Han SoHyun, Eun Seulgi, Cho HyungJoon, Uludaǧ Kamil, Kim Seong-Gi
Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, South Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, South Korea.
Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, South Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, South Korea.
Neuroimage. 2022 Dec 1;264:119675. doi: 10.1016/j.neuroimage.2022.119675. Epub 2022 Oct 13.
The most widely used gradient-echo (GE) blood oxygenation level-dependent (BOLD) contrast has high sensitivity, but low specificity due to draining vein contributions, while spin-echo (SE) BOLD approach at ultra-high magnetic fields is highly specific to neural active sites but has lower sensitivity. To obtain high specificity and sensitivity, we propose to utilize a vessel-size-sensitive filter to the GE-BOLD signal, which suppresses macrovascular contributions and to combine selectively retained microvascular GE-BOLD signals with the SE-BOLD signals. To investigate our proposed idea, fMRI with 0.8 mm isotropic resolution was performed on the primary motor and sensory cortices in humans at 7 T by implementing spin- and gradient-echo (SAGE) echo planar imaging (EPI) acquisition. Microvascular-passed sigmoidal filters were designed based upon the vessel-size-sensitive ΔR*/ΔR value for retaining GE-BOLD signals originating from venous vessels with ≤ 45 μm and ≤ 65 μm diameter. Unlike GE-BOLD fMRI, the laminar profile of SAGE-BOLD fMRI with the vessel-size-sensitive filter peaked at ∼ 1.0 mm from the surface of the primary motor and sensory cortices, demonstrating an improvement of laminar specificity over GE-BOLD fMRI. Also, the functional sensitivity of SAGE BOLD at middle layers (0.75-1.5 mm) was improved by ∼ 80% to ∼100% when compared with SE BOLD. In summary, we showed that combined GE- and SE-BOLD fMRI with the vessel-size-sensitive filter indeed yielded improved laminar specificity and sensitivity and is therefore an excellent tool for high spatial resolution ultra-high filed (UHF)-fMRI studies for resolving mesoscopic functional units.
最广泛使用的梯度回波（GE）血氧水平依赖（BOLD）对比具有高灵敏度，但由于引流静脉的贡献而特异性较低，而超高磁场下的自旋回波（SE）BOLD方法对神经活动位点具有高度特异性，但灵敏度较低。为了获得高特异性和高灵敏度，我们建议对GE-BOLD信号使用血管大小敏感滤波器，以抑制大血管的贡献，并将选择性保留的微血管GE-BOLD信号与SE-BOLD信号相结合。为了研究我们提出的想法，通过实施自旋和梯度回波（SAGE）回波平面成像（EPI）采集，在7T的人体初级运动和感觉皮层上进行了各向同性分辨率为0.8mm的功能磁共振成像（fMRI）。基于血管大小敏感的ΔR*/ΔR值设计了微血管通过的S形滤波器，以保留来自直径≤45μm和≤65μm静脉血管的GE-BOLD信号。与GE-BOLD功能磁共振成像不同，带有血管大小敏感滤波器的SAGE-BOLD功能磁共振成像的层流轮廓在距初级运动和感觉皮层表面约1.0mm处达到峰值，表明与GE-BOLD功能磁共振成像相比，层流特异性有所提高。此外，与SE-BOLD相比，SAGE BOLD在中层（0.75-1.5mm）的功能灵敏度提高了约80%至100%。总之，我们表明，结合了血管大小敏感滤波器的GE和SE-BOLD功能磁共振成像确实提高了层流特异性和灵敏度，因此是用于解析介观功能单元的高空间分辨率超高场（UHF）功能磁共振成像研究的优秀工具。
