Adaptive speckle reduction of ultrasound images based on maximum likelihood estimation

A method has been developed in this paper to gain effective speckle reduction in medical ultrasound images. To exploit full knowledge of the speckle distribution, here maximum likelihood was used to estimate speckle parameters corresponding to its statistical mode. Then the results were incorporated into the nonlinear anisotropic diffusion to achieve adaptive speckle reduction. Verified with simulated and ultrasound images, we show that this algorithm is capable of enhancing features of clinical interest and reduces speckle noise more efficiently than just applying classical filters. To avoid edge contribution, changes of contrast-to-noise ratio of different regions are also compared to investigate the performance of this approach.     

基于球壳内壁反射的球形换能器自易校准方法

基于球形换能器发射的脉冲球面声波及其在同心球壳内壁的反射,应用机电互易定理,导出了在球面波发射回波声场中,用于校准球形换能器的互易常数。以此为基础,提出一种使用封闭球壳反射器的自易校准方法,通过一次测量即可得到球形换能器的5个基本电声参数。进一步,将自易法校准所得的电压灵敏度换算成平面波声场中定义的标准灵敏度,给出了换算系数。为确定该换算系数,发展了对换能器散射系数进行测量的方法。在25~63 kHz频率范围内,对半径10 mm的球形换能器实施了自易校准。结果表明,测得的电压灵敏度的标准不确定度估计优于0.9 dB。      

Free Field Reciprocity Calibration in a Convergent Spherical Acoustic Wave of a Focusing Transducer

Based on the reciprocity theorem of the acoustic field,we derive the formula of the reciprocity coefficient of a convergent spherical acoustic wave and we calculate a series of diffraction corrective factor curves of the reciprocity coefficient of transducers.Using these formulae and corrective factors,we calibrate the free field transmitting current response and the free field voltage sensitivity of a focusing transducer using the self-reciprocity method.The experimental results of the reciprocity calibration of the focusing transducer in the frequency range of 2MHz to 5.4MHz are presented.     

一种检测十二指肠胃返流光纤传感器的研制

设计了可检测十二指肠胃返流的光纤传感器,该传感器由470 nm的信号光、595 nm参考光和光纤束构成,主要检测十二指肠返流物中的胆红素在470 nm与595 nm的吸光度,本文还对影响传感器检测的因素,诸如波长、pH、胃液中悬浮颗粒造成的散射作用以及其他的因素,做了详细评价.传感器可以达到10 mg/dl优良的动态响应范围,离体实验结果表明,该传感器可以作为临床动态检测手段.     

医用超声治疗机换能器表面辐射声动率的声光法测量

声光法测量声功率,是利用平面波超声在透明液体中对光波产生的衍射效应来测量的一种方法.它能测量紧贴换能器表面的辐射功率,并且对声场没有影响.适宜于测量医用超声治疗机换能器的表面辐射功率.此文叙述了实验方法,给出了实验结果,并把结果列成表,以便查阅.结论表明,此法测量简便,精度较高.     

SJTU-1型医用超声诊断设备声输出测量系统的研制

本系统地研究了医用超声诊断设各声输出公布要求的国家标准GB16846—1997(idt.IEC61157—1992)中规定的主要指标的定义和测量方法，给出了相关的计算公式。介绍了为实施国标而研制的专用测量设备SJTU-1型医用超声设备声输出测量系统的工作原理、系统构成和技术性能。     

振动声成像系统分辨率研究

本文从振动声成像的基本原理出发，通过引入点扩展函数PSF和定义轴向响应函数ARF，研究了由凹球面聚焦换能器分割而成的一种典型共焦换能器参数对振动声成像系统侧向分辨率和轴向分辨率的影响。计算研究表明：增大凹球面换能器的口径、减小几何焦距和提高中心频率均可以提高系统的侧向分辨率和轴向分辨率；但改变凹球面换能器的分割比例对两种分辨率影响不尽相同。综合考虑超声换能器激励、聚焦性能以及产生的辐射力效果等因素，则换能器应按等辐射面积原则分割为宜。文中还分析了介质的声衰减系数对实际轴向分辨率的影响。     

B型超声诊断仪声场参数的测量与计算的一种简化方法

本文概述了B型超声诊断仪声场特性的基本测量和计算方法，提出了一系列典型声压波形的瞬时声压平方函数的时间积分解析表达式，可用来近似计算脉冲声强积分和各种脉冲声强参数．对三种典型超声诊断仪的输出声压波形函数，分别进行数值积分和解析计算，两者的计算结果偏离值均小于±7．0％，表明利用这些公式可使测量过程中的数据采集和计算程序大为简化，在实际应用中具有推广价值．     

Adaptive speckle reduction of ultrasound images based on maximum likelihood estimation

A method has been developed in this paper to gain effective speckle reduction in medical ultrasound images.To exploit full knowledge of the speckle distribution, here maximum likelihood was used to estimate speckle parameters corresponding to its statistical mode. Then the results were incorporated into the nonlinear anisotropic diffusion to achieve adaptive speckle reduction. Verified with simulated and ultrasound images,we show that this algorithm is capable of enhancing features of clinical interest and reduces speckle noise more efficiently than just applying classical filters. To avoid edge contribution, changes of contrast-to-noise ratio of different regions are also compared to investigate the performance of this approach.     

一种基于互易原理的超声功率新测量方法

本文从换能器的互易原理出发，利用平面波自易校准法获得换能器的自由场发送电流响应．根据平面活塞型换能器的衍射规律，推导出发射声功率的表达式．由此计算互易换能器在给定驱动电流（或电压）作用下的辐射超声功率．基于上述原理，使用自易校准装置测量了互易换能器的声功率一频率曲线．估计的测量不确定优于±20％．