BACKGROUND 4D flow cardiovascular magnetic resonance (CMR) enables visualization of complex blood flow and quantification of biomarkers for vessel wall disease, such as wall shear stress (WSS). Because of the inherently long acquisition times, many efforts have been made to accelerate 4D flow acquisitions, however, no detailed analysis has been made on the effect of Cartesian compressed sensing accelerated 4D flow CMR at different undersampling rates on quantitative flow parameters and WSS. METHODS We implemented a retrospectively triggered 4D flow CMR acquisition with pseudo-spiral Cartesian k-space filling, which results in incoherent undersampling of k-t space. Additionally, this strategy leads to small jumps in k-space thereby minimizing eddy current related artifacts. The pseudo-spirals were rotated in a tiny golden-angle fashion, which provides optimal incoherence and a variable density sampling pattern with a fully sampled center. We evaluated this 4D flow protocol in a carotid flow phantom with accelerations of R = 2-20, as well as in carotids of 7 healthy subjects (27 ± 2 years, 4 male) for R = 10-30. Fully sampled 2D flow CMR served as a flow reference. Arteries were manually segmented and registered to enable voxel-wise comparisons of both velocity and WSS using a Bland-Altman analysis. RESULTS Magnitude images, velocity images, and pathline reconstructions from phantom and in vivo scans were similar for all accelerations. For the phantom data, mean differences at peak systole for the entire vessel volume in comparison to R = 2 ranged from - 2.3 to - 5.3% (WSS) and - 2.4 to - 2.2% (velocity) for acceleration factors R = 4-20. For the in vivo data, mean differences for the entire vessel volume at peak systole in comparison to R = 10 were - 9.9, - 13.4, and - 16.9% (WSS) and - 8.4, - 10.8, and - 14.0% (velocity), for R = 20, 25, and 30, respectively. Compared to single slice 2D flow CMR acquisitions, peak systolic flow rates of the phantom showed no differences, whereas peak systolic flow rates in the carotid artery in vivo became increasingly underestimated with increasing acceleration. CONCLUSION Acquisition of 4D flow CMR of the carotid arteries can be highly accelerated by pseudo-spiral k-space sampling and compressed sensing reconstruction, with consistent data quality facilitating velocity pathline reconstructions, as well as quantitative flow rate and WSS estimations. At an acceleration factor of R = 20 the underestimation of peak velocity and peak WSS was acceptable (< 10%) in comparison to an R = 10 accelerated 4D flow CMR reference scan. Peak flow rates were underestimated in comparison with 2D flow CMR and decreased systematically with higher acceleration factors.

中文翻译：

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使用拟螺旋笛卡尔笛卡尔采集和压缩传感重建技术对颈动脉血流和壁切应力进行高度加速的4D流心血管磁共振。

背景技术4D流心血管磁共振（CMR）使可视化复杂的血流和量化用于血管壁疾病例如壁剪切应力（WSS）的生物标志物。由于固有的采集时间长，已经做出了很多努力来加快4D流量的采集，但是，尚未对笛卡尔压缩感测的加速4D流量CMR在不同的欠采样率下对定量流量参数和WSS的影响进行详细分析。方法我们使用伪螺旋笛卡尔k空间填充实现了追溯触发的4D流CMR采集，这导致了kt空间的不连贯欠采样。另外，该策略导致k空间中的微小跳跃，从而使与涡流相关的伪影最小化。伪螺旋以微小的金角旋转，它提供了最佳的不相干性，并具有一个具有完整采样中心的可变密度采样模式。我们在R = 2-20的颈动脉流动体模中以及在R = 10-30的7名健康受试者（27±2岁，4名男性）的颈动脉中评估了这种4D流动方案。完全采样的2D流CMR用作流参考。使用Bland-Altman分析对动脉进行手动分段和配准，以进行速度和WSS的体素比较。结果幻像和体内扫描的幅值图像，速度图像和路径重建对于所有加速度都相似。对于幻象数据，与R = 2相比，整个血管体积在收缩期峰值的平均差在-2.3至-5.3％（WSS）和-2.4至-2.2％（速度）的范围内，加速度系数R = 4-20 。对于体内数据，与R = 10相比，在收缩期峰值时整个血管体积的平均差为-9.9，-13.4和-16.9％（WSS），以及-8.4，-10.8和-14.0％（速度），R = 20， 25和30。与单片2D流动CMR采集相比，体模的收缩压峰值流速没有差异，而随着加速的增加，体内颈动脉的收缩压峰值却越来越被低估。结论假螺旋k空间采样和压缩感测重建可大大加速颈动脉4D流CMR的采集，其一致的数据质量有助于速度路径重建以及定量流速和WSS估计。在加速因子R = 20时，可以低估峰值速度和峰值WSS（< 与R = 10的加速4D流CMR参考扫描相比，降低了10％）。与2D流量CMR相比，峰值流量被低估了，而在更高的加速因子下，峰值流量被系统地降低了。