Kim Dahan, Eisenmenger Laura, Turski Patrick, Johnson Kevin M
Department of Physics, University of Wisconsin, Madison, Wisconsin, USA.
Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA.
Magn Reson Med. 2022 Mar;87(3):1401-1417. doi: 10.1002/mrm.29060. Epub 2021 Oct 27.
To investigate the fusion of 3D time-of-flight principles into 4D-flow MRI to enhance vessel contrast and signal without an exogenous contrast agent, enabling simultaneous in-flow based angiograms.
A 4D-flow MRI technique was developed consisting of multiple overlapping slabs with intermittent magnetization transfer preparation. The scan time penalty associated with multiple slab acquisitions was mitigated by using undersampled distributed spiral trajectories and compressed sensing reconstruction. A flow phantom was used to characterize in-flow enhancement, velocity noise improvement, and flow rate measurements against the single-slab 4D-flow MRI. In a patient-volunteer cohort (n = 15), magnitude-based angiograms were radiologically evaluated against 3D time-of-flight, and velocity measurements were compared pixel-wise against single-slab and contrast-enhanced 4D-flow MRI.
Multiple-slab acquisitions, together with magnetization transfer preparation, substantially improved vessel signal, contrast, and vessel conspicuity in magnitude angiograms. Both clinical 3D time-of-flight and the proposed technique produced equivalent vessel depictions with no statistically significant difference (p < .1). Both techniques also produced clear depictions of brain aneurysms in all patients; however, very small vessels tended to show reduced conspicuity in the proposed technique. Velocity measurements agreed with contrast-enhanced and single-slab scans with high correlations (R = 0.941-0.974) and agreements (slopes = 0.994-1.071). Slab boundary and magnetization transfer-related artifacts were not observed in velocity measurements, and velocity noise was reduced with in-flow enhancement over single-slab scans (phantom).
The vessel signal and contrast can be improved in 4D-flow MRI without exogenous contrast agents by utilizing in-flow enhancement, efficient sampling, and compressed sensing. The in-flow enhancement also enables simultaneous 3D time-of-flight angiograms useful for flow quantification and diagnosis.
研究将三维飞行时间原理融入四维流动磁共振成像（4D-flow MRI），以在不使用外源性造影剂的情况下增强血管对比度和信号，从而实现基于流入的同步血管造影。
开发了一种四维流动磁共振成像技术，该技术由多个重叠层面以及间歇性磁化传递准备组成。通过使用欠采样分布式螺旋轨迹和压缩感知重建，减轻了与多个层面采集相关的扫描时间代价。使用流动模型来表征相对于单层四维流动磁共振成像的流入增强、速度噪声改善和流速测量。在一个患者-志愿者队列（n = 15）中，对基于幅度的血管造影与三维飞行时间进行放射学评估，并将速度测量逐像素地与单层和对比增强的四维流动磁共振成像进行比较。
多个层面的采集，连同磁化传递准备，在幅度血管造影中显著改善了血管信号、对比度和血管清晰度。临床三维飞行时间和所提出的技术产生了等效的血管描绘，无统计学显著差异（p < 0.1）。两种技术在所有患者中也都清晰地描绘了脑动脉瘤；然而，在所提出的技术中，非常小的血管往往显示出清晰度降低。速度测量与对比增强和单层扫描高度相关（R = 0.941 - 0.974）且一致性良好（斜率 = 0.994 - 1.071）。在速度测量中未观察到层面边界和与磁化传递相关的伪影，并且与单层扫描相比，流入增强降低了速度噪声（模型）。
通过利用流入增强、高效采样和压缩感知，在不使用外源性造影剂的情况下，四维流动磁共振成像中的血管信号和对比度可以得到改善。流入增强还能够实现用于流量量化和诊断的同步三维飞行时间血管造影。
