Phase-Sensitive Lateral Motion Estimator for Measurement of Artery-Wall Displacement-Phantom Study
Phase-Sensitive Lateral Motion Estimator for Measurement of Artery-Wall Displacement-Phantom Study
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DOI：
10.1109/tuffc.2009.1332
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发表时间：
2009-11-01
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
由于心脏搏动引起的动脉壁运动通常被测量以评估动脉壁的机械特性。这种运动被认为只发生在动脉的径向，因为运动的主要来源是血压的增加。然而，最近有报道称，动脉也沿纵向移动。因此，即使在纵向扫描动脉时，也需要2-D运动估计器，因为动脉壁在径向(轴向)和纵向(横向)都有运动。基于射频回波二维相关的方法常被用来估计横向位移和轴向位移。然而，这些方法需要对射频回波或相关函数进行大量的内插才能在估计位移时获得足够的分辨率。为了克服这个问题，Jensen等人。以设计的空间频率调制横向超声场，利用横向相位估计横向运动。这种方法，即横向调制方法，产生其相位随横向运动而变化的复数信号。因此，尽管需要特殊的波束形成器，但不需要内插就可以以良好的分辨率估计横向位移。本文描述了一种可以应用于常规波束形成器获得的超声回波的方法，该方法利用超声回波的横向起伏的相位来估计横向位移。在该方法中，通过希尔伯特变换产生复信号，并利用基于相关的估计器来估计相移。利用模拟动脉的圆柱模型验证了该方法的有效性。该方法估计的横向位移误差为0.5 mm的真实位移的13.5%，用于计算横向相关函数的核大小为0.6 mm，略小于最大横向超声场的-20d B处的宽度(约0.8 mm)。
Artery-wall motion due to the pulsation of the heart is often measured to evaluate mechanical properties of the arterial wall. Such motion is thought to occur only in the arterial radial direction because the main source of the motion is an increase of blood pressure. However, it has recently been reported that the artery also moves in the longitudinal direction. Therefore, a 2-D motion estimator is required even when the artery is scanned in the longitudinal direction because the arterial wall moves both in the radial (axial) and longitudinal (lateral) directions. Methods based on 2-D correlation of RF echoes are often used to estimate the lateral displacement together with axial displacement. However, these methods require much interpolation of the RF echo or correlation function to achieve a sufficient resolution in the estimation of displacement. To overcome this problem, Jensen et al. modulated the ultrasonic field in the lateral direction at a designed spatial frequency to use the lateral phase for the estimation of lateral motion. This method, namely, the lateral modulation method, generates complex signals whose phases change depending on the lateral motion. Therefore, the lateral displacement can be estimated with a good resolution without interpolation, although special beamformers are required. The present paper describes a method that can be applied to ultrasonic echoes obtained by a conventional beamformer to estimate lateral displacements using the phases of lateral fluctuations of ultrasonic echoes. In the proposed method, complex signals were generated by the Hilbert transform, and the phase shift was estimated by correlation-based estimators. The proposed method was validated using a cylindrical phantom mimicking an artery. The error in the lateral displacement estimated by the proposed method was 13.5% of the true displacement of 0.5 mm with a kernel size used for calculating the correlation function of 0.6 mm in the lateral direction, which was slightly smaller than the width at -20 dB of the maximum lateral ultrasonic field (about 0.8 mm).