Research On The Focused Ultrasound Of A Concave Spherical Phased-array

High intensity focused ultrasound(HIFU)is an advanced method for the treatment of tumor in recent years,it is in high energy ultrasonic wave through soft tissue in vivo to focus causes coagulation necrosis of the tumor cells,the realization of the treatment of tumor.Nowadays,it can be used for ultrasound ablation in the clinical treatment of tumors,including prostate cancer,pancreatic cancer,liver cancer,uterine fibroids,soft tissue sarcoma,retroperitoneal metastasis and other benign and malignant tumors.This thesis design a concave spherical array transducer,focal spot can be controlled around 200mm3.The scope of single killing cell by ultrasound focused knife is 100?150 mm3.Basically achieves focused ultrasound in the treatment of tumor requirements.It is proposed that A method for determining the focusing position in a double-layer medium under concave spherical array model and Using MATLAB to draw the distribution of sound intensity,we designed a drive board of power amplifier.Research on power amplifier used in phased array focusing field usually increases the drive voltage to 55V in China.However,our drive board can raise the voltage to 100V to drive the piezoelectric ceramic.From the result,we can see that the experimental data coincide basically with the data obtained by using MATLAB for theoretical calculation,the focal spot is small,and the focusing effect is obvious,which proves the feasibility of high intensity focused ultrasound.The thesis is mainly embodied in the following two aspects:(1)Based on the theory of sound field distribution in space,the focusing sound field distribution of concave spherical array transducer in a Single layer medium with double-layer medium is depicted by MATLAB.The pseudo inverse matrix method is used to draw the intensity distribution of multi focus and to optimize the focusing effect of multi focus by genetic algorithm.It is found that the focal spot is ellipsoidal in the distribution of sound intensity in a single layered medium,the long axis is about 1.4cm,and the short axis is about 3mm.However,in double layered media,the long axis is about 2cm,and the short axis is about 4mm.It shows that the focusing effect of acoustic wave will be weakened after refraction.When we observe the multi focus,we find that the genetic algorithm can effectively gain the intensity of the focus,inhibition of side beam and gate valve.(2)The hardware and software of the system are designed,build test platform,ultrasonic focusing is realized.The sound pressure distribution map is drawn by collecting the sound pressure value of the 7cm distance.Analyzing the data,we get the real focus of the concave spherical array transducer designed by us.Comparing the intensity distribution of the focus between the non phased array and the phased array,it is found that the acoustic intensity of the phased array is more than 7 times higher than that of the non phased array.The focusing effect is obvious,but the focal spot is slightly larger than the theoretical focal spot,which may be the error of the concave spherical array transducer being made by hand.