三维Freehand超声血流测量系统中的单平面定标方法

Single Plane Calibration Method in 3D Freehand Ultrasonic Blood Flow Measurement System

三维超声血流测量以其形象的可视效果及由此带来的临床价值 ,越来越受到广大研究人员和医疗工作者的关注。本文中 ,我们设计了一种基于电磁式定位机构的三维Freehand超声血流测量系统 ,并重点讨论其中的定标问题———即确定声束与电磁接收器间的位置关系。准确的定标将对血管解剖形态的重建起至关重要的作用。但是 ,由于探头和接收器都是密封装置 ,从外部直接测量是不可能的。因此 ,为了准确而快速地寻找到电磁式定位机构中电磁接受器与多普勒探头间的空间关系 ,我们设计了一种利用反射点共面的几何特性来计算定标参数的单平面定标模型。实验证明 ,利用这种方法得到的定标参数进行三维重建时 ,能够获得较高的重建精度和准确度。

3D Freehand ultrasonic blood flow imaging system has the potential applications in clinical evaluation of vascular diseases. In this paper, the design of a 3D Freehand ultrasonic blood flow measurement system based on electro-magnetometer position sensor is proposed. A basic problem in freehand systems is the calibration. This involves determining the position and orientation of the ultrasound probe with respect to the receiver mounted on it. Accurate calibration is essential for a consistent 3D reconstruction. However, it is not possible to do direct measurement, since the probe and the receiver are both sealed. To determine the space relations between the probe and receiver accurately and quickly, a single plane calibration method is presented in this paper. According to the co-plane geometric property of all reflection points, the position and orientation of the probe with respect to the receiver are estimated by Levenberg-Marquardt algorithm. The results of physical experiments showed the method has high accuracy of reconstruction.