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US5539800A
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Pseudolocal tomography
Assignee: University of California
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Filing: 1995-03-24
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Granted: 1996-07-23
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Expires: 2015-03-24
Abstract
Abstract Local tomographic data is used to determine the location and value of a discontinuity between a first internal density of an object and a second density of a region within the object. A beam of radiation is directed in a predetermined pattern through the region of the object containing the discontinuity. Relative attenuation data of the beam is determined within the predetermined pattern having a first data component that includes attenuation data through the region. The relative attenuation data is input to a pseudo-local tomography function, where the difference between the internal density and the pseudo-local tomography function is computed across the discontinuity. The pseudo-local tomography function outputs the location of the discontinuity and the difference in density between the first density and the second density.
Inventors
- 👤 Alexander J. Katsevich
- 👤 Alexander G. Ramm
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 22:50
CPC Classifications
G; G01; G01N; G01N23/00; G01N23/02; G01N23/04; G01N23/046; G01N2223/00; G01N2223/40; G01N2223/419; Y; Y10; Y10S; Y10S378/00; Y10S378/901
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
137 words
A method for determining by tomography the location and value of a discontinuity between a first internal density of an object and a second density of a region within said object, comprising the steps of: directing a beam of radiation in a predetermined pattern through said region of said object containing said discontinuity; determining relative attenuation data of said beam within said predetermined pattern having a first data component that includes attenuation data through said region; inputting said relative attenuation data to a pseudo-local tomography function, where the difference between said first internal density and said pseudo-local tomography function is continuous everywhere and said pseudo-local tomography function is computed across said discontinuity; and outputting from said pseudo-local tomography function the location of said discontinuity and the difference in density between said first density and said second density.
Claim 2
Independent Claim
137 words
A method for determining by tomography the location and value of a discontinuity between a first internal density of an object and a second density of a region within said object, comprising the steps of: directing a beam of radiation in a predetermined pattern through said region of said object containing said discontinuity; determining relative attenuation data of said beam within said predetermined pattern having a first data component that includes attenuation data through said region; inputting said relative attenuation data to a pseudo-local tomography function, where the difference between said first internal density and said pseudo-local tomography function is continuous everywhere and said pseudo-local tomography function is computed across said discontinuity; and outputting from said pseudo-local tomography function the location of said discontinuity and the difference in density between said first density and said second density.
Claim 3
Dependent Claim
51 words
A method according to claim 1, wherein said pseudo-local tomography function is ##EQU17## so that the function ƒ.sub.σd (x) is computed at a point x using ƒ(θ,p) for (θ,p) satisfying |Θ·x-p|≦d, wherein integrals of f are taken along only lines passing at a distance not exceeding d from the point x.
Claim 4
Dependent Claim
12 words
A method according to claim 2, wherein σ d =1 and ##EQU18##
Claim 5
Dependent Claim
125 words
A method according to claim 3, wherein the step of outputting the location of said discontinuity and the difference in density includes the steps of: computing at nodes of a grid (x ij )=(ih,jh) around the function ##EQU19## arrange the values of f d ε is ascending order to define a sequence of values; compute Φ(x i .sbsb.0 j .sbsb.0) as the difference between values of local maximum and local minimum of ƒ d ε ; occurring in the neighborhood of x i .sbsb.0 j .sbsb.0 : normalize Φ(x 0 ); and locate maxima of Φ(x 0 ) to output the location and value of said discontinuity between said first internal density of said object and said second density of said region within said object.
Claim 6
Dependent Claim
50 words
A method according to claim 2, further including the steps of determining the constant ##EQU20## determining a gradient ∇ƒ.sub.σd,ε (x) related to the attenuation coefficient f at grid points located on opposite sides of said location of said density discontinuity; determining said value of said density discontinuity from said gradient.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-07-23 | 2000-01-22 | 2000-07-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-07-23 | 2004-01-22 | 2004-07-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-07-23 | 2008-01-22 | 2008-07-23 | $7700.00 | Window Closed / Lapsed |