Analysis of the influence of image resolution on the discriminating power of trabecular bone architectural parameters.

In the study the influence of image resolution on the discriminating power of different parameters quantifying the architecture of trabecular bone is investigated. High-resolution images of 200-microm-thick sections of young and old trabecular bone are collected. Different architectural parameters are evaluated and shown to be statistically different in both groups of images. Then the resolution of the images is artificially degraded to the level comparable with resolution achievable in vivo. It is shown that although the errors of evaluation are quite large for low-resolution images, the statistical difference present in the original data is still observed for parameters that depend only on the global characteristics of trabecular structure or marrow space, or depend only linearly on the number and area of disconnected parts of marrow space or trabecular structure. The parameters that fulfill such conditions are Euler number, mean area of marrow cavities, star volume and trabecular spacing. The statistical difference disappears for parameters that depend on the number and area of disconnected parts of marrow space or trabecular structure in a nonlinear manner, that is, marrow and trabecular disconnection probabilities, two-point distance and second moment of marrow cavities area distribution. It is shown that the mechanism that leads to the losing of discriminating power does not depend crucially on the estimation error or noise level. This mechanism, which involves an interplay between changes of mean values and standard deviations, is the manifestation of partial volume effect amplified with image segmentation.