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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使用伪螺旋笛卡尔采集和压缩传感重建来实现颈动脉血流和壁剪切应力的高度加速 4D 血流心血管磁共振。


背景技术 4D 血流心血管磁共振 (CMR) 能够实现复杂血流的可视化和血管壁疾病生物标志物的量化，例如壁剪切应力 (WSS)。由于采集时间本身较长，人们为加速4D流量采集做出了许多努力，但是，没有详细分析不同欠采样率下笛卡尔压缩传感加速4D流量CMR对定量流量参数和WSS的影响。方法我们通过伪螺旋笛卡尔 k 空间填充实现了回顾性触发的 4D 流 CMR 采集，这会导致 kt 空间的不相干欠采样。此外，该策略会导致 k 空间中的小跳跃，从而最大限度地减少与涡流相关的伪影。伪螺旋以微小的黄金角方式旋转，提供最佳的不相干性和具有完全采样中心的可变密度采样模式。我们在加速度为 R = 2-20 的颈动脉血流模型以及 R = 10-30 的 7 名健康受试者（27 ± 2 岁，4 名男性）的颈动脉中评估了该 4D 血流协议。完全采样的 2D 流 CMR 用作流参考。动脉被手动分割和注册，以便使用 Bland-Altman 分析对速度和 WSS 进行体素比较。结果 对于所有加速度，体模和活体扫描的幅度图像、速度图像和路径重建都是相似的。对于模型数据，与 R = 2 相比，整个血管体积在峰值收缩时的平均差异范围为 - 2.3 至 - 5.3% (WSS)，对于加速因子 R = 4-20，范围为 - 2.4 至 - 2.2%（速度） 。对于体内数据，收缩期峰值时整个血管体积与 R = 10 相比的平均差异分别为 - 9.9、- 13。对于 R = 20、25 和 30，分别为 - 4、- 16.9%（WSS）和 - 8.4、- 10.8 和 - 14.0%（速度）。与单层 2D 血流 CMR 采集相比，模型的收缩期峰值流速没有显示差异，而体内颈动脉的收缩期峰值流速随着加速度的增加而被越来越低估。结论 通过伪螺旋 k 空间采样和压缩感知重建可以高度加速颈动脉 4D 血流 CMR 的采集，一致的数据质量有利于速度路径重建以及定量流速和 WSS 估计。与 R = 10 加速 4D 流 CMR 参考扫描相比，在加速因子 R = 20 时，峰值速度和峰值 WSS 的低估是可以接受的 (< 10%)。与 2D 流 CMR 相比，峰值流速被低估，并且随着加速因子的增加而系统地降低。