Reducing inhomogeneity artifacts in functional MRI of human brain activation - Thin sections vs gradient compensation
Reducing inhomogeneity artifacts in functional MRI of human brain activation - Thin sections vs gradient compensation
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DOI：
10.1006/jmre.2000.2105
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发表时间：
2000-08-01
影响因子：
2.2
通讯作者：
Frahm, J
中科院分区：
文献类型：
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作者：
Merboldt, KD;Finsterbusch, J;Frahm, J
我们评估了两种校正磁共振梯度回波成像中不均匀性引起的信号损失的方法，它们要么使用梯度补偿，要么简单地采集薄片。这些策略在人脑中进行了测试，测试了海马体水平 T2* 加权图像和视觉皮层功能激活图可达到的质量。实验在 2.0 T 下进行，基于分辨率为 2.0 x 2.0 mm(2)、切片厚度为 4 mm、时间分辨率为 2.0 s 的单次回波平面成像。梯度补偿涉及切片选择梯度的重聚焦波瓣的连续 16 步变化（TR/TE = 125/53 ms，翻转角 15 度），而薄切片将 4 毫米目标平面分为四个 1 毫米或八个 0.5 毫米交错多切片采集（TR/TE = 2000/54 毫秒，翻转角 70 度）。这两种方法都能够缓解大脑底部结构的不均匀性问题。与标准 4 毫米 EPI 相比，视觉皮层的功能映射受到部分影响，因为这两种方法的不均匀性校正图像的信噪比较低。相对于彼此，使用连续的薄片，尤其是厚度为 1 毫米的薄片，始终获得更好的结果。薄片的多切片采集需要最少的技术调整。 (C) 2000 年学术出版社。
We evaluated two methods for correcting inhomogeneity-induced signal losses in magnetic resonance gradient-echo imaging that either use gradient compensation or simply acquire thin sections. The strategies were tested in the human brain in terms of achievable quality of T2*-weighted images at the level of the hippocampus and of functional activation maps of the visual cortex. Experiments were performed at 2.0 T and based on single-shot echo-planar imaging at 2.0 x 2.0 mm(2) resolution, 4 mm section thickness, and 2.0 s temporal resolution. Gradient compensation involved a sequential 16-step variation of the refocusing lobe of the slice-selection gradient (TR/TE = 125/53 ms, flip angle 15 degrees), whereas thin sections divided the 4-mm target plane into either four 1-mm or eight 0.5-mm interleaved multislice acquisitions (TR/TE = 2000/54 ms, flip angle 70 degrees). Both approaches were capable of alleviating the inhomogeneity problem for structures in the base of the brain. When compared to standard 4-mm EPI, functional mapping in the visual cortex was partially compromised because of a lower signal-to-noise ratio of inhomogeneity-corrected images by either method. Relative to each other, consistently better results were obtained with the use of contiguous thin sections, in particular for a thickness of 1 mm. Multislice acquisitions of thin sections require minimal technical adjustments. (C) 2000 Academic Press.