Optimizing diffusion MRI acquisition efficiency of rodent brain using simultaneous multislice EPI.,NMR in Biomedicine

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Optimizing diffusion MRI acquisition efficiency of rodent brain using simultaneous multislice EPI.
NMR in Biomedicine ( IF 2.7 ) Pub Date : 2020-08-24 , DOI: 10.1002/nbm.4398
Hsu-Lei Lee _{1,

2} , Xiaoqing Alice Zhou ₁ , Zengmin Li ₁ , Kai-Hsiang Chuang _{1,

2}

Affiliation

Diffusion tensor imaging (DTI) of the brain provides essential information on the white matter integrity and structural connectivity. However, it suffers from a low signal‐to‐noise ratio (SNR) and requires a long scan time to achieve high spatial and/or diffusion resolution and wide brain coverage. With recent advances in parallel and simultaneous multislice (multiband) imaging, the SNR efficiency has been improved by reducing the repetition time (T_R). However, due to the limited number of RF coil channels available on preclinical MRI scanners, simultaneous multislice acquisition has not been practical. In this study, we demonstrate the ability of multiband DTI to acquire high‐resolution data of the mouse brain with 84 slices covering the whole brain in 0.2 mm isotropic resolution without a coil array at 9.4 T. Hadamard‐encoding four‐band pulses were used to acquire four slices simultaneously, with the reduction in the T_R maximizing the SNR efficiency. To overcome shot‐to‐shot phase variations, Hadamard decoding with a self‐calibrated phase was developed. Compared with single‐band DTI acquired with the same scan time, the multiband DTI leads to significantly increased SNR by 40% in the white matter. This SNR gain resulted in reduced variations in fractional anisotropy, mean diffusivity, and eigenvector orientation. Furthermore, the cerebrospinal fluid signal was attenuated, leading to reduced free‐water contamination. Without the need for a high‐density coil array or parallel imaging, this technique enables highly efficient preclinical DTI that will facilitate connectome studies.

中文翻译：

使用同时多层 EPI 优化啮齿动物大脑的扩散 MRI 采集效率。

大脑的弥散张量成像 (DTI) 提供有关白质完整性和结构连接性的重要信息。然而，它的信噪比（SNR）较低，并且需要较长的扫描时间才能实现高空间和/或扩散分辨率以及广泛的大脑覆盖范围。随着并行_和同时多切片（多波段）成像的最新进展，通过减少重复时间（ TR ）提高了信噪比效率。然而，由于临床前 MRI 扫描仪上可用的射频线圈通道数量有限，同步多层采集尚未实用。在这项研究中，我们展示了多波段 DTI 能够以 84 个切片覆盖整个大脑，以 0.2 毫米各向同性分辨率获取小鼠大脑的高分辨率数据，而无需 9.4 T 的线圈阵列。使用哈达玛编码四波段脉冲同时采集四个切片，通过减少T _R来最大化 SNR 效率。为了克服镜头间的相位变化，开发了具有自校准相位的哈达玛解码。与相同扫描时间获得的单波段 DTI 相比，多波段 DTI 导致白质中的 SNR 显着提高了 40%。这种信噪比增益导致分数各向异性、平均扩散率和特征向量方向的变化减少。此外，脑脊液信号减弱，导致游离水污染减少。该技术无需高密度线圈阵列或并行成像，即可实现高效的临床前 DTI，从而促进连接组研究。

更新日期：2020-08-24

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