Holographic medical imaging: the laser as a visual scalpel-issuesand observations on 3-D display

Holographic techniques are being applied to medical imaging with greater focus and increasing benefit than ever before. Exploratory uses for the hologram in medicine go back more than 15 years, but the recent increased appreciation of three-dimensional (3-D) rendering of medical radiological data has provided the opportunity to employ holographic rendering as an additional means of displaying the radiological volume. Our work in this area is described. With the increasing availability and use of 3-D in radiology, and especially the more advanced technology of the hologram, a number of issues have emerged which bear directly on the 3-D radiological image and precede the utilization of holography in the practice of medicine. These issues may well affect the acceptability and adoption of true 3-D radiology as a beneficial part of the medical practice. Issues include: resolution of the image; clarity of the image; usefulness of the third dimension; incremental cost in terms of time and reimbursement; and the means to evaluate the clinical effectiveness of the volumetric image in medical practice. Discussions include: limitations derived from the holographic transformation; a review of the underlying “data” from which the radiological imagery is derived; factors that enhance or degrade the apprehension of the image; and the assumptions that guide the interpretation of the radiological image. Conclusions indicate that the limitations of holographic 3-D radiological image is due more to the underlying data rather than by the holographic transformation. Further, an initial evaluation protocol for 3-D versus 2-D formats of radiological imagery is referenced, and clarification of issues regarding the evaluation of safety, effectiveness, reliability and appropriateness of the holographic rendering of 3-D radiology for use in medicine are encouraged, so that this important technique can benefit the practice of medicine and enhance the quality of health care     

3-D ultrasound imaging: a review

The development of 3-D ultrasound imaging is a way to address the disadvantages of conventional ultrasound imaging. In this article the authors review approaches that have been attempted in the development of 3-D ultrasound imaging such as 3-D B-mode, color Doppler, and power Doppler systems. Acquisition, reconstruction, and rendering techniques for 3-D imaging are discussed, as well as applications and limitations     

磁性固位体磁场的有限元分析

磁性固位体是一种应用于口腔及颌面修复的新型医疗器件。本文采用有限元法对磁性固位体的磁场进行分析 ,将麦克斯韦张量法与虚位移法的计算结果与实验值进行比较 ,通过对固位体固位力地计算得到合适的固位体尺寸。在DELPHI5 .0环境下编制了一套通用的可视化二维有限元软件     

智能三维磁场强度测量仪的设计

针对近年来电磁研究的空间性发展的需求,提出一种采用三维传感器探头测量动态磁场强度的方法,并设计了一种基于单片机的智能化三维磁场测量仪。设计采用基于霍尔传感器的探头检测3个方向的磁场强度,通过单片机和FPGA控制数据采集与存储、计算并由LCD实时显示三维磁场峰值,再由USB通讯接口将数据传输至上位机。上位机采用Labwindows/CVI软件开发平台设计的程序对数据进行进一步处理,并绘制三维磁场时域波形图。测试结果表明,该仪器各功能均已基本实现,达到了预期的目标。     

复杂地形尾矿库三维渗流场的数值模拟

采用有限元对复杂地形的尾矿库渗流场进行数值模拟分析时,提出了三维数值模型概化的新方法：将地形剖面上的主要控制点拟合成曲线,然后再将曲线拟合成曲面,最后由曲面生成概化的三维数值模型。在此基础上进行了某尾矿库的三维渗流场计算,计算结果与该尾矿库的实测资料吻合良好,表明了模型概化的合理性。     

故障录波分析中的三维分析方法

根据目前国内各种故障录波分析软件的现状和计算机技术的发展趋势,提出一种电力故障三维分析方法.通过分析电力故障分析方法的优点,介绍了OpenGL技术.以阻抗轨迹为例给出了三维矢量数据的生成算法及其他多种电力故障分析算法的三维分析模块图例.讨论了电力故障三维分析模块的实时交互技术和数据接口设计,总结并指出了电力故障三维分析方法在电力故障分析中的应用前景.     

拱坝-坝肩整体动力稳定分析方法研究

三维变形体离散元是模拟不连续介质力学行为的有效数值分析方法，在拱坝-坝肩整体耦合系统静、动力力抗滑稳定分析方面有突出的优点。本文利用三维变形体离散元（3DEC）考虑坝体与坝肩的相互作用，采用坝肩滑裂体动态安全系数时程、坝体应力、坝肩推力、坝肩滑裂体位移曲线联合对拱坝．坝肩系统的稳定进行安全评估。算例分析结果表明：某拱坝-坝肩系统在峰值强度为0．321g的三向地震荷载作用下，该拱坝坝肩最危险滑裂体最小瞬时抗滑稳定安全系数为2．14，同时拱坝坝体压应力没有超过容许应力，坝肩滑裂体顺河向位移收敛，因而拱坝．坝肩整体系统满足抗滑稳定安全要求。     

基于STL格式的三维电磁场有限元自动剖分方法

在分析三维实体造型STL数据结构的基础上,提出了采用分层切片法来进行三维电磁场有限元自动剖分的方法。首先,建立了STL文件的拓扑结构数据,然后结合实体结构及材料特性确定一个垂直于z坐标轴的特征面域,并在此面域形成三角形单元网格,最后对实体在z方向分层切片,通过对面域逐层延拓投影,形成三维有限元单元网格。采用该方法开发了基于STL文件格式的三维网格自动剖分程序,并用于两个STL实体的自动剖分,结果表明,该方法可降低数据量,节省计算时间,实用可行。     

微波三维成像离散点目标回波数据模拟

成像雷达一般可分为合成孔径雷达(SAR)和逆合成孔径雷达(ISAR).研究目标的RCS特性当前普遍应用ISAR成像技术,而这些目标的成像能力都依赖于目标的回波信号.在ISAR三维成像理论的基础上,模拟离散点目标的回波信号,为三维成像软件提供三维空间的模拟数据,用来验证成像软件的正确性.基于已有的一维和二维成像软件对模拟数据进行了分析.从三维数据中提取出一维和二维数据,成像结果证明了模拟数据在一维和二维的有效性,从而保证了模拟数据三维成像可靠性.     

Real-time direct volume rendering in functional magnetic resonance imaging

Direct volume rendering is a visualization method that allows display of all information hidden in three-dimensional data sets of, for example, computed tomography or magnetic resonance imaging (MRI). In contrast to commonly used surface rendering methods, these algorithms need no preprocessing but suffer from a high computational complexity. A real-time rendering system, VIRIM (Vitec: Visualization Technology GmbH, Mannheim, Germany), cuts down rendering times of minutes on normal workstations to an interactive rate of 1 second or less. The immediate visual feedback allows interactive steering of the visualization process to achieve insight into the internal three-dimensional structure of objects. Additional information is obtained by using an interactive gray-value segmentation tool that both allows segmentation of the data set according to bone, tissue, and liquor and display of multifunctional data sets (e.g., functional MRI [fMRI] data sets). Thus, real-time direct volume rendering allows segmentation and volume data processing of functional and anatomical MR data sets simultaneously. As this method can be integrated in the clinical routine, it is of great importance for real-time motion artifact detection and the interpretation of fMRI data acquired during cognitive experiments with normal subjects and psychiatric patients. Because of the free programmability of VIRIM, more complex matching procedures are currently being investigated for future implementation.     

An effective and accurate method for the design of directional couplers

A new method which combines the three-dimensional (3-D) beam propagation method with the overlap integral method is presented for the design of directional couplers. A backward beam propagation is calculated for the output region to reduce the computation time greatly. The design method is illustrated with buried silica-on-silicon waveguide couplers. Results obtained with the 3-D model are compared with those from the two-dimensional model and it is shown that the 3-D model should be used. The design results are verified by both 3-D simulations and experiments. The new design method is shown to be effective and accurate.     

Embedded coding of medical images with regions of interest based on 3-D zerotree

In order to satisfy the need of diagnoses, based on the characteristic of medical images that a sequence of frames are formed in one body inspection, a new strategy for medical images compression is proposed. The 3-D wavelet is adopted and the planar zerotree is extended to the 3-D zerotree. By making use of the 3-D zerotree structure, a simple method for region of interest (ROI) mask generation is put forward. Medical images are compressed by three-dimensional embedded coding with the compression of regions of interest. Simulation results have shown that it can efficiently improve the compression ratio without affecting the diagnoses. Translated from Journal of Xidian University, 2006, 33(2): 182–185 [译自: 西安电子科技大学学报]     

可调色温白光LED能效和显色性仿真分析(英文)

白光LED的能效和显色性是其作为普通照明光源最重要的两项指标,对于可调色温的白光LED照明光源,同时实现高能效和高显色性非常重要。多芯片白光LED的色温、能效(辐射光效)和显色性可以通过选择LED芯片的峰值波长以及改变各个LED芯片的相对功率来进行调节与优化。本文提出了一个新的更接近实际的LED相对光谱功率分布曲线数学模型,在此模型的基础上利用软件仿真的方法分析了可调色温白光LED的能效和显色性,并且给出了几个比较满意的典型结果,可用于指导白光LED的设计,而且运用此方法还可以预测出白光LED在某些物理条件下的极限能效。     

基于二维提升小波的火电厂周期性数据压缩算法

针对火电厂生产运行中产生的大量周期性实时数据，提出了一种新的数据压缩与解压缩算法。为了更加有效地降低周期性数据中存在的冗余，该算法首先将待压缩的周期性数据从一维空间转换到二维空间，然后采用基于二维提升格式的对称双正交小波滤波器组对数据进行压缩和解压缩。利用实际测取的电力生产过程中的周期性数据对算法进行验证，试验结果表明，在相同的压缩比下，基于二维小波压缩的重构效果优于基于一维小波压缩的重构效果。因此该算法是一种有效和实用的周期性数据压缩方法，具有较大的应用潜力。     

具有公共联接定子铁心的横向磁场永磁电机二维场模型及磁场分析

介绍一种新型具有公共联接铁心的横向磁场永磁电机的定子组成及其结构特点,主要讨论了采用传统基于单元极三维等效磁网络法进行这种特殊结构形式电机磁场分析的局限性和存在的问题;进而建立了相应的二维场物理模型,并进行了有限元计算,重点分析了公共联接铁心所造成的极间磁路耦合及其对绕组磁链和感应电动势等所产生的影响.样机试验证明了上述分析的正确性.     

3-D imaging and stereotactic radiosurgery

Three-dimensional image processing and analysis applications in stereotactic radiosurgery are discussed. Only simple and rapid methods of 3-D image analysis have been used. However, volumetric image techniques, such as volume rendering and fusion, would give more useful information in treatment planning. The topics dealt with include: treatment space specification; segmentation of structures of interest; model/knowledge-based approach; tumor targeting; beam's eye viewing; dose-volume fusion; isocentric parameter optimization     

Three-dimensional optical coherence tomography employing a 2-axis microelectromechanical scanning mirror

We present a three-dimensional (3-D) optical coherence tomography (OCT) system based on a dual axis microelectromechanical system (MEMS) mirror. The MEMS mirror provides high-speed, high resolution 2-axis scanning while occupying a very small volume with extremely low power consumption. The dimensions of the mirror are 600/spl times/600 /spl mu/m, and both axes are capable of scanning up to 30 degree angles at frequencies greater than 3 kHz with good linearity. A 3-D image set is acquired when the MEMS mirror is integrated with the fiber-based OCT system. Via 2-axis lateral scanning, combined with an axial scan, a volume (2/spl times/2/spl times/1.4 mm) image of tissue, including a cancerous region, from a hamster cheek pouch was obtained. Using a signal processing technique, image data is normally presented by 3-volume showing views at arbitrary angles and locations. The objective of this work is to show the capabilities of a 3-D OCT system utilizing a MEMS scanner as this technology can readily by applied to realize OCT beam delivery systems such as hand held scanners and endoscopic probes. A MEMS based 3-D OCT system employing a high speed, small volume scanner may have the potential to expand the application area of OCT and revolutionize areas of clinical medicine as well as medical research.     

MRI data compression using a 3-D discrete wavelet transform

A low-power system that can be used to compress MRI data and for other medical applications is described. The system uses a low power 3-D DWT processor based on a centralized control unit architecture. The simulation results show the efficiency of the wavelet processor. The prototype processor consumes 0.5 W with total delay of 91.65 ns. The processor operates at a maximum frequency of 272 MHz. The prototype processor uses 16-bit adder, 16-bit Booth multiplier, and 1 kB cache with a maximum of 64-bit data bandwidth. Lower power has been achieved by using low-power building blocks and the minimal number of computational units with high throughput.     

三维激光扫描测量系统标定方法研究

三维坐标法是一种经常使用的三维激光扫描测量系统标定方法。本文通过分析三维坐标法标定精度的限制因素,提出了一种基于一维坐标的标定方法。由于回避了激光扫描传感器无法准确获得某特定点三维坐标的劣势,一维坐标法可以不受扫描点间距的影响,使得标定精度比常规的三维坐标法大大提高了。本文对这种一维坐标法进行了详细地理论分析和数学仿真,并给出了一个典型工程应用实例。