Accelerated dual-venc 4D flow MRI for neurovascular applications.
Accelerated dual-venc 4D flow MRI for neurovascular applications.
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DOI：
10.1002/jmri.25595
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发表时间：
2017-07
期刊：
影响因子：
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通讯作者：
Markl M
中科院分区：
文献类型：
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作者：
Schnell S;Ansari SA;Wu C;Garcia J;Murphy IG;Rahman OA;Rahsepar AA;Aristova M;Collins JD;Carr JC;Markl M
采用双速度编码（dual-venc）和k-t GRAPPA加速度，提高四维流MRI的速度噪声比（VNR）和动态速度范围。采用共享参考扫描，然后进行三方向低、高通道扫描（TR/TE/FA=6.1ms/3.4ms/15°，时间/空间分辨率=43.0ms/1.2×1.2×1.2mm3），开发了具有k-t GRAPPA加速的双通道4D血流MRI序列。利用高速率数据对低速率数据中的混叠进行校正，得到具有低速率数据良好的VNR但没有速度混叠的单数据集。该序列在3特斯拉MRI扫描仪上进行了幻影实验验证，并在16名志愿者身上进行了应用，以研究其在颅内主要血管处评估颅内血流动力学（净流量和峰值速度）的可行性。此外，在活体采集中对图像质量和图像噪声进行了评估。所有4D血流MRI扫描均获得成功，获取时间为20±4min。与两次单独扫描相比，共享参考扫描减少了12.5%的总采集时间。幻影实验表明，与高venc相比，双venc的噪声降低了51.4%，速度一致性很好（ρ=0.8, p<0.001）。志愿者数据显示，与高venc相比，双venc数据的噪声降低（降低54.6%），图像质量得到改善，由两名观察者评分：伪影减少（P<0.0001），血管显著性改善（P<0.0001），噪声降低（P<0.0001）。双通道四维流MRI显示出优越的低通道采集VNR，可靠地同时结合了低、高速场。体外和体内数据表明，改进了血流可视化、图像质量和图像噪声。
To improve velocity–to-noise ratio (VNR) and dynamic velocity range at 4D flow MRI by using dual-velocity encoding (dual-venc) with k-t GRAPPA acceleration. 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 (TR/TE/FA=6.1ms/3.4ms/15°, temporal/spatial resolution=43.0ms/1.2×1.2×1.2mm3). The high-venc data was 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 at a 3 Tesla 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 was assessed in the in-vivo acquisitions. All 4D flow MRI scans were acquired successfully with an acquisition time of 20±4min. 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: less artifacts (P<0.0001), improved vessel conspicuity (P<0.0001), and reduced noise (P<0.0001). 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.