基于GPU并行计算的超声波束合成方法

逐列扫描式的聚焦成像方法会限制超声成像帧频的提高。采用平面波发射模式只需要一次发射和接收即可获得一幅完整的超声图像,平面波成像是可以大幅度地提高成像帧频,从而实现超声超高速成像的方法之一。但是现有的超声波束合成器无法达到超声超高速成像对于计算能力的要求。对基于平面波成像的超声延时-叠加波束合成算法进行并行性分析,在此基础上设计并实现两种基于图形处理器(GPU)并行计算的超声平面波成像波束合成方法——基于2个Kernel和基于1个Kernel的并行波束合成方法。两种方法的主要区别在于波束合成中对延时值的计算和存储策略的不同处理,仿体实验证明两种方法的计算帧频分别达到2 178 和2 453 帧/s。相比于普通的方法,这两种基于GPU的并行波束合成方法的计算帧频分别提速99倍和111倍。实验结果表明,GPU波束合成器相比于传统方法,可以大幅度提高计算能力。     

医学超声关键技术研究和进展(一) 超声换能器与超声编码技术

医学超声技术的发展使得超声成像成为临床诊断领域的重要组成部分。许多新的医学超声技术仍然在不断涌现。医疗换能器及阵列,不仅直接影响到医学超声图像的质量,同时也决定了系统设备的应用。宽频带、多维高密度、高频、微型化腔内集成探头是未来超声换能器发展的主要方向。该文对国内外医疗超声换能器材料发展、结构创新、应用三个方面作了简要综述。超声编码技术具有可以提高医学超声成像系统的信噪比、帧频和探查深度等优点,目前仍是超声成像技术的研究热点之一。该文介绍了超声编码检测原理、超声编码检测研究现状、技术难点,并对超声编码技术的前景进行了展望。     

基于Golay互补序列的20 MHz眼科超声成像方法

目的研究一种新型20 MHz眼科超声扫描成像方法,可在满足临床成像分辨力和声能安全性要求的前提下,显著提高图像的探测深度,拓展20 MHz超声频段的临床应用范围。方法通过8位Golay互补序列,激励超声换能器产生超声波。回波信息经高速采集与匹配滤波后,采用相邻正、反编码扫描线数据复用的方法交替相加,完成解码运算。在保证图像扫描线数和扫描帧频的前提下,实现实时显像。最后通过钨丝靶线和仿组织超声体模实验,验证了新的成像方法在保持原有分辨能力与扫描帧频不变的前提下,提高了图像的探测深度。结果与传统单脉冲模式相比,Golay互补编码模式成像中轴向分辨率与侧向分辨率分别达到80μm和150μm,小信号探测深度增加约0.5 cm,图像信噪比也得到显著改善。结论基于Golay互补序列实现20 MHz眼部组织超声成像,相对于传统成像方式可极大改善图像质量,具有很好的临床应用前景。     

超声换能器在医学成像中的发展

换能器是超声波发射和回波接收器件,是超声医学成像中最重要的声学部件。在医疗超声设备中,换能器直接影响了超声医学成像质量。概述了各种超声医学成像换能器现状,以及换能器聚焦和数字波束成像技术。     

超声换能器在医学成像中的发展

换能器是超声波发射和回波接收器件,是超声医学成像中最重要的声学部件.在医疗超声设备中,换能器直接影响了超声医学成像质量.概述了各种超声医学成像换能器现状,以及换能器聚焦和数字波束成像技术.     

超声成像换能器技术的发展

作为超声波发射和回波接收器件的换能器,始终是医学超声成像系统中最为关键的声学部件.随着超声成像换能器技术的不断发展使超声图像更清晰,更直观.主要论述新型压电复合材料换能器、压电单晶材料换能器、宽频带换能器、三维成像换能器和电容式微加工换能器的技术发展及其展望.     

一种改进的最小方差自适应波束形成超声成像方法

目的为提高医学超声成像过程中的对比度并改善自适应算法的鲁棒性,提出了融合相干系数（coherencefactor,CF）与前后向平滑的自适应波束形成（forward．backwardminimumvariance,FBMV）超声成像方法。方法首先对阵元接收数据进行延时聚焦处理,利用前后向空间平滑技术去除回波信号的相关性,然后进行最小方差波束形成,同时计算回波信号的相干系数。最后利用相干系数加权前后向平滑的最小方差波束形成的结果,得到回波数据进行成像。结果仿真结果表明,相对于最小方差波束形成算法与传统的延时叠加波束形成算法,本文算法在对比度及鲁棒性方面均得到有效提高。结论本算法为实现高质量的超声成像系统提供了理论依据。     

基于二维阵列换能器的实时三维超声成像技术综述

基于二维阵列换能器的实时三维超声成像技术是现代医学超声成像技术的重要发展方向,可以产生对称聚焦的超声束,实现多平面成像,代表三维超声成像技术的最新发展趋势.系统介绍二维阵列换能器的工作原理、阵列设计与制作、三维重建与显示等关键问题,结合临床应用,讨论该技术的局限和改进方法.     

广义相干系数加权的超声虚拟源成像算法研究

超声虚拟源成像相对于传统的聚焦成像和合成孔径成像,使阵列孔径在虚拟意义上得到了扩大,增加了探测深度,提高图像对比度。自适应加权成像技术能够根据回波信号本身的特征进行动态加权,提升成像质量。本研究将广义相干系数(general coherence factor, GCF)与虚拟源成像(virtual source imaging,VS)相结合,提出GCF加权的VS成像算法(GCF-VS),进一步提高虚拟源成像效果。Field Ⅱ仿真和实验结果证明该算法相对于传统的VS成像和相干系数(coherence factor,CF)加权的VS成像,具有更高的成像质量。     

基于平均短阶相干系数的平面波复合成像算法

相干平面波复合成像(coherent plane-wave compounding, CPWC)可以实现高帧率、高质量成像,但未考虑平面波成像结果间的相干性。相干系数(coherence factor, CF)加权CPWC算法可以提高成像的分辨率和对比度,但降低了背景组织成像质量。短阶相干系数(short-lag coherence factor, SLCF)加权算法,可以进一步改善对比度和背景成像质量,但未考虑到较大发射角度平面波成像结果的相干性,导致分辨率降低。我们研究的平均短阶相干系数(average short-lag coherence factor,ASLCF)先计算出不同范围的发射角度的成像结果对应的SLCF,然后进行均值处理,最后作为加权系数对CPWC进行加权成像。实验和仿真证明在保持其他性能基本不变的情况下,相对于SLCF,ASLCF加权算法可以明显提高分辨率和背景组织的成像质量。     

Photoacoustic-guided ultrasound therapy with a dual-mode ultrasound array

Photoacoustics has recently been proposed as a potential method to guide and/or monitor therapy based on high-intensity focused ultrasound (HIFU). We experimentally demonstrate the creation of a HIFU lesion at the location of an optical absorber, by use of photoacoustic signals emitted by the absorber detected on a dual mode transducer array. To do so, a dedicated ultrasound array intended to both detect photoacoustic waves and emit HIFU with the same elements was used. Such a dual-mode array provides automatically coregistered reference frames for photoacoustic detection and HIFU emission, a highly desired feature for methods involving guidance or monitoring of HIFU by use of photoacoustics. The prototype is first characterized in terms of both photoacoustic and HIFU performances. The probe is then used to perform an idealized scenario of photoacoustic-guided therapy, where photoacoustic signals generated by an absorbing thread embedded in a piece of chicken breast are used to automatically refocus a HIFU beam with a time-reversal mirror and necrose the tissue at the location of the absorber.     

Phased-array ultrasound technology enhances accuracy of dual frequency ultrasound measurements – towards improved ultrasound bone diagnostics

Overlying soft tissues attenuate ultrasound backscattered from bone, complicating diagnostics of osteoporosis at the most important fracture sites. Dual-frequency ultrasound technique (DFUS) has been proposed to solve this problem through determination of thickness and composition of overlying soft tissue. This study applies DFUS technique for the first time with a phased-array transducer to investigate if the thickness of two interfering layers (oil and water) can be accurately determined in a variety of configurations. Results indicate that DFUS may be used with phased-array ultrasound systems, making them a suitable combination to consider in future development of clinical in vivo ultrasound methodologies.     

An ultrasound mini-balance for measurement of therapy level ultrasound

This paper describes a cost-effective method for measuring acoustic power using a radiation force balance. The device is based around a long established balance design with a gantry arrangement fitted with an absorbing target. The notion of this balance design is that it can easily be constructed from materials that would be readily available within a clinical or industrial environment. The mini-balance was calibrated using a transfer standard against an NPL Reference balance, so a comparison of the performance between the two systems could be assessed. The measurements were completed at 1 MHz and 3 MHz and over the acoustic power range of 1 W to 15 W. The results show the acoustic power measured on the mini-balance to be within 5% of the reference measurements made on the NPL Balance. A separate systematic uncertainty budget is also presented based on studies made on the balance and on similar systems. The overall expanded uncertainty was calculated to be within 14% at 1 W level, decreasing with increasing power level to 7.4% above 5 W.     

Three-dimensional ultrasound imaging

Ultrasound is an inexpensive and widely used imaging modality for the diagnosis and staging of a number of diseases. In the past two decades, it has benefited from major advances in technology and has become an indispensable imaging modality, due to its flexibility and non-invasive character. In the last decade, research investigators and commercial companies have further advanced ultrasound imaging with the development of 3D ultrasound. This new imaging approach is rapidly achieving widespread use with numerous applications. The major reason for the increase in the use of 3D ultrasound is related to the limitations of 2D viewing of 3D anatomy, using conventional ultrasound. This occurs because: (a) Conventional ultrasound images are 2D, yet the anatomy is 3D, hence the diagnostician must integrate multiple images in his mind. This practice is inefficient, and may lead to variability and incorrect diagnoses. (b) The 2D ultrasound image represents a thin plane at some arbitrary angle in the body. It is difficult to localize the image plane and reproduce it at a later time for follow-up studies. In this review article we describe how 3D ultrasound imaging overcomes these limitations. Specifically, we describe the developments of a number of 3D ultrasound imaging systems using mechanical, free-hand and 2D array scanning techniques. Reconstruction and viewing methods of the 3D images are described with specific examples. Since 3D ultrasound is used to quantify the volume of organs and pathology, the sources of errors in the reconstruction techniques as well as formulae relating design specification to geometric errors are provided. Finally, methods to measure organ volume from the 3D ultrasound images and sources of errors are described.     

Scanning ultrasound diagnostic instruments

All-Union Scientific-Research Institute for Medical Instrument Engineering, Moscow. Translated from Meditsinskaya Tekhnika, No. 4, pp. 24–28, July–August, 1991.     

Design of double ultrasound pulse transmission and receiving circuit used in ultrasound thermometry

Hyperthermia treatments of tumours are attracting more and more attention from physical doctors and researchers. In particular, invasive microwave coagulation (IMC) therapy is a newly developed and effective method for the treatment of liver tumours. Generally successful applications of IMC are based on accurate temperature measurements of the tissues as the microwaves take effect. As a noninvasive technology, ultrasonic thermometry is based on the correlation between temperature and ultrasound speed or ultrasound decay coefficients of tissues. This paper presents the design of a double ultrasonic pulse transmission/receiving circuit used in ultrasonic thermometry. The circuit can synchronously produce the double ultrasonic pulse required by ultrasonic thermometry and can successfully receive weak ultrasonic echo signals. Some key wave-shapes used in experiments are presented. The experimental results indicate that the circuit is reliable and has good functionality.