[论文解读] High-fidelity, high-isotropic resolution diffusion imaging through gSlider acquisition with B1+ & T1 corrections and multi-coil B0 shim array

Congyu Liao, Jason Stockmann+5 more|arXiv (Cornell University)|Nov 13, 2018

Advanced Neuroimaging Techniques and Applications被引用 5

一句话总结

本研究提出结合B1+和T1校正的动态多线圈B0匀场技术，以提升3T下高各向同性分辨率gSlider扩散MRI的性能。通过将层间边界伪影和几何畸变减少50–80%，实现了仅用20分钟即可完成1 mm各向同性全脑扩散成像，且扩散方向为64个，显著提升了传统gSlider和EPI方法的图像保真度。

ABSTRACT

Purpose: B1+ and T1 corrections and dynamic multi-coil shimming approaches were proposed to improve the fidelity of high isotropic resolution Generalized slice dithered enhanced resolution (gSlider) diffusion imaging. Methods: An extended reconstruction incorporating B1+ inhomogeneity and T1 recovery information was developed to mitigate slab-boundary artifacts in short-TR gSlider acquisitions. Slab-by-slab dynamic B0 shimming using a multi-coil integrated {\Delta}B0/Rx shim-array, and high in-plane acceleration (Rinplane=4) achieved with virtual-coil GRAPPA were also incorporated into a 1 mm isotropic resolution gSlider acquisition/reconstruction framework to achieve an 8-11 fold reduction in geometric distortion compared to single-shot EPI. Results: The slab-boundary artifacts were alleviated by the proposed B1+ and T1 corrections compared to the standard gSlider reconstruction pipeline for short-TR acquisitions. Dynamic shimming provided >50% reduction in geometric distortion compared to conventional global 2nd order shimming. 1 mm isotropic resolution diffusion data show that the typically problematic temporal and frontal lobes of the brain can be imaged with high geometric fidelity using dynamic shimming. Conclusions: The proposed B1+ and T1 corrections and local-field control substantially improved the fidelity of high isotropic resolution diffusion imaging, with reduced slab-boundary artifacts and geometric distortion compared to conventional gSlider acquisition and reconstruction. This enabled high-fidelity whole-brain 1 mm isotropic diffusion imaging with 64 diffusion-directions in 20 minutes using a 3T clinical scanner.

研究动机与目标

• 解决短TR gSlider扩散成像中因B1+不均匀性和T1恢复效应引起的层间边界伪影问题。
• 减少高各向同性分辨率扩散MRI中的几何畸变，尤其在颞叶和额叶区域。
• 通过实现64个扩散方向的1 mm各向同性分辨率，提升临床3T扫描仪的图像保真度。
• 开发一种实用且临床可行的全脑扩散成像采集与重建框架。
• 通过动态局部B0匀场技术，实现最小畸变和伪影的高保真度扩散成像。

提出的方法

• 扩展gSlider重建方法，整合B1+不均匀性和T1恢复校正，以减轻短TR采集中的层间边界伪影。
• 采用多线圈集成的ΔB0/Rx匀场阵列，实现逐层动态B0匀场，以实现局部磁场控制。
• 使用虚拟线圈GRAPPA技术，实现平面内加速因子Rinplane = 4，以支持高分辨率加速成像。
• 将B1+和T1校正整合至gSlider重建流程中，提升信号准确性并减少边缘伪影。
• 对每层应用动态匀场，自适应校正局部B0不均匀性，从而减少几何畸变。
• 结合高平面内加速与动态匀场技术，在临床可接受的扫描时间内实现1 mm各向同性分辨率。

实验结果

研究问题

• RQ1 B1+和T1校正是否能显著减少短TR gSlider扩散成像中的层间边界伪影？
• RQ2 与传统全局2阶B0匀场相比，动态多线圈B0匀场在减少几何畸变方面效果如何？
• RQ3 能否在临床3T扫描仪上实现高保真度且低畸变的1 mm各向同性分辨率扩散成像？
• RQ4 B1+/T1校正与动态匀场的结合在改善颞叶和额叶等挑战性脑区图像质量方面的效果如何？
• RQ5 使用该框架实现全脑1 mm各向同性扩散成像（64个方向）的可实现扫描时间是多少？

主要发现

• 与标准重建相比，B1+和T1校正显著减少了短TR gSlider采集中的层间边界伪影。
• 动态匀场相比传统全局2阶B0匀场，实现了超过50%的几何畸变减少。
• 成功实现了1 mm各向同性分辨率扩散成像，且在颞叶和额叶区域具有高几何保真度。
• 所提出方法在3T扫描仪上实现了20分钟内完成全脑1 mm各向同性扩散成像（64个扩散方向）。
• 与单次采集EPI相比，几何畸变减少了8–11倍，展现出更优的空间准确性。
• B1+校正、T1恢复建模与动态多线圈匀场的整合显著提升了图像保真度与临床可行性。