Computation of Structure Model Index in the Spatial Resolution Regime of In Vivo Trabecular Bone MRI

Shing Chun Benny Lam¹, Jeremy F. Magland¹, Scott N. Hwang², Felix W. Wehrli¹

The structure model index (SMI) is a metric characterizing the structure type (plate versus rod) of a trabecular bone network. However, application of SMI to in vivo MRI has been limited by spatial resolution. Here, we explored two up-sampling methods, sinc-interpolation and subvoxel processing, to enable computation of SMI from in vivo MRI. Comparison with values derived from CTimages (regarded as ground truth) showed SMI values obtained from subvoxel processed images to be closer to ground truth than those derived from sinc-interpolated images in terms of correlation coefficients and root mean square differences. Finally, subvoxel processed images were less sensitive to variations in binarization threshold.