In vivo ultra-high-field magnetic resonance imaging of trabecular bone microarchitecture at 7 T.
OBJECTIVE
To investigate the feasibility of 7 T magnetic resonance imaging (MRI) to visualize and quantify trabecular bone structure in vivo by comparison with 3T MRI and in vivo three-dimensional (3D) high-resolution peripheral quantitative computed tomography (HR-pQCT).


METHODS
The distal tibiae of 10 healthy volunteers were imaged. Therefore, fully balanced steady state free precession (bSSFP) and spin-echo (bSSSE) pulse sequences were implemented and optimized for 7 T. Structural bone parameters, such as apparent bone-volume over total-volume fraction (app.BV/TV), apparent trabecular plate separation (app.TbSp), apparent trabecular plate thickness (app.TbTh), and apparent trabecular plate number (app.TbN), were derived.


RESULTS
All structural trabecular bone parameters correlated well (r > 0.6) between 7T and 3T, and between 7 T and HR-pQCT (r > 0.69), with the exception of app.TbTh, which correlated modestly (r = 0.41) between field strengths and very low with HR-pQCT (r < 0.16). Regarding absolute values, app.TbN varied only 4% between field strengths, and only 0.6% between 7 T and HR-pQCT. App.TbSp correlated best between 7 T and HR-pQCT (r = 0.89). Using bSSSE, significant smaller trabecular thickness and significant higher trabecular number were found compared to bSSFP.


CONCLUSIONS
We concluded that imaging and quantification of the trabecular bone architecture at 7 T is feasible and preferably done using bSSSE. There exists great potential for ultra-high-field (UHF) MRI applied to trabecular bone measurements.
Krug
Roland
R
Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA. Roland.Krug@radiology.ucsf.edu
Carballido-Gamio
Julio
J
Banerjee
Suchandrima
S
Burghardt
Andrew J
AJ
Link
Thomas M
TM
Majumdar
Sharmila
S
D005240:Feasibility Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D013977:Tibia / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed