PRIME序列在不延长扫描时间的前提下，实现高加速无畸变扩散MRI。
PRIME: Phase Reversed Interleaved Multi-Echo acquisition enables highly accelerated distortion-free diffusion MRI
- 利用相位反转的多回波设计，在同一TR内获取多个回波，提升成像效率。
- 在临床与连接组2.0扫描仪上实现5倍平面加速和490微米各向同性分辨率。
- 适用于需要高精度场图、相位校正与扩散松弛测量的研究场景。
目的：开发并评估一种新型脉冲序列，结合广义切片抖动增强分辨率（gSlider）射频编码技术，实现高加速、无畸变的扩散MRI（dMRI），在不延长重复时间（TR）的情况下插入额外回波。方法：提出相位反转交错多回波采集（PRIME）序列，包含多个回波：首个回波用于高分辨率扩散加权成像（DWI），其余回波以低分辨率或高分辨率分别用于高保真场图估计、逐段相位校正、运动导航或高保真扩散松弛测量。在健康志愿者的临床及连接组2.0扫描仪上进行体内验证。结果：1）利用第二回波提供的高保真场图，实现了5倍平面加速（2D部分傅里叶），其有效回波间距与首读出匹配；2）通过三回波PRIME数据，采用白质多回波球均值技术（MTE-SMT）模型估算出高分辨率扩散松弛参数；3）借助连接组2.0扫描仪的高性能梯度，成功获取490微米各向同性分辨率的高保真介观尺度DWI。结论：当使用gSlider编码时，所提出的PRIME序列可在不延长扫描时间的前提下，实现高加速、高分辨率、无畸变的扩散MRI。
原文摘要 · Abstract (English)
Purpose: To develop and evaluate a new pulse sequence for highly accelerated distortion-free diffusion MRI (dMRI) by inserting additional echoes without prolonging TR, when generalized slice dithered enhanced resolution (gSlider) radiofrequency encoding is used for volumetric acquisition. Methods: A phase-reversed interleaved multi-echo acquisition (PRIME) was developed for rapid, high-resolution, and distortion-free dMRI, which includes several echoes where the first echo is for target diffusion-weighted imaging (DWI) acquisition with high-resolution and additional echoes are acquired with either lower resolution for 1) high-fidelity field map estimation, 2) phase navigation for shot-to-shot phase correction, 3) motion navigation across diffusion directions, or with high resolution to enable 4) high fidelity diffusion relaxometry acquisitions. The sequence was evaluated on in vivo data acquired from healthy volunteers on clinical and Connectome 2.0 scanners. Results: In vivo experiments demonstrated that 1) high in-plane acceleration (Rin-plane of 5-fold with 2D partial Fourier) was achieved using the high-fidelity field maps estimated from the second echo, which was made at a lower resolution/acceleration to increase its SNR while matching the effective echo spacing of the first readout, 2) high-resolution diffusion relaxometry parameters were estimated from triple-echo PRIME data using a white matter model of multi-TE spherical mean technique (MTE-SMT), and 3) high-fidelity mesoscale DWI at 490 um isotropic resolution was obtained in vivo by capitalizing on the high-performance gradients of the Connectome 2.0 scanner. Conclusion: The proposed PRIME sequence enabled highly accelerated, high-resolution, and distortion-free dMRI using additional echoes without prolonging scan time when gSlider encoding is utilized.
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