优化快速径向极短回波时间（UTE）采集的轨迹排序。
Optimizing trajectory ordering for fast radial ultra-short TE (UTE) acquisitions.
机构信息
UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, San Francisco and University of California, Berkeley, CA, United States; Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States; GE Healthcare, Menlo Park, CA, United States.
UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, San Francisco and University of California, Berkeley, CA, United States; Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States.
出版信息
J Magn Reson. 2021 Jun;327:106977. doi: 10.1016/j.jmr.2021.106977. Epub 2021 Apr 2.
PURPOSE
Additional spoiler gradients are required in 3D UTE sequences with random view ordering to suppress magnetization refocusing. By leveraging the encoding gradient induced spoiling effect, the spoiler gradients could potentially be reduced or removed to shorten the TR and increase encoding efficiency. An analysis framework is built that models the gradient spoiling effects and a new ordering scheme is proposed for fast 3D UTE acquisition.
THEORY AND METHODS
UTE signal evolution and spatial encoding gradient induced spoiling effect are derived from the Bloch equations. And the concept is validated in 2D radial UTE simulation. Then an optimized ordering scheme, named reordered 2D golden angle (r2DGA) scheme, for 3D UTE acquisition is proposed. The r2DGA scheme is compared to the sequential and 3D golden angle schemes in both phantom and volunteer studies.
RESULTS
The proposed r2DGA ordering scheme was applied to two applications, single breath-holding and free breathing 3D lung MRI. With r2DGA ordering scheme, breath-holding lung MRI scan increased 60% scan efficiency by removing the spoiler gradients and the free breathing scan reduced 20% scan time compared to the 3D golden angle scheme by reducing the spoiler gradients.
CONCLUSIONS
The proposed r2DGA ordering scheme UTE acquisition reduces the need of spoiler gradients and increases the encoding efficiency, and shows improvements in both breath-holding and free breathing lung MRI applications.
目的
在随机视图排序的 3D UTE 序列中需要额外的扰相梯度来抑制磁化重聚焦。通过利用编码梯度引起的扰相效应，可以减少或去除扰相梯度，从而缩短 TR 并提高编码效率。构建了一个分析框架，对梯度扰相效应进行建模，并提出了一种新的快速 3D UTE 采集排序方案。
理论与方法
从 Bloch 方程推导出 UTE 信号演化和空间编码梯度引起的扰相效应。并在 2D 径向 UTE 模拟中验证了该概念。然后提出了一种优化的排序方案，称为重排二维黄金角（r2DGA）方案，用于 3D UTE 采集。在体模和志愿者研究中，将 r2DGA 方案与顺序和 3D 黄金角方案进行了比较。
结果
将提出的 r2DGA 排序方案应用于两个应用，单屏气和自由呼吸 3D 肺 MRI。采用 r2DGA 排序方案，通过去除扰相梯度，屏气肺 MRI 扫描的扫描效率提高了 60%；通过减少扰相梯度，自由呼吸扫描的扫描时间比 3D 黄金角方案减少了 20%。
结论
所提出的 r2DGA 排序方案的 UTE 采集减少了扰相梯度的需求，提高了编码效率，并在屏气和自由呼吸肺 MRI 应用中均得到了改善。
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