value in vertebral fracture cases (1.746+/-0.169) than in control cases (1.548+/-0.136); P <10(-4), and the difference persisted after removal of the subjects with hormonal replacement therapy. The analysis of the receiver operating characteristics (ROC) has shown the best results with DA and Hmean: areas under curves (AUCs) respectively of 0.765 and 0.683, while AUCs associated to LS-BMD and FN-BMD were 0.614 and 0.591 lower, respectively. We determined the odds ratios (OR) by uni- and multivariate analysis. Crude ORs were respectively 3.91 (95% CI: 2.22-6.87) and 3.08 (95% CI: 1.72-5.52) for DA and Hmean. Crude ORs were respectively 1.71 (95% CI: 1.15-2.56) and 1.56 (95% CI: 1.05-2.31) for LS-BMD and FN-BMD. All ORs were statistically significant, and those associated to Hmean and anisotropy indices were higher than those of BMD measurements. From a multivariate analysis including anisotropy indices, Hmean, age and FN-BMD, the remaining significant ORs were respectively 6.33 (95% CI: 2.80-14.30) and 3.08 (95% CI: 1.48-6.37) for DA and Hmean. These data have shown that anisotropy indices on calcaneus radiographs can distinguish vertebral fracture cases from control cases. This analysis provides complementary information concerning the BMD and fractal parameter. These data suggest that we can improve the fracture risk evaluation by adding information related to the directional organization of trabecular bone derived from the FFT spectrum on conventional radiogra...

Fractal lacunarity of trabecular bone and magnetic resonance imaging: New perspectives for osteoporotic fracture risk assessment

“…In the last decades, a lot of studies have been performed in both central and mirror sites with different image acquisition techniques. Most of them always propose histo morphometricbased methods alone or combined with other methods for TB texture analysis, among are anisotropy, cooccurrence, gradient matrices, gray level histogram, and runlength [81,82] . All of them provide quite a few parameters to be checked and analyzed thus limiting their application in clinical practice.…”

Fractal Analysis of Trabecular Bone Pattern in the Mandible as an Indicator of Osteoporosis in Women - A Clinical Study

“…Many studies have shown that the problem in the fractal analysis of binary images is the effect of noise [9]. Since no estimation methods work well universally, the relative discrepancies of all estimating techniques need to gain insights [20]. In our study using digital images, FD values did not change when spatial resolution is the same by box-counting method.…”

Bone Trabecular Analysis of Femur Radiographs for the Assessment of Osteoporosis Using DWT and DXA

“…In yet another similar study Chappard et al [12], detailed about the gradient based texture analysis on hip radiograph from which the fact of close correlation in site-matched areas was figured out in between extracted texture features and BMD. The structural analysis of trabecular bone from clinical radiographs utilizing Radon transform method, gray-level Fourier transform and fractal analysis of heel X-ray images and extracted features in order to discriminate fracture group from the controls as reported by Boehm et al [13] and Chappard et al [14]. However, the finding from this study shows that the healthiest bones, which are having the highest energy and the porous bones, which are having the lowest energy.…”