診斷超聲寬帶聲束形成技術(shù)研究與實(shí)現(xiàn)
發(fā)布時(shí)間：2018-12-11 21:35
【摘要】：診斷超聲成像具有安全無(wú)創(chuàng)、實(shí)時(shí)、廉價(jià)、便攜等優(yōu)點(diǎn),被廣泛用于人體軟組織病變與流態(tài)組織特性的診斷,目前已成為必不可缺的臨床醫(yī)學(xué)診斷方法之一。作為診斷超聲成像系統(tǒng)的前端數(shù)據(jù)獲取與信號(hào)處理單元,聲束形成器性能的優(yōu)劣直接決定了成像的質(zhì)量。傳統(tǒng)的基于延時(shí)累加的聲束形成技術(shù)采用動(dòng)態(tài)聚焦技術(shù)、動(dòng)態(tài)孔徑技術(shù)以及動(dòng)態(tài)變跡技術(shù)改善聲束的指向性,但仍存在著聲束旁瓣較高、主瓣寬度不夠窄等問題,導(dǎo)致最終成像的空間分辨率和對(duì)比度分辨率不足。本文針對(duì)動(dòng)態(tài)聚焦中數(shù)字時(shí)延精度不足導(dǎo)致的旁瓣幅值大,以及傳統(tǒng)窗函數(shù)變跡方法導(dǎo)致的主瓣展寬問題,著重進(jìn)行了如下幾個(gè)方面的研究:1、對(duì)超聲成像系統(tǒng)及其性能評(píng)價(jià)指標(biāo)進(jìn)行了分析,研究了聲束形成技術(shù)的相關(guān)理論,給出了聲束形成技術(shù)的三種不同實(shí)現(xiàn)結(jié)構(gòu)的對(duì)比分析,重點(diǎn)分析了聲束形成技術(shù)中的時(shí)延精度與成像性能指標(biāo)之間的關(guān)系,并對(duì)寬帶聲束形成技術(shù)進(jìn)行了討論。2、研究了基于可變分?jǐn)?shù)時(shí)延Farrow濾波器的動(dòng)態(tài)聚焦方法。對(duì)用于擬合可變分?jǐn)?shù)時(shí)延Farrow濾波器的三種原型濾波器組的設(shè)計(jì)方法進(jìn)行了仿真分析,并給出了三個(gè)有關(guān)時(shí)延幅度誤差和相位誤差的對(duì)比分析,仿真表明,可變分?jǐn)?shù)時(shí)延Farrow濾波器可提高延時(shí)精度,有效消除圖像尾影。3、針對(duì)傳統(tǒng)延時(shí)累加聲束形成器中變跡導(dǎo)致的主瓣寬度展寬的問題,研究了寬帶FIR聲束形成技術(shù)的原理及實(shí)現(xiàn)結(jié)構(gòu),并基于通用囊性分辨率準(zhǔn)則,詳細(xì)論述了利用約束最小二乘(CLS)最佳變跡法設(shè)計(jì)寬帶FIR聲束形成器變跡系數(shù)的方法。仿真表明,寬帶FIR聲束形成器能夠在降低旁瓣的同時(shí)獲得更窄的聲束主瓣。4、對(duì)基于FPGA的寬帶聲束形成器的優(yōu)化實(shí)現(xiàn)方法進(jìn)行了研究。首先,針對(duì)分?jǐn)?shù)時(shí)延Farrow濾波器的結(jié)構(gòu)特性,對(duì)聲束形成器的實(shí)現(xiàn)結(jié)構(gòu)進(jìn)行了優(yōu)化,提出了雙分?jǐn)?shù)時(shí)延值輸入Farrow濾波器;其次,在節(jié)約乘法器資源方面,對(duì)Farrow濾波器的實(shí)現(xiàn)提出了優(yōu)化方法;最后驗(yàn)證、分析了寬帶聲束形成的成像效果及其硬件資源消耗。
[Abstract]:Diagnostic ultrasound imaging has the advantages of safe, non-invasive, real-time, cheap and portable. It has been widely used in the diagnosis of soft tissue lesions and fluid tissue characteristics, and has become one of the indispensable clinical diagnostic methods. As the front-end data acquisition and signal processing unit of diagnostic ultrasonic imaging system, the quality of imaging is directly determined by the performance of acoustic beam forming device. The traditional acoustic beam forming technology based on delay accumulation uses dynamic focusing technology, dynamic aperture technology and dynamic apodization technology to improve the directivity of sound beam, but there are still some problems such as high sidelobe and narrow width of main lobe. As a result, the spatial resolution and contrast resolution of the final imaging are insufficient. In this paper, we focus on the following aspects: 1. Aiming at the large amplitude of sidelobe caused by the lack of digital delay precision in dynamic focusing and the main lobe broadening caused by traditional window function change method, this paper focuses on the following aspects: 1. This paper analyzes the ultrasonic imaging system and its performance evaluation index, studies the relevant theory of acoustic beam formation technology, and gives a comparative analysis of three different structures of acoustic beam formation technology. The relationship between delay accuracy and imaging performance in acoustic beam forming technology is analyzed, and the wideband acoustic beam forming technique is discussed. 2. Dynamic focusing method based on variable fractional delay Farrow filter is studied. The design methods of three kinds of prototype filter banks used to fit Farrow filters with variable fractional delay are simulated and analyzed, and three comparative analysis of delay amplitude error and phase error are given. The simulation results show that, The variable fractional delay Farrow filter can improve the delay accuracy and effectively eliminate the image tail. 3. Aiming at the problem of widening the width of the main lobe caused by the change point in the traditional time-delay accumulative acoustic beam formator, The principle and structure of broadband FIR acoustic beam formation technology are studied. Based on the general cystic resolution criterion, the method of designing the acoustical coefficient of broadband FIR acoustic beam forming device using constrained least square (CLS) optimal apodization method is discussed in detail. The simulation results show that the wideband FIR acoustic beam formator can obtain narrower main lobe while reducing the sidelobe. 4. The optimization method of the broadband acoustic beam generator based on FPGA is studied. Firstly, according to the structural characteristics of fractional delay Farrow filter, the structure of acoustic beam formator is optimized, and a double fractional delay input Farrow filter is proposed. Secondly, in the aspect of saving multiplier resources, the optimization method of Farrow filter is proposed. Finally, the imaging effect of broadband acoustic beam formation and the consumption of hardware resources are analyzed.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TP391.41;TB559
本文編號(hào)：2373259
[Abstract]:Diagnostic ultrasound imaging has the advantages of safe, non-invasive, real-time, cheap and portable. It has been widely used in the diagnosis of soft tissue lesions and fluid tissue characteristics, and has become one of the indispensable clinical diagnostic methods. As the front-end data acquisition and signal processing unit of diagnostic ultrasonic imaging system, the quality of imaging is directly determined by the performance of acoustic beam forming device. The traditional acoustic beam forming technology based on delay accumulation uses dynamic focusing technology, dynamic aperture technology and dynamic apodization technology to improve the directivity of sound beam, but there are still some problems such as high sidelobe and narrow width of main lobe. As a result, the spatial resolution and contrast resolution of the final imaging are insufficient. In this paper, we focus on the following aspects: 1. Aiming at the large amplitude of sidelobe caused by the lack of digital delay precision in dynamic focusing and the main lobe broadening caused by traditional window function change method, this paper focuses on the following aspects: 1. This paper analyzes the ultrasonic imaging system and its performance evaluation index, studies the relevant theory of acoustic beam formation technology, and gives a comparative analysis of three different structures of acoustic beam formation technology. The relationship between delay accuracy and imaging performance in acoustic beam forming technology is analyzed, and the wideband acoustic beam forming technique is discussed. 2. Dynamic focusing method based on variable fractional delay Farrow filter is studied. The design methods of three kinds of prototype filter banks used to fit Farrow filters with variable fractional delay are simulated and analyzed, and three comparative analysis of delay amplitude error and phase error are given. The simulation results show that, The variable fractional delay Farrow filter can improve the delay accuracy and effectively eliminate the image tail. 3. Aiming at the problem of widening the width of the main lobe caused by the change point in the traditional time-delay accumulative acoustic beam formator, The principle and structure of broadband FIR acoustic beam formation technology are studied. Based on the general cystic resolution criterion, the method of designing the acoustical coefficient of broadband FIR acoustic beam forming device using constrained least square (CLS) optimal apodization method is discussed in detail. The simulation results show that the wideband FIR acoustic beam formator can obtain narrower main lobe while reducing the sidelobe. 4. The optimization method of the broadband acoustic beam generator based on FPGA is studied. Firstly, according to the structural characteristics of fractional delay Farrow filter, the structure of acoustic beam formator is optimized, and a double fractional delay input Farrow filter is proposed. Secondly, in the aspect of saving multiplier resources, the optimization method of Farrow filter is proposed. Finally, the imaging effect of broadband acoustic beam formation and the consumption of hardware resources are analyzed.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TP391.41;TB559
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，本文編號(hào)：2373259
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