Computer Simulation Of A Blood-Flow Ultrasound System

Ultrasound is sound that has a frequency above the audible range of man that is greater than 20 kHz. In imaging the usual range of frequencies used is between 2 MHz and 10 MHz. It is now widely used, especially in medical applications. Because ultrasonic examinations are non-invasive, cost effective and free of ion-radiation, the ultrasound imaging is one of the fastest growing image modalities. The demand of ultrasound machines is very big. Moreover, ultrasound instrument is a high-tech product and the capacity to make high quality ultrasound system may show the competitiveness of a country's technology advantage.Doppler effect has been discovered for measuring the frequency (or the speed) change from sound reflection on moving targets. Technologies based on the Doppler effect has been used to estimate the velocity of blood flow and also the fast tissue motion (e.g., the heart motion) in clinical ultrasound exams.There are three development stages of Doppler ultrasound: the continuous wave (CW) Doppler during 1950s to 1960s; the pulse wave Doppler (PW) in 1970s; and the color flow imaging (CFM) starting from 1980s. The CFM technique can estimate flow velocity and direction shown as pseudo-color overlapped on 2-D B-mode display.From 1990, relevant technologies along the CFM image have been Doppler Energy Imaging, Color Doppler Energy, and Color Doppler Tissue Imaging. In China, there are more and more researchers active in this field.In Doppler blood flow measurements, the signal scattered from blood (the red cells) will be corrupted by signals scattered from muscular tissue. Therefore, for a high quality color flow imaging, it is important to suppress the clutter signal whichis typically 40 to 100 dB stronger than the blood signal. The clutter signal reflected from slowly moving tissue with frequency around dc, therefore, a high-pass filter should be used to separate the signals from blood and tissue. To investigate the performance of the wall filters, it's necessary to have computer simulations of Doppler signals with varying mean blood frequencies plus clutter components.The aim of this paper is to provide a software package to simulate and analyze an ultrasound color flow imaging (CFM) system. Using this package, one can generate computer simulated ultrasound Doppler signals , simulated Doppler signals should handle a mixture of flow and wall signals under noisy environment. Design and implement CFM wall filters for short length Doppler signals, is the critical task for a high performance color Doppler system . Besides the design and implementation of the CFM wall filter , we propose a simulation platform for estimating the flow velocity governed by a laminar flow inside a tube . The derived velocity will be color-coded and displayed on the PC monitor through a user interface shown like that in the commercial ultrasound product.