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Nuclear Science, IEEE Transactions on

Issue 2  Part 2 • Date April 1979

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Displaying Results 1 - 25 of 63
  • [Front cover]

    Page(s): c1
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    Freely Available from IEEE
  • IEEE Transactions on Nuclear Science

    Page(s): c2
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    Freely Available from IEEE
  • Contents

    Page(s): 2661 - 2662
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    Freely Available from IEEE
  • Foreword

    Page(s): 2663
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    Freely Available from IEEE
  • Image Reconstruction with Limited Angle Projection Data

    Page(s): 2665 - 2669
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    A new image reconstruction technique for computed tomography is described. Projection data obtained by a smaller angle rotation less than 180 degrees around the object are used to make the image. The main feature of the method is the estimation of missing region in the Fourier transformed domain by extrapolation employing analytic continuity. Numerical simulations were carried out using computer generated pattern data. The results show strong effects of the content of noisy component on the reconstructed image. The method might be, however, practically applied to some real fields for medical diagnosis. View full abstract»

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  • Convolution Algorithms for Arbitrary Projection Angles

    Page(s): 2670 - 2673
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    The point response function ¿ of a convolution algorithm for reconstructing a function from a finite set of its projections is the sum of the back-projections of the filters used. An effective method is given for choosing the filters so that ¿ is as close as possible to a specified point response ¿. The weighted mean square error in approximating ¿ by ¿ goes to 0 as the number of projection angles goes to infinity, independent of their placement. Compensation for additive noise in the projections is discussed and numerical results are presented. View full abstract»

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  • On the Problem of Reconstructing Images of Non-Scalar Parameters from Projections. Application to Vector Fields

    Page(s): 2674 - 2677
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    It is demonstrated that in some cases it is possible to reconstruct images of fields whose local values are not scalars but are instead anisotropic. The approach taken relies upon Fourier analysis of the angular dependence and separation of scalar and non-scalar contributions by symmetry, and is applicable to anisotropies that do not have even symmetry. Although there are only a limited number of cases in which the problem can be analytically solved, there appears to be a variety of applications for which good approximations are available. The proposed algorithm, a hybrid of well known image reconstruction techniques, has been applied to calculated projections of test patterns, local regions of which having been assigned either scalar or vector behavior or both. View full abstract»

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  • Ultra - Fast Convolution Approximations for Computerized Tomography

    Page(s): 2678 - 2681
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    The amount of computation required to convolve projection data with a filter array may be reduced by implementing the required multiplications with reduced precision or by approximating the filter with a function which is piecewise constant over intervals several times longer than the projection sampling increment. We investigate an extreme form of the above approximations, for which multiplication by any filter element (except the central one) requires only a simple binary shift. Using this approximation, a projection of M samples may be filtered in an extremely straightforward manner using only M full-precision multiplications, representing a significant advantage over convolution implementations using Fourier or number-theoretic transforms. Simulations are presented which show that in most cases only an insignificant amount of error in the reconstructed image results from the use of this form of convolution approximation. View full abstract»

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  • Convolutional Reconstruction from Cone-Beam Projection Data

    Page(s): 2682 - 2684
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    A convolutional formula is obtained for the direct reconstruction of a three-dimensional structure function from cone-beam projection measurements. The cone apex is assumed to move on a circle to generate the two-dimensional projected images. The derivation starts from the three-dimensional form of the Radon inversion formula. A transformation of variables is applied to adapt this formula to the cone-beam projection geometry. View full abstract»

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  • Reconstruction of Fuel Pin Bundles by a Maximum Entropy Method

    Page(s): 2685 - 2686
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    Tomographic reconstructions from several views of a 37-pin reactor fuel core bundle are presented. A maximum entropy method is used to produce reconstructions from three, six, and eighteen views of a fuel bundle with voids and partial voids. View full abstract»

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  • A Stochastic Filter for Transverse Section Reconstruction

    Page(s): 2687 - 2690
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    A new algorithm, based on minimum-mean-square reconstruction error, involves modification of the filter kernel based on the signal-to-noise of each projection target. This algorithm gives improved resolvability relative to other algorithms for the resolution phantom chosen for simulations with Poisson noise. View full abstract»

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  • Rigorous Error Bounds in Computerized Tomography

    Page(s): 2691 - 2692
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    Practically speaking, how can one utilize x-ray projection data so that the reconstruction obtained is in fact an approximation to the attenuating object? An answer is given which depends on the use of special projeition angles but provides an upper bound in the L2 topology for the difference between the reconstruction and the x-ray attenuating object. The keys to this solution include two theorems and an important assumption: some a priori knowledge of the attenuating object. The article is somewhat of a review of [3], but focused on the development of the error bound. View full abstract»

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  • High Speed Convolving Kernels for CT Having Triangular Spectra and/or Binary Values

    Page(s): 2693 - 2696
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    An algorithm is described to transform sampled CT convolution kernels into "binary" kernels having values which are even powers of 2. Multiplication in the convolution operation can then be replaced by a much faster shift operation. A technique for further reducing the number of shift and addition operations using new computationally fast CT kernels is also given. The binary kernels are computationally faster by about 80-90% on a conventional computer. Reconstructed CT images using both conventional kernels and their transformed binary equivalents are compared. View full abstract»

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  • Transverse Section Imaging with the MGH Positron Camera

    Page(s): 2697 - 2702
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    Transverse section emission imaging provides a method to quantitatively measure physiological parameters on a three dimensional basis in the body. PCII, the MGH Positron Camera, is widely used for such studies. New instruments promise higher sensitivity and resolution. The ultimate instrument would use as many of the annihilation events occurring with the body as possible. View full abstract»

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  • Engineering Aspects of PETT V

    Page(s): 2703 - 2706
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    PETT V1 is a high sensitivity, multislice positron emission tomograph designed for the imaging of the human brain. The design concepts incorporated in PETT V such as maximum circumferential detection efficiency, flexible linear and angular sampling, high and low resolution, and minimum data acquisition times of 1 second, enable it to be used in low resolution dynamic mode or high resolution static imaging modes. The engineering aspects of PETT V and its special "wobble" sampling are discussed. View full abstract»

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  • The Fluoroscopic Image as Input Data for Computed Tomography

    Page(s): 2707 - 2709
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    The use of a fluoroscopic imaging system for providing the projection data required in computerized tomography has been explored. The capability of both conventional systems and large flat screen-low light level vidio systems are discussed. The highlights of previously published data are also presented. Specific applications to radiation therapy are illustrated and the equipment described. The differential contrast senditivity is of the order of 0.5%, spatial resolution less than 0.5 mm, and slice thickness approximately 1 mm. Patient skin exposure is expected to be between 150 mR and 300 mR per scan. View full abstract»

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  • A New Development in Single Gamma Transaxial Tomography Union Carbide Focused Collimator Scanner

    Page(s): 2710 - 2712
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    The evolution of gamma-ray imaging is traced and a new gamma-ray transverse section tomographic instrument is described which matches the favorable properties of wide-aperture focusing collimators to a form of the Radon equation which requires only angular averages of line integrals for reconstructions. Single slice scans of less than 5 minutes are accomplished with amounts of radioactivity that are standard for procedures using gamma cameras. View full abstract»

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  • The DSR: A High-Speed Three-Dimensional X-Ray Computed Tomography System for Dynamic Spatial Reconstruction of the Heart and Circulation

    Page(s): 2713 - 2717
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    High temporal resolution, full three-dimensional imaging of the heart and circulation is required for accurate basic physiological studies of the structural-to-functional relationships of these organ systems, and for improved diagnostic evaluation and treatment of patients with cardiovascular disorders. A new generation, fully electronic and very rapid whole-body computed tomography system called the Dynamic Spatial Reconstructor (DSR) will provide stop-action (0.01 sec), rapidly sequential (60-per-second), synchronous volume (240 simultaneous transaxial sections) reconstructions and display of the full anatomic extent of the heart throughout successive cardiac cycles, and will permit visualization of the three-dimensional vascular anatomy and circulatory functions in all regions of the body of patients with cardiovascular and other pathological disabilities. The feasibility and potential of a DSR system has been demonstrated by studies using a currently operational single source prototype assembly, the SSDSR, from which full three-dimensional dynamic reconstructions of the thorax and its contents have been obtained. View full abstract»

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  • High Speed Array Processing Method Applied to 2-D and 3-D Image Processing

    Page(s): 2718 - 2719
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    This paper presents an overview of the methods of array processing as practiced at Floating Point Systems, Inc. The concepts of parallel, pipelined processing - both in hardware and software - are shown to produce very fast computations when applied to highly repetitive calculations. Examples of times for computing 2D FFT's are given. View full abstract»

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  • A Proposed Dynamic Cardiac 3-D Densitometer for Early Detection and Evaluation of Heart Disease

    Page(s): 2724 - 2727
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    An inexpensive, high-speed multiple section computed-tomographic X-ray transmission scanner has been designed. This scanner utilizes a novel multipleanode, scanning-electron-beam, X-ray source to obtain scan times of 50 msec for two adjacent tomographic sections. Up to 8 sections may be scanned in sequence in 200 msec. A conventional stationary detector array and data processing system is used. Dynamic scanning at a rate of 1/sec for 20 seconds (up to 160 images) in combination with intravenous contrast media injections will be used to determine regional myocardial perfusion and to quantify the volume of ischemic and infarcted tissue. Image quality comparable to conventional body scanners is expected. View full abstract»

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  • "Positology"-the search for suitable detector arrangements for a positron ECT with continuous rotation

    Page(s): 2728 - 2731
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    This paper proposes a continuously rotating positron ECT system, in which the detectors are arranged on a circular ring with "non-uniform" spacing so as to provide much finer sampling interval in the projections than the conventional circular ring system. The address signals on the coincidence events are read out through a rotary photo-coupler, and the detector system can be rotated at a desired speed. Suitable detector arrangements are searched which provide sufficiently fine sampling interval with reasonable sampling density uniformity. Assuming about 50 detectors are arranged on a circle, the sampling characteristics of various detector arrangements have been examined. An iterative search method has also been applied to find a reasonable arrangement. The best arrangement has been obtained by the iterative method. It has an effective sampling interval of the order of (1/200)R, where R is the radius of the detector array, and the sampling density uniformity after 5-point smoothing is -7.8 ˜/spl I.chemo/18 % in the range of /spl I.chemo/ R/2. View full abstract»

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  • Initial Performance of SPRINT: A Single Photon System for Emissi on Tomography

    Page(s): 2732 - 2735
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    SPRINT is a transaxial tomograph for use with single photon emitting nuclides. It consists of an aperture cylinder surrounded by a ring of NaI(Tl) detectors. The singles count rate for each detector is correlated with the aperture cylinder position. This provides a view of the image plane activity distribution from each detector's perspective. These views are then combined to form a slice image. Preliminary operation of the device has recently been accomplished. The structure of operation and calibration procedures has been defined. The statistical behavior of single detector data agrees with expectations. Individual point source data for a variety of positions agree with calculations for both resolution and sensitivity. These data arrays have been used with a modified ART routine to provide two dimensional source images. View full abstract»

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  • Electrical Impedance Computed Tomography (ICT): A New CT Imaging Technique

    Page(s): 2736 - 2739
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    The results of our initial studies of a new method of CT imaging are presented. The technique does not use x rays, but rather employs a weak electrical current to map out the electrical properties of the tissues in a tomographic slice. Results of preliminary computer simulations are described and discussed. Compared to x-ray CT, we expect ICT to have the following advantages: (1) reduced biological hazard, (2) less expensive hardware, (3) easily extended to full 3-D image, (4) very high data rates, (5) ability to make unique physiological measurements. View full abstract»

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Aims & Scope

IEEE Transactions on Nuclear Science focuses on all aspects of the theory and applications of nuclear science and engineering, including instrumentation for the detection and measurement of ionizing radiation; particle accelerators and their controls; nuclear medicine and its application; effects of radiation on materials, components, and systems; reactor instrumentation and controls; and measurement of radiation in space.

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