Coded Aperture Imaging with X-rays (Flashing Tomosynthesis)
TL;DR: In this paper, four different versions of flash tomosynthesis are compared, and the obtainable image qualities and other practical features of these four new methods are compared in terms of image quality and image quality.
Abstract: So far, three-dimensional X-ray imaging methods like tomography, etc. require exposure times of a few seconds or more. Hence, moving objects like the pulsating heart cannot be observed. This obstacle can be overcome by using an array of synchronously flashed X-ray sources. The source array acts as the coded aperture. The X-ray photograph is decoded optically, showing arbitrary layers of the object. We present four new versions of ‘flashing tomosynthesis’, as this approach is called. The obtainable image qualities and other practical features of these four new methods will be compared.
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TL;DR: Methods for synthesizing sets of one-dimensional Welti codes with vanishing cross-correlation functions, and conditions upon their existence are discussed, and construction methods of sets of two and higher dimensional WeltI codes are presented.
Abstract: A Welti code is a binary sequence with an impulse-like autocorrelation function. A set of such codes may possess vanishing cross-correlation functions. The elements of Welti codes must be members of a set of at least two orthogonal vectors or subcodes. First, methods for synthesizing sets of one-dimensional Welti codes with vanishing cross-correlation functions, and conditions upon their existence are discussed. Then, construction methods of sets of two and higher dimensional Welti codes are presented. Based on these constructions, further sets of mutually orthogonal complementary codes in one or more dimensions can be derived. The use of such signals relates to various topics such as communication, radar and navigation systems, measuring and identification in one or higher dimensional systems, synchronization and spatial alignment, or coded aperture imaging.
74 citations
TL;DR: The current status of holography and its applications with some historical background to place the current activity in perspective is discussed in this article, where basic types of holograms are described together with their properties.
Abstract: The current status of holography and its applications are discussed with some historical background to place the current activity in perspective. Basic types of holograms are described together with their properties. Applications in optical image formation include photography, microscopy, image storage and image replication. Acoustic, X-ray, electron beam and microwave holography are briefly commented upon. The second major area of application is contour generation and interferometry. Finally, the current status of holographic optical elements is assessed.
44 citations
TL;DR: Pairs of binary odd-periodic complementary sequences are introduced, which can be constructed using q-ary m-sequences for many more lengths.
Abstract: A pair of binary sequences is called complementary if the sum of their aperiodic autocorrelation functions is zero except for zero shift Such sequences are known for relatively few lengths This correspondence therefore introduces pairs of binary odd-periodic complementary sequences, which can be constructed using q-ary m-sequences for many more lengths
43 citations
TL;DR: This system is feasible for both an ambulatory basis to allow high-volume cardiovascular angiographic screening by only one X-ray snapshot, and for quantification of natural progression or potential regression of coronary artery disease resulting from interventional or pharmacological therapy.
Abstract: A system for digital flashing tomosynthesis (DFTS) consists of four ECG-gated simultaneously flashed X-ray tubes, a 14-in image intensifier, a unit for digital subtraction angiography (DSA), a PC-hosted transputer network for three-dimensional (3-D) reconstruction as well as for quantitative coronary angiography and ventriculography, a display unit, and an individual digital archive. A presentation of DFTS tomoangiograms as a single slice or multiple slices of arbitrary thickness is available. DFTS also offers rotating and stereographic presentation of 3-D images. DFTS represents a system for standardized digital angiocardiography with digital archiving, and assures optimal reproducibility and safety. This system is feasible for both an ambulatory basis to allow high-volume cardiovascular angiographic screening by only one X-ray snapshot, and for quantification of natural progression or potential regression of coronary artery disease resulting from interventional or pharmacological therapy. >
42 citations
Cites background from "Coded Aperture Imaging with X-rays ..."
...Flashing tomosynthesis is an innovative concept to avoid these problems [7]-[ 9 ]; a system with 24 or 16 X-ray tubes has been tested for visualization of the cerebral [lo]-[ 111 and coronary arteries [12]-[14]....
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TL;DR: The reduction of the sensitivity gain of a Hadamard measurement and an upper limit for the gain of any cyclic multiplexing strategy in the presence of photon noise are derived.
Abstract: Hadamard multiplexing is a measurement strategy that yields best sensitivity improvements over scanning measurements for signal-independent detector noise. The presence of photon noise degrades the performance of Hadamard multiplexing because of the increase of photon noise by the superposition of multiple signals. I derive the reduction of the sensitivity gain of a Hadamard measurement and an upper limit for the gain of any cyclic multiplexing strategy in the presence of photon noise. This upper limit clearly exceeds the reduced Hadamard gain and can be achieved by multiplexing sequences that differ from Hadamard S sequences but also share some similarities with respect to their autocorrelation. Examples of such sequences are given. As the analysis shows, the presence of photon noise limits the gain of multiplexing strategies to a finite value, which depends on the ratio between photon noise and detector noise and cannot be exceeded by increasing the number of multiplexed channels. In addition, only switching multiplex schemes, which superpose either all the light or no light of individual channels, can achieve the upper limit of the gain.
31 citations
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TL;DR: A new field of engineering that promises to have a revolutionary impact on almost every field of science and technology is created, based upon mathematical concepts known as coherent or Fourier optics and holography.
Abstract: Dozens of research workers in more than a hundred leading laboratories of the world are working on creating the foundations for a new field of engineering that promises to have a revolutionary impact on almost every field of science and technology. Resulting from the introduction of a variety of new techniques and devices?including the laser?as well as from the development of new photo-sensitive and electron-beam recording materials?including thermoplastics, codable films, and mass-storage holographic memories?this new technology, known as optical computing, is based upon mathematical concepts known as coherent or Fourier optics and holography. In terms of future developments and applications, the most dramatic results very likely will emerge from the implementation of real-time image processing in various forms. But the great power of optical computing derives primarily from its newly recognized capability of parallel processing, a natural property of the lens! In a general way, all aspects of this new field can be characterized by established concepts of electric and electronic signal processing and communications.
167 citations
TL;DR: In this article, an optical waveguide was produced in n-type GaAs by implantation with 300-keV protons, and the guiding was due to the elimination of charge carriers from the implanted region.
Abstract: We have produced optical waveguides in n‐type GaAs by implantation with 300‐keV protons. The guiding is shown to be due to the elimination of charge carriers from the implanted region. Annealing of the waveguide leads to very large reductions in the 1.15‐μ guided‐wave absorption.
143 citations
TL;DR: In this article, the advantages and problems arising with such a camera are discussed, and expressions are derived to describe the relative efficacy of three exposure/postprocessing schemes using multiple-pinhole cameras.
Abstract: When making photographs in x rays or γ rays with a multiple‐pinhole camera, the individual images of an extended object such as the sun may be allowed to overlap; then the situation is in many ways analogous to that in a multiplexing device such as a Fourier spectroscope. Some advantages and problems arising with such use of the camera are discussed, and expressions are derived to describe the relative efficacy of three exposure/postprocessing schemes using multiple‐pinhole cameras.
69 citations