| Emboli in human blood flow may block blood vessels and lead to high risk diseases such as stroke,which poses a great threat to human health.There are many types of emboli,mainly divided into solid embolus and gas embolus,which have different clinical diagnosis methods.Therefore,the detection and identification of emboli is of great significance in clinical treatment.With the rapid development of ultrasonic Doppler technology in the direction of medicine,transcranial Doppler technology has been widely used in clinic for embolus detection,but its detection and classification of embolus are very limited.To solve the problem that solid and gas emboli in human blood flow are difficult to be detected and identified,a new ultrasonic Doppler detection method for emboli in multiphase flow environment is proposed.In the study of emboli detection,the characteristic parameters such as Doppler amplitude and Doppler frequency shift extracted from echo signals based on autocorrelation technology are analyzed by using the characteristics of solid emboli,gas emboli and red blood cells that have different interfacial acoustic intensity reflectance to ultrasonic waves,to realize the characteristic detection of solid emboli and gas emboli.In the aspect of embolus recognition,firstly,the ultrasonic signal characteristics of embolus and its differences from those of red blood cells were analyzed.Field＿II software was used to build a blood flow tissue model and conduct simulation to verify the correctness of the proposed algorithm in measuring blood flow velocity.Then the angle between the blood vessel and the horizontal plane was simulated to study the influence of the incident angle on the simulation results.The embolus Doppler signal model was established and simulated to verify the feasibility of the embolus identification method and provide reference for subsequent experiments.In this paper,nylon particles,diatom particles and bubbles were used to simulate red blood cells,solid embolus and gas embolus to carry out the simulation experiment of blood flow embolus detection.Through the experiment,the Doppler amplitude,Doppler shift and velocity distribution of three kinds of particles were obtained.The Doppler amplitudes of the above three kinds of particles are analyzed statistically,and the probability density function is obtained.According to the distribution characteristics of the probability density function,the Doppler amplitude threshold is set.Based on the preliminary classification of threshold values,red blood cells,suppositories and gas suppositories were classified according to velocity distribution characteristics,which realized the online identification of suppositories.In order to improve the detection rate of embolus,the influence of key parameters of ultrasonic incidence angle on detection results was studied.After setting the center frequency,ultrasonic signals were transmitted at different incident angles,and the above experiments were repeated using only red blood cells and bubbles.The fluid velocity distribution characteristics and Doppler amplitude parameters obtained from the experiments were analyzed.The experimental results showed that when the incident angle increased,the velocity distribution of gas emboli and red blood cells,the effective measurement interval and the distance between blood vessel and ultrasonic transducer increased.Resulting in increased acoustic attenuation.By analyzing the experimental error and the bubble detection rate at different incidence angles,it was found that the detection effect is best when the incidence angle is 60°.The method proposed in this paper can detect and identify emboli effectively.The autocorrelation technique is used to process echo signals quickly,and real-time detection can be realized.This method has important application value for the clinical detection of emboli in blood,and can provide reference for the selection of optimal incidence angle of ultrasonic signal in clinical imaging detection. |
PDF Full Text Request