Guo Liheng, Derbyshire J Andrew, Herzka Daniel A
Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Functional MRI Facility, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, USA.
Magn Reson Med. 2016 Aug;76(2):417-29. doi: 10.1002/mrm.25834. Epub 2015 Oct 31.
To develop and evaluate a novel two-dimensional self-gated imaging technique for free-breathing cardiac cine MRI that is free of motion-detection overhead and requires minimal planning for motion tracking.
Motion along the readout direction was extracted solely from normal Cartesian imaging readouts near ky = 0. During imaging, the readouts below a certain |ky | threshold were scaled in magnitude and filtered in time to form "pseudo-projections," enabling projection-based motion tracking along readout without frequently acquiring the central phase encode. A discrete golden step phase encode scheme allowed the |ky | threshold to be freely set after the scan while maintaining uniform motion sampling.
The pseudo-projections stream displayed sufficient spatiotemporal resolution for both cardiac and respiratory tracking, allowing retrospective reconstruction of free-breathing non-electrocardiogram (ECG) cines. The technique was tested on healthy subjects, and the resultant image quality, measured by blood-myocardium boundary sharpness, myocardial mass, and single-slice ejection fraction was found to be comparable to standard breath-hold ECG-gated cines.
The use of pseudo-projections for motion tracking was found feasible for cardiorespiratory self-gated imaging. Despite some sensitivity to flow and eddy currents, the simplicity of acquisition makes the proposed technique a valuable tool for self-gated cardiac imaging. Magn Reson Med 76:417-429, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
开发并评估一种用于自由呼吸心脏电影磁共振成像（MRI）的新型二维自门控成像技术，该技术无需运动检测开销，且运动跟踪所需的规划最少。
仅从靠近ky = 0的常规笛卡尔成像读出中提取沿读出方向的运动。在成像过程中，低于某个|ky|阈值的读出在幅度上进行缩放并在时间上进行滤波，以形成“伪投影”，从而实现沿读出方向基于投影的运动跟踪，而无需频繁采集中心相位编码。离散黄金步长相位编码方案允许在扫描后自由设置|ky|阈值，同时保持均匀的运动采样。
伪投影流显示出足够的时空分辨率用于心脏和呼吸跟踪，从而允许对自由呼吸非心电图（ECG）电影进行回顾性重建。该技术在健康受试者身上进行了测试，通过血液 - 心肌边界清晰度、心肌质量和单层射血分数测量得到的图像质量与标准屏气ECG门控电影相当。
发现使用伪投影进行运动跟踪对于心肺自门控成像可行。尽管对流动和涡流有些敏感，但采集的简单性使所提出的技术成为自门控心脏成像的有价值工具。《磁共振医学》76:417 - 429, 2016。© 2015作者。《磁共振医学》由威利期刊公司代表国际磁共振医学学会出版。这是一篇根据知识共享署名 - 非商业性 - 禁止演绎许可条款的开放获取文章，允许在任何媒介中使用和分发，前提是正确引用原始作品，使用是非商业性的，且不进行修改或改编。
