Modification of the phased-tracking method for reduction of artifacts in estimated artery wall deformation
Modification of the phased-tracking method for reduction of artifacts in estimated artery wall deformation
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DOI：
10.1109/tuffc.2006.145
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发表时间：
2006-11-01
影响因子：
3.6
通讯作者：
Kanai, Hiroshi
中科院分区：
文献类型：
--
作者：
Hasegawa, Hideyuki;Kanai, Hiroshi
无创测量动脉壁的机械特性，如弹性，对于动脉粥样硬化的诊断是有用的。为了评估机械性能，有必要测量动脉壁的变形。在这项研究中，对先前提出的相位跟踪方法进行了修改，以改善由于心跳引起的动脉壁厚度（变形）的微小变化的测量。在我们之前的方法中，最初分配了沿超声束沿着的两个点的集合，并且估计了在整个心动周期期间这两个点之间的层厚度的变化。在利用超声的运动估计中，可以通过估计回波的时间延迟的变化来获得生成回波的界面或散射体的运动。例如，在健康受试者的颈动脉的情况下，仅存在来自管腔-内膜和中膜-外膜界面的两个主要回波。因此，只能估计内腔-内膜和中膜-外膜界面的位移，这意味着超声只能估计这两个界面之间的距离（厚度）的变化。然而，即使在这种情况下，我们之前的方法也会根据两个初始指定点的深度（动脉径向方向上的位置）对厚度变化给出不同的估计。在这项研究中，修改了以前的方法在分配层的策略和所需的厚度的分配层，以减少这种人为的空间变化的估计厚度的变化。使用所提出的方法，估计的厚度变化的误差从21.2 +/- 24.1%减少到0.19 +/- 0.04%（平均值+/-标准差）在模拟实验。与模拟实验的情况一样，在健康受试者的颈动脉中的体内实验和使用两个切除的患病动脉的体外实验中，厚度的估计变化的空间变化也减小。
Noninvasive measurement of mechanical properties, such as elasticity, of the arterial wall, is useful for diagnosis of atherosclerosis. For assessment of mechanical properties, it is necessary to measure the deformation of the arterial wall. In this study, a modification of the previously proposed phased-tracking method was conducted to improve measurement of the small change in thickness (deformation) of the arterial wall due to the heartbeat. In our previous method, a set of two points along an ultrasonic beam was initially assigned, and the change in thickness of the layer between these two points during an entire cardiac cycle was estimated. In motion estimation with ultrasound, the motion of an interface or a scatterer, which generates an echo, can be obtained by estimating the change in time delay of the echo. For example, in the case of a carotid artery of a healthy subject, there are only two dominant echoes from the lumen-intima and media-adventitia interfaces. Thus, only the displacements of the lumen-intima and media-adventitia interfaces can be estimated, which means that ultrasound can estimate only the change in distance (thickness) between these two interfaces. However, even in this case, our previous method gives different estimates of the change in thickness, depending on the depths (positions in the arterial radial direction) of the two initially assigned points. In this study, modifications of the previous method in terms of the strategy for assignment of layers and the required thickness of an assigned layer were made to reduce such an artificial spatial variation in the estimated changes in thickness. Using the proposed method, errors in estimated changes in thickness were reduced from 21.2 +/- 24.1% to 0.19 +/- 0.04% (mean +/- standard deviation) in simulation experiments. As in the case of the simulation experiments, the spatial variation in estimated changes in thickness also was reduced in in vivo experiments in a carotid artery of a healthy subject and in vitro experiments using two excised, diseased arteries.