微泡对高强度聚焦超声焦域影响的研究

发布时间：2018-06-27 15:23

本文选题：高强度聚焦超声 + 微泡造影剂　；参考：《天津医科大学》2017年硕士论文

【摘要】：近年兴起的无创或微创高强度聚焦超声肿瘤治疗方法受到众多研究者的关注。该治疗方法是将人体外发射的低功率密度超声波聚焦到人体内肿瘤部位,通过组织吸收超声波能量而使肿瘤组织温度在短时间内达到60℃以上凝固性坏死的一种疗法。该疗法在治疗人体深部肿瘤时,由于声波需传播的距离较远且传播途中可能需穿过强衰减的骨骼组织,使超声能量大幅度衰减出现焦点能量不足,无法凝固性致死肿瘤组织的问题,同时HIFU一次性形成的可治疗焦域体积一般较小,对于大体积肿瘤治疗时采用焦域多次叠加进行,所需治疗时间长并可能引发并发症。为了安全有效地治疗人体深部肿瘤和大体积肿瘤,焦域能量不足和治疗时间过长是HIFU临床治疗的迫切需要解决的问题,具有HIFU治疗增效作用的超声微泡造影剂受到众多研究者的关注。目的为了安全有效地利用HIFU治疗人体深部肿瘤和大体积肿瘤,解决焦域能量不足和治疗时间过长等问题,众多研究者提出利用微泡造影剂增效HIFU治疗效果。本研究建立仿组织数值仿真模型,采用数值仿真法对不同条件下的焦域分布进行仿真研究,通过分析讨论换能器输入功率、工作频率、仿组织体模参数和微泡初始分布条件对HIFU形成焦域的影响,并以含蛋清和微泡造影剂的仿组织体模为实验对象加以验证,为微泡造影剂在HIFU临床治疗的应用提供参考数据。方法本研究结合凹球面自聚焦超声换能器结构参数,建立仿组织数值仿真模型,利用声传播方程、生物热传导方程、Yang-Church气泡运动方程,基于圆柱轴对称坐标系通过时域有限差分(Finite Difference Time Domain,FDTD)法和龙格-库塔(Runge-Kutta,RK)法数值仿真HIFU在含气泡仿组织体模中的声压场和温度场,并以含蛋清和微泡造影剂的仿组织体模为实验对象,研究对HIFU形成焦域的影响。结果随着体模中初始气体体积分数的增大,60℃以上焦域体积不断增大且焦域向靠近换能器方向移动;当气体体积分数为2.5×10-6时,在体模表面聚焦未能形成有效焦域。随着输入功率的增大,60℃以上焦域逐渐增大,焦域峰值温度逐渐升高、焦域位置几乎不变,当功率为30W时数值仿真所得焦域体积与体模实验所得焦域体积大小几乎相同,当功率为40W~60W时数值仿真所得焦域体积比体模实验所得焦域体积略小。随着换能器工作频率的增大,60℃以上焦域逐渐增大,焦域峰值温度逐渐升高、焦域向远离换能器方向移动,焦域的长轴与短轴均随着工作频率的升高而增大,且斜率变小。随着仿组织体模粘度的增大,60℃以上焦域逐渐减小,焦域峰值温度逐渐降低、焦域向远离换能器方向移动,焦域的长轴与短轴均随着粘度的变大而减小。随着仿组织体模剪切模量的增大,60℃以上焦域先增大后减小,焦域峰值温度、最大绝对声压先升高后降低、焦域位置几乎不发生偏移;焦域的长轴与短轴均随着粘度的变大而先增大后减小。随着体模中气泡初始半径的增大,60℃以上焦域逐渐增大,焦域峰值温度逐渐升高、焦域向远离换能器方向移动,焦域的长轴与短轴均随着气泡初始半径的增大而增大,且斜率变小。结论微泡造影剂可以增大HIFU形成60℃以上的可治疗焦域;增大输入功率、气泡初始半径和提升工作频率均可增大焦域,增大输入功率,焦域形状可能发生变化;升高工作频率和增大气泡初始半径,焦域向远离换能器的方向移动;仿组织体模的粘度越大,焦域峰值温度越低、焦域越小、焦域向远离换能器方向移动;随着仿组织体模剪切模量的增大,焦域先增大后减小,且向远离换能器方向移动。
[Abstract]:The recent development of non-invasive or minimally invasive high intensity focused ultrasound therapy has attracted the attention of many researchers. The treatment is to focus the human body's external emission low power density ultrasound to the body of the human body. By absorbing the ultrasonic energy, the tumor tissue temperature can reach more than 60 degrees centigrade in a short time. In the treatment of deep tumors of the human body, the treatment is far away from sound wave and may need to pass through strong attenuation of bone tissue during the transmission, so that the ultrasonic energy is greatly attenuated to the problem of lack of focal energy and the inability to solidify the tumor tissue. At the same time, the disposable focal area of HIFU is formed. In order to treat the human deep tumor and large volume tumor, the insufficiency of the focal area and the long treatment time are the urgent problems to be solved in the clinical treatment of HIFU, with the effect of HIFU therapy. The ultrasonic microbubble contrast agent is concerned by many researchers. In order to use HIFU to treat the deep tumor and large volume tumor in human body safely and effectively, to solve the problem of insufficient energy and long treatment time in the focal area, many researchers have proposed the use of microbubble contrast agent to increase the effect of HIFU in the treatment of fruit. The numerical simulation method is used to simulate the focal region distribution under different conditions. The influence of the input power of the transducer, the working frequency, the parameters of the tissue model and the initial microbubble distribution on the HIFU focal region are analyzed and discussed, and the microbubbles are verified by the imitated fabric model containing the egg white and the microbubble contrast agent. This study provides reference data in the application of HIFU clinical treatment. Method this study combines the structural parameters of concave spherical autofocus transducer, establishes a numerical simulation model of mimic tissue, uses sound propagation equation, biologic heat conduction equation, Yang-Church bubble motion equation, and is based on the finite difference time domain (Finite Difference T) coordinate system based on cylindrical axis. IME Domain, FDTD) method and Runge Kutta (Runge-Kutta, RK) method are used to simulate the sound pressure field and temperature field of HIFU in a bubble imitating tissue model. The effects of the simulated tissue model containing egg white and microbubble contrast medium on the focal region of HIFU are studied. The results are over 60 degrees with the increase of the volume fraction of the initial gas in the body model. When the volume fraction is 2.5 * 10-6, the focal region will not form an effective focal region when the volume fraction of the gas is 2.5 * 10-6. With the increase of the input power, the focal region of the focal region is gradually increased, the peak temperature of the focal region is gradually increased and the focal region is almost unchanged. When the power is 30W, the focal region is obtained by numerical simulation. The size of the focal area obtained by the volume and the body model is almost the same. When the power is 40W~60W, the focal volume of the focal area is slightly smaller than that in the body model experiment. With the increase of the working frequency of the transducer, the focal region above 60 degrees increases gradually, the peak temperature of the focal region increases gradually, the focal region moves away from the transducer direction and the focal region is long. Both the axis and the short axis increase with the increase of the working frequency, and the slope decreases. With the increase of the viscosity of the imitated tissue, the focal region of the focal region decreases gradually, the peak temperature of the focal region decreases gradually, the focal region moves away from the transducer direction. The long axis and the short axis of the focal region decrease with the increase of the viscosity. With the shear modulus of the imitated tissue die. The focal region above 60 C increases first and then decreases, the peak temperature of the focal region increases first and then decreases, and the focal region is almost no offset; the long axis and the short axis of the focal region increase first and then decrease with the increase of the viscosity. With the increase of the initial bubble radius in the body model, the focal area above 60 degrees increases gradually, the peak temperature of the focal region is heated by the temperature. Gradually, the focal region moves away from the transducer direction. Both the long axis and the short axis of the focal region increase with the increase of the initial radius of the bubble, and the slope becomes smaller. Conclusion the microbubble contrast agent can increase the HIFU formation of the treatable focal region above 60 degrees C. The increase of the input power, the initial radius of the bubble and the lifting frequency can increase the focal region and increase the input power. In addition, the shape of the focal region may change, and the working frequency and the initial radius of the bubble are increased, the focal region moves toward the direction of the transducer, the greater the viscosity of the model, the lower the peak temperature of the focal region, the smaller the focal region and the direction of the focal region moving away from the transducer, and the focal region increases first and then decreases with the increase of the modulus of the imitated fabric. Move away from the transducer direction.
【学位授予单位】：天津医科大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R730.5;TB552

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