ESIME Zacatenco, Instituto Politécnico Nacional (IPN), Avenue IPN, s/n, 07738 Mexico, DF, Mexico.
Departamento de Materiales, Facultad de Ciencias, Universidad de la Republica, 14200 Montevideo, Uruguay.
Comput Math Methods Med. 2014;2014:606202. doi: 10.1155/2014/606202. Epub 2014 Feb 13.
By locally measuring changes on arterial wall thickness as a function of pressure, the related Young modulus can be evaluated. This physical magnitude has shown to be an important predictive factor for cardiovascular diseases. For evaluating those changes, imaging segmentation or time correlations of ultrasonic echoes, coming from wall interfaces, are usually employed. In this paper, an alternative low-cost technique is proposed to locally evaluate variations on arterial walls, which are dynamically measured with an improved high-resolution calculation of power spectral densities in echo-traces of the wall interfaces, by using a parametric autoregressive processing. Certain wall deformations are finely detected by evaluating the echoes overtones peaks with power spectral estimations that implement Burg and Yule Walker algorithms. Results of this spectral approach are compared with a classical cross-correlation operator, in a tube phantom and "in vitro" carotid tissue. A circulating loop, mimicking heart periods and blood pressure changes, is employed to dynamically inspect each sample with a broadband ultrasonic probe, acquiring multiple A-Scans which are windowed to isolate echo-traces packets coming from distinct walls. Then the new technique and cross-correlation operator are applied to evaluate changing parietal deformations from the detection of displacements registered on the wall faces under periodic regime.
通过局部测量动脉壁厚度随压力的变化，可以评估相关的杨氏模量。这一物理量已被证明是心血管疾病的一个重要预测因素。为了评估这些变化，通常采用超声回波的成像分割或时间相关技术，这些回波来自壁界面。在本文中，提出了一种替代的低成本技术，用于局部评估动脉壁的变化，该技术通过使用参数自回归处理，以改进的高分辨率计算壁界面回波迹的功率谱密度，来动态测量。通过评估回波泛音峰值的功率谱估计，使用 Burg 和 Yule Walker 算法，可以精细地检测到某些壁变形。该光谱方法的结果与经典的互相关运算符在管腔模型和“体外”颈动脉组织中进行了比较。采用循环回路模拟心动周期和血压变化，使用宽带超声探头对每个样本进行动态检查，获取多个 A 扫描，将其划分为窗口以隔离来自不同壁的回波迹包。然后，新的技术和互相关运算符被用于评估周期性状态下壁面位移的周期性变化。
