High-speed ultrasound volumetric imaging system. I. Transducer design and beam steering

Transducer design and phased array beam steering are developed for a volumetric ultrasound scanner that enables the 3-D visualization of dynamic structures in real time. The authors describe the design considerations and preliminary evaluation of a high-speed, online volumetric ultrasound imaging system that uses the principles of pulse-echo, phased array scanning with a 2-D array transducer. Several 2-D array designs are analyzed for resolution and main lobe-side lobe ratio by simulation using 2-D fast Fourier transform methods. Fabrication techniques are described for 2-D array transducer. Experimental measurements of pulse-echo point spread responses for 2-D arrays agree with the simulations. Measurements of pulse-echo sensitivity, bandwidth, and crosstalk are included     

Computer-aided reverse engineering of the human musculoskeletal system

The objective of this study is to extend the applications of reverse engineering technology from manufacturing industries to the biomedical industry. By obtaining nearly exact geometric data of human tissues, such as bones, tendons, and ligaments, in a high-speed and inexpensive manner, potentially groundbreaking research becomes possible for applications in injury rehabilitation, injury prevention and strengthening. Previous applications of reverse engineering technologies in the biomedical community have dealt largely with prosthetic design and plastic surgery. This study expands this research to include muscular and skeletal applications. The primary advantage provided by scanning technologies is an improved quality of data. Secondly, the time investment for the medical researcher is greatly reduced. And finally, the use of a scanning technology will occasionally provide a less expensive alternative to the medical imaging counterparts. The goal of the research is to develop guidelines and methodologies for reverse engineering human structures.     

Computer-aided reverse engineering of the human musculoskeletal system

The objective of this study is to extend the applications of reverse engineering technology from manufacturing industries to the biomedical industry. By obtaining nearly exact geometric data of human tissues, such as bones, tendons, and ligaments, in a high-speed and inexpensive manner, potentially groundbreaking research becomes possible for applications in injury rehabilitation, injury prevention and strengthening. Previous applications of reverse engineering technologies in the biomedical community have dealt largely with prosthetic design and plastic surgery. This study expands this research to include muscular and skeletal applications. The primary advantage provided by scanning technologies is an improved quality of data. Secondly, the time investment for the medical researcher is greatly reduced. And finally, the use of a scanning technology will occasionally provide a less expensive alternative to the medical imaging counterparts. The goal of the research is to develop guidelines and methodologies for reverse engineering human structures.     

Low-cost, scalable laser scanning module for real-time reflectance and fluorescence confocal microscopy

We present a low-cost, high-speed, retrofitted laser scanning module for microscopy. The cage-mounted system, with various available fiber-coupled sources, offers a real-time imaging alternative to costly commercial systems with capabilities for conventional or confocal reflectance and fluorescence applications as well as advanced laser scanning microscopy implementations. Reflectance images of a resolution target and confocal images of fluorescent polystyrene beads are presented for system characterization. Confocal fluorescence image stacks of T84 epithelial cancer cells are presented to demonstrate application to biological studies. This laser scanning module is a flexible, scalable, high-speed alternative to commercial laser scanning systems suitable for applications requiring a simple imaging tool and for teaching laboratories.     

Supercontinuum dynamically visualizes a dividing single cell

During cell division, various organelles behave dynamically. Visualization of these dynamic behaviors of organelles is a promising one step forward for understanding life at the molecular level. One- or two-photon excited fluorescence microscopy has so far been used for visualizing these cell dynamics. The fluorescent probe introduced into a living cell can visualize the spatial distribution of a target molecule in real time, enabling the tracing of cell dynamics at the molecular level. Introducing a fluorescent probe into a cell, however, may alter the physical and chemical conditions of the cell. Here we show a new method for direct (no need for staining cells) visualization of living cell processes with coherent anti-Stokes Raman scattering (CARS) spectroscopy. A new light source, supercontinuum generated from a photonic crystal fiber, has facilitated ultrabroadband (>3500 cm(-1)) multiplex CARS spectroscopy and imaging with high molecular specificity. Using this multiplex CARS technique, we have been successful in tracing the whole cell division process, the splitting of a mother cell into two daughter cells, appearance and disappearance of septum, and dynamic distribution changes of organelles consisting of lipid membrane. The supercontinuum has also facilitated simultaneous measurement of the CARS and two-photon excited fluorescence (TPEF) spectra, enabling what we call multiple nonlinear spectral imaging. Three-dimensional image reconstruction of a living cell with high speed is now possible to elucidate more detailed molecular-level dynamics inside a dividing living cell.     

纳秒级紫外/软X射线条纹相机

纳秒级紫外/软X射线条纹相机是一种利用高速扫描电路实现将纳秒级光信号转化为图像信 号的高速图像设备,它主要包括了条纹管、高速高压扫描单元、高压单元以及控制记录单元等部分。系统设计中采用近贴聚焦电子光学系统和雪崩管电路使得目前所能达到的指标为:能谱响应范围紫外～1keV,空间分辨力静态15Lp/mm,动态5Lp/mm,时间分辨力为500ps。     

基于高速A／D卡的全波形采集超声自动检测系统

设计了一种全波形采集超声自动检测系统,实现了A,B,C 3种扫描方式且具有记录被检材料上所有检测点超声A扫描波形的功能,支持材料超声检测、评价技术研究.该系统由高速A/D卡、超声检测仪、自动扫描器、运动控制系统和CSCAN软件等组成,作为核心部件的高速A/D卡选用PCI-9820型,负责从超声检测仪采集A扫描波形信号.自动扫描过程中,A/D卡与超声检测仪、运动控制系统之间通过硬件信号实现同步,使A扫描波形数据的采集与被检材料上声传播的渡越时间、预定测量点位置相对应,采集得到的A扫描波形数据通过A/D卡的板载SDRAM及DMA功能异步传输至计算机内存,并由CSCAN软件进一步实现数据压缩、滤波、存储以及不同方式成像等处理.测试结果证明,该系统运行速度快,成像精度高且性能稳定. 更多还原     

High speed data collection system for magnetic field imaging by CTtechnique

A method of high-speed data collection used in imaging the magnetic-field distribution leaking from magnetic devices along any plane is proposed. The method uses the computed tomography (CT) technique. A high-speed data collection system developed for demonstrating the method is described. An image of the magnetic field is reconstructed from projection data provided by the voltage induced in the sensors of a line conductor and a rectangular coil moving in the plane of observation. Rotational scanning of the sensors is used for collecting the projections so that data-acquisition time can be reduced. To demonstrate the performance of the system, the reconstructed images of the magnetic-field distributions made by some permanent magnets are shown     

Femtosecond imaging of surface plasmon dynamics in a nanostructured silver film

Light interacting with nanostructured metals excites the collective charge density fluctuations known as surface plasmons (SP). Through excitation of the localized SP eigenmodes incident light is trapped on the nanometer spatial and femtosecond temporal scales and its field is enhanced. Here we demonstrate the imaging and quantum control of SP dynamics in a nanostructured silver film. By inducing and imaging the nonlinear two-photon photoemission from the sample with a pair of identical 10-fs laser pulses while scanning the pulse delay, we record a movie of SP fields at a rate of 330-attoseconds/frame.     

High-speed multiresolution scanning probe microscopy based on Lissajous scan trajectories

A novel scan trajectory for high-speed scanning probe microscopy is presented in which the probe follows a two-dimensional Lissajous pattern. The Lissajous pattern is generated by actuating the scanner with two single-tone harmonic waveforms of constant frequency and amplitude. Owing to the extremely narrow frequency spectrum, high imaging speeds can be achieved without exciting the unwanted resonant modes of the scanner and without increasing the sensitivity of the feedback loop to the measurement noise. The trajectory also enables rapid multiresolution imaging, providing a preview of the scanned area in a fraction of the overall scan time. We present a procedure for tuning the spatial and the temporal resolution of Lissajous trajectories and show experimental results obtained on a custom-built atomic force microscope (AFM). Real-time AFM imaging with a frame rate of 1 frame s?1 is demonstrated.     

Two-photon excitation fluorescence microscopy with a high depth of field using an axicon

In conventional two-photon excitation fluorescence microscopy, the numerical aperture of the objective determines the lateral resolution and the depth of field. In some situations, as with functional imaging of dynamic events distributed in live biological tissue, an improved temporal resolution is needed; as a consequence, it is imperative to use optics with a high depth of field to simultaneously image objects at different axial positions. With a conventional microscope objective, increasing the depth of field is achieved at the expense of lateral resolution. To overcome this limitation, we have incorporated an axicon in a two-photon excitation fluorescence microscopy system; measurements have shown that an axicon provides a depth of field in excess of a millimeter, while the lateral resolution is maintained at the micrometer scale. Thus axicon-based two-photon microscopy has been shown to yield a high-resolution projection image of a sample with a single 2D scan of the laser beam while maintaining the improved tissue penetration typical of two-photon microscopy.     

基于压电扫描管动态特性分析的AFM成像方法研究

针对原子力显微镜(AFM)在高速扫描下成像误差大的缺点,提出了一种基于压电扫描管动态特性的改进成像方法,并对这种成像方法的性能进行了理论分析和实验验证.分析和实验结果表明,该成像方法可以较好地处理压电扫描管的动态特性,有效地提高 AFM 在 Z 方向上的成像精度,因此得到的扫描图像能够更加真实地反映样品的形貌.     

Monte carlo analysis of two-photon fluorescence imaging through a scattering medium

The behavior of two-photon fluorescence imaging through a scattering medium is analyzed by use of the Monte Carlo technique. The axial and transverse distributions of the excitation photons in the focused Gaussian beam are derived for both isotropic and anisotropic scatterers at different numerical apertures and at various ratios of the scattering depth with the mean free path. The two-photon fluorescence profiles of the sample are determined from the square of the normalized excitation intensity distributions. For the same lens aperture and scattering medium, two-photon fluorescence imaging offers a sharper and less aberrated axial response than that of single-photon confocal fluorescence imaging. The contrast in the corresponding transverse fluorescence profile is also significantly higher. Also presented are results comparing the effects of isotropic and anisotropic scattering media in confocal reflection imaging. The convergence properties of the Monte Carlo simulation are also discussed.     

Imaging flaws in soldered joints of integrated circuits using an ultrasound electronic scanning technique

An electronic scanning c-scopic 25-MHz ultrasonic imaging system has been developed for high-speed precise testing of electronic parts such as ICs. Two-dimensional scanning is performed, one axis being electronic and the other mechanical. A focused beam is formed so as to be a longitudinal wave in solid samples. Voids equal to or larger than 0.2 mm in diameter in the solder are accurately detected and their sizing data agree within 0.1 mm with those measured visually through an optical microscope after destruction. The imaging performance was examined for fatigue cracks in soldered joints. In 1000 heat cycles between -55 and +150 degrees C, cracks resulted in the soldered joints of most samples, and their growth was clearly visible. By comparing the images with those observed by a scanning electron microscope, minimum cracks of 1-mum separation were found to be detectable. The c-scan imaging of a 14x14 mm area of the joints was completed in 1.2 s by the system.     

基于复用模型的高速光电扫描仪性能的改进研究

提出了一种基于FPGA和DDRⅡ的JPEG图像压缩模式。在此基础上完成了A3高速光电扫描仪的设计与实现,解决了高速扫描仪中硬件资源与扫描速度相互制约的问题。通过内外存储器流水式复用模型,在降低片上RAM消耗的同时构建灵活、快速的大数据量存储与传输模式。采用高效的分时复用数据链路实现JPEG图像压缩,进一步提高硬件模块的压缩和传输速度。对采用中低端FPGA芯片设计的A3高速扫描仪的测量结果表明,在300 dpi分辨率下扫描A3幅面纸张的速度可达140面/min,扫描延时小于1 ms,压缩前后峰值信噪比高达86.9dB,完全满足高端高速扫描仪的要求。该模式的实现极大地降低了高端高速光电扫描仪对于硬件资源的要求,也可推广应用到其它幅面的高速光电扫描仪中。     

Random access three-dimensional two-photon microscopy

We propose a two-photon microscope scheme capable of real-time, three-dimensional investigation of the electric activity pattern of neural networks or signal summation rules of individual neurons in a 0.6 mm x 0.6 mm x 0.2 mm volume of the sample. The points of measurement are chosen according to a conventional scanning two-photon image, and they are addressed by separately adjustable optical fibers. This allows scanning at kilohertz repetition rates of as many as 100 data points. Submicrometer spatial resolution is maintained during the measurement similarly to conventional two-photon microscopy.     

Real-time imaging of protein internalization using aptamer conjugates

Angiogenin is a potent angiogenic factor that is known to play an important role in tumor angiogenesis. In this paper, we investigate the cellular internalization of angiogenin conjugated with its highly specific aptamer. By using fluorophore-labeled aptamer and confocal laser scanning microscopy, we have developed a novel and simple method by which to visualize the real-time process of angiogenin internalization. Specifically, when aptamer-angiogenin conjugates were added into cell cultures, conjugates could be selectively bound to HUVE cells (human umbilical vein endothelial cells) and MCF-7 cells (human breast cancer cells). Nuclear staining and Z-axis scanning studies demonstrated that the aptamer-angiogenin conjugates were internalized to intracellular organelles, and dynamic confocal imaging studies indicated that the conjugates were quickly internalized. These results provide the first evidence that a fluorophore-labeled aptamer can be used as a fluorescent probe to visualize the spatiotemporal process of protein internalization in real time.     

用于集成电路制造中良率监控的国产化电子束缺陷检测设备

电子束缺陷检测设备是集成电路制造中不可或缺的良率监控设备。其基本原理是结合扫描电镜成像技术、高精度运动控制技术、高速图像数据处理和自动检测分类算法等,在集成电路制造环节对晶圆及集成电路的物理缺陷和电性缺陷进行检测。为填补此类设备国产化空白,通过自主研发,突破了高分辨力大视场扫描成像、三维高精度定位补偿、智能化缺陷检测和分类等技术难点,研发了国产化电子束缺陷检测设备并应用于集成电路产线,填补了国内空白,为推动我国集成电路领域检测技术的发展起到了重要作用。     

Imaging of metal ion dissolution and electrodeposition by anodic stripping voltammetry-scanning electrochemical microscopy

We have developed a new imaging method for scanning electrochemical microscopy (SECM) employing fast-scan anodic stripping voltammetry (ASV) to provide sensitive and selective imaging of multiple chemical species at interfaces immersed in solution. A rapid cyclic voltammetry scan (100 V/s) is used along with a short preconcentration time (300-750 ms) to allow images to be acquired in a normal SECM time frame. A Hg-Pt film electrode is developed having an equivalent Hg thickness of 40 nm that has good sensitivity at short preconcentration times and also retains thin-film behavior with high-speed voltammetric stripping. Fast-scan anodic stripping currents are shown to be linear for 1-100 microM of Pb (2+) and Cd (2+) solutions using a preconcentration time of 300 ms. SECM images showing the presence of Pb (2+) and Cd (2+) at concentrations as low as 1 microM are presented. In addition, a single ASV-SECM image is shown to produce unique concentration maps indicating Cd (2+) and Pb (2+), generated in situ from a corroding sample, while simultaneously detecting the depletion of O 2 at this sample. The transient voltammetric response at the film electrode is simulated and shows good agreement with the experimental behavior. We discuss the behavior of images and concentration profiles obtained with different imaging conditions and show that mass-transport limitations in the tip-substrate gap can induce dissolution. ASV-SECM can thus be used to detect and study induced dissolution not only at bulk metal surfaces but also on underpotential deposition layers, in this case Cd and Pb on Pt. In addition, we discuss how surface diffusion phenomena may relate to the observed ASV-SECM behavior.