Dong Zijing, Reese Timothy G, Lee Hong-Hsi, Huang Susie Y, Polimeni Jonathan R, Wald Lawrence L, Wang Fuyixue
Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA.
Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA.
Magn Reson Med. 2025 Apr;93(4):1535-1555. doi: 10.1002/mrm.30365. Epub 2024 Nov 18.
To overcome the major challenges in diffusion MRI (dMRI) acquisition, including limited SNR, distortion/blurring, and susceptibility to motion artifacts.
A novel Romer-EPTI technique is developed to achieve SNR-efficient acquisition while providing distortion-free imaging, minimal spatial blurring, high motion robustness, and simultaneous multi-TE imaging. It introduces a ROtating-view Motion-robust supEr-Resolution technique (Romer) combined with a distortion/blurring-free Echo Planar Time-resolved Imaging (EPTI) readout. Romer enhances SNR through simultaneous multi-thick-slice acquisition with rotating-view encoding, while providing high motion-robustness via a high-fidelity, motion-aware super-resolution reconstruction. Instead of EPI, the in-plane encoding is performed using EPTI readout to prevent geometric distortion, T/T*-blurring, and importantly, dynamic distortions that could introduce additional blurring/artifacts after super-resolution reconstruction due to combining volumes with inconsistent geometries. This further improves effective spatial resolution and motion robustness. Additional developments include strategies to address slab-boundary artifacts, achieve minimized TE and optimized readout for additional SNR gain, and increase robustness to strong phase variations at high b-values.
Using Romer-EPTI, we demonstrated distortion-free whole-brain mesoscale in-vivo dMRI at both 3T (500-μm isotropic [iso] resolution) and 7T (485-μm iso resolution) for the first time. Motion experiments demonstrated the technique's motion robustness and its ability to obtain high-resolution diffusion images in the presence of subject motion. Romer-EPTI also demonstrated high SNR gain and robustness in high b-value (b = 5000 s/mm) and time-dependent dMRI.
The high SNR efficiency, improved image quality, and motion robustness of Romer-EPTI make it a highly efficient acquisition for high-resolution dMRI and microstructure imaging.
克服扩散磁共振成像（dMRI）采集中的主要挑战，包括信噪比（SNR）有限、失真/模糊以及对运动伪影敏感。
开发了一种新型的罗默 - 回波平面时间分辨成像（Romer - EPTI）技术，以实现高效的SNR采集，同时提供无失真成像、最小空间模糊、高运动鲁棒性以及同步多回波时间（multi - TE）成像。它引入了一种旋转视图运动鲁棒超分辨率技术（罗默），并结合无失真/模糊的回波平面时间分辨成像（EPTI）读出。罗默通过旋转视图编码的同步多厚层采集来提高SNR，同时通过高保真、运动感知的超分辨率重建提供高运动鲁棒性。平面内编码使用EPTI读出而不是回波平面成像（EPI），以防止几何失真、T/T*模糊，重要的是，防止由于组合具有不一致几何形状的体素而在超分辨率重建后可能引入额外模糊/伪影的动态失真。这进一步提高了有效空间分辨率和运动鲁棒性。其他改进包括解决层边界伪影的策略、实现最小化的回波时间（TE）并优化读出以获得额外的SNR增益，以及提高在高b值下对强相位变化的鲁棒性。
首次使用罗默 - EPTI在3T（500μm各向同性[iso]分辨率）和7T（485μm iso分辨率）下展示了无失真的全脑介观体内dMRI。运动实验证明了该技术的运动鲁棒性以及在受试者运动情况下获得高分辨率扩散图像的能力。罗默 - EPTI在高b值（b = 5000 s/mm²）和时间依赖的dMRI中也展示了高SNR增益和鲁棒性。
罗默 - EPTI的高SNR效率、改进的图像质量和运动鲁棒性使其成为高分辨率dMRI和微观结构成像的高效采集方法。
