An adaptive gating approach for X-ray dose reduction during cardiac interventional procedures

The increasing number of cardiac interventional procedures has resulted in a tremendous increase in the absorbed X-ray dose by radiologists as well as patients. A new method is presented for X-ray dose reduction which utilizes adaptive tube pulse-rate scheduling in pulsed fluoroscopic systems. In current pulsed systems, the X-ray tube is pulsed at a fixed rate of 30 pulses/sec (or higher) and an image is formed at the end of each pulse. In the proposed system, pulse-rate scheduling depends on the heart muscle activity phase determined through continuous guided segmentation of the patient's electrocardiogram (ECG). Displaying images generated at the proposed adaptive nonuniform rate is visually unacceptable; therefore, a frame-filling approach is devised to ensure a 30 frame/sec display rate. The authors adopted two approaches for the frame-filling portion of the system depending on the imaging mode used in the procedure. During cine-mode imaging (high X-ray dose), collected image frame-to-frame pixel motion is estimated using a pel-recursive algorithm followed by motion-based pixel interpolation to estimate the frames necessary to increase the rate to 30 frames/sec. The other frame-filling approach is adopted during fluoro-mode imaging (low X-ray dose), characterized by low signal-to-noise ratio images. This approach consists of simply holding the last collected frame for as many frames as necessary to maintain the real-time display rate. Results of simulated system performance on an image sequence from a diagnostic study of left ventricular volume produced an average of approximately 3:1 dose reduction without compromising the diagnostic quality of the generated images. The adaptive pulsed-progressive system concept is viewed as the next evolutionary step in X-ray fluoroscopic systems.     

Collaborative work during interventional radiological procedures based on a multicast satellite-terrestrial network.

Collaboration is a key requirement in several contemporary interventional radiology procedures (IRPs). This work proposes a multicast hybrid satellite system capable of supporting advanced IRP collaboration, and evaluates its feasibility and applicability. Following a detailed IRP requirements study, we have developed a system which supports IRP collaboration through the employment of a hybrid satellite-terrestrial network, a prototype multicast version of wavelet based interactive communication system (WinVicos) application, and a partition aggregation and conditional coding (PACC) wavelet codec. A semistructured questionnaire was also used to receive evaluative feedback from collaborating participants. The departments of interventional radiology of University Hospital of Patras, Greece and of Charite Hospital of Berlin, Germany have been connected on the system. Eight interventional radiologists and a vascular surgeon participated periodically in three satellite-terrestrial "fully collaborative" IRPs (average time 90 min) of high complexity and in four terrestrial educational sessions with great success, evidenced by considerable improving the IRP outcomes (clinical and educational). In case of high complexity, where the simultaneous presence of remote interventional expert and/or surgeon is required, advanced collaboration among staff of geographically dispersed international centers is feasible via integration of existing networking and other technologies.     

精确定点环境信息探测的可移动装置设计

近几年来,人们对环境信息的要求越来越多,单一的温度信息已无法满足人们的需求。根据现有方案的不足,文中设计分析了一种利用可遥控的智能小车来精确定点探测环境信息的设计。设计以单片机STC89C52为核心部件,通过单片机、GPS探测模块和温、湿度检测模块之间的无线通讯,实现对定点环境信息的获取。操作简便,有良好的人机交互界面。     

Methods for measuring small displacements of television images

Various techniques are described to measure, small displacements of television images. If two successive video frames are considered, their differences are approximately a linear combination of the components of the displacement of the object. If all the points of the frame undergo the same movement, then the velocity estimation problem is solved using linear estimation. However, if some points belong to the moving object and the others to the background, the problem can be stated in the same way only if an algorithm is available to segment the image into fixed and moving areas. Afterwards, linear estimation can be applied to the moving area only. In this paper a segmentation algorithm is proposed which uses dynamic programming (Viterbi algorithm with three states). A more complex situation arises when the points belonging to the moving area are subjected to different movements. The problem can be solved once more using dynamic programming if the displacement components are quantized into(2M + 1) (2M + 1)values, and the number of states of the Viterbi algorithm is augmented to(2M + 1)^{2}. To reduce the technical difficulties of this approach, a simpler method that makes possible the estimation of thenmost probable displacements is proposed. Then the image is segmented into n moving areas with different displacements and a background area using a Viterbi algorithm withn + 1states. Experimental results show that the precision obtainable is about 0.1 pel when the displacements are up to 2-3 pels, the object had approximate dimensions of90 times 90pels, and the signal-to-noise ratio was higher than 33 dB.     

基于邻域信息的SAR图像变化检测

为了减少合成孔径雷达(SAR)图像中乘性斑点噪声对变化检测结果的影响,充分地利用了像素的邻域信息。首先使用邻域比值(NR)方法构造差异图像,然后提出基于邻域信息的模糊C均值聚类(FCM)算法。NR算子在构造差异图像时能够较好地保留图像信息并抑制噪声的干扰。同时将邻域信息引入到FCM算法的目标函数,以邻域加权距离改进了FCM算法在欧式距离计算中的不足,并约束了隶属度函数,减少了噪声对邻域中心像素的干扰。通过以上考虑像素邻域信息的算法,得到了差异图像的聚类结果,从而实现了SAR图像的变化检测。实验结果表明,所提算法较传统的FCM和K-means聚类算法,可以较好地保留图像变化区域的信息,同时提高了SAR图像变化检测的准确度。     

构成“直接读出”温度探头的IC和DMM

对于电子线路的故障排除和调试,图1中的简单温度测量探头可充当一种不可缺的工具。如需测量几个点的温度,可为IC1(Maxim MAX6610)配备一个探头,或者可以永久地将一个或多个器件整合到印制电路板上,或把它们连接到各个元件。电阻器R1、R2、R3把电路的温度定标电压输出设定为各个值(表1)。图2展示了电路在各个温度的代表性输出。     

Methods for digital analysis of AVHRR sea ice images

Algorithms for obtaining information on sea ice conditions from Advanced Very High Resolution Radiometer (AVHRR) digital imagery are presented. These algorithms comprise three steps: discrimination of cloud-covered areas from ice-covered and open water areas, estimation of ice concentration, and measurement of the sizes of ice floes and open water areas (polynyas) within the ice field. For ice-water-cloud discrimination, a dynamic threshold technique is applied to six combinations of the five spectral channels of the AVHRR. This results in an image that is useful for ice analyses. To derive ice concentration estimates, a simple linear relationship between pixel intensity values and amount of ice cover is applied to the visible channel reflectance data. The method for obtaining size frequency distributions is based on a size transform of binary realizations of the ice concentration result and is equally applicable to measuring polynyas and ice floes     

Wall position and thickness estimation from sequences of echocardiographic images

Presents a new method for endocardial (inner) and epicardial (outer) contour estimation from sequences of echocardiographic images. The framework herein introduced is fine-tuned for parasternal short axis views at the papillary muscle level. The underlying model is probabilistic; it captures the relevant features of the image generation physical mechanisms and of the heart morphology. Contour sequences are assumed to be two-dimensional noncausal first-order Markov random processes; each variable has a spatial index and a temporal index. The image pixels are modeled as Rayleigh distributed random variables with means depending on their positions (inside endocardium, between endocardium and pericardium, or outside pericardium). The complete probabilistic model is built under the Bayesian framework. As estimation criterion the maximum a posteriori (MAP) is adopted. To solve the optimization problem, one is led to (joint estimation of contours and distributions' parameters), the authors introduce an algorithm herein named iterative multigrid dynamic programming (IMDP). It is a fully data-driven scheme with no ad-hoc parameters. The method is implemented on an ordinary workstation, leading to computation times compatible with operational use. Experiments with simulated and real images are presented.     

Using edge direction information for measuring blocking artifacts of images

Block-based transform coding is the most popular approach for image and video compression. The objective measurement of blocking artifacts plays an important role in the design, optimization, and assessment of image and video coding systems. This paper presents a new algorithm for measuring blocking artifacts in images and videos. Instead of using the traditional pixel discontinuity along the block boundary, we use the edge directional information of the images. The new algorithm does not need the exact location of the block boundary thus is invariant to the displacement, rotation and scaling of the images. Experiments on various still images and videos show that the new blockiness measure is very efficient in terms of computational complexity and memory usage, and can produce blocking artifacts measurement consistent with subjective rating.     

《信息安全管理体系审核认证机构的要求》标准解读

在分析《信息安全管理体系审核认证机构的要求》标准产生背景的基础上,介绍了标准的结构和主要内容,并重点阐释了原则部分和要求部分。供有关人员在实施和贯彻标准时参考。     

Methods for engine supervision and control based on cylinderpressure information

The increasing demands for low emissions and low fuel consumption in modern combustion engines require improved methods for online diagnosis and best possible control of the combustion process. It is demonstrated that the cylinder pressure signal can successfully be used for this task. After introduction of some theoretical background, several application examples are presented: an online supervision of fuel injection, some results on feedforward emission control, and a concept for feedback control of spark timing. Experimental results obtained from stock car diesel and spark ignition engines are included to support the automation concepts     

Proposal for a new tomographic device providing information on the chemical properties of a body section

A system to analyze the chemical properties of a region of tissue located deep inside the human body without having to access it is proposed. The method is based on a high precision detection of X-rays or gamma-rays (photons) from an external source Compton scattered from the tissue under inspection. The method provides chemical information of plane regions lying not too deep inside the body (<6 cm). The amount of radiation absorbed by the body is about the same as needed for a standard X-ray tomography. The exposure time is estimated to be shorter than 10 min.     

植基于人类视觉系统之二色调图像信息隐藏技术

二色调图像（halftone image）是一种非常特殊的黑白图像，即在一定的距离观看它时，二色调图像仍具有灰阶图像的视觉效果。此种图像被广泛地使用在新闻报纸或杂志中。本文提出了一个利用了人类视觉特性的方法，有效地将机密信息隐藏在二色调图像中，实验结果显示此方法具有很高的实用价值。     

基于图像信息的红外与可见光图像融合方法研究

研究了红外图像与可见光图像的融合问题,提出了一种基于图像信息的图像融合新算法.首先利用非采样Contourlet变换的多分辨率特性和平移不变性对图像进行多尺度和多方向分解,得到一系列子带图像,然后针对图像变换后各带通方向子带高频系数的特点,提出了度量图像信息的融合规则.图像的低频部分决定了图像的轮廓,对低频子带应用简单...     

An algorithm for interconnection of RTLS and RLS during object images obtaining

It is proposed an algorithm for interconnection of on-board RLS and RTLS operation in case of objects images observation, allowing to increase images resolution and improve of images recognition.     

Deformable boundary finding in medical images by integrating gradient and region information

Accurately segmenting and quantifying structures is a key issue in biomedical image analysis. The two conventional methods of image segmentation, region-based segmentation, and boundary finding, often suffer from a variety of limitations. Here the authors propose a method which endeavors to integrate the two approaches in an effort to form a unified approach that is robust to noise and poor initialization. The authors' approach uses Green's theorem to derive the boundary of a homogeneous region-classified area in the image and integrates this with a gray level gradient-based boundary finder. This combines the perceptual notions of edge/shape information with gray level homogeneity. A number of experiments were performed both on synthetic and real medical images of the brain and heart to evaluate the new approach, and it is shown that the integrated method typically performs better when compared to conventional gradient-based deformable boundary finding. Further, this method yields these improvements with little increase in computational overhead, an advantage derived from the application of the Green's theorem.     

A temperature and emissivity separation algorithm for AdvancedSpaceborne Thermal Emission and Reflection Radiometer (ASTER)images

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scanner on NASA's Earth Observing System (EOS)-AM1 satellite (launch scheduled for 1998) will collect five bands of thermal infrared (TIR) data with a noise equivalent temperature difference (NEΔT) of ⩽0.3 K to estimate surface temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTER's TES algorithm hybridizes three established algorithms, first estimating the normalized emissivities and then calculating emissivity band ratios. An empirical relationship predicts the minimum emissivity from the spectral contrast of the ratioed values, permitting recovery of the emissivity spectrum. TES uses an iterative approach to remove reflected sky irradiance. Based on numerical simulation, TES should be able to recover temperatures within about ±1.5 K and emissivities within about ±0.015. Validation using airborne simulator images taken over playas and ponds in central Nevada demonstrates that, with proper atmospheric compensation, it is possible to meet the theoretical expectations. The main sources of uncertainty in the output temperature and emissivity images are the empirical relationship between emissivity values and spectral contrast, compensation for reflected sky irradiance, and ASTER's precision, calibration, and atmospheric compensation     

Recognition and storage of metal heart marker position from biplane X-ray images at video rates

We have developed a semiautomatic microcomputer-based instrument for recording the three-dimensional positions of metal heart markers from biplane X-ray images at 60 frames/s. This instrument eliminates the need for film processing and tedious digitizing by human operators. Markers are recognized electronically on each video line using criteria of density changes (edge detection), size, and location. Only the X-Y or Z-Y location of each marker is stored. This transformation of the gray scale image into a list of coordinates achieves a data compression of 250 fold. A small fast memory and a second large one provide an effective slowing of the high peak rates of the marker location data. This buffering allows the marker coordinates to be permanently stored on a floppy disk for later analysis. Four s of data can be stored in one burst when 20 markers are used. The instrument was designed to measure the pumping action of the heart through the calculation of instantaneous local strain, wall thickness, and chamber volume. This paper compares alternate recognition strategies and storage methods.