Single-shot dual-z-shimmed sensitivity-encoded Spiral-in/out imaging for functional MRI with reduced susceptibility artifacts
Single-shot dual-z-shimmed sensitivity-encoded Spiral-in/out imaging for functional MRI with reduced susceptibility artifacts
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DOI：
10.1002/mrm.21473
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发表时间：
2008-01-01
影响因子：
3.3
通讯作者：
Song, Allen W.
中科院分区：
文献类型：
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作者：
Truong, Trong-Kha;Song, Allen W.
血氧水平依赖(BOLD)功能磁共振成像(FMRI)由于磁化率引起的静磁场(B-0)在空气/组织界面附近的不均匀性而导致信号丢失，严重阻碍了fMRI的成像。先前提出了在两次采集之间嵌入z-填补梯度的单触发螺旋输入/输出序列，以有效地恢复信号。然而，尽管结果令人振奋，这项技术仍有几个局限性，下面将对其进行说明。首先，通过在螺旋输入捕获之前添加第二个z填补梯度，并逐片地优化两个z填补梯度，可以实现明显更均匀的信号恢复。其次，通过获取B-0图，可以直接、高效、准确地确定每个受试者的最佳z-填补梯度。第三，通过使用灵敏度编码(SENSE)来补充z-Shiming方法，可以提高平面内空间分辨率，从而进一步减少敏感性伪影，同时为fMRI应用保持高的时间分辨率。这些优势在人类功能研究中得到了证实。
Blood oxygenation level-dependent (BOLD) functional MRI (fMRI) can be severely hampered by signal loss due to susceptibility-induced static magnetic field (B-0) inhomogeneities near air/tissue interfaces. A single-shot spiral-in/out sequence with a z-shim gradient embedded between the two acquisitions was previously proposed to efficiently recover the signal. However, despite promising results, this technique had several limitations, which are addressed here as follows. First, by adding a second z-shim gradient before the spiral-in acquisition and optimizing both z-shim gradients slice-by-slice, a significantly more uniform signal recovery can be achieved. Second, by acquiring a B-0 map, the optimal z-shim gradients can be directly, efficiently, and accurately determined for each subject. Third, by complementing the z-shimming approach with sensitivity encoding (SENSE), the in-plane spatial resolution can be increased and, hence, susceptibility artifacts further reduced, while maintaining a high temporal resolution for fMRI applications. These advantages are demonstrated in human functional studies.