基于超声造影剂谐波图像的流场测量技术

本文研究了基于超声造影剂的血流运动场估计与显示技术，通过在血液中注入超声造影剂作为示踪粒子，对造影谐波图像进行时域相关处理，可得到成像部位的二维流场分布图。相对于常规Ｄｏｐｐｌｅｒ方法中用Ｄｏｐｐｌｅｒ回波信号的频偏计算流速值，该技术可直接从超声图像提取与夹角无关的流速矢量信息。本文通过流动模型验证该方法，浸入超声水槽中的乳胶管中流动着血液替代品，沿水流方向进行超声成像，对实验所得的造影后的Ｂ超图像以及谐波图像，用一种节省计算量的多尺度相关算法进行处理，并相互比较。结果显示，谐波图像相对Ｂ超基波图像具有更高的信杂比，从根本上解决了基波图像低信噪比对时域相关测量精度的限制，可以得到与夹角无关的二维血流场分布图，该方法是医学和有关工业领域中超声流场测量的一种有效的方法。

Flow Field Tracking And Display Technique Based on Harmonic Images of Ultrasound Contrast Agents

A new approach for time domain flow field measurement by tracking speckle in ultrasound harmonic images of flow following injection of a bolus of the contrast agent is described.This approach differs from conventional Doppler method in that angle independent velocity, not just the value of velocity of blood flow is directly extracted from ultrasound images of blood tracers rather than from the Doppler shift of backscattered signals.This method is verified with a flowing model, in the direction of flowing of mimicking blood in latex tube submerged in water, the flow was imaged and contrast fundamental and second harmonic images of the flow are used for time domain processing with a time saving,multiple scale correlation algorithm and compared.The results demonstrated that harmonic images own better signal to noise ratio than contrast fundamental B Scan images. The poor signal to noise ratio of signal from blood that affects the time domain velocity estimation very much is completely overcome by nonlinearly imaging.Based on harmonic images and with time domain method, the angle independent ultrasound 2 D blood flow field of imaged area can be acquired and this technique holds greatest promises in medical and some industrial applications.