Characterization of ¹H NMR signal in human cortical bone for magnetic resonance imaging

Abstract

Recent advancements in MRI have enabled clinical imaging of human cortical bone, providing a potentially powerful new means for assessing bone health with molecular-scale sensitivities unavailable to conventional X-ray-based diagnostics. In human cortical bone, MRI is sensitive to populations of protons ( 1 H) partitioned among water and protein sources, which may be differentiated according to intrinsic NMR properties such as chemical shift and transverse and longitudinal relaxation rates. Herein, these NMR properties were assessed in human cortical bone donors from a broad age range, and four distinct 1 H populations were consistently identified and attributed to five microanatomical sources. These findings show that modern human cortical bone MRI contrast will be dominated by collagen-bound water, which can also be exploited to study human cortical bone collagen via magnetization transfer. Magn Reson Med 64:680-687,

Qualitative and quantitative ultrashort echo time (UTE) imaging of cortical bone

“…5A) without long T 2 signal suppression is probably due to out-of-slice long T 2 signal contamination. Lipids found in the cement line spaces may also contribute to this signal oscillation [30,31].…”

Changes in skeletal collagen cross-links and matrix hydration in high- and low-turnover chronic kidney disease

“…The NMR analysis to separate proton signals within the bone was then performed in a 4.7T horizontal-bore magnet (Varian Medical Systems, Santa Clara, CA) using 90°/180° RF pulses of ~ 9/18 μs duration and collecting Carr-Purcell-Meiboom-Gill (CPMG) measurements with 10,000 echoes at 100 μs spacing. To generate the spectrum of transverse relaxation time constants (T 2 ), the echo magnitudes were fitted with multiple exponential decay functions [40]. Upon normalizing the integrated areas of bound water (T 2 = 100 μs-800 μs) and pore water (T 2 = 800 μs – 600 ms) to the area of the reference (T 2 = 600 ms-10 s) [41], the volume of bound water and the volume of pore water were divided by the specimen volume (calculated from Archimedes’ principle) to give bound water (bw) and pore water (pw) volume fractions.…”

The accuracy of ultrashort echo time MRI sequences for medical additive manufacturing

“…This is because MR image acquisition is based on water microenvironments and other sources of protons in the human body. Since the cortical bone has a low proton density and a very short T 2 relaxation time of about 1.5 ms, 21 conventional spin echo and gradient echo MRI sequences are too slow to acquire a sufficient signal from the bone. As a result, new ultrashort echo time (UTE) sequences have been recently developed and successfully used for bone imaging.…”