基于生理反馈的电影磁共振成像中 K 空间采样的闭环控制。

Closed-loop control of k-space sampling via physiologic feedback for cine MRI.

机构信息

Department of Bioengineering, Jacobs School of Engineering, University of California, San Diego, CA, United States of America.

Department of Radiology, School of Medicine, University of California, San Diego, CA, United States of America.

出版信息

PLoS One. 2020 Dec 29;15(12):e0244286. doi: 10.1371/journal.pone.0244286. eCollection 2020.

DOI:10.1371/journal.pone.0244286

PMID:33373391

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC7771662/

Abstract

BACKGROUND

Segmented cine cardiac MRI combines data from multiple heartbeats to achieve high spatiotemporal resolution cardiac images, yet predefined k-space segmentation trajectories can lead to suboptimal k-space sampling. In this work, we developed and evaluated an autonomous and closed-loop control system for radial k-space sampling (ARKS) to increase sampling uniformity.

METHODS

The closed-loop system autonomously selects radial k-space sampling trajectory during live segmented cine MRI and attempts to optimize angular sampling uniformity by selecting views in regions of k-space that were not previously well-sampled. Sampling uniformity and the ability to detect cardiac phase in vivo was assessed using ECG data acquired from 10 normal subjects in an MRI scanner. The approach was then implemented with a fast gradient echo sequence on a whole-body clinical MRI scanner and imaging was performed in 4 healthy volunteers. The closed-loop k-space trajectory was compared to random, uniformly distributed and golden angle view trajectories via measurement of k-space uniformity and the point spread function. Lastly, an arrhythmic dataset was used to evaluate a potential application of the approach.

RESULTS

The autonomous trajectory increased k-space sampling uniformity by 15±7%, main lobe point spread function (PSF) signal intensity by 6±4%, and reduced ringing relative to golden angle sampling. When implemented, the autonomous pulse sequence prescribed radial view angles faster than the scan TR (0.98 ± 0.01 ms, maximum = 1.38 ms) and increased k-space sampling mean uniformity by 10±11%, decreased uniformity variability by 44±12%, and increased PSF signal ratio by 6±6% relative to golden angle sampling.

CONCLUSION

The closed-loop approach enables near-uniform radial sampling in a segmented acquisition approach which was higher than predetermined golden-angle radial sampling. This can be utilized to increase the sampling or decrease the temporal footprint of an acquisition and the closed-loop framework has the potential to be applied to patients with complex heart rhythms.

摘要

背景

分段电影心脏 MRI 结合了来自多个心跳的数据，以实现高时空分辨率的心脏图像，但预定义的 k 空间分段轨迹可能导致 k 空间采样不理想。在这项工作中，我们开发并评估了一种用于径向 k 空间采样（ARKS）的自主闭环控制系统，以提高采样均匀性。

方法

闭环系统在实时分段电影 MRI 期间自主选择径向 k 空间采样轨迹，并通过选择以前未充分采样的 k 空间区域中的视图来尝试优化角采样均匀性。使用从 10 名正常受试者在 MRI 扫描仪中采集的心电图数据评估采样均匀性和体内检测心脏相位的能力。然后，在全身临床 MRI 扫描仪上使用快速梯度回波序列实施该方法，并在 4 名健康志愿者中进行成像。通过测量 k 空间均匀性和点扩散函数，将闭环 k 空间轨迹与随机、均匀分布和黄金角视图轨迹进行比较。最后，使用心律失常数据集评估该方法的潜在应用。

结果

自主轨迹使 k 空间采样均匀性提高了 15±7%，主瓣点扩散函数（PSF）信号强度提高了 6±4%，并减少了相对于黄金角采样的振铃。当实施时，自主脉冲序列规定的径向视图角度比扫描 TR 更快（0.98±0.01ms，最大值=1.38ms），并使 k 空间采样平均均匀性提高了 10±11%，均匀性变异性降低了 44±12%，PSF 信号比提高了 6±6%相对黄金角采样。