Banerjee Suchandrima, Han Eric T, Krug Roland, Newitt David C, Majumdar Sharmila
Department of Radiology, University of California, San Francisco, San Francisco, California 94107, USA.
J Magn Reson Imaging. 2005 Jun;21(6):818-25. doi: 10.1002/jmri.20348.
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.
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.
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.
Single-acquisition SSFP (at 1.5 T) and multiple-acquisition SSFP (at 3 T) hold great potential for HR-MRI of trabecular bone.
通过模拟和实验方法，评估完全平衡稳态自由进动（SSFP）序列在1.5和3 T场强下对小梁骨进行体内高分辨率（HR）MRI检查的潜力。
利用模拟研究，针对我们的成像目的优化重聚焦SSFP采集，重点关注信噪比（SNR）和SNR效率。使用小梁骨和骨髓的静磁模型估计小梁骨中的信号行为。8名正常志愿者在GE Signa扫描仪上，于1.5和3 T场强下，采用优化的单次采集SSFP序列（三维FIESTA）和优化的多次采集SSFP序列（三维FIESTA-c）对股骨近端、跟骨和胫骨远端进行成像。还使用快速梯度回波（FGRE）序列采集图像，以评估SSFP方法的SNR性能。
在两种场强下，重聚焦SSFP图像在SNR和SNR效率方面均优于FGRE采集。在3 T时，FIESTA和FGRE图像中可见磁化率效应，而FIESTA-c图像中的该效应明显减弱。模拟结果准确预测了3 T时SNR提升的幅度。
单次采集SSFP（1.5 T）和多次采集SSFP（3 T）在小梁骨HR-MRI方面具有很大潜力。
