基于聚焦超声中微泡动态行为估计并补偿在位声场的研究

发布时间：2018-04-27 02:02

本文选题：聚焦超声 + 造影剂微泡　；参考：《深圳大学》2017年硕士论文

【摘要】：聚焦超声治疗中靶区组织状态对超声参数具有很高的依赖性,当超声经过人体组织到达治疗靶区后,由于20-200mm的超声路径上组织介质对超声的声衰减,造成关键的在位超声参数未知。在开始治疗前的预治疗阶段,针对不同体质的病人,有必要获取组织对治疗超声的声衰减值,在正式开始治疗时,补偿治疗超声参数,推进精准的个性化治疗。针对此问题我们提出将生物可兼容的微泡作为体内“探针”,利用其回波信号特征,估算组织声衰减,从而推算出在位声场参数。而不同病人个体的超声回波信号会受到声衰减、散射、声速、灌注率等多个因素的影响,要从超声回波信号中分离出声衰减因子非常困难,本研究独创性的提出利用造影剂微泡在聚焦超声作用下产生的高特异性破坏动态行为,无创地估算组织声衰减,确定在位声场参数,初步验证了在正式治疗开始时,利用预治疗阶段确定的有效声衰减值对治疗声场参数进行补偿的可行性,对优化聚焦超声治疗具有一定的科学指导意义。本研究针对聚焦超声治疗中关键的组织特征-组织声衰减和治疗靶区组织环境,设计出模拟人体脏器环境的可控的中空PVA仿体,制作了具有不同声衰减值的硅胶仿体,可有效地模拟治疗超声路径上不同体质病人的组织。基于开放式超声系统Verasonics Vantage 256系统开发出高帧率高时长的平面波数据采集平台,用于获取微泡破坏过程中产生的丰富的动态行为数据。以中心频率为1.12MHz的水囊探头治疗系统作为治疗声源,制定了治疗超声与成像超声间的时序,在多参数组治疗超声的干预下,利用高帧率数据采集平台获取高时空分辨率的微泡回波信号,以平面波成像方式重建图像,帧率高达1kHz。以图像ROI中灰度信息的均方根值量化微泡的破坏程度,建立了庞大的微泡声学响应数据库。对比加入衰减材料硅胶仿体前后所获得的微泡的破坏动态行为特征,分别利用图像匹配、数学统计的方法在位估算出了多块仿人体组织硅胶的声衰减,与脉冲插入法标定的声衰减值相比,误差都小于1.5dB,相应的在位声场的估计值误差小于1.5dB;在一定的范围内改变微泡的浓度,具有一致的估计结果。本文初步探讨了微泡的流动和基于2.1MHz多通道相控阵HIFU治疗系统,对在位声场估计的影响。
[Abstract]:The tissue state of the target area is highly dependent on the ultrasonic parameters in the focused ultrasound treatment. When the ultrasound passes through the human body to the target area of the treatment, the attenuation of ultrasound is due to the tissue media on the ultrasonic path of 20-200mm. The key in situ ultrasonic parameters are unknown. In the pre-treatment stage before the beginning of treatment, it is necessary for patients with different physique to obtain the sound attenuation value of the tissue to the treatment ultrasound, to compensate the ultrasonic parameters of the treatment and to promote the accurate individualized treatment when the treatment is officially started. In order to solve this problem, we propose to use biocompatible microbubbles as a "probe" in vivo, using the characteristics of echo signal to estimate the attenuation of tissue sound, and then calculate the parameters of sound field in situ. However, the ultrasonic echo signal of different patients will be affected by many factors, such as sound attenuation, scattering, sound velocity, perfusion rate and so on, so it is very difficult to separate the sound attenuation factor from the ultrasonic echo signal. The purpose of this study is to present a highly specific destructive dynamic behavior produced by contrast agent microbubbles under focused ultrasound, to estimate tissue acoustic attenuation and to determine sound field parameters in situ, which is preliminarily verified at the beginning of formal treatment. The feasibility of compensating the parameters of the sound field by using the effective sound attenuation value determined in the pre-treatment stage has certain scientific guiding significance for optimizing the treatment of focused ultrasound. In this study, aiming at the key tissue characteristics of focused ultrasound therapy, tissue sound attenuation and target tissue environment, a controllable hollow PVA imitating human organ environment was designed, and silica gel imitating body with different sound attenuation values was made. It can effectively simulate the tissue of patients with different physique on ultrasonic pathway. Based on the open ultrasonic system Verasonics Vantage 256, a plane wave data acquisition platform with high frame rate, high time and long time is developed, which is used to obtain rich dynamic behavior data generated during the destruction of microbubbles. A water capsule probe therapy system with a central frequency of 1.12MHz was used as the sound source for the treatment. The timing between the therapeutic ultrasound and the imaging ultrasound was determined, and the intervention of the multi-parameter group was carried out. The high space-time resolution microbubble echo signal is obtained by using the high frame rate data acquisition platform, and the image is reconstructed by plane wave imaging. The frame rate is as high as 1 kHz. Based on the root mean square (RMS) of gray level information in image ROI, a large database of acoustic response of microbubbles is established. The dynamic behavior characteristics of microbubbles obtained before and after imitating silica gel were compared, and the sound attenuation of silicon gel was estimated by image matching and mathematical statistics respectively. Compared with the acoustic attenuation values calibrated by the pulse insertion method, the errors are less than 1.5 dB, and the estimation errors of the corresponding in-situ sound fields are less than 1.5 dB, and the estimation results are consistent when the concentration of microbubbles is changed in a certain range. In this paper, the effect of microbubble flow and multichannel phased array HIFU therapy system based on 2.1MHz on in situ sound field estimation is discussed.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB559;R454.3

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