Alan C. Seifert1,
Suzanne L. Wehrli2, Alexander C. Wright1, Henry H. Ong1,
Felix W. Wehrli1
1Department
of Radiology, University of Pennsylvania, Philadelphia, PA, United States; 2NMR
Core Facility, Children's Hospital of Philadelphia, Philadelphia, PA, United
States
X-ray-based bone mineral density examinations measure apparent, rather than true, density. Solid-state 31P and 1H MRI have the potential to quantify true density. Bone mineral 31P has unfavorable relaxation properties, which may vary with bone mineralization. In order to better understand the mechanisms responsible for these unfavorable relaxation times and assess their dependence on mineralization, we have measured the effects of partial demineralization and deuterium exchange on the relaxation times of bone mineral phosphorus. 31P T1 was decreased by demineralization, but T2* was unaffected. Deuterium exchange shows that ~76% of longitudinal relaxation rate is due to 1H-31P heteronuclear dipolar interaction.