Henry Ong
Post-Doctoral Fellow
Last active: 4/25/2016

31P NMR relaxation of cortical bone mineral at multiple magnetic field strengths and levels of demineralization.

Seifert AC, Wright AC, Wehrli SL, Ong HH, Li C, Wehrli FW
NMR Biomed. 2013 26 (9): 1158-66

PMID: 23505120 · PMCID: PMC3715596 · DOI:10.1002/nbm.2930

Recent work has shown that solid-state (1) H and (31) P MRI can provide detailed insight into bone matrix and mineral properties, thereby potentially enabling differentiation of osteoporosis from osteomalacia. However, (31) P MRI of bone mineral is hampered by unfavorable relaxation properties. Hence, accurate knowledge of these properties is critical to optimizing MRI of bone phosphorus. In this work, (31) P MRI signal-to-noise ratio (SNR) was predicted on the basis of T1 and T2 * (effective transverse relaxation time) measured in lamb bone at six field strengths (1.5-11.7 T) and subsequently verified by 3D ultra-short echo-time and zero echo-time imaging. Further, T1 was measured in deuterium-exchanged bone and partially demineralized bone. (31) P T2 * was found to decrease from 220.3 ± 4.3 µs to 98.0 ± 1.4 µs from 1.5 to 11.7 T, and T1 to increase from 12.8 ± 0.5 s to 97.3 ± 6.4 s. Deuteron substitution of exchangeable water showed that 76% of the (31) P longitudinal relaxation rate is due to (1) H-(31) P dipolar interactions. Lastly, hypomineralization was found to decrease T1, which may have implications for (31) P MRI based mineralization density quantification. Despite the steep decrease in the T2 */T1 ratio, SNR should increase with field strength as B0 (0.4) for sample-dominated noise and as B0 (1.1) for coil-dominated noise. This was confirmed by imaging experiments.

Copyright © 2013 John Wiley & Sons, Ltd.

MeSH Terms (12)

Animals Bone and Bones Calcification, Physiologic Deuterium Magnetic Fields Magnetic Resonance Spectroscopy Minerals Phosphorus Radio Waves Sheep Signal-To-Noise Ratio Time Factors

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