Lee Wei-Ning, Qian Zhen, Tosti Christina L, Brown Truman R, Metaxas Dimitris N, Konofagou Elisa E
Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA.
Ultrasound Med Biol. 2008 Dec;34(12):1980-97. doi: 10.1016/j.ultrasmedbio.2008.05.007. Epub 2008 Oct 26.
Myocardial elastography (ME), a radio-frequency (RF) based speckle tracking technique, was employed in order to image the entire two-dimensional (2D) transmural deformation field in full echocardiographic views and was validated against tagged magnetic resonance imaging (tMRI) in normal as well as reperfused (i.e., treated myocardial infarction [MI]) human left ventricles. RF ultrasound and tMRI frames were acquired at the papillary muscle level in 2D short-axis (SA) views at the frame rates of 136 (fps; real-time) and 33 fps (electrocardiogram [ECG]-gated), respectively. In ME, in-plane, 2D (lateral and axial) incremental displacements were iteratively estimated using one-dimensional (1D) cross-correlation and recorrelation techniques in a 2D search with a 1D matching kernel. In tMRI, cardiac motion was estimated by a template-matching algorithm on a 2D grid-shaped mesh. In both ME and tMRI, cumulative 2D displacements were obtained and then used to estimate 2D Lagrangian finite systolic strains, from which polar (i.e., radial and circumferential) strains, namely angle-independent measures, were further obtained through coordinate transformation. Principal strains, which are angle-independent and less centroid-dependent than polar strains, were also computed and imaged based on the 2D finite strains using methodology previously established. Both qualitatively and quantitatively, angle-independent ME is shown to be capable of (1) estimating myocardial deformation in good agreement with tMRI estimates in a clinical setting and of (2) differentiating abnormal from normal myocardium in a full left-ventricular view. The principal strains were concluded to be a potential diagnostic measure for detection of cardiac disease with reduced centroid dependence.
心肌弹性成像（ME）是一种基于射频（RF）的散斑跟踪技术，用于在完整的超声心动图视图中对整个二维（2D）透壁变形场进行成像，并在正常以及再灌注（即治疗后的心肌梗死[MI]）的人体左心室中与标记磁共振成像（tMRI）进行了验证。分别以136帧/秒（实时）和33帧/秒（心电图[ECG]门控）的帧率，在二维短轴（SA）视图的乳头肌水平获取RF超声和tMRI图像帧。在ME中，使用一维（1D）互相关和再相关技术，在具有一维匹配内核的二维搜索中迭代估计平面内二维（横向和轴向）增量位移。在tMRI中，通过二维网格状网格上的模板匹配算法估计心脏运动。在ME和tMRI中，均获得累积二维位移，然后用于估计二维拉格朗日有限收缩期应变，通过坐标变换进一步从中获得极坐标（即径向和周向）应变，即与角度无关的测量值。还基于二维有限应变，使用先前建立的方法计算并成像了主应变，主应变与角度无关且比极坐标应变对质心的依赖性更小。定性和定量研究均表明，与角度无关的ME能够（1）在临床环境中估计与tMRI估计值高度一致的心肌变形，以及（2）在完整的左心室视图中区分正常心肌和异常心肌。得出结论，主应变是一种潜在的诊断指标，可用于检测对质心依赖性降低的心脏疾病。
