诊断超声剂量对人胚绒毛细胞作用的实验研究

长期以来人们一直在为攻克癌症作不懈的努力，超声肿瘤热疗作为肿瘤热疗的一种手段，从７０年代才开始发展起来。相当长的一段时期内，超声热疗主要以温热疗法为主，温热疗法要求把肿瘤的温度加热在４２～４５℃范围内，而相应的体内测温技术还未成熟，因此超声温热疗法一直进展缓慢。直到８０年代末９０年代初，高强度聚焦超声（ｈｉｇｈｉｎｔｅｓｉｔｙｆｏｃｕｓｅｄｕｌｔｒａｓｏｕｎｄＨＩＦＵ）的兴起，才再次引起了人们对超声热疗的关注，ＨＩ－ＦＵ除了具有超声加热对人体无附加损害、穿透力强、对脂肪组织不选择加温等优点外，它…     

固体结构内部温度的超声测量

针对固体结构内部温度测量的工程需求,比较了目前工业中应用较多的热电偶测温法、光纤光栅测温法、中子共振谱法和超声测温技术,发现超声测温技术具有非接触式测量、测温范围广、响应速度快等特点而更适用于固体结构内部温度的测量.调研了超声测温技术的发展历史与国内外现状,重点对超声温度场重建方法进行了介绍与分析,发现现有的重建方法主要是针对一维温度场的而且都存在参数获取困难的局限性,导致重建方法的适用性较差并且重建精度较低.综述了超声测温技术在火灾损伤、医疗卫生、核力发电、冶炼制造等领域中的应用,讨论了超声测温技术在测温机理、声时测量算法和时间测量分辨率等方面存在的技术问题,总结了超声测温技术在今后发展中的重点研究方向并提出了展望.     

超声检测的信号处理与模式识别

超声检测在近几１０年中得到了较大的发展，它已成为材料或结构的无损检测与评价最常用的手段。目前超声检测的研究与发展重点大致可分为４方面，（１）新的超声检测方式研究，（２）散射与过散射的理论与实验研究，（３）成像方法与手段的研究，（４）信号处理及模式识别的应用研究。新的检测方法始终是超声检测的研究重点之一，近期激光超声成为这一内容的主角，但至今为止激光超声的研究大多还处于理论与实验阶段，真正走向商品化或工业性应用还很少。散射研究方面，尽管不少学者已经进行了大量深入细致、有时甚至是艰苦的研究，但这项工…     

高强度聚焦超声作用下的组织温度场测量技术的研究进展

高强度聚焦超声是近年来兴起的一种肿瘤无创治疗新技术,而温度监控是该治疗的关键,故温度场检测成为超声医学工程学研究的热点。该测量方法中的有损测温对实验操作要求较高,且易引起肿瘤细胞的转移;无损测温方法包括超声、微波辐射、电阻抗成像和MRI(磁共振)等,文章对这些新技术的优点和局限性作出综述。     

反射超声无损测温

反射超声无损测温于洪斌王鸿樟（上海交通大学，生命科学技术学院，生物医学工程系·２０００３０）１引言近年加热治癌愈益受到重视。热疗（Ｈｙｐｅｒｔｈｅｒ－ｍｉａ）是使癌组织升温到４３～４６℃，保持适当时间，以抑制癌肿，达到治疗目的。热疗中测温和控温是关键...     

基于小波变换的裂谱分析法

 为了提高超声无损检测（UNDT）和无损评价（UNDE）中基础数据的信噪比（SNR）,提出了一种基于小波变换多分辨率分析的裂谱分析新方法．该方法在分析传统裂谱分析（SSP）方法原理及其局限性的基础上,通过采用小波变换多分辨率分析能力将原始超声回波信号进行等Q子带分解,然后按照一定的信噪分离规则来消除噪声,达到提高信噪比的目的．实验结果表明,与传统裂谱分析方法相比,该方法提高了消噪性能的稳定性,增强了湮没晶粒(或其他散射体)散射中的缺陷回波信号能力．     

基于提升小波变换的超声信号消噪技术

为了提高超声无损检测（UNDT）和无损评价（UNDE）中基础数据的信噪比（SNR）,提出了一种基于提升小波变换多分辨率分析的超声信号消噪新技术.在分析传统裂谱分析（SSP）方法原理及其局限性的基础上,通过采用提升小波变换多分辨率分析能力将原始超声回波信号进行子带分解,然后按照一定的信噪分离规则来消除噪声,达到提高信噪比的目的.实验结果表明,与传统裂谱分析方法相比,该方法增强了消噪性能的稳定性,提高了超声回波信号的信噪比.     

用于肿瘤治疗的高强度聚焦超声换能器及其温度场测量

高强度聚焦超声（HIFU）作为一种具有巨大潜力的、无损的、有效的肿瘤治疗手段,已得到普遍认同。本文介绍了所研制的HIFU治疗系统,对其关键部分高强度聚焦超声换能器的温度场特性,从理论上和实验上进行了深入的研究,并提出了超声声场的理论算法.     

磁流体超声检测的原理和应用

研究在超声检测中应用磁流体（ＭＦ）作为声触点。报道了ＭＦ的声学性能，它们对无损检测装置中声学通道的影响和超声扫描时流体的损失等有关问题所作探索性研究的结果。     

无损检测技术在装备中的应用

无损检测技术对构成系统的部件进行检测，确保装备可靠性，避免损失，提高部队战斗力，节约经费。本文介绍了无损检测技术在装备硷测中的作用，以及现代无损检测技术的发展，介绍了红外热成像法、超声检测法、涡流法和磁检测法在无损检测中的应用，并阐明了各种方法的优劣及适用领域。     

A method for radiation-force localized drug delivery using gas-filled lipospheres

We have developed a method using ultrasound and acoustically active lipospheres (AALs) that might be used to deliver bioactive substances to the vascular endothelium. The AALs consist of a small gas bubble surrounded by a thick oil shell and enclosed by an outermost lipid layer. The AALs are similar to ultrasound contrast agents: they can be nondestructively deflected using ultrasound radiation force, and fragmented with high-intensity ultrasound pulses. The lipid-oil complex might be used to carry bioactive substances at high concentrations. An optimized sequence of ultrasound pulses can deflect the AALs toward a vessel wall then disrupt them, painting their contents across the vascular endothelium. This paper presents results from a series of in vitro and ex vivo experiments demonstrating localization of a fluorescent model drug. In experiments using a human melanoma cell (A2085) monolayer, a specific radiation force-fragmentation ultrasound pulse sequence increased cell fluorescence more than 10-fold over no ultrasound or fragmentation pulses alone, and by 50% over radiation force pulses alone. We observe that dye transfer is limited to cells that are in the region of ultrasonic focus, indicating that the application of radiation force pulses to bring the delivery vehicle into proximity with the cell is required for successful adhesion of the vehicle fragments to the cell membrane. We also demonstrate dye transfer from flowing AALs, both in a mimetic vessel and in excised rat cecum. We believe that this method could be successfully used for drug delivery in vivo.     

Parametric Studies of Laser Generated Ultrasonic Signals in Ablative Regime: Time and Frequency Domains

A laser pulse incident on a material may generate ultrasound by means of two different phenomena: thermoelastic effect at low power density and ablation effect at high power density. Ablative generation of ultrasound is necessary for some critical applications such as on-line weld quality monitoring in which strong signals are required to compensate the elevated temperature and the long path length. While the waveform in time domain has been discussed extensively in the literature, there is little knowledge about the frequency components of laser ultrasound, although this information is necessary for practical applications. In this paper, analytical results from both thermoelastic and ablative regimes are reviewed. Laser ultrasonic signals (longitudinal waves and surfaces waves) generated by laser ablation are measured in a number of metal samples (2024 A1, 6061 A1, 7075 A1, mild steel, and copper) with a broadband laser interferometer. The frequency spectra are analyzed and compared for different thicknesses (50.8 mm, 25.4 mm, 12.7 mm, and 6.4 mm) and for different power densities. Hanning windowing is applied to the longitudinal pulses in time domain before frequency analysis is performed. The experimental data match the theoretical predictions very well. The results show that the frequency spectrum extends from 0 to 15 MHz, while the center frequency occurs near 2 MHz. The detailed distribution of the spectrum is dependent on the material, thickness, and laser power density.     

On the Optimization of the Transmitted Beam in Contrast-Enhanced Ultrasound Medical Imaging

The optimization of the ultrasound pulses transmitted by an echographic scanner is considered here in order to attain an insonification beam having a quasi-constant pressure profile over a large depth interval. An equalized pressure intensity allows a correct exploitation of the ultrasound contrast agent injected into the human body and, in turn, permits one to fully exploit its nonlinear response. A stochastic method of synthesis (based on the simulated annealing scheme) that is able to produce the desired transmission beam profile, acting simultaneously on the carrier frequencies of the acoustic pulses emitted by the array's transducers and on the apodizing weights, has been developed and assessed. The results obtained by the joint optimization, in terms of acoustic pressure profile, sidelobe level, and main lobe shape, are reported, discussed, and compared with those obtained by the traditional emission strategy and by the exclusive optimization of the apodizing weights or the carrier frequencies. A significant improvement of the ultrasound beam generated by the joint optimization over those generated by the exclusive optimization is pointed out.     

SURF imaging for contrast agent detection

A contrast agent detection method is presented that potentially can improve the diagnostic significance of ultrasound contrast agents. Second order ultrasound field (SURF) contrast imaging is achieved by processing the received signals from transmitted dual frequency band pulse complexes with overlapping high-frequency (HF) and low-frequency (LF) pulses. The transmitted HF pulses are used for image reconstruction, whereas the transmitted LF pulses are used to manipulate the scattering properties of the contrast agent. In the present paper, we discuss how SURF contrast imaging potentially can overcome problems and limitations encountered with available contrast agent detection methods, and we give a few initial examples of in vitro measurements. With SURF contrast imaging, the resonant properties of the contrast agent may be decoupled from the HF imaging pulses. This technique is thus especially interesting for imaging contrast bubbles above their resonance frequency. However, to obtain adequate specificity, it is typically necessary to estimate and correct for accumulative nonlinear effects in the forward wave propagation.     

Noninvasive surgery of prostate tissue by high-intensity focusedultrasound

Modern ultrasound transducer material and matching layer technology has permitted us to combine the ultrasound visualization capability with production of high-intensity focused ultrasound (HIFU) on the same ceramic crystal. This development has lead to the design of a transrectal probe for noninvasive surgery of prostate tissue by HIFU. The combined capability using the same ceramic crystal simplifies treatment planning, targeting, and monitoring of tissue before and during the HIFU treatment. This mechanically scanning transrectal probe was introduced for clinical use in 1992 for noninvasive surgery of the prostate to treat benign prostatic hyperplasia (BPH) condition. This paper reviews major steps progressing from conception to the present clinical trial status of the HIFU device. During these clinical studies generation of microbubbles and cavitation were observed. Data from microbubble generation, temperature monitoring in tissue, and autopsy of HIFU-treated animal prostates are presented. Results of human clinical studies are briefly summarized to indicate performance of the device     

Differential multiplexing of fiber bragg gratings by means of optical time domain refractometry

A differential method of detection and multiplexing of signals from fiber Bragg gratings based on optical time domain reflectometry is developed. The method is based on probing of a system of gratings by means of short laser pulses and measurement of the power of the resulting reflected pulses by means of standard fiber-optic reflectometry. The proposed method may find extensive use in the area of monitoring of deformation and temperature distributions by means of fiber-optic sensors based on Bragg gratings.     

Phase series echography with prior waveform distortion for evaluating posterior waveform distortion

We describe a pulse-echo ultrasound method for measuring nonlinear waveform distortion. First, two artificially distorted ultrasound pulses, one of which is transformed into the other by using a linear transform, are prepared prior to the measurement. The linear relationship does not hold for nonlinear propagation. Second, different initial-phase versions of the two pulses are separately transmitted to a specimen one after another, then the echoes with the same turnaround time are placed in order of the initial phase. The placed echoes, called a phase series, have complete information on the posterior waveform distortion. We formulate a waveform distortion index by using these two techniques. The waveform distortion index has a monotonic increasing relationship with the nonlinear parameter B/A. As an example application, we performed tissue characterization of boiled eggs. As a result, egg whites and yolks were clearly distinguished. This method should be useful for biological tissue characterization.     

Current-Temperature Diagram of Resistive States in Long Superconducting Niobium Filaments

By applying nanosecond current pulses to narrow superconducting Nb strips, we have observed the induced resistive states expected for quasi 1-D transport, namely localized phase-slip centres (PSC) and hot spots (HS). The current-controlled drive discriminates stable-in-time PSC structures near T _c from expanding HS at lower temperatures. HS-PSC exchange and return towards equilibrium are studied by using two-step current pulses. Remarkably, it appears that a hot spot never forms unless a PSC has first been nucleated. Then from a plot of the threshold currents I _c (T) and I _h (T), corresponding to PSC and HS, respectively, one can predict the response to current, temperature, or luminous excitation, as well as the effect of an applied magnetic field.     

Pulsed laser energy through fiberoptics for generation of ultrasound

Laser pulses are an effective, noncontacting technique for generating ultrasound in materials. However, for this approach to be practical, a versatile and safe method of delivering the laser pulses must be developed that eliminates exposed beams steered by mirrors and focused by lenses. Investigations by several researchers using fiberoptic delivery systems indicate that fiberoptics may be a viable method for the delivery of laser energy to generate acoustic energy. The main problem experienced with the fiberoptic delivery systems has been the inability to deliver high-energy, short-duration pulses via a fiber for thousands of pulses with no fiber damage and with constant energy output. This paper presents a technique for laser generation of sound using fiberoptics that continuously delivers sustained 20 ns pulses at a pulsing rate of 30 Hz from a doubled, Q-switched Nd:YAG laser operating at 532 nm with output energy from the fiber-optic system up to 26 mJ/pulse. The delivery system is used to excite ultrasound in a molten weld pool as part of a research effort to develop a noncontacting sensing system for real-time weld inspection.     

A new ultrasound contrast imaging approach based on the combination of multiple imaging pulses and a separate release burst

A new ultrasound contrast imaging technique is described that optimally employs the rupture of the contrast agent. It is based on a combination of multiple high frequency, broadband, imaging pulses and a separate release burst. The imaging pulses are used to survey the target before and after the rupture and release of free gas bubbles. In this way, both processes (imaging and release) can be optimized separately. The presence of the contrast agent is simply detected by correlating or subtracting the signal responses of the imaging pulses. Because the time delay between the imaging pulses can be very short, the subtraction is less affected by tissue motion and can be done in real time. In vitro measurements showed that by using a release burst, the detection sensitivity increased 12 to 43 dB for different types of contrast agents. In the presence of a moving phantom, the increase in sensitivity was 22 dB. This new method is very sensitive for contrast agent detection in fundamental imaging mode and, therefore, non-linear propagation effects do not limit the maximum obtainable agent-to-tissue ratio. However, because of the inherent destruction of the contrast agent, it has to operate in an intermittent way. Through experiments, we have demonstrated the potential of the method to achieve simultaneous high sensitivity for contrast detection, i.e., high agent-to-tissue ratio, and high spatial resolution performance for different types of contrast agents