【作者】 龚强；

【导师】 张国雄；

【作者基本信息】 天津大学 ， 测试计量技术及仪器， 2004， 硕士

【摘要】 超声组织的表征是七十年代以后在生物医学工程领域中的一个研究热点。它主要是通过处理软组织在应力作用下利用超声回波信号提取软组织弹性特性参数，获得反映软组织特性的声弹性图一种方法。弹性估计的关键在于对应力作用下的应变估计。以此为基础，目前在这一领域已经提出许多算法，但是估计效果不尽相同。尽管在理论研究上取得巨大进步，但是在国内还没有关于能够应用于临床诊断的便携式仪器报道。因此，有必要设计一种便携式超声软组织弹性特性测试仪，以证明其在实际应用的可行性。本论文完成了这种便携式仪器的设计，并且完成超声的发射、数据采集电路的软硬件调试。为了验证目前研究领域中的估计算法的有效性，本文还对几种目前来说比较典型应用的算法进行了比对，并由此计算出不同算法下得到的生物软组织弹性特性参数，以比较定量检测软组织病变时的差别。这种便携式仪器的设计与开发，是以 DSP 作为中央处理器，利用目前普遍应用的 CPLD 技术实现的。为实现超声与应力数据的实时采集，采用了直接存储器寻址模式（DMA）来完成数据采集（DAQ）。为了评定弹性估计算法的差别，本文在实验室已有的条件下，设计和开发的基于 PC 机的超声软组织弹性系数测量系统，实现超声信号和压力信号的接收和调理，及两路信号的同步采集及实时显示。对于应力作用下的应变估计，目前应用比较广泛的是互相关估计法，即通过压缩前后回波的互相关最大值对应的时间点实现应变估计，本文对这种算法的最大值估计过程做了一定的改进。另外，本文使用了一种新的算法来减小互相关引起的误差。最后，对这些算法进行了实验分析与比对。更多还原

【Abstract】 The technology of ultrasonic tissue characterization is a hotspot in the field ofbiomedical engineering after 70’s of last century, which mainly extracts soft-tissueelasticity parameters by processing the signals of ultrasound echo from soft tissueunder certain loads, and serves as a method for obtaining acousto-elasticity pictures.The key of elasticity estimation is estimating the strains under different loads.Currently, many algorithms with quite different effects have been proposed. In spiteof the significant progresses in theoretical researches, no report on portable clinicinstruments has been announced in our country. Therefore, it is necessary to develop aportable tester for measuring soft-tissue elasticity parameters based on ultrasound andto prove the feasibility of the technology. The design of the portable tester, including the transmission of ultrasound, thehardware and software debugging of the DAQ circuit has been accomplished in thethesis. In order to prove the effectiveness of various estimation algorithms, sometypical algorithms are compared. Then, soft-tissue elasticity parameters are obtainedby using the proposed algorithms and the elasticity parameters revealed during thepathological changes of the soft-tissues are compared. The DSP is used as the CPU in the design and development of portable tester,and they are developed by CPLD technology. By using DMA, the real-time DAQ ofultrasound and load signals is obtained. An ultrasonic diagnostic system formeasuring elastical properties of soft tissues based on PC has been developed byutilizing the existing resources in our lab. The system can deal with the data sampling,conditioning, synchronous acquisition and display of the ultrasonic and force signals.The cross-correlation algorithm, which estimates the strain by measuring the timedifference between ultrasound echoes before and after compression for obtainingmaximum cross-correlation coefficient, is used. Some improvements in maximumsearching have been made in the thesis. Besides, a novel algorithm has been proposedto reduce the error from cross-correlation. Finally, an analysis and comparison ofexperiment data are presented.更多还原