Research On Ultrasonic Imaging Algorithm Based On Dynamic Microbubble Model

High Intensity Focused Ultrasound(HIFU)focuses the sound energy to the target area and thermally abates the tumor tissue without damaging the surrounding normal tissue.It is a noninvasive tumor treatment technology.Cavitation is an important mechanism of HIFU treatment.In order to achieve accurate and efficient HIFU treatment,cavitation must be monitored and imaged.In this paper,the plane wave emission mode is used to study the ultra-fast active cavitation imaging method based on the Cavitation Bubble Wavelet Transform(CBWT),and from the plane wave beam synthesis algorithm,the microbubble dynamic model and parameter optimization,Three aspects of the cavitation microbubble mother wavelet technology are carried out to improve the quality of cavitation imaging.The specific research contents are as follows:(1)This paper studies the plane wave beam synthesis algorithm,and proposes a second iterative minimum variance and coherence coefficient fusion beam synthesis algorithm(Coherence-Factor-based-Second-Minimum-Variance,2NDMVCF),and respectively designs based on Field II simulation Multi-point scattering daughter body membrane and cyst body membrane,from the image resolution,contrast,cyst characteristics and multiple image quality evaluation indicators,the performance of this method is evaluated,and it is combined with existing beams such as DAS,MV,ESBMV,MVCF,etc.The algorithm is compared and analyzed,and the results show that the 2NDMVCF beam synthesis algorithm has the least influence of surrounding noise and artifacts in the multi-point scattering sub-images.In the cyst image,this method has the strongest ability to suppress speckle noise,and the image contrast is the best.The method is further applied to the original radio frequency data of ultrasonic cavitation plane wave,and the effectiveness of the algorithm is verified.(2)This paper studies the microbubble dynamic model,and on this basis,analyzes the CBWT-based ultrasonic cavitation imaging method under different models and different parameters.Firstly,the initial radius settings of three microbubble dynamic models are discussed,including the RPNNP model,Morgan model and Church model,to verify the state of the microbubble motion and whether the prediction echo signal can be used to construct the microbubble mother wavelet,and then the wavelet is discussed.The influence of scale on CNR verifies that the wavelet scale chosen in this paper is the best.The comparative analysis through simulation and experiment shows that RPNNP is more suitable for cavitation model,and Morgan model is also suitable for studying cavitation imaging,but its effect is worse than RPNNP and more suitable for contrast imaging.The Church model has a larger damping effect due to the thickness of the membrane,which makes the vibration of the microbubble slower and weaker,and the resulting nonlinearity is weaker.(3)This paper proposes an ultra-fast active cavitation imaging method CBWT-2NDMVCF-SSD that combines CBWT,2NDMVCF beam synthesis algorithm and Sum-ofSquared Differences SSD.First,the ultra-fast ultrasonic cavitation active imaging method based on plane waves is used to obtain the original echo signals of cavitation microbubble;second,the cavitation microbubble mother wavelet is constructed based on the RPNNP model,and the original echo signals of the cavitation microbubble are continuous Wavelet transform;again,beam synthesis is performed on the obtained wavelet coefficients and combined with the SSD subtraction algorithm to improve the quality of the cavitation image.In order to verify the effectiveness of the method,this paper discusses the influence of CBWT,2NDMVCF beam synthesis algorithm and SSD digital subtraction algorithm on the CNR value of cavitation image.The results show that CBWT-2NDMVCF-SSD cavitation image is 38.01 d B higher than MV cavitation image.Due to the high frame frequency of plane waves,high-time resolution ultrasound cavitation sequence images can be obtained to achieve high-quality dynamic monitoring of cavitation activities.The above three aspects of work have improved the image quality of ultrasonic cavitation imaging,and can perform high-quality dynamic monitoring and imaging of cavitation activities during ultrasound treatment,which can provide a reference for solving potential clinical safety and accuracy problems.