本文關(guān)鍵詞： 放療光聲效應(yīng) K-Wave仿真 圖像質(zhì)量 換能器陣列 信噪比　出處：《深圳大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：惡性腫瘤是危害人類生命的殺手,隨著治療手段的進(jìn)步,癌癥的臨床治愈率在不斷上升。放療、手術(shù)、化療是目前治愈惡性腫瘤的重要手段,其中約2/3的患者將接受放療。放療使用高能量束的電離輻射引起DNA雙鏈的斷裂,導(dǎo)致細(xì)胞死亡。目前臨床放療的最主要技術(shù)是圖像引導(dǎo)放療,對腫瘤靶區(qū)高劑量照射,避免周圍正常組織和器官受到劑量照射。現(xiàn)階段的圖像引導(dǎo)放療技術(shù)在擺位時采集圖像,給患者增加了額外的照射劑量,且無法在放療過程中實時監(jiān)控腫瘤位置變化與射束的關(guān)系。針對這一問題,本論文提出在放療過程中使用X-光光聲成像的方法實時監(jiān)控X-光射野與靶區(qū)的相對位置,減少額外的照射劑量。X-光光聲成像的基本原理是周期性脈沖X-光照射在物質(zhì)上,物質(zhì)發(fā)生熱膨脹向外輻射超聲波,換能器放置在物質(zhì)的一側(cè)采集超聲波,使用圖像重建算法重建出物質(zhì)對X-光的吸收分布。本論文主要目的是通過理論仿真探索影響X-光光聲信號采集、光聲圖像質(zhì)量的關(guān)鍵因素,通過自制換能器和光聲信號采集實驗為多通道快速采集提供基礎(chǔ)。本論文基于Matlab的工具箱K-Wave完成了理論仿真,分析了影響X-光光聲信號采集、光聲成像圖像質(zhì)量的主要因素。(1)X-光脈沖寬度影響光聲信號產(chǎn)生效率和圖像分辨率,當(dāng)脈沖寬度為100ns時圖像質(zhì)量更好,脈沖寬度為4μs時,光聲信號為微伏級,頻率低于100kHz。(3)換能器陣列設(shè)計影響光聲成像的圖像質(zhì)量,仿真結(jié)果表明換能器陣列數(shù)目為128時、換能器陣元面積為10mm、曲率半徑為500mm時,重建出的圖像質(zhì)量更好。換能器陣列的設(shè)計對光聲信號的采集具有重要作用,影響著圖像分辨率。本論文設(shè)置不同換能器陣列結(jié)構(gòu),使用時間反演圖像重建方法優(yōu)化陣列設(shè)計。本論文在理論仿真的指導(dǎo)下,和深圳市人民醫(yī)院腫瘤放療科專家合作,使用單通道光聲信號采集系統(tǒng)采集了鉛塊與水的光聲信號。針對放療時直線加速器脈沖寬度為4us的脈沖X-光照射下,光聲信號幅值低、頻率低、干擾強(qiáng)的特點(diǎn),自制法拉第籠屏蔽放療環(huán)境中的電磁干擾,使光聲信號的信噪比有15dB左右的提高;制作了壓電陶瓷換能器探頭,使采集的光聲信號幅值提高4倍左右,同時成本也降低10倍左右,為多通道換能器的物理設(shè)計提供了基礎(chǔ)。
[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.
【學(xué)位授予單位】：深圳大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：R730.55;TP391.41

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本文編號：1491041