Miao Xinyuan, Li Yinghao, Zhou Xinyi, Luo Yu, Paez Adrian G, Liu Dapeng, van Zijl Peter C M, Hua Jun
Neurosection, Division of MRI Research, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, United States.
F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States.
Front Neurosci. 2023 Mar 2;17:1114045. doi: 10.3389/fnins.2023.1114045. eCollection 2023.
T2-prepared (T2prep) blood oxygenation level dependent (BOLD) functional MRI (fMRI) is an alternative fMRI approach developed to mitigate the susceptibility artifacts that are typically observed in brain regions near air-filled cavities, bleeding and calcification, and metallic objects in echo-planar-imaging (EPI) based fMRI images. Here, T2prep BOLD fMRI was evaluated in an event-related paradigm for the first time. Functional experiments were performed using gradient-echo (GRE) EPI, spin-echo (SE) EPI, and T2prep BOLD fMRI during an event-related visual task in 10 healthy human subjects. Each fMRI method was performed with a low (3.4 × 3.4 × 4 mm) and a high (1.5 mm isotropic) spatial resolution on 3T and a high resolution (1.5 mm isotropic) on 7T. Robust activation were detected in the visual cortex with all three fMRI methods. In each group of fMRI scans (3T low resolution, 3T high resolution, and 7T high resolution), GRE EPI showed the highest signal change (ΔS/S), largest full-width-at-half-maximum (FWHM) and longest time-to-peak (TTP) extracted from the hemodynamic response functions (HRF), indicating substantial signal contribution from large draining veins which have longer response times than microvessels. In contrast, T2prep BOLD showed the lowest ΔS/S, smallest FWHM, and shortest TTP, suggesting that T2prep BOLD may have a purer T2-weighted BOLD contrast that is more sensitive to microvessels compared to GRE/SE EPI BOLD. This trend was more obvious in fMRI scans performed with a lower spatial resolution on a lower field (3T with a 3.4 × 3.4 × 4 mm voxel). Scan-rescan reproducibility in the same subjects was comparable among the three fMRI methods. The results from the current study are expected to be useful to establish T2prep BOLD as a useful alternative fMRI approach for event-related fMRI in brain regions with large susceptibility artifacts.
T2 准备（T2prep）血氧水平依赖（BOLD）功能磁共振成像（fMRI）是一种替代性的 fMRI 方法，其开发目的是减轻在基于回波平面成像（EPI）的 fMRI 图像中，通常在充满空气的腔隙、出血和钙化以及金属物体附近的脑区所观察到的磁化率伪影。在此，首次在事件相关范式中对 T2prep BOLD fMRI 进行了评估。在 10 名健康人类受试者执行事件相关视觉任务期间，使用梯度回波（GRE）EPI、自旋回波（SE）EPI 和 T2prep BOLD fMRI 进行了功能实验。每种 fMRI 方法均在 3T 的低空间分辨率（3.4×3.4×4 毫米）和高空间分辨率（各向同性 1.5 毫米）以及 7T 的高分辨率（各向同性 1.5 毫米）下进行。使用所有三种 fMRI 方法均在视觉皮层中检测到了稳健的激活。在每组 fMRI 扫描（3T 低分辨率、3T 高分辨率和 7T 高分辨率）中，GRE EPI 显示出从血流动力学响应函数（HRF）中提取的最高信号变化（ΔS/S）、最大半高宽（FWHM）和最长峰值时间（TTP），表明来自大引流静脉的大量信号贡献，其响应时间比微血管更长。相比之下，T2prep BOLD 显示出最低的 ΔS/S、最小的 FWHM 和最短的 TTP，这表明与 GRE/SE EPI BOLD 相比，T2prep BOLD 可能具有更纯的 T2 加权 BOLD 对比度，对微血管更敏感。这种趋势在较低场强（3T，体素为 3.4×3.4×4 毫米）下以较低空间分辨率进行的 fMRI 扫描中更为明显。三种 fMRI 方法在同一受试者中的扫描 - 重扫描再现性相当。当前研究的结果有望有助于将 T2prep BOLD 确立为在具有大磁化率伪影的脑区进行事件相关 fMRI 的一种有用的替代性 fMRI 方法。
