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The application of computerised X-ray tomography to ordnance
theoretically determining the kind of materials which can be scanned, which is a function of the CT-System at hand, and the interdependent contrast and spatial resolutions. The tradeoff between these two factors is discussed. Furthermore it is shown how the smallest detectable flaw sizes for given materials can bc estimated. Ways to enhance the quality of a tomogram, with respect to resolution, noise, flaw detection and artifacts are discussed. Experimental results with a medical system and examples verifying the theoretical predictions will be discussed. Also presented are initial results obtained with a high resolution tomography system presently developed at the lnstitut fuer zerstoerungsfreie Pruefverfahren (IzfP).
Feldkamp, L.A.; Kubinski, D.J.; Jesion, G. Application of high magnification to 3D X-ray computed tomography
40123
Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7A, pp. 381-388. Edited by D . D . T h o m p s o n and D . E . C h i m e n t i , Plenum Press, 1988. A system for direct three-dimensional x-ray computed tomography is described which is designed to inspect small objects, typically volumes of about 1 cubic centimeter, with substantially better spatial resolution than available from conventional CT scanners. Recently improvements to the system have included replacing the microfocus source, which had a minimum spot size of approximately 50 micrometers or less. At this spot size, the x-ray intensity is larger than that of the old source at its minimum spot size. The result for reconstruction is improved signal-to-noise and improved spatial resolution, Under standard conditions, the system resolution is now determined primarily by the spatial resolution of the x-ray image intensifier that serves as the two dimensional detector. In this paper initial findings are described for the conventional full-field configuration and in a configuration in which only a limited volume of a sample can be reconstructed. 39918 Hentea, T.; Ellingson, W.A.; Roberts, R.A.; Kriz, R.J. Deblurring of conventional tomography images with applications to the NDE of advanced ceramics Ceramic E n g i n e e r i n g and Science Proceedings, Vol. 9, Nos. 9-10, pp. 1471-1481 (1988). 12th A n n u a l Conference on Composites and A d v a n c e d Ceramic Materials, Part 2 of 2, Sep. Oct. 1988. Low-cost X-ray tomographic imaging methods may be useful for detecting defects in structural ceramics. Conventional film-based tomography systems, although potentially inexpensive, produce images that are affected by blurring caused by the structure of the object above and below the tomographic plane of interest. The blur can be removed by using digital image processing techniques. Three methods for deblurring images of ceramic specimens will be discussed, inverse filtering, iterative approximation, and multiplane approximation.
Lindegaard-Andersen, A.; Vedel, T.; Jeppesen, L.," Gottlieb, B. Film-based X-ray tomography combined with digital image processing: investigation of an ancient pattern-welded sword 39910
NDT International, Vol. 21, No. 6, pp. 407-410 (Dec. 1988) Film-based X-ray tomography and digital image processing have been used to investigate an inhomogeneous object of non-circular cross-section. The feasibility of using digital image processing to compensate for the poor contrast resolution inherent in film-based tomography has been demonstrated.
GeneralElectric Company Reconstructing objects from limited-angle scannings in computerized tomography 39809
British Patent No. 2,192,120 (31 Dec. 1987) The accuracy of limited-angle x-ray computerized tomography scannings is improved by incorporating additional a priori information on the object. In industrial nondestructive testing and other situations the object A contains a medium which is the dominant component whose density is known: flaws inside the medium are to be imaged. The contribution of the medium is eliminated and an image is reconstructed which is the difference between the original object and a hypothetical object made up entirely of the medium which has the same boundary as the original object. Calculated projections of the hypothetical object at various scan angles are subtracted from measured projections to yield difference productions d i . The latter are backprojectcd to derive image strips to which the flaws are confined and these are overlapped to construct a region enclosing the flaws. Using the difference projections and flaw-enclosing regions, the shape and density of the flaws are reconstructed by limited-angle reconstruction algorithms.
Kabushiki Kaisha Toshiba Radiation-detecting device for computed tomography 39777
U.S. Patent No. 4,725,734 (16 Feb. 1988) This radiation detecting device is used in computer tomography. A number of detector blocks are arranged end to end in a circle, with specific distances between them. The detector blocks consist of scintillation elements for converting X ray radiation into fluorescence, and two sets of collimator plates which prevents fluorescence emission crossing between adjacent scintillation elements. Two of the scintillation elements in each block are terminals and face the space between the blocks. One set of collimator plates is thicker than the other.
Steinboch, L. A line-scan camera for radiography and tomography of nuclear fuel elements 39630
288
Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, London (United Kingdom), 13-17 Sep. 1987. Vol. 3, pp. 2150-2155. Pergamon Press, 3173 pp. (1988) An electronic line-scan camera was developed which allows the acquisition of X-ray and neutron radiographs without films or etch foils. With proper collimation and different scintillators the camera is sensitive to X-rays and gamma-rays between 10keV and 10MeV and to neutrons between 0.025eV and 5eV. The camera and the object positioning is controlled by a personal computer which generates the images on a monitor and on a hard-copy device. According to the movement of the object the final image is either a shadow radiograph (axial scanning) or a tomograph (azimuthal scanning).
Heut, J.; Pauton, M.; Thomas, G.; Casagrande, J.M.; Lagnier, P.; Glasser, F. The industrial X-ray tomography study of high resolution analyzers 39628
Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, London (United Kingdom), 13-17 Sep. 1987. Vol. 3, pp. 2133-2141. Pergamon Press, 3173 pp. (1988) In conjunction with the CEA Company, the INTERCONTROLE Company has made two models of 420 kV X-ray scanners. The characteristics of these machines, some recent results and the high X-ray energy development are presented. 39626 Goebbels, J.; Heidt, H.; Kettschau, A.; Reimers, P. Computerized tomography of glass-fiber reinforced plastic components Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, London (United Kingdom), 13-17 Sep. 1987. Vol. 3, pp. 2111-2117. Pergamon Press, 3173 pp. (1988) X-ray computerized tomography was used to characterize defects like density variations, voids and delaminations in glass-fiber reinforced plastic components. Within the limitations of the used tomography the possibility to determine the porosity or air content in these components is discussed.
Hunt, C.A. The application of computerised X-ray tomography to ordnance 39625
Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, London (United Kingdom), 13-17 Sep. 1987. Vol. 3, pp. 2105-2110. Pergamon Press, 3173 pp. (1988) The use of Computerised Axial Tomography (CAT) has been slow to develop in the industrial field. However some research equipments have been operated, in the Royal Armament Research and Development Establishment (RARDE) U.K. a machine for the CAT scanning of Ordnance has been operating for over 5 years. The operating parameters and imaging qualities of this equipment are discussed, and a few of its uses are illustrated.
Annis, M.; B]orkholm, P. ZT: A tomographic backscatter technique for nondestructive evaluation 39605
Proceedings of the 16th Symposium on Nondestructive Evaluation, San A nt oni o, Texas (United States), 21-23 Apr. 1987. pp. 272-281. Nondestructive Testing Information Analysis Center, Texas, USA. A new X-ray imaging technique has been developed at American Science and Engineering, Inc. (AS&E) which has unique capabilities. This tomographic, backscatter system is called ZT. It images thin slices of the object under inspection parallel to the front surface of the object, and is sensitive to the electron density of the material. The system is particularly sensitive to delaminations within the first ten or twenty centimeters of the material. The system is more sensitiveto the detection of delaminations but at a smaller size and it can detect amounts of water as small as 0.1 cubic centimeter within composite materials. A laboratory system is described in detail, compared to CT, and applications of the technique to nondestructive evaluation will be given with quantitative results.
Ellingson, W.A.; Vannier, M.W.; Kriz, R.J. A comparison of analog tomography and computed tomography for nondestructive evaluation of advanced ceramic materials 39603
Proceedings of the 16th Symposium on Nondestructive E v alu atio n , San Antonio, Texas (United States), 21-23 Apr. 1987. pp. 252-263. Nondestructive Testing Information Analysis Center, Texas, USA. An X-ray computed tomography (CT) imaging system and an analog tomographic system were used to examine a green-state Si3N4 test specimen. The CT system used was a state-of-the-art medical CT scanner with a polychromatic source. The analog tomography system was a Siemens Optiplanimat with a tungsten target and 2.5-mm AI filtration. It was operated in one scan pattern. Single-emulsion industrial film was used to increase spatial resolution. Results show that with the equipment and test specimens used, smaller defects could be detected with CT than with analog tomography.
Devaney, A.J. Inverse scattering theory foundations of tomography with diffracting wavefields \ 39540
A n International Symposium on Pattern Recognition and Acoustical Imaging, Newport Beach, California (United States), 4-6 Feb. 1987. pp. 2-6. Proceedings of the SPIE - The International Society for Optical Engineering, Vol. 768 (1987) The underlying mathematical models employed in reflection and transmission computed tomography using diffracting wavefields (called diffraction
NDT International October 1990
Feldkamp, L.A.; Kubinski, D.J.; Jesion, G. Application of high magnification to 3D X-ray computed tomography
40123
Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7A, pp. 381-388. Edited by D . D . T h o m p s o n and D . E . C h i m e n t i , Plenum Press, 1988. A system for direct three-dimensional x-ray computed tomography is described which is designed to inspect small objects, typically volumes of about 1 cubic centimeter, with substantially better spatial resolution than available from conventional CT scanners. Recently improvements to the system have included replacing the microfocus source, which had a minimum spot size of approximately 50 micrometers or less. At this spot size, the x-ray intensity is larger than that of the old source at its minimum spot size. The result for reconstruction is improved signal-to-noise and improved spatial resolution, Under standard conditions, the system resolution is now determined primarily by the spatial resolution of the x-ray image intensifier that serves as the two dimensional detector. In this paper initial findings are described for the conventional full-field configuration and in a configuration in which only a limited volume of a sample can be reconstructed. 39918 Hentea, T.; Ellingson, W.A.; Roberts, R.A.; Kriz, R.J. Deblurring of conventional tomography images with applications to the NDE of advanced ceramics Ceramic E n g i n e e r i n g and Science Proceedings, Vol. 9, Nos. 9-10, pp. 1471-1481 (1988). 12th A n n u a l Conference on Composites and A d v a n c e d Ceramic Materials, Part 2 of 2, Sep. Oct. 1988. Low-cost X-ray tomographic imaging methods may be useful for detecting defects in structural ceramics. Conventional film-based tomography systems, although potentially inexpensive, produce images that are affected by blurring caused by the structure of the object above and below the tomographic plane of interest. The blur can be removed by using digital image processing techniques. Three methods for deblurring images of ceramic specimens will be discussed, inverse filtering, iterative approximation, and multiplane approximation.
Lindegaard-Andersen, A.; Vedel, T.; Jeppesen, L.," Gottlieb, B. Film-based X-ray tomography combined with digital image processing: investigation of an ancient pattern-welded sword 39910
NDT International, Vol. 21, No. 6, pp. 407-410 (Dec. 1988) Film-based X-ray tomography and digital image processing have been used to investigate an inhomogeneous object of non-circular cross-section. The feasibility of using digital image processing to compensate for the poor contrast resolution inherent in film-based tomography has been demonstrated.
GeneralElectric Company Reconstructing objects from limited-angle scannings in computerized tomography 39809
British Patent No. 2,192,120 (31 Dec. 1987) The accuracy of limited-angle x-ray computerized tomography scannings is improved by incorporating additional a priori information on the object. In industrial nondestructive testing and other situations the object A contains a medium which is the dominant component whose density is known: flaws inside the medium are to be imaged. The contribution of the medium is eliminated and an image is reconstructed which is the difference between the original object and a hypothetical object made up entirely of the medium which has the same boundary as the original object. Calculated projections of the hypothetical object at various scan angles are subtracted from measured projections to yield difference productions d i . The latter are backprojectcd to derive image strips to which the flaws are confined and these are overlapped to construct a region enclosing the flaws. Using the difference projections and flaw-enclosing regions, the shape and density of the flaws are reconstructed by limited-angle reconstruction algorithms.
Kabushiki Kaisha Toshiba Radiation-detecting device for computed tomography 39777
U.S. Patent No. 4,725,734 (16 Feb. 1988) This radiation detecting device is used in computer tomography. A number of detector blocks are arranged end to end in a circle, with specific distances between them. The detector blocks consist of scintillation elements for converting X ray radiation into fluorescence, and two sets of collimator plates which prevents fluorescence emission crossing between adjacent scintillation elements. Two of the scintillation elements in each block are terminals and face the space between the blocks. One set of collimator plates is thicker than the other.
Steinboch, L. A line-scan camera for radiography and tomography of nuclear fuel elements 39630
288
Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, London (United Kingdom), 13-17 Sep. 1987. Vol. 3, pp. 2150-2155. Pergamon Press, 3173 pp. (1988) An electronic line-scan camera was developed which allows the acquisition of X-ray and neutron radiographs without films or etch foils. With proper collimation and different scintillators the camera is sensitive to X-rays and gamma-rays between 10keV and 10MeV and to neutrons between 0.025eV and 5eV. The camera and the object positioning is controlled by a personal computer which generates the images on a monitor and on a hard-copy device. According to the movement of the object the final image is either a shadow radiograph (axial scanning) or a tomograph (azimuthal scanning).
Heut, J.; Pauton, M.; Thomas, G.; Casagrande, J.M.; Lagnier, P.; Glasser, F. The industrial X-ray tomography study of high resolution analyzers 39628
Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, London (United Kingdom), 13-17 Sep. 1987. Vol. 3, pp. 2133-2141. Pergamon Press, 3173 pp. (1988) In conjunction with the CEA Company, the INTERCONTROLE Company has made two models of 420 kV X-ray scanners. The characteristics of these machines, some recent results and the high X-ray energy development are presented. 39626 Goebbels, J.; Heidt, H.; Kettschau, A.; Reimers, P. Computerized tomography of glass-fiber reinforced plastic components Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, London (United Kingdom), 13-17 Sep. 1987. Vol. 3, pp. 2111-2117. Pergamon Press, 3173 pp. (1988) X-ray computerized tomography was used to characterize defects like density variations, voids and delaminations in glass-fiber reinforced plastic components. Within the limitations of the used tomography the possibility to determine the porosity or air content in these components is discussed.
Hunt, C.A. The application of computerised X-ray tomography to ordnance 39625
Proceedings of the 4th E u r o p e a n Conference on Non-Destructive Testing, London (United Kingdom), 13-17 Sep. 1987. Vol. 3, pp. 2105-2110. Pergamon Press, 3173 pp. (1988) The use of Computerised Axial Tomography (CAT) has been slow to develop in the industrial field. However some research equipments have been operated, in the Royal Armament Research and Development Establishment (RARDE) U.K. a machine for the CAT scanning of Ordnance has been operating for over 5 years. The operating parameters and imaging qualities of this equipment are discussed, and a few of its uses are illustrated.
Annis, M.; B]orkholm, P. ZT: A tomographic backscatter technique for nondestructive evaluation 39605
Proceedings of the 16th Symposium on Nondestructive Evaluation, San A nt oni o, Texas (United States), 21-23 Apr. 1987. pp. 272-281. Nondestructive Testing Information Analysis Center, Texas, USA. A new X-ray imaging technique has been developed at American Science and Engineering, Inc. (AS&E) which has unique capabilities. This tomographic, backscatter system is called ZT. It images thin slices of the object under inspection parallel to the front surface of the object, and is sensitive to the electron density of the material. The system is particularly sensitive to delaminations within the first ten or twenty centimeters of the material. The system is more sensitiveto the detection of delaminations but at a smaller size and it can detect amounts of water as small as 0.1 cubic centimeter within composite materials. A laboratory system is described in detail, compared to CT, and applications of the technique to nondestructive evaluation will be given with quantitative results.
Ellingson, W.A.; Vannier, M.W.; Kriz, R.J. A comparison of analog tomography and computed tomography for nondestructive evaluation of advanced ceramic materials 39603
Proceedings of the 16th Symposium on Nondestructive E v alu atio n , San Antonio, Texas (United States), 21-23 Apr. 1987. pp. 252-263. Nondestructive Testing Information Analysis Center, Texas, USA. An X-ray computed tomography (CT) imaging system and an analog tomographic system were used to examine a green-state Si3N4 test specimen. The CT system used was a state-of-the-art medical CT scanner with a polychromatic source. The analog tomography system was a Siemens Optiplanimat with a tungsten target and 2.5-mm AI filtration. It was operated in one scan pattern. Single-emulsion industrial film was used to increase spatial resolution. Results show that with the equipment and test specimens used, smaller defects could be detected with CT than with analog tomography.
Devaney, A.J. Inverse scattering theory foundations of tomography with diffracting wavefields \ 39540
A n International Symposium on Pattern Recognition and Acoustical Imaging, Newport Beach, California (United States), 4-6 Feb. 1987. pp. 2-6. Proceedings of the SPIE - The International Society for Optical Engineering, Vol. 768 (1987) The underlying mathematical models employed in reflection and transmission computed tomography using diffracting wavefields (called diffraction
NDT International October 1990