Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, Republic of Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.
Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, Republic of Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.
Neuroimage. 2021 Nov 1;241:118435. doi: 10.1016/j.neuroimage.2021.118435. Epub 2021 Jul 27.
Mapping mesoscopic cortical functional units such as columns or laminae is increasingly pursued by ultra-high field (UHF) functional magnetic resonance imaging (fMRI). The most popular approach for high-resolution fMRI is currently gradient-echo (GE) blood oxygenation level-dependent (BOLD) fMRI. However, its spatial accuracy is reduced due to its sensitivity to draining vessels, including pial veins, whereas spin-echo (SE) BOLD signal is expected to have higher spatial accuracy, albeit with lower sensitivity than the GE-BOLD signal. Here, we introduce a new double spin-echo (dSE) echo-planar imaging (EPI) method to improve the sensitivity of SE-BOLD contrast by averaging two spin-echoes using three radiofrequency pulses. Human fMRI experiments were performed with slices perpendicular to the central sulcus between motor and sensory cortices at 7 T during fist-clenching with touching. First, we evaluated the feasibility of single-shot dSE-EPI for BOLD fMRI with 1.5 mm isotropic resolution and found that dSE-BOLD fMRI has higher signal-to-noise ratio (SNR), temporal SNR (tSNR), and higher functional sensitivity than conventional SE-BOLD fMRI. Second, to investigate the laminar specificity of dSE-BOLD fMRI, we implemented a multi-shot approach to achieve 0.8-mm isotropic resolution with sliding-window reconstruction. Unlike GE-BOLD fMRI, the cortical profile of dSE-BOLD fMRI peaked at ~ 1.0 mm from the surface of the primary motor and sensory cortices, demonstrating an improvement of laminar specificity in humans over GE-BOLD fMRI. The proposed multi-shot dSE-EPI method is viable for high spatial resolution UHF-fMRI studies in the pursuit of resolving mesoscopic functional units.
超高场 (UHF) 功能磁共振成像 (fMRI) 越来越多地用于绘制诸如柱或层之类的介观皮质功能单位。目前，用于高分辨率 fMRI 的最流行方法是梯度回波 (GE) 血氧水平依赖 (BOLD) fMRI。然而，由于其对引流血管（包括软脑膜静脉）敏感，因此其空间精度降低，而自旋回波 (SE) BOLD 信号预计具有更高的空间精度，尽管其灵敏度低于 GE-BOLD 信号。在这里，我们引入了一种新的双自旋回波 (dSE) 回波平面成像 (EPI) 方法，通过使用三个射频脉冲对两个自旋回波进行平均，从而提高 SE-BOLD 对比度的灵敏度。在 7T 下，我们在握拳时用触摸进行了垂直于运动和感觉皮质之间中央沟的切片的 fMRI 实验。首先，我们评估了具有 1.5mm 各向同性分辨率的单次激发 dSE-EPI 用于 BOLD fMRI 的可行性，并发现 dSE-BOLD fMRI 具有比传统 SE-BOLD fMRI 更高的信噪比 (SNR)、时间 SNR (tSNR) 和更高的功能灵敏度。其次，为了研究 dSE-BOLD fMRI 的层特异性，我们实现了一种多shot 方法，以实现具有滑动窗口重建的 0.8mm 各向同性分辨率。与 GE-BOLD fMRI 不同，dSE-BOLD fMRI 的皮质轮廓在主运动和感觉皮质表面下约 1.0mm 处达到峰值，在人类中相对于 GE-BOLD fMRI 改善了层特异性。提出的多shot dSE-EPI 方法适用于超高场 fMRI 研究中追求解析介观功能单元的高空间分辨率研究。
