Non-invasive bone biopsy: a new method to analyse and display the three-dimensional structure of trabecular bone

Abstract

Three-dimensional (3D) structure is one of the main factors influencing the mechanical behaviour of cancellous bone. To analyse the trabecular bone structure nondestructively the authors used a peripheral QCT system and applied a special thin-slice technique to create high-resolution volumetric data sets serving as a basis for something they would like to call noninvasive bone biopsy. In order to obtain binary data sets, the mineralized bone in the CT volume was separated from bone marrow and muscle tissue with the help of a sophisticated 3D segmentation algorithm based on the analysis of directional derivatives, which are computed from a locally approximated fit function of the original CT volume. Binary volumes including either a solid representation of trabecular plates and rods or a topological representation of the cancellous bone architecture were acquired. Such volumes can be processed nondestructively and, even more important, repetitively. By using a surface reconstruction algorithm based on interpolating triangulation it was possible to visualize the 3D surface of the trabecular bone structure. The results showed that surface representation and visualization in combination with a multiple thin-slice measuring technique are valuable tools in studying 3D bone architecture. In the future, the noninvasive bone biopsies will be evaluated by means of 3D mechanical analysis incorporating finite element modelling and direct morphological investigations of the cancellous bone architecture for a better prediction of bone strength as an index for fracture risk or osteoporosis.