In Vivo Quantitative MR Imaging of Bound and Pore Water in Cortical Bone

Abstract

).q RSNA, 2015 Purpose:To translate and evaluate an in vivo magnetic resonance (MR) imaging protocol for quantitative mapping of collagen-bound and pore water concentrations in cortical bone that involves relaxation-selective ultrashort echo time (UTE) methods. Materials and Methods:All HIPAA-compliant studies were performed with institutional review board approval and written informed consent. UTE imaging sequences were implemented on a clinical 3.0-T MR imaging unit and were used for in vivo imaging of bound and pore water in cortical bone. Images of the lower leg and wrist were acquired in five volunteers each (lower leg: two men and three women aged 24, 24, 49, 30, and 26 years; wrist: two men and three women aged 31, 23, 25, 24, and 26 years) to generate bound and pore water concentration maps of the tibia and radius. Each volunteer was imaged three times, and the standard error of the measurements at the region-of-interest (ROI) level was computed as the standard deviation across studies, pooled across volunteers and ROIs. Results:Quantitative bound and pore water maps in the tibia and radius, acquired in 8-14 minutes, had per-voxel signal-tonoise ratios of 18 (bound water) and 14 (pore water) and inter-study standard errors of approximately 2 mol 1 H per liter of bone at the ROI level. Conclusion:The results of this study demonstrate the feasibility of quantitatively mapping bound and pore water in vivo in human cortical bone with practical human MR imaging constraints.q RSNA, 2015

Measurement of bound and pore water T1relaxation times in cortical bone using three-dimensional ultrashort echo time cones sequences

“…However, T 1 of bound water ( ) and pore water ( ) have not been well investigated using clinical MR scanners, although and have been reported using high‐performance NMR spectrometers . Accurate measurement of bound and pore water concentrations require compensation of T 1 and effects . Reliability and fast measurements of and would also be necessary to be performed in vivo in the clinical setting.…”

Solid-State Quantitative 1H and 31P MRI of Cortical Bone in Humans

“…Manhard et al 61 proved the reproducibility of this method by reporting a bound water 1 H concentration of 27.9 ± 2.0 mol/L in 15 measurements across 5 subjects ( Figure 3c,d ). The same group of investigators also introduced a double adiabatic full passage (DAFP) method to isolate and image pore water 42,46 : two successive adiabatic pulses invert and immediately restore long-T 2 pore water magnetization, while saturating short-T 2 bound water.…”

“…As SR values increase, histograms become increasingly asymmetric with long tails toward high SR values, commensurate with the notion of elevated T 2 of the water in larger pores (reproduced from 12 ). Maps of bound (c) and pore (d) water concentration, measured by adiabatic inversion-recovery and double adiabatic full passage UTE MRI, respectively (reproduced from 61 ).…”

MRI assessment of bone structure and microarchitecture

“…Again, we focus on in vivo studies. Manhard et al used a double adiabatic full passage (DAFP) sequence and an adiabatic inversion recovery (AIR) sequence to scan five healthy subjects (two males, three females, ages = 24–49 years) three times each at the distal radius and distal tibia at 3T . The DAFP sequence suppresses CBW while maintaining CPW signal, and the AIR sequence selectively nulls CPW while retaining CBW signal.…”