Informatics infrastructure of CAD system.

A computer aided diagnosis (CAD) system requires several components which influence its effectiveness. An image processing methodology is responsible for the analysis, database structure archives and distributes the patient demographics, clinical information, and image data. A graphical user interface is applied in order to enter the data and present it to the user. By designing dynamic Web pages a remote access to the entire is granted. The computer aided diagnosis system includes three layers, which might be installed on various platforms. Elements of the application software are designed independently. Integration of all components is another issue discussed in the presented paper. Implementation of a computer aided diagnosis system improves and accelerates the analysis by giving to the user objective measurement tools. It also standardizes the decision-making process and solves the problem of replicability. Finally, it permits a set of images and features to be collected and recognized as a medical standard and be applied in education and research.     

Perception of detail and greyscale range in X-ray fluoroscopy images captured with a personal computer and frame-grabber

Objective: To assess the dynamic range of radiological images captured with a personal computer frame-grabbing system coupled to an X-ray fluoroscopy machine. Methods: A 386DX-40 MHz, IBM compatible, computer with an SVGA monochrome graphics subsystem and a 387 co-processor, installed with a Screen Machine frame-grabber and controlled by a program specially written was used. Various systems were examined and the observer's perceptions of the results assessed. Results: The dynamic range available to an ordinary X-ray fluoroscopy system was found to be restricted to about 750 mV. Similar measurements showed that the dynamic range was always restricted to 3/4–1/2 of the full available signal because of a high value of the dark voltage of the TV camera's target on all seven systems measured. The dynamic range of the computer — frame grabber system was found to be significantly wider than the Image Intensifier — TV camera chain but, surprisingly, it was affected by the type of file format used for image storing on disk. Clinical images from a barium meal examination as well as CT images captured after optimisation of the frame-grabber were found to contain large quantities of noise in the first two least significant bit planes making them redundant and limiting the grey levels needed for image display to less than 64. This number was also less than the 80 grey levels that could be discriminated by the human eye on the computer monitor. Conclusions: It was concluded that 6 bit digitisation would have been sufficient for image capture. The advantages of the wider dynamic range of the frame-grabber and the processing capabilities of the computer were tested for the possibility of improving the perception of detail. However, the results were negative. The limiting spatial resolution measured with a variable density bar pattern at all magnifications was about 0.4 lp/mm lower from that measured directly on the fluoroscopic screen. A detail perception test had the same result. The perception success was significantly lower with the digital images at all but the highest of the exposure rates and despite the use of image processing filters.     

Computer graphics for digitally formatted images

The increasing use of digitally formatted imaging systems requires high-quality interactive gray-scale computer raster graphics systems for the management, display, and analog film recording of digital image and alphanumeric information. These systems are a combination of computer hardware and software and implement a set of graphics protocols. This paper describes a set of interactive graphics protocols that has been developed for clinical use.     

Accelerated multidimensional radiofrequency pulse design for parallel transmission using concurrent computation on multiple graphics processing units

Multidimensional radiofrequency (RF) pulses are of current interest because of their promise for improving high‐field imaging and for optimizing parallel transmission methods. One major drawback is that the computation time of numerically designed multidimensional RF pulses increases rapidly with their resolution and number of transmitters. This is critical because the construction of multidimensional RF pulses often needs to be in real time. The use of graphics processing units for computations is a recent approach for accelerating image reconstruction applications. We propose the use of graphics processing units for the design of multidimensional RF pulses including the utilization of parallel transmitters. Using a desktop computer with four NVIDIA Tesla C1060 computing processors, we found acceleration factors on the order of 20 for standard eight‐transmitter two‐dimensional spiral RF pulses with a 64 × 64 excitation resolution and a 10‐μsec dwell time. We also show that even greater acceleration factors can be achieved for more complex RF pulses. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.     

Computers in radiology. Interfacing with peripheral devices

A fundamental part of building a computer system is control of and communication with peripheral devices. With use of graphics display terminals, video image digitizers, and array processors as examples, the basics of peripherals are discussed as they affect radiologic applications.     

Neuron imaging with Neurolucida--a PC-based system for image combining microscopy

Neurolucida is a new software package for performing 3-D neuron mapping and tracing to 0.5 micron precision through the oculars of a microscope. It incorporates computer controlled stage movement in three dimensions. Sections are limited in size only by the stage dimensions. An on-line, direct view image editor is provided as are dynamic image rotations in color and morphometric analyses. Neurolucida is written in 'C' and runs on PC ATs, XTs, and PS/2s using DOS and VGA, EGA, or NTSC graphics. Neurolucida has a video mode compatible with frame grabbers, thereby permitting its application to video microscopy.     

Image analysis and quantification of atherosclerosis using MRI

This paper describes an image processing, pattern recognition, and computer graphics system for the noninvasive identification and evaluation of atherosclerosis using multidimensional Magnetic Resonance Imaging (MRI). Particular emphasis has been placed on the problem of developing a pattern recognition system for noninvasively identifying the different plaque classes involved in atherosclerosis using minimal a priori information. This pattern recognition technique involves an extension of the ISODATA clustering algorithm to include an information theoretic criterion (Consistent Akaike Information Criterion) to provide a measure of the fit of the cluster composition at a particular iteration to the actual data. A rapid 3-D display system is also described for the simultaneous display of multiple data classes resulting from the tissue identification process. This work demonstrates the feasibility of developing a "high information content" display which will aid in the diagnosis and analysis of the atherosclerotic disease process. Such capability will permit detailed and quantitative studies to assess the effectiveness of therapies, such as drug, exercise, and dietary regimens.     

Digitization and image processing methods for enhancement and quantification of grazing-incidence x-ray topographs

The conventional photographic prints obtained from double crystal x-ray topography are often hard to interprete and reproduce. Photographic enhancement methods require skillful work by an experienced photographer. They are time consuming and the image information is difficult to present quantitatively. Alternatively, image processing methods may be applied by digitization of the original topographic recording. Image processing computer programs may be applied, e.g., for image enhancement and for quantification of image information. This paper's main interest is related to-obtaining a sufficiently high magnification ratio;-correcting for intensity variations within the image;-applying spatial filtering techniques in order to reduce film grain noise;-improving contrast, and-retrieving quantative information on image details.The application of such image processing routines is exemplified on topographs obtained by a double-crystal diffractometer set to the (+, -) asymmetric-asymmetric setting. A silicon single crystal was used as the monochromator, while the sample was a silicon single crystal which had undergone both surface damage and metallic contamination before the application of Rapid Thermal Annealing (RTA). Hence, well-defined microdefects are found within the sample. These computer-processed images are compared with corresponding images enhanced by conventional techniques. The results provide indications of which enhancement procedures should be applied for qualitative image improvement and for quantification of image details within different types of topographic recordings.     

A data exchange format for neuroanatomy workstations

The development of the microprocessor has enabled biomedical researchers to use powerful computers as single user workstations. Many such systems are now in use--some developed for use within individual laboratories, and others purchased commercially. These systems typically mix computer graphics and image processing capabilities. No standard exists that allows users of these workstations to exchange anatomical data in graphical or image form. This paper considers issues involved in designing a flexible format for exchanging digital anatomical data between laboratories.     

Functional image data acquisition and processing

In the production of functional images certain hardware and software considerations are necessary for the rapid and accurate determination of kinetic parameters. The advent of the digital scintillation camera has made available increased accuracy of quantitation and ease of image handling, although its integrated computer system may not be optimal for program development presently. To reduce the deleterious effects of Poisson noise on parameter estimation, the single or multiple application of easily implemented smoothing operators in space and time is recommended as a first step in image processing. The properties of these operators are conveniently expressed in terms of their variance. Following smoothing, count or variance thresholding is performed to reduce computer processing time and eliminate extraneous background from functional images. Time-activity curves can be fit by a variety of mathematical functions, the most useful of which is probably the finite Fourier series. In a simulated gated blood-pool study of the left ventricle, with and without an aneurysm, it is found that increased smoothing of the original image data results in more accurate parameter determinations, to the extent that small regions of dissimilar temporal behavior are not obliterated.     

Visualization of MR angiographic data with segmentation and volume-rendering techniques.

Novel image processing and computer graphics techniques were developed to create three-dimensional (3D) models of vasculature from magnetic resonance (MR) angiographic images of the head or neck. Region growing was used to produce a mask that isolated the vascular signal in the MR angiographic data. The masked images were subjected to gradient-shaded volume rendering to create 3D views of the vasculature. The computer-derived model of intracranial vasculature was then merged with a 3D model of brain parenchyma derived from a set of MR images. The combined display of vascular and gyral anatomy may be useful for neurosurgical planning.     

Cardiac reconstruction imaging in relation to other ultrasound systems and computed tomography.

A computer-controlled system is described for the generation of two-dimensional motion images of the heart. A standard B scanner is used to scan the area of interest during 40-50 cardiac cycles, and the computer controls recording of the ultrasound signals, beam position indicators, and physiologic data. The ultrasonic echoes are reformatted by the computer into sequential frames by reference to the ECG. Images are displayed in motion on a large monitor, and hard copy is obtained on 35 mm cine film. Off-line computer-controlled signal processing is utilized for image enhancement of clinical studies. Real-time systems for the production of two-dimensional motion images of the heart are discussed and compared to computer reconstruction of ultrasound cardiac imaging. The advantages of ultrasound imaging of the heart and other body areas are presented, and prospectives are offered by which the present and future roles of ultrasound can be evaluated in respect and future roles of ultrasound can be evaluated in respect to computed tomography. It is concluded that ultrasound will remain the primary noninvasive modality for cardiac motion study and that ultrasound will continue to provide important clinical information in all parts of the body where it is currently employed.     

Compressed sensing reconstruction for whole‐heart imaging with 3D radial trajectories: A graphics processing unit implementation

A disadvantage of three‐dimensional (3D) isotropic acquisition in whole‐heart coronary MRI is the prolonged data acquisition time. Isotropic 3D radial trajectories allow undersampling of k‐space data in all three spatial dimensions, enabling accelerated acquisition of the volumetric data. Compressed sensing (CS) reconstruction can provide further acceleration in the acquisition by removing the incoherent artifacts due to undersampling and improving the image quality. However, the heavy computational overhead of the CS reconstruction has been a limiting factor for its application. In this article, a parallelized implementation of an iterative CS reconstruction method for 3D radial acquisitions using a commercial graphics processing unit is presented. The execution time of the graphics processing unit‐implemented CS reconstruction was compared with that of the C++ implementation, and the efficacy of the undersampled 3D radial acquisition with CS reconstruction was investigated in both phantom and whole‐heart coronary data sets. Subsequently, the efficacy of CS in suppressing streaking artifacts in 3D whole‐heart coronary MRI with 3D radial imaging and its convergence properties were studied. The CS reconstruction provides improved image quality (in terms of vessel sharpness and suppression of noise‐like artifacts) compared with the conventional 3D gridding algorithm, and the graphics processing unit implementation greatly reduces the execution time of CS reconstruction yielding 34–54 times speed‐up compared with C++ implementation. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

计算机X线摄影与屏片系统摄影对比分析

目的:评价计算机X线摄影(CR)的应用价值。方法:抽取我院CR照片和常规X线摄影照片各1200 例,由2位主管技师和1位副主任技师对照片进行分析,统计出甲、乙、丙及废片率。并对乙、丙级片及废片产生的 原因进行了分析。结果:①照片影像质量:CR照片甲级片率51.6%,乙级片率35.5%,丙级片率12.2%,废片率 0.7%。常规X线摄影照片甲级片率40.6%,乙级片率42.5%,丙级片率15.2%,废片率1.7%。②摄影条件:数字 比模拟摄影电压高1～5kV,曝光量高20%左右。结论:CR摄影影像质量好于模拟摄影(即甲级片率高,废片率 小),可为临床提供可靠诊断。但曝光条件比屏 片系统高,增加了病人的X线接受剂量。     

Interactive multiplanar reformation of conventional two-dimensional MR images

In this report, we describe a new application for three-dimensional computer image processing that can provide for improved depiction of anatomical structures on routine nonvolumetric magnetic resonance (MR) examinations. The technique can be applied to standard two-dimensional MR images of the brain, spine, musculoskeletal system, and body including those obtained with relatively thick slices and with an intersection gap. This report demonstrates use of the reformation technique to establish retrospectively the symmetry in bilateral structures that were displayed out of alignment due to suboptimal patient positioning or patient motion during image acquisition and to improve the depiction of anatomical structures that were oriented out of the plane of original image acquisition. This method can be performed interactively in near real time, requires no increase in patient examination time, and has potential application throughout the body.     

An efficient and cost effective nuclear medicine image network

An image network that is in use in a large nuclear medicine department is described. This network was designed to efficiently handle a large volume of clinical data at reasonable cost. Small, limited function computers are attached to each scintillation camera for data acquisition. The images are transferred by cable network or floppy disc to a large, powerful central computer for processing and display. Cost is minimized by use of small acquisition computers not equipped with expensive video display systems or elaborate analysis software. Thus, financial expenditure can be concentrated in a powerful central computer providing a centralized data base, rapid processing, and an efficient environment for program development. Clinical work is greatly facilitated because the physicians can process and display all studies without leaving the main reading area.     

An efficient and cost effective nuclear medicine image network

An image network that is in use in a large nuclear medicine department is described. This network was designed to efficiently handle a large volume of clinical data at reasonable cost. Small, limited function computers are attached to each scintillation camera for data acquisition. The images are transferred by cable network or floppy disc to a large, powerful central computer for processing and display. Cost is minimized by use of small acquisition computers not equipped with expensive video display systems or elaborate analysis software. Thus, financial expenditure can be concentrated in a powerful central computer providing a centralized data base, rapid processing, and an efficient environment for program development. Clinical work is greatly facilitated because the physicians can process and display all studies without leaving the main reading area.     

肺小病灶穿刺诊断同步实时跟踪X线立体定位系统的研究

目的研制新型的用于肺小病灶穿刺诊断的同步实时跟踪x线立体定位系统。方法采用x线电视影像技术及x线准直技术，结合双C臂双管x线机，从垂直向和水平向2个不同平面同步实时获取图像，经计算机图像处理和计算机视觉处理，确定并动态跟踪肺小病灶和穿刺细针的三维空间位置。结果垂直和水平向同时相交成像的两束x射线之间没有干扰，可以完成两路图像的同步实时采集，实现正常呼吸状态下肺部小病灶和穿刺细针空间位置的同步实时跟踪。组建的x线立体定位系统的平均定位误差为0．5mm左右，最大定位误差为1．0mm左右，实时显示速度为5帧／s。结论建立一种新型的双C臂双管同步实时跟踪x线立体定位系统是可行的，为肺小病灶同步实时跟踪立体定位穿刺肺癌早期诊断提供了可能。     

Digital processing of film radiographs

Initial clinical experience with a system for the digitization, processing, and display of film radiographs is described. Film is digitized using a high-intensity laser scanner; the recorded image data may then be subjected to a wide variety of processing options, with display of processed images on television monitors. The possibilities of clinical applications to processing and display of chest radiographs and film mammograms are described. A comparison of conventional analog subtraction and digitized film subtraction angiography indicated equivalent diagnostic capability, with the advantage of flexible, interactive image processing with the digital technique. A specially designed, energy-selective cassette permits dual-energy imaging from two films effectively exposed to different x-ray energy spectra. Dual-energy imaging may be capable of the characterization of body materials, including lung nodules, and useful for eliminating obscuring radiographic shadows overlying regions of interest.