Study Of The Temperature Rise And The Radiation Force Induced By The Annular Focused Transducer With A Wide Aperture Angle

High intensity focused ultrasound(HIFU)is an important technology of modern medicine physical therapy for cancer treatment.The principle is to focus the sound energy emitted by the external ultrasonic focused transducer on the small area of focus(i.e.target area).It can achieve a high temperature(above 65?)in a short period of time,which can lead target tissue to undergo thermal coagulation necrosis then kill cancerous cells.The uncontrollability of temperature rise and the rise of temperature rise in target area is still the most serious problem in clinical treatment of HIFU.In order to solve these problem,meanwhile improve operability and accuracy of high intensity focused ultrasound(HIFU),an annular focused transducer where a B-ultrasound probe can be placed in its center is used to realize the real time monitoring and control of the treatment.An annular focused transducer with a wide aperture angle is an annular focused transducer with a spherical half-angle greater than 16.6°.Compared with the traditional focused transducer with a wide transducer,the annular focused transducer has smaller radiation area but more flexible middle area which offer possibility to realize the real-time monitoring.In this paper,the first chapter mainly introduces the development course and basic principle of high intensity focused ultrasound(HIFU)and vibro-acoustography,as well as the problems encountered in the current situation and practical application.In the second chapter,the spheroidal beam equation(SBE)is used to calculate the sound field by an annular focused transducer with a wide aperture angle to get heat deposition firstly and the Pennes equation was used to calculate the temperature field in multi-layer tissue.We study the effect of different parameters on the temperature of the tissues.By choosing suitable parameters,proper temperature rise both on the target tissue and skin via an annular focused transducer with a wide aperture angle can be obtained.This work provides theoretical guidance for the clinical treatment of liver cancer with an annular focused transducer with a wide aperture angle.The third and fourth chapter respectively solve the radiation force and shear displacement by a confocal focused transducer with a wide aperture angle,and by changing the size of the opening angle and frequency,their effects on acoustic radiation and shear displacement are studied.This work provides theoretical guidance for the vibro-acoustography with a confocal focused transducer with a wide aperture angle.