TY - JOUR
T1 - Bone mineral 31P and matrix-bound water densities measured by solid-state 31P and 1H MRI
AU - Seifert, Alan C.
AU - Li, Cheng
AU - Rajapakse, Chamith S.
AU - Bashoor-Zadeh, Mahdieh
AU - Bhagat, Yusuf A.
AU - Wright, Alexander C.
AU - Zemel, Babette S.
AU - Zavaliangos, Antonios
AU - Wehrli, Felix W.
PY - 2014/7
Y1 - 2014/7
N2 - 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 27-97years, were acquired by zero-echo-time 31-phosphorus (31P) and 1-hydrogen (1H) 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 31P density was 6.74±1.22mol/l (corresponding to 1129±204mg/cc mineral), and mean bound water 1H density was 31.3±4.2mol/l (corresponding to 28.3±3.7 %v/v). Both 31P and bound water (BW) densities were correlated negatively with porosity (31P: R2=0.32, p<0.005; BW: R2=0.63, p<0.0005) and age (31P: R2=0.39, p<0.05; BW: R2=0.70, p<0.0001), and positively with pQCT density (31P: R2=0.46, p<0.05; BW: R2=0.50, p<0.005). In contrast, the bone mineralization ratio (expressed here as the ratio of 31P 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.
AB - 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 27-97years, were acquired by zero-echo-time 31-phosphorus (31P) and 1-hydrogen (1H) 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 31P density was 6.74±1.22mol/l (corresponding to 1129±204mg/cc mineral), and mean bound water 1H density was 31.3±4.2mol/l (corresponding to 28.3±3.7 %v/v). Both 31P and bound water (BW) densities were correlated negatively with porosity (31P: R2=0.32, p<0.005; BW: R2=0.63, p<0.0005) and age (31P: R2=0.39, p<0.05; BW: R2=0.70, p<0.0001), and positively with pQCT density (31P: R2=0.46, p<0.05; BW: R2=0.50, p<0.005). In contrast, the bone mineralization ratio (expressed here as the ratio of 31P 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.
KW - Bone
KW - Bone matrix density
KW - Bone mineral density
KW - MRI
KW - Ultra-short echo time MRI
KW - Zero echo time MRI
UR - http://www.scopus.com/inward/record.url?scp=84902340801&partnerID=8YFLogxK
U2 - 10.1002/nbm.3107
DO - 10.1002/nbm.3107
M3 - Article
C2 - 24846186
AN - SCOPUS:84902340801
SN - 0952-3480
VL - 27
SP - 739
EP - 748
JO - NMR in Biomedicine
JF - NMR in Biomedicine
IS - 7
ER -