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In vivo bone and cartilage MRI using fully-balanced steady-state free-precession at 7 tesla.

Krug R, Carballido-Gamio J, Banerjee S, Stahl R, Carvajal L, Xu D, Vigneron D, Kelley DA, Link TM, Majumdar S

Department of Radiology, University of California, San Francisco, San Francisco, California, USA. Roland.Krug@radiology.ucsf.edu

The purpose of this work was to investigated the feasibility of fully-balanced steady-state free-precession (bSSFP) pulse sequence for trabecular bone and knee cartilage imaging in vivo using ultra-high-field (UHF) MRI at 7T in comparison with pulse sequences previously used at 3T. We showed that bSSFP and spin-echo imaging is possible at higher field strengths within 3.2 W/kg specific absorption rate (SAR) constraints. All pulse sequences were numerically optimized based on measured tissue relaxation parameters from six healthy volunteers (T(1) = 820 +/- 128 ms, T(2) = 43.5 +/- 3 ms for bone marrow and T(1) = 1745 +/- 104 ms and T(2) = 30 +/- 4 ms for cartilage). From simulations of the Bloch equation, a signal-to-noise ratio (SNR) increase of more than 1.9 was predicted. Cartilage SNR of bSSFP was 2.4 times higher at 7T (51.3 +/- 4.3) compared with 3T (21.3 +/- 3.3). Bone SNR increased from 11.8 +/- 2.0 to 13.2 +/- 2.5 at the higher field strength. We concluded that there is SNR benefit and great potential for bone and cartilage imaging at higher field strength.

Published 6 December 2007 in Magn Reson Med, 58(6): 1294-8.
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