Department of Radiology, Stanford University, Stanford, California, USA.
Department of Electrical Engineering, Stanford University, Stanford, California, USA.
Magn Reson Med. 2025 Jan;93(1):121-137. doi: 10.1002/mrm.30255. Epub 2024 Sep 9.
To develop a 3D spherical EPTI (sEPTI) acquisition and a comprehensive reconstruction pipeline for rapid high-quality whole-brain submillimeter and QSM quantification.
For the sEPTI acquisition, spherical k-space coverage is utilized with variable echo-spacing and maximum k ramp-sampling to improve efficiency and signal incoherency compared to existing EPTI approaches. For reconstruction, an iterative rank-shrinking B estimation and odd-even high-order phase correction algorithms were incorporated into the reconstruction to better mitigate artifacts from field imperfections. A physics-informed unrolled network was utilized to boost the SNR, where 1-mm and 0.75-mm isotropic whole-brain imaging were performed in 45 and 90 s at 3 T, respectively. These protocols were validated through simulations, phantom, and in vivo experiments. Ten healthy subjects were recruited to provide sufficient data for the unrolled network. The entire pipeline was validated on additional five healthy subjects where different EPTI sampling approaches were compared. Two additional pediatric patients with epilepsy were recruited to demonstrate the generalizability of the unrolled reconstruction.
sEPTI achieved 1.4 faster imaging with improved image quality and quantitative map precision compared to existing EPTI approaches. The B update and the phase correction provide improved reconstruction performance with lower artifacts. The unrolled network boosted the SNR, achieving high-quality and QSM quantification with single average data. High-quality reconstruction was also obtained in the pediatric patients using this network.
sEPTI achieved whole-brain distortion-free multi-echo imaging and and QSM quantification at 0.75 mm in 90 s which has the potential to be useful for wide clinical applications.
开发一种用于快速高质量全脑亚毫米级和 QSM 定量的 3D 球形 EPTI（sEPTI）采集和全面重建管道。
对于 sEPTI 采集，利用球形 k 空间覆盖范围，采用可变回波间距和最大 k 斜坡采样，与现有 EPTI 方法相比，提高了效率和信号不一致性。对于重建，迭代秩收缩 B 估计和奇偶数高阶相位校正算法被合并到重建中，以更好地减轻来自场不均匀性的伪影。利用物理信息展开网络来提高 SNR，分别在 3T 下以 45 和 90s 实现 1mm 和 0.75mm 各向同性全脑成像。这些协议通过模拟、体模和体内实验进行了验证。招募了 10 名健康受试者，为展开网络提供了足够的数据。在另外 5 名健康受试者上验证了整个管道，并比较了不同的 EPTI 采样方法。另外招募了 2 名患有癫痫的儿科患者，以证明展开重建的通用性。
sEPTI 实现了 1.4 倍的更快成像，与现有 EPTI 方法相比，提高了图像质量和定量图精度。B 更新和相位校正提供了改进的重建性能，降低了伪影。展开网络提高了 SNR，仅使用单平均数据即可实现高质量成像和 QSM 定量。该网络也可在儿科患者中获得高质量的重建。
sEPTI 实现了全脑无失真多回波成像和 0.75mm 分辨率下 90s 的 QSM 定量，有望在广泛的临床应用中具有实用性。
