The mechanical behavior and functional properties of all tissues are intimately associated with their micro-structural organization. Bone - a composite biomaterial - has evolved so as to provide the compressive and tensile strength needed for weight-bearing and locomotion. Trabecular bone (TB) - the bone most prone to fracture - consists of a meshwork of interconnected plates and struts that confer the tissue its unique mechanical properties. In recent years it has become evident that besides apparent density - the metric used clinically to assess fracture risk - the bone's structural arrangement as well as its intrinsic material properties, loosely termed """"""""bone quality"""""""", are essential in determining static and dynamic strength. Advances in imaging technology (notably MRI) now allow imaging of selected anatomic sites at a resolution enabling analysis of the trabecular network. However, these methods, although promising, are only applicable to peripheral skeletal sites where sufficient SNR can be achieved but not at the most common fracture sites. In this pilot study, we wish to evaluate the potential of intermolecular double-quantum coherences (iDQC), as a means to obtain structural information without the need to actually resolve individual trabeculae. The signal derived from CRAZED-type pulse sequences is known to be sensitive to the correlation distance, the wavelength of the magnetization helix created by two RF pulses in the presence of a correlation gradient. The presence of quasi-periodic structures such as those pertaining to TB lattices causes a modulation of the signal when the correlation distance approaches the spatial wavelength of the structure. We have demonstrated the feasibility of this approach in preliminary work. However, the functional relationship between the CRAZED signal and architecture at the present is not understood. Here we propose to investigate the potential of the method by simulation in model lattices and micro-CT images of animal and human TB and compare the results with data obtained with a new volume-selective CRAZED-type pulse sequence. The hypothesis to be evaluated is that spatially-resolved iDQC MRI can provide quantitative information on TB spacing and structural anisotropy, both key parameters determining the mechanical competence of trabecular bone.
