Showing papers on "Iterative reconstruction published in 1974"
TL;DR: The paper considers both the diffuse and nondiffuse illumination schemes and discusses the relative advantages and disadvantages of digital and optical reconstruction schemes.
Abstract: Digital and optical reconstruction techniques are applied to synthetic holograms that are recorded at suboptical frequencies. The first section of the paper considers digital reconstruction that entails the application of the inverse diffraction transform to the diffraction pattern of an object illuminated with a suboptical source. Different cross sections of the object are displayed on a CRT in a sequential fashion. Image enhancement techniques are also employed in the process of digital reconstruction. The second section outlines a method for partially alleviating the longitudinal distortion that is inherent in optical reconstruction from synthetic holograms because of the difference between the recording and reconstructing wavelengths. The paper considers both the diffuse and nondiffuse illumination schemes and discusses the relative advantages and disadvantages of digital and optical reconstruction schemes.
88 citations
TL;DR: In this article, general views on the physical aspects, mathematical image reconstruction methods and algorithms, and associated detection electronics are given; however, the technique can be applied to emission studies, for instance in positron camera.
Abstract: General views on the physical aspects, mathematical image reconstruction methods and algorithms, and associated detection electronics are given. Transmission techniques are emphasized; however, the technique can be applied to emission studies, for instance in positron camera.
83 citations
TL;DR: A work-in-progress report is presented dealing with several methods of iterative 3-dimensional reconstruction that are more accurate than the usual methods and the behavior of a number of algorithms upon varying the number of iterations.
Abstract: A work-in-progress report is presented dealing with several methods of iterative 3-dimensional reconstruction that are more accurate than the usual methods, and the behavior of a number of algorithms upon varying the number of iterations, the number of projections, the counts per projection, and the field of view of the detector.
67 citations
TL;DR: The general problems associated with multiple scan photon/X-ray transmission image reconstruction are formulated and a technique which leads to a highly accurate solution is presented.
Abstract: The general problems associated with multiple scan photon/X-ray transmission image reconstruction are formulated and a technique which leads to a highly accurate solution is presented. The method, 'Technique of Linear Superposition with Compensation', is detailed, together with the computer algorithm and simulation results.
41 citations
01 Jan 1974
TL;DR: The filtered back-projection technique (convolution method) is superior in speed; however, for quantitative results that take into account both noise and attenuation, the iterative least-squares method gives the best approximation to the real source distributions.
Abstract: Quantitative three-dimensional distribution of radioisotopes in patients is determined by digital reconstruction of data from many views taken by rotating the subject at 10 deg intervals before the gamma camera. The superiority of these techniques over conventional tomography is demonstrated by comparisons between reconstruction algorithms such as back-projection, simultaneous iterative reconstruction, iterative least-squares, and back-projection of filtered projection. The filtered back-projection technique (convolution method) is superior in speed; however, for quantitative results that take into account both noise and attenuation, the iterative least-squares method gives the best approximation to the real source distributions. Resolution is 1.25 cm for detection of holes in 20-cm-diamieter objects. Mathematical basis and FOR-TRAN listings applicable to transmission and emission imaging are given, as well as results of phantom and patient studies. (60 references) (auth)
41 citations
01 Aug 1974
TL;DR: In this paper, a family of DEFT cameras employed coupling between surface strain waves, the image intensity, and electrical charge to produce electronic signals representing the spatial Fourier transform of the image at a single pair of terminals.
Abstract: A family of novel devices for electronic imaging is described and several different realizations age presented. Direct electronic Fourier transform (DEFT) cameras employ coupling between surface strain waves, the image intensity, and electrical charge to produce electronic signals representing the spatial Fourier transform of the image at a single pair of terminals. This signal can be easily processed to accomplish pattern recognition, all-electronic image magnification (zoom) and stabilization, motion detection, and focusing. Reproduction of the image is expected to be accomplished by a light valve employing strain-induced modulation of uniform light. Experimental results for light intensity variation in one dimension are reviewed for a silicon chip bulk acoustic wave camera and for a CdS surface wave camera. Some preliminary results are also reported for a fused quartz elastobirefringent light valve image reconstruction device.
25 citations
TL;DR: It is shown that digital and optical linear spatial filtering techniques may be employed to remove the blurring that is present in the tomographic image obtained with the new transverse tomographic apparatus.
Abstract: A new transverse tomographic apparatus is described that enables the tomogram to be related to the ideal image by a linear blurring operation. It is shown that digital and optical linear spatial filtering techniques may be employed to remove the blurring that is present in the tomographic image obtained with the new device. Experimental verification of both restoration methods is presented.
23 citations
TL;DR: An improved alogrithm for solving iteratively the linear equations relating a three-dimensional density to a given set of its projections, when the unknown density is expressed as samples on a grid is described.
Abstract: WE describe an improved alogrithm (EFIRT) for solving iteratively the linear equations relating a three-dimensional density to a given set of its projections, when the unknown density is expressed as samples on a grid. The need to solve such equations arises in electron microscopy, medical radiography, radio and X-ray astronomy and other fields. The projection equations comprise a very large, sparse and often under-determined set. If the number of unknowns is not too large, the equations may be solved by a least squares procedure, using filtering to combat the ill-conditioning1. The number of unknowns is often too great for such a procedure to be computationally feasible and iterative techniques2,3 must be used. Alternatively the Fourier transform provides a stable and computationally efficient means of solution1. Sometimes use of the Fourier transform is not convenient; for example, if point rather than plane projections are given or if the projection data are weighted by a non-uniform but linear response of the measuring device. Such problems are much more readily expressed in terms of projection equations and the development of stable methods for their solution is therefore important.
22 citations
Journal Article•
TL;DR: In this paper, new inversion procedures are derived for one-dimensional object reconstruction which use sampling values of known distributions, and a reconstruction procedure is discussed where the sampling points can be chosen at will.
15 citations
TL;DR: In this paper, a theoretical investigation of the imaging of extended objects using a Fresnel zone plate as a coded aperture with coherent-optical image reconstruction is presented, where artifacts are introduced in the images of large objects.
Abstract: A theoretical investigation of the imaging of extended objects is presented using a Fresnel zone plate as a coded aperture with coherent-optical image reconstruction. Faithful images are obtained only for small objects; artifacts are introduced in the images of large objects. Attempts to increase image fidelity are shown to be only moderately successful.
7 citations
01 Jan 1974
TL;DR: The present system configuration is such that, although in actual operation it does not constitute a real-time imaging system, in every other way one can evaluate its capabilities.
Abstract: The application of ultrasonic holography to medicine has been suggested by many researchers as an alternative to the use of pulse-echo systems for medical diagnosis. This program has as an ultimate objective the development of a real-time holographic imaging system with digital image reconstruction and its evaluation for medical research. The present system configuration is such that, although in actual operation it does not constitute a real-time imaging system, in every other way one can evaluate its capabilities. Data acquisition, recording, and image reconstruction are performed under control of an Alpha-16 minicomputer. Image reconstruction is performed, however, off-line by a CDC 7 600 computer system. The system offers a variety of modes of operation. Holographic data may be collected by means of a piezoelectric sensing array, or may be modeled by means of digital computation. Although the system is being built with a particular array sensor, through the use of modeling, the performance of arrays with different elements and different spacings may be readily evaluated.
01 Jan 1974
TL;DR: In acoustical holography, the optical reconstruction is mostly investigated for its excellent capability for processing large amount of twodimensional holographic information and its easiness in reproducing images with visible light but the image reconstruction by non-optical waves is used for special purpose and few investigations are conducted on this technique.
Abstract: In acoustical holography the reconstruction techniques of images from recorded acoustical holograms are classified mainly into three categories, that is, 1) optical reconstruction,1 2) numerical reconstruction,2–4 3) reconstruction by non-optical waves.5 In these reconstruction techniques, the optical reconstruction is mostly investigated for its excellent capability for processing large amount of twodimensional holographic information and its easiness in reproducing images with visible light. However the optical reconstruction has its inconvenience, that is it needs a photographic process when the acoustical holograms are recorded on films, making it impossible to reconstruct images in real time. The image reconstruction by non-optical waves, for example acoustical waves,5 now is used for special purpose and few investigations are conducted on this technique.
TL;DR: In this article, a procedure based on the envelope concept of differential geometry is described that permits the reconstruction of the contour of a smooth, moving, conducting target, satisfying the geometrical optics approximation.
Abstract: A procedure based on the envelope concept of differential geometry is described that permits the reconstruction of the contour of a smooth, moving, conducting target, satisfying the geometrical optics approximation. The target reflections are assumed to be specular in nature with either one reflection point or multiple resolvable reflection points. The time variation of the range to the reflection point of the target (assumed derivable from a high-resolution radar) and the general motion of the target (assumed derivable from tracking or trajectory information) are employed to reconstruct the contour of that portion of the assumed target surface that is illuminated by the radar. The reconstruction is accomplished by the simultaneous solution of two nonlinear differential equations which are derived using the envelope concept of differential geometry. Several reconstruction examples based on computer analysis are presented which indicate the results obtainable using this method.
01 Mar 1974
TL;DR: In this article, a description of various 3D image re-construction algorithms are given, with par- ticular reference to transmission tomography, and Fourier, Fourier-convolution and analytical methods are presented in detail.
Abstract: MATHEMATICAL ASPECTS OF TRANSMISSION THREE -DIMENSIONAL IMAGE RECONSTRUCTIONZ.H. Cho* Laboratory of Nuclear Medicine and Radia-tion Biology, and'Dept. of Electrical Scienceand Engineering, University of CaliforniaLos Angeles, California 90024 called Transverse Axial Tomography (TAT) or CTAT (C for computerized). One may start byinvestigating the algorithmic development from the CTAT concept. Let us assume that a projection at a iven angle e and position 9, is denoted as(see Fig. 1),f(2.0) =f f(x,y)ds L A description of various 3 -D image re- construction algorithms are given, with par- ticular reference to transmission tomography.Fourier, Fourier -convolution and analyticalmethods are presented in detail. I. INTRODUCTION3- Dimensional image reconstruction applied to transverse axial scanning has cre-ated great excitation in many areas of sci-entific disciplines, such as the brain scan- ning in medicine. This development may well have great potential applications in biomedi-cal applications, electron microscopy, radio
Dissertation•
01 Jan 1974
TL;DR: In this paper, the development and performance of a transistor scanned solid state ultrasonic image converter are described and the results of investigations into various applicable signal processing techniques to produce visible pictures are presented.
Abstract: The development and performance of a transistor scanned solid state ultrasonic image converter are described and the results of investigations into various applicable signal processing techniques to produce visible pictures are presented, The general requirements of an ultrasonic imaging system are considered and this is followed by a critical survey of the more sensitive ultrasonic image conversion methods. The operation and basic performance of the transistor scanned converter are discussed and its resolution and sensitivity investigated , resulting in an apparent practical limit to the resolution in. the image plane of ⅓ mm, and an estimated limiting sensitivity of approximately 10-13 W cm-2. Possible methods for the fabrication of a multielement converter are suggested and discussed. Three signal processing techniques are investigated and compared; ;that using an acoustic lens in a conventional camera arrangement, an on-line computer which effectively performs electrically the function of a lens, and a scanned array Doppler system on which only a feasibility study was carried out. It is argued that if flexibility is important then the computer "lens" is the most fitting method, and results for both near field focusing and far field beam deflection are presented) although at the moment.in 1-dimension only , A relatively simple extension to the program will make 2-dimensional image reconstruction possible.. The Doppler system described provides a simple electrical method of determining the range and bearing of far field targets and results adequately confirm the developed theory.
01 Oct 1974
TL;DR: In this paper, the effects of changes in both, the hologram-structure, and in the measured amplitude and phase values by quantization upon the reconstructed image are shown, and the appearance of hot spots, caused by the imaging of three-dimensional metallic objects is reduced by aspect-angle diversity or by frequency diversity.
Abstract: This paper shows the results of holographic imaging experiments at the 35 GHz band. The hologram was reduced by an inserted lens and the images were reconstructed by computer. The effects of changes in both, the hologram-structure, i.e. hologram-size and sampling, and in the measured amplitude and phase values by quantization upon the reconstructed image are shown. The disturbance of the images, i.e. the appearance of 'hot spots', caused by the imaging of three-dimensional metallic objects is reduced by aspect-angle diversity or by frequency diversity. Applying two different reference-phase measurements, the limitations of the object's translational and rotational movements during the hologram recording are given.
15 Aug 1974