一种新的超声成像方法振动声成像

文章介绍一种新的超声成像方法———振动声成像。首先从理论上分析了振动声成像的基本原理;然后分别介绍了该方法在钙化动脉血管成像、乳房中微钙化灶的检测以及受热疗和HIFU治疗的肿瘤组织焦斑检测等方面的应用;最后比较了振动声成像与传统超声成像不同点并指出了振动声成像独特的优势。     

低场永磁MRI导引聚焦超声肿瘤消融系统的研究

研究了低场永磁磁共振(Magnetic Resonance Imaging,MRI)导引的高强度聚焦超声(High Intensity Focused Ultrasound,HIFU)系统,使两者融合为一体。把磁共振的磁体设计为U字形,这样HIFU治疗头就可以放置于磁共振开口的上方;同时,在磁兼容、磁共振的快速成像、磁共振的测温、相控阵换能器、HIFU的治疗计划等方面做了一些研究。研究结果表明,在低场永磁的磁共振导引下,可以实现系统的所有设计功能,系统定位的图像比上一代B超导引的HIFU清晰,提高了实用性。     

High-frequency rapid B-mode ultrasound imaging for real-time monitoring of lesion formation and gas body activity during high-intensity focused ultrasound ablation

The goal of this study was to examine the ability of high-frame-rate, high-resolution imaging to monitor tissue necrosis and gas-body activities formed during high-intensity focused ultrasound (HIFU) application. Ex vivo porcine cardiac tissue specimens (n = 24) were treated with HIFU exposure (4.33 MHz, 77 to 130 Hz pulse repetition frequency (PRF), 25 to 50% duty cycle, 0.2 to 1 s, 2600 W/cm(2)). RF data from Bmode ultrasound imaging were obtained before, during, and after HIFU exposure at a frame rate ranging from 77 to 130 Hz using an ultrasound imaging system with a center frequency of 55 MHz. The time history of changes in the integrated backscatter (IBS), calibrated spectral parameters, and echo-decorrelation parameters of the RF data were assessed for lesion identification by comparison against gross sections. Temporal maximum IBS with +12 dB threshold achieved the best identification with a receiver-operating characteristic (ROC) curve area of 0.96. Frame-to-frame echo decorrelation identified and tracked transient gas-body activities. Macroscopic (millimetersized) cavities formed when the estimated initial expansion rate of gas bodies (rate of expansion in lateral-to-beam direction) crossed 0.8 mm/s. Together, these assessments provide a method for monitoring spatiotemporal evolution of lesion and gas-body activity and for predicting macroscopic cavity formation.     

Annular phased-array high-intensity focused ultrasound device for image-guided therapy of uterine fibroids

An ultrasound (US), image-guided high-intensity focused ultrasound (HIFU) device was developed for noninvasive ablation of uterine fibroids. The HIFU device was an annular phased array, with a focal depth range of 30-60 mm, a natural focus of 50 mm, and a resonant frequency of 3 MHz. The in-house control software was developed to operate the HIFU electronics drive system for inducing tissue coagulation at different distances from the array. A novel imaging algorithm was developed to minimize the HIFU-induced noise in the US images. The device was able to produce lesions in bovine serum albumin-embedded polyacrylamide gels and excised pig liver. The lesions could be seen on the US images as hyperechoic regions. Depths ranging from 30 to 60 mm were sonicated at acoustic intensities of 4100 and 6100 W/cm2 for 15 s each, with the latter producing average lesion volumes at least 63% larger than the former. Tissue sonication patterns that began distal to the transducer produced longer lesions than those that began proximally. The variation in lesion dimensions indicates the possible development of HIFU protocols that increase HIFU throughput and shorten tumor treatment times.     

The role of numerical simulation for the development of an advanced HIFU system

High-intensity focused ultrasound (HIFU) has been used clinically and is under clinical trials to treat various diseases. An advanced HIFU system employs ultrasound techniques for guidance during HIFU treatment instead of magnetic resonance imaging in current HIFU systems. A HIFU beam imaging for monitoring the HIFU beam and a localized motion imaging for treatment validation of tissue are introduced briefly as the real-time ultrasound monitoring techniques. Numerical simulations have a great impact on the development of real-time ultrasound monitoring as well as the improvement of the safety and efficacy of treatment in advanced HIFU systems. A HIFU simulator was developed to reproduce ultrasound propagation through the body in consideration of the elasticity of tissue, and was validated by comparison with in vitro experiments in which the ultrasound emitted from the phased-array transducer propagates through the acrylic plate acting as a bone phantom. As the result, the defocus and distortion of the ultrasound propagating through the acrylic plate in the simulation quantitatively agree with that in the experimental results. Therefore, the HIFU simulator accurately reproduces the ultrasound propagation through the medium whose shape and physical properties are well known. In addition, it is experimentally confirmed that simulation-assisted focus control of the phased-array transducer enables efficient assignment of the focus to the target. Simulation-assisted focus control can contribute to design of transducers and treatment planning.     

Detection of magnetic nanoparticles in tissue using magneto-motive ultrasound

The purpose of this study was to demonstrate the magneto-motive ultrasonic detection of superparamagnetic iron oxide (SPIO) nanoparticles as a marker of macrophage recruitment in tissue. The capability of ultrasound to detect SPIO nanoparticles (core diameter ～20?nm) taken up by murine liver macrophages was investigated. Eight mice were sacrificed two days after the intravenous administration of four SPIO doses (1.5, 1.0, 0.5, and 0.1?mmol Fe/kg body weight). In the iron-laden livers, ultrasound Doppler measurements showed a frequency shift in response to an applied time-varying magnetic field. M-mode scan and colour power Doppler images of the iron-laden livers also demonstrated nanoparticle movement under focused magnetic field excitation. In the livers of two saline injected control mice, no movement was observed using any ultrasound imaging modes. The results of our experiments indicate that ultrasound imaging of magneto-motive excitation is a candidate imaging modality to identify tissue-based macrophages containing SPIO nanoparticles.     

Single-element ultrasound transducer for combined vessel localization and ablation

This report describes a system that utilizes a single high-intensity focused ultrasound (HIFU) transducer for both the localization and ablation of arteries with internal diameters of 0.5 and 1.3 mm. In vitro and in vivo tests were performed to demonstrate both the imaging and ablation functionalities of this system. For imaging mode, pulsed acoustic waves (3 cycles for in vitro and 10 cycles for in vivo tests, 2 MPa peak pressure) were emitted from the 2-MHz HIFU transducer, and the backscattered ultrasonic signal was collected by the same transducer to calculate Doppler shifts in the target region. The maximum signal amplitude of the Doppler shift was used to determine the location of the target vessel. The operation mode was then switched to the therapeutic mode and vessel occlusion was successfully produced by high-intensity continuous HIFU waves (12 MPa) for 60 s. The system was then switched back to imaging mode for residual flow to determine the need for a second ablation treatment. The new system might be used to target and occlude unwanted vessels such as vasculature around tumors, and to help with tumor destruction.     

Implementation of vibro-acoustography on a clinical ultrasound system

Vibro-acoustography is an ultrasound-based imaging modality that uses two ultrasound beams of slightly different frequencies to produce images based on the acoustic response caused by harmonic ultrasound radiation force excitation at the difference frequency between the two ultrasound frequencies. Vibro-acoustography has demonstrated feasibility and usefulness in imaging of breast and prostate tissue. However, previous studies have been performed either in controlled water tank settings or a prototype breast scanner equipped with a water tank. To make vibro-acoustography more accessible and relevant to clinical use, we report here on the implementation of vibro-acoustography on a General Electric Vivid 7 ultrasound scanner. In this paper, we will describe software and hardware modifications that were performed to make vibro- acoustography functional on this system. We will discuss aperture definition for the two ultrasound beams and beamforming using a linear-array transducer. Experimental results from beam measurements and phantom imaging studies will be shown. The implementation of vibro-acoustography provides a step toward clinical translation of this imaging modality for applications in various organs including breast, prostate, thyroid, kidney, and liver.     

高强度聚焦超声(HIFU)技术迅速发展的五年

自2001年“首届高强度聚焦超声(HIFU)在医学中应用的国际学术交流会议”在我国重庆召开并同时成立了“国际超声治疗学会”五年来,HIFU技术得到了蓬勃发展!本文首先讨论了HIFU外科与传统超声热疗技术的本质区别,继而从HIFU工程研究、超声生物物理基础研究和HIFU技术的临床应用及国际学术发展等方面扼要地予以介绍以此展示我国科技工作者对国际HIFU发展的卓越贡献和面临的巨大挑战。     

高强度聚焦超声消融滋养动脉治疗子宫肌瘤的临床价值

目的：探讨高强度聚焦超声消融滋养动脉治疗子宫肌瘤的可行性及有效性。方法：47例直径4~10cm肌壁间肌瘤,高强度聚焦超声治疗前通过彩色多普勒及超声造影确定肌瘤滋养动脉的蒂,对该区域进行消融,观察治疗前后肌瘤内部彩色多普勒及超声造影等影像学变化、随访临床症状及并发症。结果：治疗后肌瘤体积有不同程度的缩小,瘤体假包膜环状血流信号消失,肌瘤内部处于持续无灌注状态,部分患者临床症状消失或明显改善。结论：HIFU消融滋养动脉治疗子宫肌瘤能够缩短治疗时间,减少并发症,是一种微创和有效的方法。     

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。     

超声影像方法在预测HIFU治疗子宫肌瘤疗效中的应用

子宫肌瘤是育龄期女性最常见的良性肿瘤,高强度聚焦超声(High Intensity Focused Ultrasound,HIFU)作为一种微创治疗技术,已经广泛运用于子宫肌瘤的治疗,但是对于某些特殊类型的肌瘤消融效率较低,并导致很多严重的并发症.这类肌瘤在二维灰阶超声、多普勒超声、超声造影方面有特殊的表现.对上述超声...     

Large improvement of the electrical impedance of imaging and high-intensity focused ultrasound (HIFU) phased arrays using multilayer piezoelectric ceramics coupled in lateral mode

With a change in phased-array configuration from one dimension to two, the electrical impedance of the array elements is substantially increased because of their decreased width (w)-to-thickness (t) ratio. The most common way to compensate for this impedance increase is to employ electrical matching circuits at a high cost of fabrication complexity and effort. In this paper, we introduce a multilayer lateral-mode coupling method for phased-array construction. The direct comparison showed that the electrical impedance of a single-layer transducer driven in thickness mode is 1/(n2(1/(w/t))2) times that of an n-layer lateral mode transducer. A large reduction of the electrical impedance showed the impact and benefit of the lateral-mode coupling method. A one-dimensional linear 32-element 770-kHz imaging array and a 42-element 1.45-MHz high-intensity focused ultrasound (HIFU) phased array were fabricated. The averaged electrical impedances of each element were measured to be 58 Ω at the maximum phase angle of -1.2° for the imaging array and 105 Ω at 0° for the HIFU array. The imaging array had a center frequency of 770 kHz with an averaged -6-dB bandwidth of approximately 52%. For the HIFU array, the averaged maximum surface acoustic intensity was measured to be 32.8 W/cm2 before failure.     

Use of modulated excitation signals in medical ultrasound. Part III: High frame rate imaging

This paper, the last from a series of three papers on the application of coded excitation signals in medical ultrasound, investigates the possibility of increasing the frame rate in ultrasound imaging by using modulated excitation signals. Linear array-coded imaging and sparse synthetic transmit aperture imaging are considered, and the trade-offs between frame rate, image quality, and SNR are discussed. It is shown that FM codes can be used to increase the frame rate by a factor of two without a degradation in image quality and by a factor of 5, if a slight decrease in image quality can be accepted. The use of synthetic transmit aperture imaging is also considered, and it is here shown that Hadamard spatial encoding in transmit with FM emission signals can be used to increase the frame rate by 12 to 25 times with either a slight or no reduction in signal-to-noise ratio and image quality. By using these techniques a complete ultrasound-phased array image can be created using only two emissions.     

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.     

Pulsed high-intensity focused ultrasound enhances the relative permeability of the blood-tumor barrier in a glioma-bearing rat model

The use of pulsed high-intensity focused ultrasound (HIFU) with an ultrasound contrast agent (UCA) has been shown to disrupt the blood-brain barrier (BBB) noninvasively and reversibly in the targeted regions. This study evaluated the relative permeability of the blood-tumor barrier (BTB) after sonication by pulsed HIFU. Entry into the brain of chemotherapeutic agents is impeded by the BBB even though the permeability of this barrier may be partially reduced in the presence of a brain tumor. F98 glioma-bearing rats were injected intravenously with Evans blue (EB) with or without BTB disruption induced by pulsed HIFU. Sonication was applied at an ultrasound frequency of 1 MHz with a 5% duty cycle, and a repetition frequency of 1 Hz. The accumulation of EB in brain tumor and the tumor-to-contralateral brain ratio of EB were highest after pulsed HIFU exposure. Sonication followed by EB injection showed a tumor-to-contralateral brain ratio in the target tumors which was about 2 times that of the control tumors. This research demonstrates that pulsed HIFU enhances the relative permeability of the BTB in glioma- bearing rats. The results of this pilot study support the idea that further evaluation of other treatment strategies, such as HIFU exposure in addition to combined chemotherapy or repeated pulsed HIFU exposure to increase delivery of drugs into brain tumors, might be useful.     

高强度聚焦超声联合全氟戊烷液滴在乳腺癌治疗增效中的实验研究

目的:探讨高强度聚焦超声(High-Intensity Focused Ultrasound,HIFU)联合全氟戊烷液滴(Perfluoropentane droplets,PFP),对小鼠乳腺癌4T1细胞治疗的增效作用。方法:制备PFP,检测其平均粒径及形态结构。试验设立三组:HIFU假照组,单纯HIFU治疗组,HIFU联合PFP治疗组。流式细胞仪检测HIFU分组治疗乳腺癌细胞后细胞存活率及死亡率;体内动物试验分组处理后,二维超声观察HIFU辐照前后肿瘤回声灰度变化情况,超声造影剂灌注缺损面积占总面积百分比评价不同治疗方式对裸鼠皮下移植瘤的消融能力。结果:所制备的PFP平均粒径为1.2μm,形态呈规则球形。细胞试验显示,HIFU联合PFP治疗组乳腺癌细胞死亡率(23.50±1.34)%显著高于单纯HIFU治疗组(14.34±0.55)%和HIFU假照组(11.76±0.62)%(P<0.05);动物试验显示HIFU联合PFP治疗组肿瘤消融面积占总面积百分比(84.03±4.47)%显著高于单纯HIFU治疗组(41.23±4.24)%(P<0.05),HIFU假照组无明显灌注缺损区域。结论:HIFU联合PFP可显著增强对乳腺癌细胞及组织的消融能力。     

An Intelligent Nanotheranostic Agent for Targeting,Redox‐Responsive Ultrasound Imaging,and Imaging‐Guided High‐Intensity Focused Ultrasound Synergistic Therapy

A novel multifunctional nanotheranostic agent with targeting, redox‐responsive ultrasound imaging and ultrasound imaging‐guided high‐intensity focused ultrasound (HIFU) therapy (MSNC‐PEG‐HA_SS‐PFH, abbreviated as MPH_SS‐PFH) capabilities is developed. The redox‐responsive guest molecule release and ultrasound imaging functions can be both integrated in such a “smart” theranostic agent, which is accomplished by the redox‐triggered transition from the crosslinking state to retrocrosslinking state of the grafted polyethylene glycol‐disulfide hyaluronic acid molecules on the particle surface when reaching a reducing environment in vitro. More importantly, under the tailored ultrasound imaging guiding, in vivo Hela tumor‐bearing nude mice can be thoroughly and spatial‐accurately ablated during HIFU therapy, due to the targeted accumulation, responsive ultrasound imaging guidance and the synergistic ablation functions of nanotheranostic agent MPH_SS‐PFH in the tumors. This novel multifunctional nano‐platform can serve as a promising candidate for further studies on oncology therapy, due to its high stability, responsive and indicative ultrasound imaging of tumors, and enhanced HIFU therapeutic efficiency and spatial accuracy under ultrasound‐guidance.     

Effects of gas pockets on high-intensity focused ultrasound field

The paper describes experimental and numerical studies of the effects of gas pockets on a high-intensity focused ultrasound (HIFU) field. Air bubbles ranging from 0.8 to 2.4 mm in radius were produced in transparent polyacrylamide tissue-mimicking gels. A single-element 3.5-MHz HIFU transducer was used to sonicate the gel phantoms. The changes in the HIFU beam pattern for air bubbles at different positions were visualized by the Schlieren method. Quantitative measurements of pressure at the HIFU focus by a calibrated needle hydrophone showed considerable reduction in the focal pressure with the presence of an air pocket. The presence of a single 1.2-mm-radius air bubble, at a 5 mm axial pre-focal position, reduced the focal intensity by 50% and increased the lateral focal dimension by 50%. For air bubbles at pre-focal position close to the focus, lesion formation was observed not at the theoretical focus, but in front of the air bubble and the air bubble became a barrier for the post-focal ultrasound propagation. The effects of reflection were simulated numerically and were compared with the experiments. The results can be used as guidelines for evaluation of potential safety concerns produced by trapped gas-pockets in various HIFU therapies.     

高强度聚焦超声损伤兔肌肉组织的超声影像学变化的初步研究

探讨高强度聚焦超声损伤兔肌肉组织的超声图像变化。采用高强度聚焦超声经皮照射20只新西兰大白兔双侧后肢肌肉,其中18只于照射前1d、照射后10min、照射后1d,3d,7d,14d,21d,28d进行二维超声、彩色多普勒和能量多普勒超声检查,并于照射后28天处死后测量凝固灶大小。另2只分别于照射后1d及照射后50d解剖,行病理学检查。(1)HIFU照射后凝固灶外周可见强回声带至低回声带的演变过程。(2)HIFU照射后第1d,测量的凝固灶体积最大(1476.59±308.64mm3),第3d～第21d,凝固灶体积逐渐缩小(612.47±127.98mm3)。第28d凝固灶体积最小(343.29±54.79mm3)。超声检查在兔肌肉组织HIFU照射后的随访中发挥了重要的作用,为监测HIFU治疗人体软组织肿瘤超声图像的变化提供了实验依据。