Finite element modeling of trabecular bone from multi-row detector CT imaging

ACKNOWLEDGMENTS First of all, I would like to give my most sincere thanks to my advisor Professor Punam K. and Ryan Amelon for their help on my research. In the end, I want to thank all the faculty, staff and students of The Iowa Institute for Biomedical Imaging and Electrical and Computer Engineering for their improving lectures and kind help. iii ABSTRACT The finite element method (FEM) has been widely applied to various medical imaging applications over the past two decades. The remarkable progress in high-resolutio n imaging techniques has allowed FEM to draw great research interests in computing trabecular bone (TB) stiffness from three-dimensional volumetric imaging. However, only a few results are available in literature on applying FEM to multi-row detector CT (MDCT) imaging due to the challenges posed by limited spatial resolution. The research presented here develops new methods to preserve TB structure connectivity and to generate high-quality mesh representation for FEM from relatively low resolution images available at MDCT imaging. Specifically, it introduced a space-variant hysteresis algorithm to threshold local trabecular structure that preserves structure connectivity. Also, mesh generation algorithms was applied to represent TB micro-architecture and mesh quality was compared with that generated by traditional methods. TB stiffness was computed using FEM simulation on micro-CT (µ-CT) and MDCT images of twenty two cadaveric specimens of distal tibia. Actual stiffness of those specimens were experimenta lly determined by mechanical testing and its correlation with computed stiffness was analyzed. The observed values of linear correlation (r 2) between actual bone stiffness and computed stiffness from µ-CT and MDCT imaging were 0.95 and 0.88, respectively. Also, reproducibility of the FEM-based computed bone stiffness was determined from repeat MDCT scans of cadaveric specimens and the observed intra-class correlation coeffic ie nt was a high value of 0.98. Experimental results demonstrate the feasibility of application of FEM with high sensitivity and reproducibility on MDCT imaging of TB at distal tibia under in vivo condition. iv PUBLIC ABSTRACT Over the past two decades, trabecular bone (TB) study has drawn research interests to determine bone quality, understand causes of diseases, and assess risks of fractures. The finite element method (FEM) is an advanced computer-aided method that computes stiffness and simulates behaviors of target object. With the remarkable progress of high-resolution imaging techniques, FEM has been widely applied in TB study. However, only a few research focuses on FEM application on multi-row detector CT …