用于神经血管应用的加速双静脉4D流动磁共振成像
Accelerated dual-venc 4D flow MRI for neurovascular applications.
作者信息
Schnell Susanne, Ansari Sameer A, Wu Can, Garcia Julio, Murphy Ian G, Rahman Ozair A, Rahsepar Amir A, Aristova Maria, Collins Jeremy D, Carr James C, Markl Michael
机构信息
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Department of Neurosurgery, Northwestern University, Chicago, Illinois, USA.
出版信息
J Magn Reson Imaging. 2017 Jul;46(1):102-114. doi: 10.1002/jmri.25595. Epub 2017 Feb 2.
PURPOSE
To improve velocity-to-noise ratio (VNR) and dynamic velocity range of 4D flow magnetic resonance imaging (MRI) by using dual-velocity encoding (dual-venc) with k-t generalized autocalibrating partially parallel acquisition (GRAPPA) acceleration.
MATERIALS AND METHODS
A dual-venc 4D flow MRI sequence with k-t GRAPPA acceleration was developed using a shared reference scan followed by three-directional low- and high-venc scans (repetition time / echo time / flip angle = 6.1 msec / 3.4 msec / 15°, temporal/spatial resolution = 43.0 msec/1.2 × 1.2 × 1.2 mm ). The high-venc data were used to correct for aliasing in the low-venc data, resulting in a single dataset with the favorable VNR of the low-venc but without velocity aliasing. The sequence was validated with a 3T MRI scanner in phantom experiments and applied in 16 volunteers to investigate its feasibility for assessing intracranial hemodynamics (net flow and peak velocity) at the major intracranial vessels. In addition, image quality and image noise were assessed in the in vivo acquisitions.
RESULTS
All 4D flow MRI scans were acquired successfully with an acquisition time of 20 ± 4 minutes. The shared reference scan reduced the total acquisition time by 12.5% compared to two separate scans. Phantom experiments showed 51.4% reduced noise for dual-venc compared to high-venc and an excellent agreement of velocities (ρ = 0.8, P < 0.001). The volunteer data showed decreased noise in dual-venc data (54.6% lower) compared to high-venc, and improved image quality, as graded by two observers: fewer artifacts (P < 0.0001), improved vessel conspicuity (P < 0.0001), and reduced noise (P < 0.0001).
CONCLUSION
Dual-venc 4D flow MRI exhibits the superior VNR of the low-venc acquisition and reliably incorporates low- and high-velocity fields simultaneously. In vitro and in vivo data demonstrate improved flow visualization, image quality, and image noise.
LEVEL OF EVIDENCE
2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:102-114.
目的
通过使用双速度编码（dual-venc）结合k-t广义自校准部分并行采集（GRAPPA）加速技术，提高四维流动磁共振成像（MRI）的速度噪声比（VNR）和动态速度范围。
材料与方法
开发了一种采用k-t GRAPPA加速的双速度编码四维流动MRI序列，先进行一次共享参考扫描，随后进行三个方向的低速度编码和高速度编码扫描（重复时间/回波时间/翻转角 = 6.1毫秒/3.4毫秒/15°，时间/空间分辨率 = 43.0毫秒/1.2×1.2×1.2毫米）。利用高速度编码数据校正低速度编码数据中的混叠现象，从而得到一个具有低速度编码良好VNR且无速度混叠的单一数据集。该序列在体模实验中通过3T MRI扫描仪进行了验证，并应用于16名志愿者，以研究其评估颅内主要血管颅内血流动力学（净流量和峰值速度）的可行性。此外，还在活体采集过程中评估了图像质量和图像噪声。
结果
所有四维流动MRI扫描均成功完成，采集时间为20±4分钟。与两次单独扫描相比，共享参考扫描使总采集时间减少了12.5%。体模实验显示，与高速度编码相比，双速度编码的噪声降低了51.4%，速度一致性良好（ρ = 0.8，P < 0.001）。志愿者数据显示，与高速度编码相比，双速度编码数据的噪声降低（低54.6%），图像质量得到改善，两名观察者对其评级如下：伪影减少（P < 0.0001）、血管清晰度提高（P < 0.0001）和噪声降低（P < 0.0001）。
结论
双速度编码四维流动MRI具有低速度编码采集的卓越VNR，能够可靠地同时纳入低速和高速血流场。体外和体内数据均表明血流可视化、图像质量和图像噪声均得到改善。
证据水平
2 技术效能：1期 《磁共振成像杂志》2017年；46:102 - 114。
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