Objectives

To demonstrate the advantages of radial k-space trajectories over conventional Cartesian approaches for accelerating the acquisition of vessel-selective arterial spin labeling (ASL) dynamic angiograms, which are conventionally time consuming to acquire.

Materials and methods

Vessel-encoded pseudocontinuous ASL was combined with time-resolved balanced steady-state free precession (bSSFP) and spoiled gradient echo (SPGR) readouts to obtain dynamic vessel-selective angiograms arising from the four main brain-feeding arteries. Dynamic 2D protocols with acquisition times of one minute or less were achieved through radial undersampling or a Cartesian parallel imaging approach. For whole-brain dynamic 3D imaging, magnetic field inhomogeneity and the high acceleration factors required rule out the use of bSSFP and Cartesian trajectories, so the feasibility of acquiring 3D radial SPGR angiograms was tested.

Results

The improved SNR efficiency of bSSFP over SPGR was confirmed for 2D dynamic imaging. Radial trajectories had considerable advantages over a Cartesian approach, including a factor of two improvements in the measured SNR (p < 0.00001, N = 6), improved distal vessel delineation and the lack of a need for calibration data. The 3D radial approach produced good quality angiograms with negligible artifacts despite the high acceleration factor (R = 13).

Conclusion

Radial trajectories outperform conventional Cartesian techniques for accelerated vessel-selective ASL dynamic angiography.

中文翻译：

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径向轨迹在动脉自旋标记血管选择性动态血管造影中的优势

目标

为了证明径向k空间轨迹相对于传统的笛卡尔方法在加速血管选择性动脉自旋标记（ASL）动态血管造影照片的采集方面的优势，该过程通常是耗时的。

材料和方法

血管编码的伪连续ASL与时间分辨的平衡稳态自由进动（bSSFP）和变差的梯度回波（SPGR）读数相结合，获得了由四个主要的大脑供血动脉产生的动态血管选择性血管造影照片。通过径向欠采样或笛卡尔并行成像方法，可以实现采集时间为一分钟或更短时间的动态2D协议。对于全脑动态3D成像，所需的磁场不均匀性和高加速因子排除了使用bSSFP和笛卡尔轨迹的可能性，因此测试了获取3D径向SPGR血管造影照片的可行性。

结果

对于二维动态成像，证实了bSSFP优于SPGR的SNR效率提高。径向轨迹相对于笛卡尔方法具有相当大的优势，包括在测量的SNR方面有两个改进（p  <0.00001，N  = 6），改善了远端血管的轮廓以及无需校准数据。尽管加速度因数较高（R  = 13），但3D径向方法产生的血管造影质量良好，伪影可忽略不计。

结论

径向轨迹优于传统的笛卡尔技术，可加速血管选择性ASL动态血管造影。