用于光声内窥的中空声透镜聚焦PVDF换能器的研究

针对目前光声内窥成像中常用的基于压电陶瓷的中空聚焦超声换能器制作工艺复杂、定制费用高的问题,本文利用PVDF压电薄膜声阻抗低、频响宽、易于加工等优点,以及环氧树脂介于PVDF和生物组织的声阻抗特性,制作了一款基于110μm PVDF压电薄膜的中空声透镜聚焦超声换能器。声场测试实验表明,该换能器纵向分辨率为0.22 mm,焦点处横向分辨率约为0.65 mm,和理论设计值相符。随后又利用多模光纤和宽带介质膜反射镜,通过仿体实验对其内窥成像效果进行了初步验证。相比于基于压电陶瓷的聚焦超声换能器,本方案极大的降低了内窥光声成像中所需的中空聚焦超声换能器的设计和制作成本,方便了实验室条件下内窥光声系统的开发。     

高强度聚焦超声治疗中测温技术的研究

高强度聚焦超声(HIFU)是一种新兴的非侵入性局部治疗技术,它以其治疗中安全、有效、无创的优点被医学界所关注.然而,对生物组织温度的准确测量是制约该治疗技术发展的关健环节,因此,HIFU治疗中的测温技术成为人们关注的热点.本文主要介绍了近年来在HIFU治疗中,测温技术的研究现状以及两大测温方法(无损测温和有损测温),并对测温技术的发展进行展望.     

面向经颅聚焦超声的多阵元相控阵关键技术

经颅聚焦超声是一种有效的神经调控技术，具有非侵入性、聚焦靶点多和焦点可调控等优势。但由于颅骨的强声衰减和非均质特性，聚焦超声经颅后存在焦点偏移、焦域能量不足以及颅骨烫伤等问题。多阵元超声相控阵可以修正超声经颅后的相位偏差和幅值衰减，实现准确、有效的颅内聚焦。本文首先介绍了换能器的阵元排布方式，进一步归纳了相控阵激励信号的调控方法，最后对其基础研究和临床应用进行了回顾与展望。     

高强度聚焦超声的原理和应用

高强度聚焦超声(High Intensity Focused Ultrasound,简称HIFU)技术是近年来蓬勃发展起来的一种无创外科工具,并已应用于临床的治疗中.该技术的主要生物效应包括:热效应、空化效应和机械效应.该技术的应用已经涉及到肿瘤学、过敏性鼻炎、泌尿学等方面.本文就HIFU技术的应用、现状和前景作以综述.     

肿瘤的超声波治疗

文中就超声波热疗,高强度聚焦超声以及低频超声波在肿瘤治疗中的应用进行了描述。早期主要是利用超声波的热效应来治疗肿瘤,近年来兴起的高强度聚焦超声是热疗法的另一发展。它瞬间使肿瘤组织温度升至65℃以上,导致靶区组织凝固和坏死来达到对肿瘤的“热切除”,是一种安全、有效的肿瘤治疗手段,具有无限潜力。尽管低频超声治疗肿瘤的机制尚不明了,但因其可以诱导细胞凋亡,为肿瘤的治疗提供了新的途径,其治疗作用已受到重视。     

肿瘤的超声波治疗

文中就超声波热疗,高强度聚焦超声以及低频超声波在肿瘤治疗中的应用进行了描述。早期主要是利用超声波的热效应来治疗肿瘤,近年来兴起的高强度聚焦超声是热疗法的另一发展。它瞬间使肿瘤组织温度升至65℃以上,导致靶区组织凝固和坏死来达到对肿瘤的“热切除”,是一种安全、有效的肿瘤治疗手段,具有无限潜力。尽管低频超声治疗肿瘤的机制尚不明了,但因其可以诱导细胞凋亡,为肿瘤的治疗提供了新的途径,其治疗作用已受到重视。     

声衰减测量法对人体内软组织的应用

一、声衰减测量中几个误差的原因及其修正 按目前超声诊断仪器情况,用各种方法在各种条件下测量体内软组织的声衰减,常会受到各种干扰而引入测量误差,必须作相应的修正。其误差源主要有:1)衍射效应;2)相位相消效应;3)镜像反射效应;4)时间增益控制;5)聚焦效应;6)对数压缩等等。如衍射效应如果不修正,造成的误差可达30％。 1.衍射效应 衰减效应是衍射效应(超声场的不均匀     

经颅超声在帕金森病治疗中的应用

帕金森病是仅次于阿尔茨海默病的第二大常见神经退行性疾病，临床常用的治疗方法为药物治疗和神经外科手术。然而，目前尚无确切的方法阻止疾病的发展，新的治疗方案亟待探索。超声波因其具有非侵入性、高空间分辨率和高穿透性的特点，现已被广泛关注并用于帕金森病的治疗之中。近些年兴起的磁共振成像（MRI）引导聚焦超声消融技术、MRI引导聚焦超声开放血脑屏障给药技术、低强度聚焦超声调控技术和声遗传技术都已经在临床研究或临床前动物模型中取得可喜的成果。本文从以上4个方面综述近5年经颅超声技术在帕金森病治疗中的主要进展，并对其中的一些科学问题进行了探讨，以期为研究帕金森病发病机制和治疗方案的同行提供参考。     

昆虫消化酶抑制剂与害虫防治

生物源昆虫消化酶抑制剂主要包括蛋白酶抑制剂和淀粉酶抑制剂。昆虫消化酶抑制剂能通过降低或抑制昆虫蛋白酶或淀粉酶的活性,而影响昆虫的正常生长发育,使其生长缓慢,虚弱,甚至导致死亡。本文就生物源昆虫消化酶抑制剂对昆虫生化、生理代谢和生长发育的影响,消化酶抑制剂的作用机理,植物中昆虫消化酶抑制剂的诱导产生等进行了介绍。同时,探讨了生物源蛋白酶和淀粉酶抑制剂在害虫防治中的应用前景。     

聚焦超声辐射高血脂大鼠涌泉穴对血脂水平的影响

目的研究聚焦超声辐射涌泉穴对血脂的影响.方法采用高脂饲料喂养建立高血脂大鼠模型,通过聚焦超声辐射高血脂模型大鼠涌泉穴,测定大鼠血清总胆固醇(tota cholesterol, TC)、甘油三脂 (triacylglycerol, TG)、高密度脂蛋白胆固醇(high density lipoprotein, HDL-c)和低密度脂蛋白胆固醇(low density lipoprotein, LDL-c)等指标.结果检测血清TC、TG、HDL-C、LDL-C水平,聚焦超声辐照涌泉穴可明显降低高血脂模型大鼠血清TC、TG(P＜0.05),而超声治疗组和针刺组无明显差异.结论聚焦超声辐射高血脂大鼠的涌泉穴位,可明显降低TC、TG,有调节血脂的作用.     

Detection of a Novel Mechanism of Acousto-Optic Modulation of Incoherent Light

A novel form of acoustic modulation of light from an incoherent source has been detected in water as well as in turbid media. We demonstrate that patterns of modulated light intensity appear to propagate as the optical shadow of the density variations caused by ultrasound within an illuminated ultrasonic focal zone. This pattern differs from previous reports of acousto-optical interactions that produce diffraction effects that rely on phase shifts and changes in light directions caused by the acoustic modulation. Moreover, previous studies of acousto-optic interactions have mainly reported the effects of sound on coherent light sources via photon tagging, and/or the production of diffraction phenomena from phase effects that give rise to discrete sidebands. We aimed to assess whether the effects of ultrasound modulation of the intensity of light from an incoherent light source could be detected directly, and how the acoustically modulated (AOM) light signal depended on experimental parameters. Our observations suggest that ultrasound at moderate intensities can induce sufficiently large density variations within a uniform medium to cause measurable modulation of the intensity of an incoherent light source by absorption. Light passing through a region of high intensity ultrasound then produces a pattern that is the projection of the density variations within the region of their interaction. The patterns exhibit distinct maxima and minima that are observed at locations much different from those predicted by Raman-Nath, Bragg, or other diffraction theory. The observed patterns scaled appropriately with the geometrical magnification and sound wavelength. We conclude that these observed patterns are simple projections of the ultrasound induced density changes which cause spatial and temporal variations of the optical absorption within the illuminated sound field. These effects potentially provide a novel method for visualizing sound fields and may assist the interpretation of other hybrid imaging methods.     

Transmission loss patterns from acoustic harassment and deterrent devices do not always follow geometrical spreading predictions

Acoustic harassment and deterrent devices have become increasingly popular mitigation tools for negotiating the impacts of marine mammals on fisheries. The rationale for their variable effectiveness remains unexplained, but high variability in the surrounding acoustic field may be relevant. In the present study, the sound fields of one acoustic harassment device and three acoustic deterrent devices were measured at three study sites along the Scandinavian coast. Superimposed onto an overall trend of decreasing sound exposure levels with increasing range were large local variations in the sound level for all sources in each of the environments. This variability was likely caused by source directionality, inter-ping source level variation and multipath interference. Rapid and unpredictable variations in the sound level as a function of range deviated from expectations derived from spherical and cylindrical spreading models and conflicted with the classic concept of concentric zones of increasing disturbance with decreasing range. Under such conditions, animals may encounter difficulties when trying to determine the direction to and location of a sound source, which may complicate or jeopardize avoidance responses.     

Numerical study of the effect of ultrasound frequency on temperature distribution in layered tissue

The high intensity focused ultrasound (HIFU) technology can produce therapeutic benefits in deep-seated tissues of interest, selectively and noninvasively. In order to control the treatment process, it is important to recognize the heat generation in biological tissue and the parameters that have an effect on temperature rising. This study investigates the influence of frequency and source intensity on temperature distribution during high-intensity focused ultrasound (HIFU). A nonlinear full wave equation model is simulated to compute the pressure field. Additionally, the absorbed coefficient of tissue is added to the nonlinear equations to simulate accurately the wave propagation in tissue with high absorbed coefficient. In addition, temperature distribution was solved by the Pennes bio-heat equation. Conclusively, frequencies in the range of 1–1.5 MHz are prescribed to have maximum heat absorption in the focal region.     

Foraging and mate-finding in the silver Y moth, Autographa gamma (Lepidoptera: Noctuidae) under the risk of predation

Animal foraging and reproductive behaviour is influenced by other simultaneous demands such as predator avoidance. The trade-offs between these demands may depend on sex or mating experience. This study demonstrates that the olfactory-mediated foraging and mate-seeking behaviours in the silver Y moths, Autographa gamma , are affected by auditory cues mimicking their bat predators. Both males and females changed their foraging behaviour under simulated predation risk. Fewer moths reached the odour source following sound stimulation and the time to find the odour source increased by up to 250%. However, there were no significant differences between male and female ability to reach the plant odour source or the duration of the flight towards the source when stimulated with ultrasound. Hence females are not more cautious than males when observed in the same behavioural context. Risk-taking in males was independent of whether they were flying toward a flower odour or sex pheromones having equal attractive value. This indicates that the trade-off between olfactory and acoustic cues is independent the type of odour. Mated females were not as strongly affected by sound as non-mated, indicating that flower odours have a higher adaptive value for mated females, suggesting that some processes following mating experience influence the trade-off between flower odours and simulated bat sounds.     

Preliminary background indoor EMF measurements in Greece

The main purpose of this work was to investigate the fluctuation of Greek indoor electromagnetic field (EMF) intensity values and identify peaks that might occur. The scientific interest is mainly focused on the bands of extremely low-frequency (ELF) magnetic fields and radiofrequency (RF) electric fields which have been suggested to be possibly carcinogenic to humans by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR).Electromagnetic radiation (EMR) measurements were performed in a variety of indoor dwellings, in Attica and in the islands of Zakynthos and Lesvos.A total number of 4540 measurements were taken in a wide frequency range (50 Hz–2100 MHz) of which 3301 in Attica, 963 in Lesvos and 276 in Zakynthos.Statistical analysis of the data revealed specific statistically significant differences between the mean values of the electric (ELF and RF) but not the magnetic (ELF) field strengths measured at different distances from the EMF source, as well as between some of the mean values of the RF electric field at different bands. Some statistically significant differences between mean electric field values at different geographic locations were also identified.As far as the RF electric field is concerned, the maximum values, in most cases, were below 0.5 V/m, however increased values above 1 V/m and up to 5.6 V/m were occasionally observed. The ELF magnetic field values were lower than 1 μT. It may be concluded that overall, the observed indoor EMF intensity values remained well below domestic and European established limits.     

The role of cavitation in liposome formation

Liposome size is a vital parameter of many quantitative biophysical studies. Sonication, or exposure to ultrasound, is used widely to manufacture artificial liposomes, yet little is known about the mechanism by which liposomes are affected by ultrasound. Cavitation, or the oscillation of small gas bubbles in a pressure-varying field, has been shown to be responsible for many biophysical effects of ultrasound on cells. In this study, we correlate the presence and type of cavitation with a decrease in liposome size. Aqueous lipid suspensions surrounding a hydrophone were exposed to various intensities of ultrasound and hydrostatic pressures before measuring their size distribution with dynamic light scattering. As expected, increasing ultrasound intensity at atmospheric pressure decreased the average liposome diameter. The presence of collapse cavitation was manifested in the acoustic spectrum at high ultrasonic intensities. Increasing hydrostatic pressure was shown to inhibit the presence of collapse cavitation. Collapse cavitation, however, did not correlate with decreases in liposome size, as changes in size still occurred when collapse cavitation was inhibited either by lowering ultrasound intensity or by increasing static pressure. We propose a mechanism whereby stable cavitation, another type of cavitation present in sound fields, causes fluid shearing of liposomes and reduction of liposome size. A mathematical model was developed based on the Rayleigh-Plesset equation of bubble dynamics and principles of acoustic microstreaming to estimate the shear field magnitude around an oscillating bubble. This model predicts the ultrasound intensities and pressures needed to create shear fields sufficient to cause liposome size change, and correlates well with our experimental data.     

一种袖珍式胎心音仪的设计和实现

研制出一种简单实用、安全可靠并具有广阔市场前景的袖珍式胎心音仪。该仪器利用超声多普勒原理,用超声探头从母体腹部提取胎儿心音信号,经过信号解调及低频放大、音频功率放大等处理,然后由耳机及扬声器输出胎心音。     

Information generated by the moving pinnae of Rhinolophus rouxi: tuning of the morphology at different harmonics

Bats typically emit multi harmonic calls. Their head morphology shapes the emission and hearing sound fields as a function of frequency. Therefore, the sound fields are markedly different for the various harmonics. As the sound field provides bats with all necessary cues to locate objects in space, different harmonics might provide them with variable amounts of information about the location of objects. Also, the ability to locate objects in different parts of the frontal hemisphere might vary across harmonics. This paper evaluates this hypothesis in R. rouxi, using an information theoretic framework. We estimate the reflector position information transfer in the echolocation system of R. rouxi as a function of frequency. This analysis shows that localization performance reaches a global minimum and a global maximum at the two most energetic frequency components of R. rouxi call indicating tuning of morphology and harmonic structure. Using the fundamental the bat is able to locate objects in a large portion of the frontal hemisphere. In contrast, using the 1st overtone, it can only locate objects, albeit with a slightly higher accuracy, in a small portion of the frontal hemisphere by reducing sensitivity to echoes from outside this region of interest. Hence, different harmonic components provide the bat either with a wide view or a focused view of its environment. We propose these findings can be interpreted in the context of the foraging behaviour of R. rouxi, i.e., hunting in cluttered environments. Indeed, the focused view provided by the 1st overtone suggests that at this frequency its morphology is tuned for clutter rejection and accurate localization in a small region of interest while the finding that overall localization performance is best at the fundamental indicates that the morphology is simultaneously tuned to optimize overall localization performance at this frequency.     

体外冲击波碎石焦点区域声压分布的时域有限差分法仿真研究

目的:研究体外冲击波碎石(Extracorporeal shock wave lithotropisy,ESWL)治疗中不同厚度人体组织对ESWL焦点区域大小、位置和声压分布的影响,为ESWL治疗计划的制定提供理论依据.方法:以Reichenberger的ESWL水中实验为参照例,分别建立三维单一人体组织和多层复合人体组织仿真模型,用时域有限差分(Finite Difference Time Domain,FDTD)数值仿真法,数值仿真ESWL治疗中形成的焦点区域.结果:高强度聚焦超声波在人体脂肪、肌肉层中形成的实际焦点区域大小、位置和焦点区域声压分布随着人体脂肪、肌肉层厚度的变化而变化.结论:ESWL治疗过程中由于人体组织厚度的不同,高强度聚焦超声非线性传播而形成的焦距和最大声压不同,对于不同体态的患者在ESWL治疗时,应该采用不同的焦距设定方法.