X-ray compton scattering density measurement at a point within an object

• US 6,563,906 B2
• Filed: 08/22/2001
• Issued: 05/13/2003
• Est. Priority Date: 08/28/2000
• Status: Expired due to Fees

• Current Assignee: University of New Brunswick
• Original Assignee: University of New Brunswick
• Inventors: Achmad, Balza, Hussein, Esam
• Primary Examiner(s): Church, Craig E.
• Application Number:
  US09/933,906
• Publication Number:
  US 20020044628A1
• Time in Patent Office: 629 Days
• Field of Search: 378/89, 378/90, 378/86
• US Class Current: 378/89
• CPC Class Codes: G01B 15/025 by measuring absorption

Abstract

The present invention pertains to a non-rotating method for non-intrusively determining the density of a point embedded within an object, without necessarily obtaining a full image for the entire object. The method consists of passing a X-ray beam through a point within an object and measuring Compton scatterings from the point from a first and second energy bands within the energy spectrum of the X-ray beam, along a first and second angles from the X-ray beam. Using the kinetics of Compton scattering at a specific angle, four equations are formulated with four measurements and four unknowns; the radiation attenuation factor along the object between the X-ray source and the point, the radiation attenuation factor between the point and each of the detectors and the density of the object at the point. The four equations are solved simultaneously to determined the four unknowns. There is also provided a matrix inversion process to facilitate the solution of the equations.

Claims

1. A method for determining the density at a point within a body, comprising the steps of:

providing a X-ray source;

providing a first and second radiation detectors;

using said X-ray source, passing a X-ray beam through a point within a body;

said X-ray beam having an energy spectrum;

selecting a first and second source energy bands within said energy spectrum;

using said first and second radiation detectors, obtaining measurements of Compton scattering from said point within said body from said first and second source energy bands, along a first and second angles from said X-ray beam;

using said measurements of Compton scattering from said point within said body from said first and second source energy bands, along said first and second angles from said X-ray beam, mathematically determining a density of said point within said body.

2. The method as claimed in claim 1, further comprising the step of;

using said measurements of Compton scattering from said point within said body from said first and second source energy bands, along said first and second angles from said X-ray beam, mathematically determining a first radiation attenuation factor between said X-ray source and said point;

a second radiation attenuation factor between said point and said first detector, and a third radiation attenuation factor between said point and said second detector.

3. The method as claimed in claim 2, further comprising the steps of:

providing a third radiation detector;

obtaining measurements of radiation transmitted through said point within said body along said X-ray beam from said first and second source energy bands, and said step of

using said measurements of Compton scattering from said point within said body from said first and second source energy bands, along said first and second angles from said X-ray beam, mathematically determining a density of said point within said body,

comprises the additional step of using said measurements of radiation transmitted through said point within said body along said X-ray beam from said first and second source energy bands.

4. The method as claimed in claim 1, wherein said first and second angles are between 30 and 60 degrees and between 120 and 150 degrees respectively from said X-ray beam.

5. The method as claimed in claim 4, further comprising the steps of:

providing a third radiation detector,

obtaining measurements of Compton scattering from said point within said body from said first and second source energy bands, along a right angle from said X-ray beam, and said step of

using said measurements of Compton scattering from said point within said body from said first and second source energy bands, along said first and second angles from said X-ray beam, mathematically determining a density of said point within said body,

comprises the additional step of using said measurements of Compton scattering from said point within said body from said first and second source energy bands, along a right angle from said X-ray beam.

6. The method as claimed in claim 1, wherein said step of mathematically determining a density of said point within said body, comprises the steps of formulating and simultaneously solving four equations containing four unknowns.

7. The method as claimed in claim 1, further comprising the step of calculating a mean energy for each of said measurements of Compton scatterings from said point within said body from said first and second source energy bands, along said first and second angles respectively.

8. The method as claimed in claim 6, wherein said step of formulating and simultaneously solving four equations with four unknowns comprises the steps of formulating and inverting a square matrix.

9. The method as claimed in claim 1, further comprising the step of selecting said first and second source energy bands where Compton scattering dominates in said energy spectrum.

10. The method as claimed in claim 9, wherein said first and second energy bands do not overlap each other along said source energy spectrum.

11. A method for determining the density at a point within a body, comprising the steps of:

providing a X-ray source;

providing a first and second radiation detectors;

using said X-ray source, passing a X-ray beam through a point within a body;

said X-ray beam having a first source energy spectrum;

selecting a first and second source energy bands within said source energy spectrum of said X-ray beam;

using said first radiation detector, obtaining measurement of Compton scattering from said point within said body along a first angle and within a first detected energy spectrum related to said source energy spectrum and said first angle;

selecting a first and second detected energy bands within said first detected energy spectrum;

said first and second detected energy bands being related to said first and second source energy bands respectively and said first angle;

using said second radiation detector, obtaining measurement of Compton scattering from said point within said body along a second angle and within a second detected energy spectrum related to said source energy spectrum and said second angle;

selecting a third and fourth detected energy bands within said second detected energy spectrum;

said third and fourth energy bands being related to said first and second source energy bands respectively and said second angle;

extracting, from said measurement of Compton scattering from said point within said body along a first angle and within a first detected energy spectrum, measurements of Compton scattering from said point within said body along said first angle and within said first and second detected energy bands;

extracting, from said measurement of Compton scattering from said point within said body along a second angle and within a second detected energy spectrum, measurements of Compton scattering from said point within said body along said second angle and within said third and fourth detected energy bands; and

using said measurements of Compton scattering from said point within said body along said first angle, within said first and second detected energy bands;

said measurements of Compton scattering from said point within said body along said second angle, within said third and fourth detected energy bands;

mathematically determining an attenuation factor of said X-ray beam between said X-ray source and said point;

an attenuation factor of Compton scattering between said point and said first detector;

an attenuation factor of Compton scattering between said point and said second detector, and a density of said point within said body;

such that a density of said point within said body is determinable by exposing said body to a single X-ray beam.

12. The method as claimed in claim 11, further comprising the steps of:

providing a third radiation detector; and

using said third radiation detector, obtaining measurement of Compton scattering from said point within said body along a third angle and within a third detected energy spectrum;

said third detected energy spectrum being related to said first source energy spectrum and said third angle,

selecting a fifth and sixth detected energy bands from said third detected energy spectrum;

said fifth and sixth detected energy bands being related to said first and second source energy bands respectively and to said third angle, and

extracting, from said measurement of Compton scattering from said point within said body along a third angle and within a third detected energy spectrum, measurements of Compton scattering within said fifth and sixth detected energy bands, and

said step of;

using said measurements of Compton scattering from said point within said body along said first angle, within said first and second detected energy bands;

said measurements of Compton scattering from said point within said body along said second angle, within said third and fourth detected energy bands;

mathematically determining an attenuation factor of said X-ray beam between said X-ray source and said point;

an attenuation factor of Compton scattering between said point and said first detector;

an attenuation factor of Compton scattering between said point and said second detector, and a density of said point within said body;

comprises the step of using said measurements of Compton scattering from said point within said body along said third angle and within said fifth and sixth detected energy bands.

13. The method as claimed in claim 12, wherein said first and second angles are between 30 and 150 degrees from said X-ray beam.

14. The method as claimed in claim 13, wherein said third angle is a right angle.

15. The method as claimed in claim 11, further comprising the steps of:

providing a third radiation detector; and

using said third radiation detector, obtaining measurement of radiation transmitted through said point within said body along said X-ray beam within a third detected energy spectrum;

said third detected energy spectrum being related to said source energy spectrum;

selecting a fifth and sixth detected energy bands from said third detected energy spectrum;

said fifth and sixth detected energy bands being related to said first and second source energy bands respectively;

extracting, from said measurement of radiation transmitted through said point within said body along said X-ray beam within said third detected energy spectrum, measurements of radiation transmitted through said point within said body within said fifth and sixth detected energy bands, and

said step of;

using said measurements of Compton scattering from said point within said body along said first angle, within said first and second detected energy bands;

said measurements of Compton scattering from said point within said body along said second angle, within said third and fourth detected energy bands;

mathematically determining an attenuation factor of said X-ray beam between said X-ray source and said point;

an attenuation factor of Compton scattering between said point and said first detector;

an attenuation factor of Compton scattering between said point and said second detector, and a density of said point within said body;

comprises the step of using said measurements of radiation transmitted through said point within said body along said X-ray beam within said fifth and sixth detected energy bands.

16. The method as claimed in claim 11 wherein said source energy spectrum has an extent of about 400 keV, said first source energy band is selected between 100 keV and 200 keV and said second source energy band is selected between about 300 keV and 400 keV.

17. A method for determining a density at a point within an object comprising the following steps;

obtaining separate measurements of Compton scatterings from a X-ray beam passing through a point within an object from each of two separate source energy bands within a X-ray source energy spectrum of said X-ray beam, from each of two different angles from said X-ray beam, and a unique relationship between said one of said measurements of Compton scatterings, one of said source energy bands and one of said angles;

formulating a number of density-measurement equations comprising said measurements, said unique relationship and said number of unknowns;

formulating a square matrix, with said equations;

inverting said matrix, and

solving said matrix and determining a density at said point within said object.

18. The method as claimed in claim 17, wherein said measurements of Compton scatterings are obtained with said angles being selected within a range of between 30 degrees and 150 degrees from said X-ray beam.

19. The method as claimed in claim 17, wherein said measurements of Compton scatterings are obtained with said source energy bands being selected with a similar band width, and being spaced apart a distance similar to said band width.

20. The method as claimed in claim 17, wherein said equations further comprise measurements of radiation transmitted from said X-ray beam through said point.

21. A method for determining the density at a point within a body, comprising the steps of:

passing a X-ray beam having an energy spectrum through a point within a body;

identifying a plurality of separate source energy bands within said energy spectrum;

obtaining separate measurements of radiation scattered from said point from each of said source energy bands, from each of different angles from said X-ray beam;

using said measurements, energies of said source energy bands, and Compton scattering principle, formulating a number of equations containing said number of unknowns comprising a density at said point within said body; and

solving said equations and determining said density.