Reduction of influence of variation in center frequencies of RF echoes on estimation of artery-wall strain
Reduction of influence of variation in center frequencies of RF echoes on estimation of artery-wall strain
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DOI：
10.1109/tuffc.884
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发表时间：
2008-09-01
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
动脉壁的粥样硬化改变导致其弹性的显著变化。为了评估弹性，需要测量动脉壁变形。对于运动估计，相关技术被广泛使用，我们已经开发了一种相敏相关方法，即相位跟踪方法，来测量由于心跳引起的动脉壁的区域应变。虽然使用解调的复信号的相敏方法与使用RF信号之间的相关性的方法或迭代方法相比需要较少的计算，但是当RF回波的中心频率明显变化时，通过这种相敏方法估计的位移是有偏差的。中心频率明显变化的原因之一是来自壁内散射体的回波的干扰。在本研究中，介绍了一种方法，以减少在使用相敏相关技术的动脉壁应变的估计时，RF回波的中心频率的变化的影响。使用体模验证了所提出的方法在应变估计方面的改进。从理论应变分布的误差和标准偏差的应变估计所提出的方法分别为12.0%和14.1%，显着小于由传统的相敏相关方法得到的（23.7%和46.2%）。此外，在初步的体外实验结果中，动脉壁的应变分布与病理学良好对应，即，具有钙化组织的区域显示出非常小的应变，而几乎均匀地由平滑肌和胶原组成的区域显示出相对较大的应变和相对于离管腔的径向距离的明显的应变衰减。
Atherosclerotic change of the arterial wall leads to a significant change in its elasticity. For assessment of elasticity, measurement of arterial wall deformation is required. For motion estimation, correlation techniques are widely used, and we have developed a phase-sensitive correlation method, namely, the phased-tracking method, to measure the regional strain of the arterial wall due to the heartbeat. Although phase-sensitive methods using demodulated complex signals require less computation in comparison with methods using the correlation between RF signals or iterative methods, the displacement estimated by such phase-sensitive methods are biased when the center frequency of the RF echo apparently varies. One of the reasons for the apparent change in the center frequency would be the interference of echoes from scatterers within the wall. In the present study, a method was introduced to reduce the influence of variation in the center frequencies of RF echoes on the estimation of the artery-wall strain when using the phase-sensitive correlation technique. The improvement in the strain estimation by the proposed method was validated using a phantom. The error from the theoretical strain profile and the standard deviation in strain estimated by the proposed method were 12.0% and 14.1%, respectively, significantly smaller than those (23.7% and 46.2%) obtained by the conventional phase-sensitive correlation method. Furthermore, in the preliminary in vitro experimental results, the strain distribution of the arterial wall well corresponded with pathology, i.e., the region with calcified tissue showed very small strain, and the region almost homogeneously composed of smooth muscle and collagen showed relatively larger strain and clear strain decay with respect to the radial distance from the lumen.