Premium
Bone mineral 31 P and matrix‐bound water densities measured by solid‐state 31 P and 1 H MRI
Author(s) -
Seifert Alan C.,
Li Cheng,
Rajapakse Chamith S.,
BashoorZadeh Mahdieh,
Bhagat Yusuf A.,
Wright Alexander C.,
Zemel Babette S.,
Zavaliangos Antonios,
Wehrli Felix W.
Publication year - 2014
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3107
Subject(s) - bone mineral , bound water , cortical bone , quantitative computed tomography , chemistry , nuclear magnetic resonance , matrix (chemical analysis) , relaxation (psychology) , porosity , nuclear medicine , analytical chemistry (journal) , materials science , osteoporosis , anatomy , physics , medicine , organic chemistry , chromatography , molecule , endocrinology
Bone is a composite material consisting of mineral and hydrated collagen fractions. MRI of bone is challenging because of extremely short transverse relaxation times, but solid‐state imaging sequences exist that can acquire the short‐lived signal from bone tissue. Previous work to quantify bone density via MRI used powerful experimental scanners. This work seeks to establish the feasibility of MRI‐based measurement on clinical scanners of bone mineral and collagen‐bound water densities, the latter as a surrogate of matrix density, and to examine the associations of these parameters with porosity and donors’ age. Mineral and matrix‐bound water images of reference phantoms and cortical bone from 16 human donors, aged 27–97 years, were acquired by zero‐echo‐time 31‐phosphorus ( 31 P) and 1‐hydrogen ( 1 H) MRI on whole body 7T and 3T scanners, respectively. Images were corrected for relaxation and RF inhomogeneity to obtain density maps. Cortical porosity was measured by micro‐computed tomography (μCT), and apparent mineral density by peripheral quantitative CT (pQCT). MRI‐derived densities were compared to X‐ray‐based measurements by least‐squares regression. Mean bone mineral 31 P density was 6.74 ± 1.22 mol/l (corresponding to 1129 ± 204 mg/cc mineral), and mean bound water 1 H density was 31.3 ± 4.2 mol/l (corresponding to 28.3 ± 3.7 %v/v). Both 31 P and bound water (BW) densities were correlated negatively with porosity ( 31 P: R 2 = 0.32, p < 0.005; BW: R 2 = 0.63, p < 0.0005) and age ( 31 P: R 2 = 0.39, p < 0.05; BW: R 2 = 0.70, p < 0.0001), and positively with pQCT density ( 31 P: R 2 = 0.46, p < 0.05; BW: R 2 = 0.50, p < 0.005). In contrast, the bone mineralization ratio (expressed here as the ratio of 31 P density to bound water density), which is proportional to true bone mineralization, was found to be uncorrelated with porosity, age or pQCT density. This work establishes the feasibility of image‐based quantification of bone mineral and bound water densities using clinical hardware. Copyright © 2014 John Wiley & Sons, Ltd.