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Relaxation Time Discriminated 1H NMR for Bone Mechanical/Fracture Property Diagnostics
Advances in modern MRI pulse sequences have enabled clinically-practical cortical bone imaging. Human cortical bone is known to contain a distribution of T1 and T2 components attributed to bound and pore water, although clinical imaging approaches have yet to discriminate bound from pore water on the basis of their relaxation properties.
The development of ultrashort-echo time and related MRI methods for imaging short T2 signals has generated considerable interest in applying MRI to dense tissues. For example, cortical bone, which is conventionally imaged using X-ray-based methods, can now be effectively imaged with MRI to characterize bone damage and mechanical properties. Recent studies show that certain NMR signals tuned to collagen-bound water and pore water are correlated (directly and inversely, respectively) to several mechanical properties of cortical bone. These findings demonstrate the potential for MRI to offer diagnostic measures of bone fracture risk, but the opposing relationships of bound and pore water content with mechanical properties requires MRI methods that distinguish signals from these two biophysical origins.
The present invention describes clinically-practical MRI methods for distinguishing bound and pore water signals from cortical bone based on T2-selective adiabatic pulses as well as T1 characteristics of cortical bone bound and pore water, and offers an improved method of assessing bone structure and fracture risk over x-ray based diagnostic techniques. The methods are validated in a population of ex vivo human cortical bones. Results show that the two MRI methods provide good estimates of bound and pore water that correlate to bone mechanical properties. As such, the bound and pore water-discriminated MRI protocols shown herein should provide diagnostically useful tools for assessing bone fracture risk.
» Quantitatively measures bone composition, useful for fracture risk or disease/therapy assessment
» Better assessment of fracture risk, accounting for soft tissue
» No ionizing radiation
» Can easily be implemented on existing MR scanners
» Compatible with two or three-dimensional imaging protocols
Intellectual Property Status
Inventors:Mark DoesR. Adam HorchJeffry NymanDaniel Gochberg