Application of refocused steady-state free-precession methods at 1.5 and 3 T to in vivo high-resolution MRI of trabecular bone: simulations and experiments.
OBJECTIVE
To evaluate the potential of fully-balanced steady-state free-precession (SSFP) sequences in in vivo high-resolution (HR) MRI of trabecular bone at field strengths of 1.5 and 3 T by simulation and experimental methods.


METHODS
Using simulation studies, refocused SSFP acquisition was optimized for our imaging purposes with a focus on signal-to-noise ratio (SNR) and SNR efficiency. The signal behavior in trabecular bone was estimated using a magnetostatic model of the trabecular bone and marrow. Eight normal volunteers were imaged at the proximal femur, calcaneus, and the distal tibia on a GE Signa scanner at 1.5 and at 3 T with an optimized single-acquisition SSFP sequence (three-dimensional FIESTA) and an optimized multiple-acquisition SSFP sequence (three-dimensional FIESTA-c). Images were also acquired with a fast gradient echo (FGRE) sequence for evaluation of the SNR performance of SSFP methods.


RESULTS
Refocused SSFP images outperformed FGRE acquisitions in both SNR and SNR efficiency at both field strengths. At 3 T, susceptibility effects were visible in FIESTA and FGRE images and much reduced in FIESTA-c images. The magnitude of SNR boost at 3 T was closely predicted by simulations.


CONCLUSIONS
Single-acquisition SSFP (at 1.5 T) and multiple-acquisition SSFP (at 3 T) hold great potential for HR-MRI of trabecular bone.
Banerjee
Suchandrima
S
Department of Radiology, University of California, San Francisco, San Francisco, California 94107, USA.
Han
Eric T
ET
Krug
Roland
R
Newitt
David C
DC
Majumdar
Sharmila
S
D000328:Adult; D001842:Bone and Bones / Q000033:anatomy & histology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged