Department of Radiology, Academic Medical Center, Amsterdam, The Netherlands.
Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
Magn Reson Med. 2018 Nov;80(5):1799-1811. doi: 10.1002/mrm.27158. Epub 2018 Mar 5.
3D time-resolved (4D) phase contrast MRI can be used to study muscle contraction. However, 3D coverage with sufficient spatiotemporal resolution can only be achieved by interleaved acquisitions during many repetitions of the motion task, resulting in long scan times. The aim of this study was to develop a compressed sensing accelerated 4D phase contrast MRI technique for quantification of velocities and strain rate of the muscles in the lower leg during active plantarflexion/dorsiflexion.
Nine healthy volunteers were scanned during active dorsiflexion/plantarflexion task. For each volunteer, we acquired a reference scan, as well as 4 different accelerated scans (k-space undersampling factors: 3.14X, 4.09X, 4.89X, and 6.41X) obtained using Cartesian Poisson disk undersampling schemes. The data was reconstructed using a compressed sensing pipeline. For each scan, velocity and strain rate values were quantified in the gastrocnemius lateralis, gastrocnemius medialis, tibialis anterior, and soleus.
No significant differences in velocity values were observed as a function acceleration factor in the investigated muscles. The strain rate calculation resulted in one positive (s ) and one negative (s ) eigenvalue, whereas the third eigenvalue (s ) was consistently 0 for all the acquisitions. No significant differences were observed for the strain rate eigenvalues as a function of acceleration factor.
Data undersampling combined with compressed sensing reconstruction allowed obtainment of time-resolved phase contrast acquisitions with 3D coverage and quantitative information comparable to the reference scan. The 3D sensitivity of the method can help in understanding the connection between muscle architecture and muscle function in future studies.
三维时分辨（4D）相位对比 MRI 可用于研究肌肉收缩。然而，在多次运动任务重复期间，通过交错采集才能实现具有足够时空分辨率的 3D 覆盖，从而导致扫描时间长。本研究旨在开发一种压缩感知加速 4D 相位对比 MRI 技术，用于定量分析小腿在主动背屈/跖屈运动期间的肌肉速度和应变速率。
九名健康志愿者在主动背屈/跖屈任务期间接受扫描。对于每个志愿者，我们采集了参考扫描，以及 4 种不同的加速扫描（k 空间欠采样因子：3.14X、4.09X、4.89X 和 6.41X），这些扫描是使用笛卡尔泊松圆盘欠采样方案获得的。使用压缩感知管道对数据进行重建。对于每个扫描，在比目鱼肌外侧、比目鱼肌内侧、胫骨前肌和腓肠肌中量化了速度和应变速率值。
在所研究的肌肉中，作为加速因子的函数，速度值没有观察到显著差异。应变速率计算导致一个正（s）和一个负（s）特征值，而所有采集的第三个特征值（s）始终为 0。应变速率特征值作为加速因子的函数没有观察到显著差异。
数据欠采样与压缩感知重建相结合，可获得具有 3D 覆盖和与参考扫描相当的定量信息的时分辨相位对比采集。该方法的 3D 灵敏度有助于在未来的研究中理解肌肉结构与肌肉功能之间的联系。
