实时放疗X-光光声成像理论与实验研究

发布时间：2018-02-04 20:08

本文关键词： 放疗光声效应 K-Wave仿真图像质量换能器阵列信噪比　出处：《深圳大学》2017年硕士论文　论文类型：学位论文

【摘要】：恶性肿瘤是危害人类生命的杀手,随着治疗手段的进步,癌症的临床治愈率在不断上升。放疗、手术、化疗是目前治愈恶性肿瘤的重要手段,其中约2/3的患者将接受放疗。放疗使用高能量束的电离辐射引起DNA双链的断裂,导致细胞死亡。目前临床放疗的最主要技术是图像引导放疗,对肿瘤靶区高剂量照射,避免周围正常组织和器官受到剂量照射。现阶段的图像引导放疗技术在摆位时采集图像,给患者增加了额外的照射剂量,且无法在放疗过程中实时监控肿瘤位置变化与射束的关系。针对这一问题,本论文提出在放疗过程中使用X-光光声成像的方法实时监控X-光射野与靶区的相对位置,减少额外的照射剂量。X-光光声成像的基本原理是周期性脉冲X-光照射在物质上,物质发生热膨胀向外辐射超声波,换能器放置在物质的一侧采集超声波,使用图像重建算法重建出物质对X-光的吸收分布。本论文主要目的是通过理论仿真探索影响X-光光声信号采集、光声图像质量的关键因素,通过自制换能器和光声信号采集实验为多通道快速采集提供基础。本论文基于Matlab的工具箱K-Wave完成了理论仿真,分析了影响X-光光声信号采集、光声成像图像质量的主要因素。(1)X-光脉冲宽度影响光声信号产生效率和图像分辨率,当脉冲宽度为100ns时图像质量更好,脉冲宽度为4μs时,光声信号为微伏级,频率低于100kHz。(3)换能器阵列设计影响光声成像的图像质量,仿真结果表明换能器阵列数目为128时、换能器阵元面积为10mm、曲率半径为500mm时,重建出的图像质量更好。换能器阵列的设计对光声信号的采集具有重要作用,影响着图像分辨率。本论文设置不同换能器阵列结构,使用时间反演图像重建方法优化阵列设计。本论文在理论仿真的指导下,和深圳市人民医院肿瘤放疗科专家合作,使用单通道光声信号采集系统采集了铅块与水的光声信号。针对放疗时直线加速器脉冲宽度为4us的脉冲X-光照射下,光声信号幅值低、频率低、干扰强的特点,自制法拉第笼屏蔽放疗环境中的电磁干扰,使光声信号的信噪比有15dB左右的提高;制作了压电陶瓷换能器探头,使采集的光声信号幅值提高4倍左右,同时成本也降低10倍左右,为多通道换能器的物理设计提供了基础。
[Abstract]:Malignant tumor is a killer of human life. With the progress of treatment, the clinical cure rate of cancer is rising. Radiotherapy, surgery and chemotherapy are the important means to cure malignant tumor. About 2/3 of the patients will be treated with radiotherapy. Radiation with high energy beam ionizing radiation causes DNA double strand breakage, resulting in cell death. At present, image guided radiotherapy is the main technique of clinical radiotherapy. In order to avoid the normal tissues and organs around the tumor being irradiated with high dose, the current image-guided radiotherapy technology is used to collect the images when the tumor is placed, which increases the additional irradiation dose to the patients. And it is impossible to monitor the relationship between tumor location and beam in real time during radiotherapy. In this paper, the X- photoacoustic imaging method is proposed to monitor the relative position of the X- photoacoustic field to the target area in the course of radiotherapy. The basic principle of reducing the additional irradiation dose. X- photoacoustic imaging is the periodic pulse X- light irradiation on the matter, the matter produces thermal expansion outward radiation ultrasonic wave, the transducer is placed on the side of the material to collect the ultrasonic wave. The main purpose of this paper is to explore the key factors that affect X- photoacoustic signal acquisition and photoacoustic image quality through theoretical simulation. The experiment of self-made transducer and photoacoustic signal acquisition provides the foundation for multi-channel fast acquisition. This paper completes the theoretical simulation based on Matlab toolbox K-Wave. The main factors that affect the quality of X- photoacoustic signal are analyzed. The main factors, I. e., the width of X- X- optical pulse, affect the efficiency of photoacoustic signal generation and the resolution of the image. When the pulse width is 100 ns, the image quality is better. When the pulse width is 4 渭 s, the photoacoustic signal is of microvolt order. The design of transducer array affects the image quality of photoacoustic imaging. The simulation results show that the area of transducer array is 10mm when the number of transducer array is 128. When the curvature radius is 500mm, the reconstructed image quality is better. The design of transducer array plays an important role in the acquisition of photoacoustic signals and affects the image resolution. Using time inversion image reconstruction method to optimize array design. Under the guidance of theoretical simulation, this paper cooperates with the expert of tumor radiotherapy department of Shenzhen people's Hospital. The photoacoustic signals of lead block and water were collected by a single channel photoacoustic signal acquisition system, and the photoacoustic signal amplitude was low and the frequency was low when the pulse width of the linear accelerator was 4us. Because of the strong interference, the electromagnetic interference in the radiation environment is shielded by the self-made Faraday cage, which improves the signal to noise ratio (SNR) of the photoacoustic signal by about 15 dB. The piezoelectric transducer probe is fabricated, which increases the photoacoustic signal amplitude by about 4 times and reduces the cost by about 10 times, which provides the basis for the physical design of the multi-channel transducer.
【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】：R730.55;TP391.41

【相似文献】