Estimating voxel volume fractions of trabecular bone on the basis of magnetic resonance images acquired in vivo

A method is described for extracting information from images acquired in the limited spatial resolution regime in which the structures to be identified are smaller than the image voxel size. Under these conditions and in the presence of noise, the voxel intensity histogram is monomodal; therefore, segmenting the image with an intensity threshold is inaccurate. The present method, which is applicable to two-phase materials of discrete intensity, relies on iterative deconvolution to obtain a noiseless histogram. A noiseless image is then generated on the basis of the noiseless histogram and the unprocessed image. In the current work, the method is referred to as bone volume fraction (BVF) mapping, since it has been applied to determine the spatial distribution of trabecular bone. BVF computed from maps generated on the basis of in vivo magnetic resonance images of the human radius has been shown to compare well with bone mineral density (R-2 = 0.8). The accuracy and precision of BVF measurements have been further evaluated by using a BVF map of the radius as a gold standard and then adding different levels of noise to generate lest images. The results suggest that the error in BVF is <0.01 for SNR > 8. (C) 1999 John Wiley & Sons, Inc.