Study On A Digital Doppler Ultrasonic Blood Flow Measurement System

Ultrasound imaging systems play important role in clinical diagnosis for thecharactristics of real-time imaging and safety. As a non-invasive method for bloodvelocity estimation, Doppler ultrasound has its particular advantages. Compare toconventional analog systems, digital systems are not susceptible to externalelectromagnetic interference, environment temperature changes and other factors, andit’s easy to implement modern signal processing algorithms to achieve more advanceddetections.In this thesis, we first introduced the recent development of Doppler ultrasound.Then, we analyzed basic principle of Doppler system. A digital Doppler ultrasonicblood flow signal acquisition and processing system was designed, and the feasibility ofthe system was proved by the phantom test and the human cerebral artery blood flowmeasurement.Difficulties in location of Transcranial ultrasound windows and blood flow incerebral vessels have limited expansion of Transcranial Doppler ultrasound. PowerM-mode Doppler applied in this system could help to solve this problem. The humancerebral artery measurement showed that this system could display the bloodinformation on the path of the ultrasound wave, and it was useful for the vesselpositioning and identification.The axial resolution of the conventional Transcranial Doppler ultrasound could beimproved by coded excitation. Experiments based on the Doppler phantom by applying2-cycle base13-chip Barker coded excitation verified the system performance.Moreover, the extraction method of the sonogram envelop and the automaticcalculation method of Doppler parameters were studied based on this system, whichwas useful to clinical examination.