Zhang Dengfu，Yang Xinhui，Zhang Feng，Jiang Dazong
(School of Life Science and Technology,Xi'an Jiaotong University,Xi'an 710049,China)
Abstract：The projection power spectrum of bone X-ray images along each orientation can be considered as fractional Brownian motion. A new fractal dimension is developed. For different orientations, the directional fractal dimension is calculated by applying a regression method to the projection power spectrum in power spectrum density space. The ratio of maximum and minimum directional fractal dimensions in polar coordinates defines an anisotropic texture feature. The ratio reflects the degree of anisotropy of trabecular patterns, and is successfully used in our pattern classification. Numerical results show that the anisotropic index has good discrimination on two different grades of osteoporosis. The anisotropic index and the spectrum features of bone compose a feature sets, and are further applied to quantitative classification of osteoporosis bone. This indicates the potential applicability of our method to the objective assessment of osteoporosis.
Keywords：osteoporosis;texture analysis;projection power spectrum;fractal dimension;trabecular pattern