利用混合式模型探討血流散射都卜勒信號特性

Abstract

本篇研究首先建立血液在血管中流動的物理及數學模型, 然後利用電 腦去模擬血液流動所產生的都卜勒散射超音波信號; 其次, 採用統計方法 去分析及探討血流都卜勒信號的統計特性, 並比較不同取樣次數對血流速 度預估準確性的影響. 研究中發現血流隨機分佈的擾動很小時, 仍可 以由都卜勒功率頻譜圖研讀流速分佈; 但是當擾動變大時, 由於平均效 應, 會造成都卜勒平均功率頻譜分佈趨近均勻, 此時將無法有效評估血管 內的血流分佈. In this research, a physical model of blood flow in the blood vesselshave been developed. Simulation of blood flows which produce Doppler ultrasonicscattering signal is made, and use statistical method to analyze the stachasticalproperty of Doppler signal and then investigate the predicting accuracy of bloodspeed for different sampling times. It is found when the perturbation of the stochastic distribution of bloodflow is small, we can study the flow speed distribution by Doppler's powerspectrum diagram; but when the perturbation is large, the distribution ofDoppler average power spectrum is toward uniform due to average effect. Thuswe cannot effectively evaluate the blood flow distribution in the blood.