School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
Department of Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, California, USA.
Magn Reson Med. 2021 Nov;86(5):2468-2481. doi: 10.1002/mrm.28882. Epub 2021 Jun 6.
We propose a new method, displacement spectrum (DiSpect) imaging, for probing in vivo complex tissue dynamics such as motion, flow, diffusion, and perfusion. Based on stimulated echoes and image phase, our flexible approach enables observations of the spin dynamics over short (milliseconds) to long (seconds) evolution times.
The DiSpect method is a Fourier-encoded variant of displacement encoding with stimulated echoes, which encodes bulk displacement of spins that occurs between tagging and imaging in the image phase. However, this method fails to capture partial volume effects as well as blood flow. The DiSpect variant mitigates this by performing multiple scans with increasing displacement-encoding steps. Fourier analysis can then resolve the multidimensional spectrum of displacements that spins exhibit over the mixing time. In addition, repeated imaging following tagging can capture dynamic displacement spectra with increasing mixing times.
We demonstrate properties of DiSpect MRI using flow phantom experiments as well as in vivo brain scans. Specifically, the ability of DiSpect to perform retrospective vessel-selective perfusion imaging at multiple mixing times is highlighted.
The DiSpect variant is a new tool in the arsenal of MRI techniques for probing complex tissue dynamics. The flexibility and the rich information it provides open the possibility of alternative ways to quantitatively measure numerous complex spin dynamics, such as flow and perfusion within a single exam.
我们提出了一种新的方法，即位移谱（DiSpect）成像，用于探测体内复杂的组织动力学，如运动、流动、扩散和灌注。基于受激发射回波和图像相位，我们的灵活方法能够观察到自旋动力学在短（毫秒）到长（秒）演化时间内的变化。
DiSpect 方法是位移编码与受激发射回波的傅里叶编码变体，它对在图像相位中标记和成像之间发生的自旋整体位移进行编码。然而，这种方法无法捕获部分体积效应和血流。DiSpect 变体通过增加位移编码步骤来进行多次扫描来减轻这种影响。然后可以通过傅里叶分析解析自旋在混合时间内表现出的多维位移谱。此外，在标记后进行重复成像可以捕获具有增加混合时间的动态位移谱。
我们使用流动体模实验和体内脑扫描演示了 DiSpect MRI 的特性。具体来说，突出了 DiSpect 在多个混合时间进行回顾性血管选择性灌注成像的能力。
DiSpect 变体是探测复杂组织动力学的 MRI 技术工具库中的一种新工具。它的灵活性和提供的丰富信息为在单次检查中定量测量许多复杂的自旋动力学（如流动和灌注）提供了替代方法的可能性。
