INSA-Lyon, Univ. of Lyon, Villeurbanne, France.
IEEE Trans Ultrason Ferroelectr Freq Control. 2009 Oct;56(10):2167-79. doi: 10.1109/TUFFC.2009.1299.
Data simulation is an important research tool to evaluate algorithms. Two types of methods are currently used to simulate medical ultrasound data: those based on acoustic models and those based on convolution models. The simulation of ultrasound data sequences is very time-consuming. In addition, many applications require accounting for the out-of-plane motion induced by the 3-D displacement of scatterers. The purpose of this paper is to propose a model adapted to a fast simulation of ultrasonic data sequences with 3-D moving scatterers. Our approach is based on the convolution model. The scatterers are moved in a 3-D continuous medium between each pair of images and then projected onto the imaging plane before being convolved. This paper discusses the practical implementation of the convolution that can be performed directly or after a grid approximation. The grid approximation convolution is obviously faster than the direct convolution but generates errors resulting from the approximation to the grid's nodes. We provide the analytical expression of these errors and then define 2 intensity-based criteria to quantify them as a function of the spatial sampling. The simulation of an image requires less than 2 s with oversampling, thus reducing these errors. The simulation model is validated with first- and second-order statistics. The positions of the scatterers at each imaging time can be provided by a displacement model. An example applied to flow imaging is proposed. Several cases are used to show that this displacement model provides realistic data. It is validated with speckle tracking, a well-known motion estimator in ultrasound imaging.
数据模拟是评估算法的重要研究工具。目前有两种类型的方法可用于模拟医学超声数据：基于声学模型的方法和基于卷积模型的方法。超声数据序列的模拟非常耗时。此外，许多应用都需要考虑到由于散射体的 3D 位移引起的离轴运动。本文旨在提出一种适用于具有 3D 运动散射体的超声数据序列快速模拟的模型。我们的方法基于卷积模型。在每对图像之间，散射体在 3D 连续介质中移动，然后在卷积之前投射到成像平面上。本文讨论了可以直接或在网格逼近后执行的卷积的实际实现。网格逼近卷积显然比直接卷积快，但会产生由于网格节点的逼近而产生的误差。我们提供了这些误差的解析表达式，然后定义了 2 个基于强度的标准，以作为空间采样的函数来量化它们。在过采样的情况下，模拟一幅图像所需的时间不到 2 秒，从而减少了这些误差。模拟模型通过一阶和二阶统计数据进行验证。在每个成像时刻，散射体的位置可以由位移模型提供。提出了一个应用于流动成像的示例。使用了几个案例来表明该位移模型提供了真实的数据。它通过超声成像中常用的运动估计器斑点跟踪进行了验证。
