Maximum entropy tomography in weapons diagnostics

Conference · Thu Oct 01 04:00:00 EDT 1987

OSTI ID:5969154

Johnson, D E

Tomographic reconstruction is a mathematical technique that has existed as a theory since the early part of this century. It was obvious that a two-dimensional image could be integrated in one direction to produce a one-dimensional curve. This curve is called a projection. The question was whether these projections could be recombined to reproduce the original image. It was shown that with continuous projections at all possible angles, the image could indeed be reproduced. The result was interesting, though not very useful. With the advent of computers large enough to handle the computation, the question became whether tomographic reconstruction could be reasonably approximated digitally, with a finite number of points representing the projections at a finite number of angles. The medical community has demonstrated that the approximation is acceptable; their reconstructions are often done with projections of 512 points at angles in increments of half a degree, from 0 to 180/sup 0/. Maximum entropy tomography allows us to do a reconstruction when only a limited number of data points are available. This technique will converge to a unique solution; it also will cope with noisy data to some degree. Maximum entropy tomography is derived by using Legrange multipliers to combine the equations relating the projections to the image with the equation defining entropy for the image. The resultant combined equation is maximized with respect to the image. The solution is in a form that can be iterated to produce a unique image from a specific set of projections. This technique has been adapted to downhole weapons diagnostics. Two different neutron imaging experiments, TITIS and TOMEX, use maximum entropy tomography. In both cases the amount of data that can be collected is limited by how much equipment can be placed downhole and by the amount of time available to collect the data.

• Research Organization: EG and G Energy Measurements, Inc., Los Alamos, NM (USA)
• DOE Contract Number: AC08-83NV10282
• OSTI ID: 5969154
• Report Number(s): CONF-8710117-4; ON: DE88000998
• Country of Publication: United States
• Language: English

Related Subjects

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
450202* -- Explosions & Explosives-- Nuclear-- Weaponry-- (-1989)
99 GENERAL AND MISCELLANEOUS
990220 -- Computers
Computerized Models
& Computer Programs-- (1987-1989)
ALGORITHMS
BOREHOLES
CAVITIES
COMPUTERIZED TOMOGRAPHY
DATA ACQUISITION
DIAGNOSTIC TECHNIQUES
ENTROPY
IMAGE PROCESSING
IMAGES
MATHEMATICAL LOGIC
MATHEMATICAL MODELS
NOISE
PHYSICAL PROPERTIES
PROCESSING
RESOLUTION
TESTING
THERMODYNAMIC PROPERTIES
TOMOGRAPHY
WEAPONS