Nasiraei-Moghaddam Abbas, Finn J Paul
Department of Biomedical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran; Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, California, USA.
Magn Reson Med. 2014 May;71(5):1750-9. doi: 10.1002/mrm.24839. Epub 2013 Jun 26.
In current magnetic resonance practice, myocardial tagging is implemented by laying down a rectilinear presaturation grid over the heart. Although both the geometry and the deformation of the heart are better described in the polar coordinate system, practical methods for laying down polar grids have been elusive. The theory and implementation of high-density tagging in the polar coordinate system is described in this study.
Tagging sequences for generating high-density tagging patterns in both radial and circular directions have been developed. The approach, theoretical basis, and experimental results of the suggested sequences for efficient polar tagging are described in this article.
A 10-ms preparation tagging sequence was tested for generating compact radial and circular tag patterns in a magnetization preparation time comparable to binomial rectilinear grid tagging. The sequence was successfully tested on both phantoms and human subjects.
Direct myocardial tagging in the polar coordinate system is practical in acquisition times similar to Cartesian tagging. The deformation patterns of radial and circular tag lines can be used to isolate and analyze the circumferential and radial components of myocardial motion. Further work remains to establish the reliability and robustness of the techniques for a variety of clinical applications.
在当前的磁共振实践中，心肌标记是通过在心脏上铺设一个直线预饱和网格来实现的。尽管心脏的几何形状和变形在极坐标系中能得到更好的描述，但铺设极坐标网格的实用方法一直难以捉摸。本研究描述了极坐标系中高密度标记的理论与实现方法。
已开发出用于在径向和圆周方向生成高密度标记图案的标记序列。本文描述了高效极坐标标记建议序列的方法、理论基础和实验结果。
测试了一个10毫秒的准备标记序列，该序列在与二项式直线网格标记相当的磁化准备时间内生成紧凑的径向和圆周标记图案。该序列在模型和人体受试者上均成功进行了测试。
在极坐标系中直接进行心肌标记在采集时间上与笛卡尔标记相似，是可行的。径向和圆周标记线的变形模式可用于分离和分析心肌运动的圆周和径向分量。对于各种临床应用，仍需进一步开展工作以确定该技术的可靠性和稳健性。
