7T磁共振下用深度学习实现代谢、磁敏感与髓磷脂水的同步定量成像。
Deep learning water-unsuppressed MRSI at ultra-high field for simultaneous quantitative metabolic, susceptibility and myelin water imaging
- 基于深度学习的端到端流水线，自动去除水信号及侧带干扰。
- 12分钟内完成2毫米各向同性分辨率成像，多指标误差小于20%。
- 适合脑代谢、铁含量和髓鞘研究者，无需额外水抑制扫描。
目的：磁共振波谱成像（MRSI）可映射大脑内源性代谢物，但需抑制强烈的水信号。无水抑制的MRSI（wu-MRSI）可同时成像水与代谢物，但大水信号侧带给代谢物拟合带来挑战。本文在7特斯拉超高场下，开发了一套端到端深度学习方法以克服此问题。方法：采用非笛卡尔ECCENTRIC采样与超短回波时间，快速获取高分辨wu-MRSI数据。提出WALINET+网络，用于去除脂质、水信号及侧带；通过DeepER与物理信息网络实现MRSI重建，并利用水信号进行绝对代谢物定量、定量磁敏感图（QSM）和髓磷脂水分数成像（MWF）。结果：仿真中WALINET+的归一化均方根误差低于2%；体内实验显示与水抑制型MRSI相比，偏差小于20%，一致性界限为±63%。多个代谢物如肌酸和谷氨酸在wu-MRSI中信噪比更高。从wu-MRSI获得的QSM和MWF与梯度回波图像对比，偏差分别为0 ppm/5.5%、一致性界限±0.05 ppm/±12.75%。结论：在7特斯拉场下，利用ECCENTRIC wu-MRSI结合WALINET+，可在12分钟内实现2毫米各向同性分辨率的脑代谢、QSM与MWF同步高质量成像，有效消除水侧带并省去水抑制步骤。
原文摘要 · Abstract (English)
Purpose: Magnetic Resonance Spectroscopic Imaging (MRSI) maps endogenous brain metabolism while suppressing the overwhelming water signal. Water-unsuppressed MRSI (wu-MRSI) allows simultaneous imaging of water and metabolites, but large water sidebands cause challenges for metabolic fitting. We developed an end-to-end deep-learning pipeline to overcome these challenges at ultra-high field. Methods:Fast high-resolution wu-MRSI was acquired at 7T with non-cartesian ECCENTRIC sampling and ultra-short echo time. A water and lipid removal network (WALINET+) was developed to remove lipids, water signal, and sidebands. MRSI reconstruction was performed by DeepER and a physics-informed network for metabolite fitting. Water signal was used for absolute metabolite quantification, quantitative susceptibility mapping (QSM), and myelin water fraction imaging (MWF). Results: WALINET+ provided the lowest NRMSE (< 2%) in simulations and in vivo the smallest bias (< 20%) and limits-of-agreement (+-63%) between wu-MRSI and ws-MRSI scans. Several metabolites such as creatine and glutamate showed higher SNR in wu-MRSI. QSM and MWF obtained from wu-MRSI and GRE showed good agreement with 0 ppm/5.5% bias and +-0.05 ppm/ +- 12.75% limits-of-agreement. Conclusion: High-quality metabolic, QSM, and MWF mapping of the human brain can be obtained simultaneously by ECCENTRIC wu-MRSI at 7T with 2 mm isotropic resolution in 12 min. WALINET+ robustly removes water sidebands while preserving metabolite signal, eliminating the need for water suppression and separate water acquisitions.
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