Research On Arbitrary Wave Focused Phased Array Ultrasound System And Applications Of Dual-frequency Thrombolysis

Ultrasound has the characteristics of non-invasive,high resolution,no side effects,etc.It has become an important means of medical imaging and is widely used in clinical diagnosis.Due to the superiority of ultrasound,in recent years,ultrasound was introduced into the field of medical treatment by more and more scholars,and it has been widely used in the field of medical treatment.For therapeutic ultrasound,according to the different doses of focused ultrasound,ultrasound can be divided into high-intensity focused ultrasound(HIFU)and low intensity focused ultrasound(LIFU).HIFU is usually applied to tumor ablation and thrombolysis.LIFU is applied to neuromodulation,blood-brain barrier opening,and targeted drug delivery.At present,the related research work is usually based on a single frequency single element transducer ultrasound system or a single frequency array transducer ultrasound system.However,some literatures have reported that dual-frequency ultrasound can improve the effect of ultrasound therapy.However,due to the limitations of the current electronic excitation system,dual-frequency ultrasound is subject to many limitations in experimental design and less research.Therefore,a dual frequency array ultrasound system for ultrasound treatment is proposed to facilitate the implementation of a new dual-frequency ultrasonic excitation sequence to achieve better therapeutic effect.Specifically,the following work has been carried out in this subject: 1)Compared to the single-element ultrasound transducer,the array ultrasound transducer can change the focus position by electronic scanning,and its application range is wider.This article,from the practical application point of view,designed a 128-channel arbitrary-wave phased array focused ultrasound system.Based on this system,dual frequency ultrasonic excitations can be implemented,as well as other novel excitation sequences.Tests were performed on the electronics performance and sound field to verify the performance of the system.The ultrasound system was collaborated with the MRI machine made by UNITED IMAGE to verify the magnetic compatibility performance.2)Large-scale ultrasound array systems can operate more complex sound fields.Especially in transcranial focused ultrasound applications,the formation of intracranial standing waves can be suppressed.The advantage is very obvious.For this reason,this subject proposes a method based on fiber-optic clock synchronization to extend the scale of the phased array.Through the optical fiber clock synchronizer,multiple 128-channel arbitrary-wave phased-array focused ultrasound subsystems can be cascaded and work together to take advantage of the large-scale ultrasound array system.3)In order to verify the performance of the system,single focus and dynamic focus experiments were conducted in homogeneous media.In addition,a sound field scanning device was used to quantitatively measure the sound field distribution.4)In the application of ultrasonic therapy,this article carried out a dual-frequency ultrasound thrombolysis experiment,and explored the influence of different excitation parameters(such as pulse repetition frequency,duty cycle,power)on thrombolysis efficiency.After a large number of comparative experiments,it was found that the dualfrequency ultrasound can increase the efficiency of single-frequency ultrasound thrombolysis by approximately 30%.With the same thrombolysis efficiency,dualfrequency ultrasound can shorten the treatment time by half of single-frequency ultrasound.In summary,this project proposed a dual-frequency array ultrasound system for ultrasound therapy applications,and an optical fiber clock synchronizer was used to expand the array element size of the transducer.This system can take advantage of the large-scale ultrasound array system.Based on the ultrasound system designed in this project,a new type dual-frequency ultrasonic excitation sequence was realized,which reduced the ultrasonic dose in thrombolysis therapy and significantly improved the therapeutic effect of ultrasound thrombolysis.