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首页> 外文期刊>NMR in biomedicine >Spatial location and strength of BOLD activation in high-spatial-resolution fMRI of the motor cortex: a comparison of spin echo and gradient echo fMRI at 7 T
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Spatial location and strength of BOLD activation in high-spatial-resolution fMRI of the motor cortex: a comparison of spin echo and gradient echo fMRI at 7 T

机译：运动皮质高空间分辨率fMRI中BOLD激活的空间位置和强度：7 T下自旋回波和梯度回波fMRI的比较

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摘要

The increased blood oxygenation level-dependent contrast-to-noise ratio at ultrahigh field (7 T) has been exploited in a comparison of the spatial location and strength of activation in high-resolution (1.5mm isotropic) gradient echo (GE) and spin echo (SE), echo planar imaging data acquired during the execution of a simple motor task in five subjects. SE data were acquired at six echo times from 30 to 55 ms. Excellent fat suppression was achieved in the SE echo planar images using slice-selective gradient reversal. Threshold-free cluster enhancement was used to define regions of interest (ROIs) containing voxels showing significant stimulus-locked signal changes from the GE and average SE data. These were used to compare the signal changes and spatial locations of activated regions in SE and GE data. T_2 and T_2* values were measured, with means of 48.3±1.1 ms and 36.5±3.4 ms in the SE ROI. In addition, we identified a dark band in SE images of the motor cortex corresponding to a region in which T_2 and T_2* were significantly lower than in the surrounding grey matter. The fractional SE signal change in the ROI was found to vary linearly as a function of TE, with a slope that was dependent on the particular ROI assessed: the mean ΔR_2 value was found to be 0.85±0.11 s~(–1) for the SE ROI and -0.37±0.05 s~(–1) for the GE ROI. The fractional signal change relative to the shortest TE revealed that the largest signal change occurred at a TE of 45 ms outside of the dark band. At this TE, the ratio of the fractional signal change in GE and SE data was found to be 0.48±0.05. Phase maps produced from high-resolution GE images spanning the right motor cortex were used to identify veins. The GE ROI was found to contain 18% more voxels overlying the venous mask than the SE ROI.
机译：在高分辨率（1.5mm各向同性）梯度回波（GE）和自旋中比较了激活的空间位置和强度，已经利用了在超高场（7 T）下增加的血液氧合水平相关的对比噪声比回声（SE），在五个对象中执行简单的运动任务期间获取的回声平面成像数据。 SE数据是在30到55 ms的六个回波时间获得的。使用切片选择性梯度反转在SE回波平面图像中实现了出色的脂肪抑制效果。无阈值聚类增强用于定义包含体素的感兴趣区域（ROI），这些体素从GE和平均SE数据显示出显着的刺激锁定信号变化。这些用于比较SE和GE数据中信号变化和激​​活区域的空间位置。测量了T_2和T_2 *值，在SE ROI中为48.3±1.1 ms和36.5±3.4 ms。另外，我们在运动皮层的SE图像中识别出一个暗带，该暗带对应于其中T_2和T_2 *显着低于周围灰质区域的区域。发现ROI中SE信号的分数变化随TE呈线性变化，其斜率取决于所评估的特定ROI：ΔR_2的平均值为0.85±0.11 s〜（–1）。 SE ROI和GE ROI的-0.37±0.05 s〜（–1）。相对于最短TE的分数信号变化表明，最大信号变化发生在暗带外45 ms的TE处。在该TE处，发现GE和SE数据中的分数信号变化比率为0.48±0.05。从跨越右运动皮层的高分辨率GE图像产生的相位图用于识别静脉。发现GE ROI比SE ROI包含多于静脉面罩的体素18％。

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