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Proceedings of the IEEE

Issue 3 • Date March 1983

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Displaying Results 1 - 25 of 31
  • [Front cover and table of contents]

    Publication Year: 1983 , Page(s): c1
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  • Scanning the issue

    Publication Year: 1983 , Page(s): 291 - 292
    Cited by:  Papers (8)
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    Freely Available from IEEE
  • Applications of computerized tomography to diagnostic radiology

    Publication Year: 1983 , Page(s): 293 - 297
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3284 KB)  

    Computerized tomography (CT) has revolutionized the practice of diagnostic radiology. The combination of greatly improved ability to distinguish between regions of similar X-ray absorption and the ability to separate overlying regions from each other has made possible the radiographic demonstration of many organs and disease processes that previously could be, at best, poorly demonstrated. CT of the brain has greatly decreased the need for the dangerous and uncomfortable procedures that were previously required to image the brain. It has also improved imaging capabilities in many other areas of the body, and thus decreased the need for other, more dangerous, imaging techniques. View full abstract»

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  • Cardiac computed tomography

    Publication Year: 1983 , Page(s): 298 - 307
    Cited by:  Papers (25)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3792 KB)  

    Diseases of the heart and blood vessels represent one of the most challenging problems for advanced diagnostic imaging systems. Not only do these diseases represent the major medical problem of our time in terms of death, acute and chronic illness, and disability, but cardiac diagnosis involves complex technical difficulties due to rapid motion and the complex structure of the heart and cardiovascular system. Computerized-tomographic scanning is potentially an ideal cardiac imaging modality since CT is a cross-sectional imaging method with potentially very high resolution. Currently available CT scanners have exposure speeds in the range of 1-5 s, a speed that is inadequate for the majority of cardiovascular imaging applications. Nevertheless, a variety of limited CT scanning techniques have been successfully applied to selected imaging problems. These methods involve the use of contrast media injected into the blood combined with either dynamic CT scanning or gated CT scanning. Currently advanced CT scanners permit visualization of major coronary arteries, imaging of normal and ischemic myocardium, and quantitation of the volumes of the major cardiac chambers. Fast, multiple-slice CT scanners are actively under development. No-motion, electronic scanning using scanning electron-beam techniques represents a promising approach to high-speed fully three-dimensional CT scanning. The CVCT scanner, under development at the University of California, San Francisco, will image up to 8 contiguous slices at a rate of 36-54 images per second. The technical feasibility of the CVCT has been demonstrated using a testbed simulation of the scanning-beam configuration. The completed prototype scanner is expected to be available for testing early in 1983. View full abstract»

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  • High-speed three-dimensional X-ray computed tomography: The dynamic spatial reconstructor

    Publication Year: 1983 , Page(s): 308 - 319
    Cited by:  Papers (36)  |  Patents (2)
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    Most X-ray CT scanners require a few seconds to produce a single two-dimensional (2-D) image of a cross section of the body. The accuracy of full three-dimensional (3-D) images of the body synthesized from a contiguous set of 2-D images produced by sequential CT scanning of adjacent body slices is limited by 1) slice-to-slice registration (positioning of patient); 2) slice thickness; and 3) motion, both voluntary and involuntary, which occurs during the total time required to scan all slices. Therefore, this method is inadequate for true dynamic 3-D imaging of moving organs like the heart, lungs, and circulation. To circumvent these problems, the Dynamic Spatial Reconstructor (DSR) was designed by the Biodynamics Research Unit at the Mayo Clinic to provide synchronous volume imaging, that is stop-action (1/100 s), high-repetition rate (up to 60/s), simultaneous scanning of many parallel thin cross sections (up to 240, each 0.45 mm thick, 0.9 mm apart) spanning the entire anatomic extent of the bodily organ(s)of interest. These capabilities are achieved by using multiple X-ray sources and multiple 2-D fluoroscopic video camera assemblies on a continually rotating gantry. Desired tradeoffs between temporal, spatial, and density resolution can be achieved by retrospective selection and processing of appropriate subsets of the total data recorded during a continuous DSR scan sequence. View full abstract»

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  • Single-photon emission computed tomography

    Publication Year: 1983 , Page(s): 320 - 329
    Cited by:  Papers (7)  |  Patents (3)
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    The subject of singl-photon emission computed tomography (SPECT) is generally reviewed. The basic interaction processes of gamma rays in matter are outlined, and the formation of conventional gamma-ray images is described. We then outline the extension of these concepts to the formation of three-dimensional or tomographic images. Of particular concern in emission tomography, the effects of gamma-ray attenuation and scattering are outlined. Several examples are given of practical SPECT systems, and representative results are given. View full abstract»

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  • Computerized tomography with ultrasound

    Publication Year: 1983 , Page(s): 330 - 337
    Cited by:  Papers (23)
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    The mathematical basis for transmission computed tomographic imaging using straight-line reconstruction equations is discussed. Both narrow-band and broad-band solutions are described. The Born and Rytov methods are discussed and the Rytov inversion equation presented with some results. Problems with implementation of the method are mentioned. Backscatter reconstruction methods of seismology are discussed as to their strengths and weaknesses for use in tissue imaging. View full abstract»

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  • An introduction to NMR imaging: From the Bloch equation to the imaging equation

    Publication Year: 1983 , Page(s): 338 - 350
    Cited by:  Papers (38)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3897 KB)  

    The emerging technology of NMR imaging is introduced here as a problem in system identification. We show how selected families of signals may be input into the system ("system," in this case, is almost synonymous with "patient") in order that the system's responses to these inputs may be directly interpreted in terms of the system parameters. Once identified, a raster display of the system parameters provides an internal image of the patient. Inputs to the system age four-component functions of time. One component describes the strength of an RF signal, and the other three components govern the strength of three spatially varying, independently controlled magnetic fields (the gradient fields) in which the patient is immersed. In response to these inputs some of the protons in the patient, acting in concordance with the Bloch equation, give rise to local fluctuations in the magnetization which are detected with a tuned antenna and a sensitive receiver. The relationship between this output signal and the system parameters is summarized in the imaging equation. View full abstract»

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  • Application of computerized tomography to radiation therapy and surgical planning

    Publication Year: 1983 , Page(s): 351 - 355
    Cited by:  Papers (9)  |  Patents (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2704 KB)  

    Computerized tomography (CT) which permits imaging the internal anatomy in axial cross section, has had a major impact in medicine, primarily in the diagnostic area. The CT scans are also useful in determining the extent of disease which is important in selecting the appropriate therapy. For therapy, the CT scan is becoming important in planning a course of radiation therapy for a cancer patient and to a lesser extent, in planning a surgical reconstruction for some patients. For both of these treatment modalities it would be desirable to have a three-dimensional reconstruction of the internal anatomy. This paper discusses the use of a three-dimensional perspective of the internal anatomy, obtained from multiple CT scans, as a guide to these two therapeutic modalities. View full abstract»

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  • Overview of computerized tomography with emphasis on future developments

    Publication Year: 1983 , Page(s): 356 - 372
    Cited by:  Papers (14)  |  Patents (3)
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    The applications of computer-assisted, or comput(eriz)ed, tomography (CT) are reviewed. The major emphasis is on medical applications, but all relevant technical sciences are covered. A unified descriptive account of the underlying principles is presented (detailed reviews of algorithms and their mathematical backgrounds can be found elsewhere in this special issue). Deficiencies in existing hardware and software are identified and the possible means of remedying the more urgent of these are outlined. Promising approaches for future research and development into CT are suggested. View full abstract»

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  • Physical problems of computerized tomography

    Publication Year: 1983 , Page(s): 373 - 378
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    A cross-sectional image of an object can be accurately reconstructed if its projections or line integrals are known at all angles. This fundamental and exciting property has been applied to a variety of applications, primarily in the area of medical imaging. In many cases, however, the physical measurements fail to accurately define the complete set of line integrals. This leads to inaccuracies and distortions in the resultant reconstruction. The physical measurements can be inadequate in a number of ways. These include nonlinearities, noise, and insufficient data. The nonlinearities can arise from a nonlinear detector process, or the inability to accurately extract the information in the exponent by taking logs. The noise can be the usual statistical uncertainty of the measurement or an interfering component such as scatter. The data can be insufficient in a number of ways including inadequate sampling or regions of missing data. Also, the measurements of a source distribution can be distorted by an unknown attenuation distribution, resulting in errors in the reconstruction. View full abstract»

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  • Mathematical problems of computerized tomography

    Publication Year: 1983 , Page(s): 379 - 389
    Cited by:  Papers (12)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1099 KB)  

    The data measured in computerized tomography; e.g., the X-ray attenuation in X-ray tomography or the resonance phenomena in nuclear magnetic resonance tomography, have to be processed to produce the pictures on which the diagnostic evaluation of the physician is based. This process consists of the solution of the following mathematical problem. The data depend on the searched-for distribution and this dependence can be described as an integral transform. To produce the final picture amounts to the inversion of the integral transform. This paper is concerned with the description of the integral transforms modeling the different techniques in computerized tomography. Among other things, the following questions are treated. Which numerical problems do we have to encounter in inverting the transforms; e.g., what accuracy in the reconstruction can we expect in dependence on the accuracy of the data. To what extent is a distribution determined by a finite number of measurements. Is it possible to recover the distribution reliably if the data are incomplete. View full abstract»

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  • Reconstruction algorithms: Transform methods

    Publication Year: 1983 , Page(s): 390 - 408
    Cited by:  Papers (78)  |  Patents (7)
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    Transform methods for image reconstruction from projections are based on analytic inversion formulas. In this tutorial paper, the inversion formula for the case of two-dimensional (2-D) reconstruction from line integrals is manipulated into a number of different forms, each of which may be discretized to obtain different algorithms for reconstruction from sampled data. For the convolution-backprojection algorithm and the direct Fourier algorithm the emphasis is placed on understanding the relationship between the discrete operations specified by the algorithm and the functional operations expressed by the inversion formula. The performance of the Fourier algorithm may be improved, with negligible extra computation, by interleaving two polar sampling grids in Fourier space. The convolution-backprojection formulas are adapted for the fan-beam geometry, and other reconstruction methods are summarized, including the rho-filtered layergram method, and methods involving expansions in angular harmonics. A standard mathematical process leads to a known formula for iterative reconstruction from projections at a finite number of angles. A new iterative reconstruction algorithm is obtained from this formula by introducing one-dimensional (1-D) and 2-D interpolating functions, applied to sampled projections and images, respectively. These interpolating functions are derived by the same Fourier approach which aids in the development and understanding of the more conventional transform methods. View full abstract»

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  • Finite series-expansion reconstruction methods

    Publication Year: 1983 , Page(s): 409 - 419
    Cited by:  Papers (89)  |  Patents (5)
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    Series-expansion reconstruction methods made their first appearance in the scientific literature and in the CT scanner industry around 1970. Great research efforts have gone into them since but many questions still wait to be answered. These methods, synonymously known as algebraic methods, iterative algorithms, or optimization theory techniques, are based on the discretization of the image domain prior to any mathematical analysis and thus are rooted in a completely different branch of mathematics than the transform methods which are discussed in this issue by Lewitt [51]. How is the model set up? What is the methodology of the approach? Where does mathematical optimization theory enter? What do these reconstruction algorithms look like? How are quadratic optimization, entropy optimization, and Bayesian analysis used in image reconstruction? Finally, why study series expansion methods if transform methods are so much faster? These are some of the questions that are answered in this paper. View full abstract»

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  • Display of 3D information in discrete 3D scenes produced by computerized tomography

    Publication Year: 1983 , Page(s): 420 - 431
    Cited by:  Papers (22)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2281 KB)  

    Imaging modalities such as X-ray computerized tomography (CT), ultrasound CT, and nuclear magnetic resonance CT all produce sequences of slice images of internal structures of medical objects. Effective methods of displaying the 3D information in such images are essential to aid in both diagnosis and treatment of diseases. Two philosophically different approaches to the display problem have been pursued. In the first approach, 3D information is displayed as a distribution of densities in a 3D space. The second approach extracts, from slice images, information about boundary surfaces of objects which is displayed on a 2D screen. The present paper reviews both of these approaches with particular emphasis on the image and graphics processing aspects of the latter approach. View full abstract»

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  • Almost-periodic linear arrays

    Publication Year: 1983 , Page(s): 436 - 437
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (217 KB)  

    A novel scheme is described here for the nonuniform placement of elements in a linear array. By leaving the constraints of the periodic-spacing domain and entering the larger domain of almost-periodic spacing, one is allowed additional degrees of freedom for optimizing the radiation characteristics of the array. View full abstract»

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  • High-frequency analysis of broad-band 0° hybrid-junction: Distributed parameter approach

    Publication Year: 1983 , Page(s): 438 - 439
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    The broad-band 0° hybrid junction constructed with a twisted-wire transmission-line transformer is analyzed by using a distributed parameter approach, with the help of the transmission-line theory. Such an analysis provides some useful information concerning the behavior of the device at higher frequencies when the line length becomes comparable to a wavelength. View full abstract»

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  • A further comment on "Analysis of 0° hybrid junction constructed with broad-band transmission-line transformer"

    Publication Year: 1983 , Page(s): 439 - 440
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  • Harmonic generation due to ballistic electron transport in GaAs

    Publication Year: 1983 , Page(s): 440 - 441
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    Harmonics produced by the nonlinearity in the current-voltage characteristics of a ballistic diode are studied for a GaAs sample of thickness 1 µm at 77 K under collision-free condition. Harmonic generation is found to be maximum at zero bias, the value for the second-harmonic current being 50 percent for a signal amplitude of 0.2 V. View full abstract»

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  • Convergence of polynomial least squares end-point and mid-point estimators

    Publication Year: 1983 , Page(s): 441 - 442
    Cited by:  Papers (2)
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    In a recent corcespondence, Leskiw and Miller [1] obtained the variance of a least squares polynomial estimator, as function of the polynomial order, for a large number of equally spaced data points, when the estimate is for the end-point. A simpler proof is given, and the result is extended to the mid-point. A mid-point estimator may be of special interest since it exhibits the lowest variance. View full abstract»

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  • Load frequency sampled-data control with unknown deterministic power demand

    Publication Year: 1983 , Page(s): 442 - 443
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    This letter presents a sampled-data load frequency control method using the Lyapunov function. The proposed method is designed so as to absorb the unknown deterministic power demand. A numerical illustration is presented in order to verify the practicality of the proposed method. View full abstract»

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  • Correction to "Error rate monitoring for digital communications"

    Publication Year: 1983 , Page(s): 443
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  • CAI sourcebook

    Publication Year: 1983 , Page(s): 444 - 445
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    Freely Available from IEEE
  • Interconnected dynamical systems

    Publication Year: 1983 , Page(s): 444
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    Freely Available from IEEE
  • Intuitive IC electronics, a sophisticated primer for engineers and technicians

    Publication Year: 1983 , Page(s): 444
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    Freely Available from IEEE

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