Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, Illinois, USA.
Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, Illinois, USA.
Magn Reson Med. 2022 May;87(5):2372-2379. doi: 10.1002/mrm.29121. Epub 2021 Dec 11.
This study aimed at developing a 3D reduced field-of-view imaging (3D-rFOVI) technique using a 2D radiofrequency (RF) pulse, and demonstrating its ability to achieve isotropic high spatial resolution and reduced image distortion in echo planar imaging (EPI).
The proposed 3D-rFOVI technique takes advantage of a 2D RF pulse to excite a slab along the conventional slice-selection direction (i.e., z-direction) while limiting the spatial extent along the phase-encoded direction (i.e., y-direction) within the slab. The slab is phase-encoded in both through-slab and in-slab phase-encoded directions. The 3D-rFOVI technique was implemented at 3T in gradient-echo and spin-echo EPI pulse sequences for functional MRI (fMRI) and diffusion-weighted imaging (DWI), respectively. 3D-rFOVI experiments were performed on a phantom and human brain to illustrate image distortion reduction, as well as isotropic high spatial resolution, in comparison with 3D full-FOV imaging.
In both the phantom and the human brain, image voxel dislocation was substantially reduced by 3D-rFOVI when compared with full-FOV imaging. In the fMRI experiment with visual stimulation, 3D isotropic spatial resolution of (2 × 2 × 2 mm ) was achieved with an adequate signal-to-noise ratio (81.5) and blood oxygen level-dependent (BOLD) contrast (2.5%). In the DWI experiment, diffusion-weighted brain images with an isotropic resolution of (1 × 1 × 1 mm ) was obtained without appreciable image distortion.
This study indicates that 3D-rFOVI is a viable approach to 3D neuroimaging over a zoomed region.
本研究旨在开发一种使用二维射频（RF）脉冲的三维小视野成像（3D-rFOVI）技术，并证明其在回波平面成像（EPI）中实现各向同性高空间分辨率和减少图像失真的能力。
所提出的 3D-rFOVI 技术利用二维 RF 脉冲来激发沿常规切片选择方向（即 z 方向）的薄片，同时将薄片沿相位编码方向（即 y 方向）的空间范围限制在薄片内。薄片在贯穿薄片和薄片内相位编码方向上进行相位编码。3D-rFOVI 技术分别在梯度回波和自旋回波 EPI 脉冲序列中在 3T 下实现，用于功能磁共振成像（fMRI）和扩散加权成像（DWI）。3D-rFOVI 实验在体模和人脑上进行，以说明与 3D 全视场成像相比，图像失真减少和各向同性高空间分辨率。
在体模和人脑上，与全视场成像相比，3D-rFOVI 显著减少了图像体素位移。在视觉刺激的 fMRI 实验中，实现了 3D 各向同性空间分辨率为（2×2×2mm），具有足够的信噪比（81.5）和血氧水平依赖（BOLD）对比度（2.5%）。在 DWI 实验中，获得了各向同性分辨率为（1×1×1mm）的无明显图像失真的扩散加权脑图像。
本研究表明，3D-rFOVI 是一种可行的方法，可以在缩放区域内进行 3D 神经成像。
