診斷超聲寬帶聲束形成技術研究與實現(xiàn)
發(fā)布時間：2018-12-11 21:35
【摘要】：診斷超聲成像具有安全無創(chuàng)、實時、廉價、便攜等優(yōu)點,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)的基于延時累加的聲束形成技術采用動態(tài)聚焦技術、動態(tài)孔徑技術以及動態(tài)變跡技術改善聲束的指向性,但仍存在著聲束旁瓣較高、主瓣寬度不夠窄等問題,導致最終成像的空間分辨率和對比度分辨率不足。本文針對動態(tài)聚焦中數(shù)字時延精度不足導致的旁瓣幅值大,以及傳統(tǒng)窗函數(shù)變跡方法導致的主瓣展寬問題,著重進行了如下幾個方面的研究:1、對超聲成像系統(tǒng)及其性能評價指標進行了分析,研究了聲束形成技術的相關理論,給出了聲束形成技術的三種不同實現(xiàn)結(jié)構的對比分析,重點分析了聲束形成技術中的時延精度與成像性能指標之間的關系,并對寬帶聲束形成技術進行了討論。2、研究了基于可變分數(shù)時延Farrow濾波器的動態(tài)聚焦方法。對用于擬合可變分數(shù)時延Farrow濾波器的三種原型濾波器組的設計方法進行了仿真分析,并給出了三個有關時延幅度誤差和相位誤差的對比分析,仿真表明,可變分數(shù)時延Farrow濾波器可提高延時精度,有效消除圖像尾影。3、針對傳統(tǒng)延時累加聲束形成器中變跡導致的主瓣寬度展寬的問題,研究了寬帶FIR聲束形成技術的原理及實現(xiàn)結(jié)構,并基于通用囊性分辨率準則,詳細論述了利用約束最小二乘(CLS)最佳變跡法設計寬帶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獲得更窄的聲束主瓣。4、對基于FPGA的寬帶聲束形成器的優(yōu)化實現(xiàn)方法進行了研究。首先,針對分數(shù)時延Farrow濾波器的結(jié)構特性,對聲束形成器的實現(xiàn)結(jié)構進行了優(yōu)化,提出了雙分數(shù)時延值輸入Farrow濾波器;其次,在節(jié)約乘法器資源方面,對Farrow濾波器的實現(xiàn)提出了優(yōu)化方法;最后驗證、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.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TP391.41;TB559
本文編號：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.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TP391.41;TB559
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