Fast 3D large-angle spin-echo imaging (3D FLASE)
Fast 3D large-angle spin-echo imaging (3D FLASE)
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DOI：
10.1002/mrm.1910350619
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发表时间：
1996-06-01
影响因子：
3.3
通讯作者：
Song, HK
中科院分区：
文献类型：
--
作者：
Ma, JF;Wehrli, FW;Song, HK
基于自旋章动角度大于90度的原理，设计了一种快速稳态3D自旋回波成像脉冲序列，并在临床1.5 T全身MR扫描仪上实现。脉冲序列，表示为快速大角度自旋回波（FLASE），已被优化为具有短T-2和T-2 * 的组织的高分辨率成像。FLASE的特征包括最小相位Shinnar-Le Roux激励脉冲以及在180度重聚焦脉冲之前和之后的相位和切片编码梯度的分布，以使剩余纵向磁化的反转和恢复之间的临界时间延迟最小化，并使回波时间最小化。通过实验数据证实的Bloch方程分析显示FLASE信噪比优于其最接近的模拟，3D快速自旋回波激发（RASEE）（Jara等人，Magn Reson Medicine 29，528（1993））和稳态3D梯度回忆采集（GRASS）。它表明，与明智的RF相位循环和稳态操作，FLASE可以产生高品质的显微图像免费的体素内相位分散体素诱导的背景梯度。该方法的性能以体外和体内人体跟骨和手腕骨小梁的超高分辨率图像为例，体素尺寸低至98 x 98 x 200 μ m（3）。最后，可以通过破坏类似于梯度回波成像的稳定状态来改变重聚焦FLASE的对比度行为。
A rapid steady-state 3D spin-echo imaging pulse sequence, based on the principle of nutating the spins by an angle greater than 90 degrees, has been designed and implemented on a clinical 1.5-T whole-body MR scanner. The pulse sequence, denoted fast large-angle spin-echo (FLASE), has been optimized for high-resolution imaging of tissues with short T-2 and T-2*. Features of FLASE include a minimum-phase Shinnar-Le Roux excitation pulse and distribution of phase- and slice-encoding gradients before and after the 180 degrees refocusing pulse to minimize the critical time delay between inversion and restoration of the residual longitudinal magnetization and for minimizing echo time, A Bloch equation analysis, corroborated by experimental data, shows FLASE signal-to-noise to be superior to its closest analog, 3D rapid spin-echo excitation (RASEE) (Jara et al., Magn Reson Medicine 29,528 (1993)), and 3D gradient-recalled acquisition in steady state (GRASS). It is demonstrated that with judicious RF phase-cycling and steady state operation, FLASE can produce high-quality microimages free of intravoxel phase dispersion from susceptibility-induced background gradients. The performance of the method is exemplified with ultra high-resolution images of trabecular bone in vitro and in vivo in the human calcaneus and wrist at voxel sizes as low as 98 x 98 x 200 mu m(3). Finally, the contrast behavior of refocused FLASE can be altered by disrupting the steady state analogous to gradient echo imaging.