Scatter Attenuation Tomography

• US 20080049899A1
• Filed: 08/22/2007
• Published: 02/28/2008
• Est. Priority Date: 08/23/2006
• Status: Active Grant

• Current Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Original Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Inventors: Rothschild, Peter
• Granted Patent: US 7,551,718 B2
• Time in Patent Office: Days
• US Class Current: 378/86
• CPC Class Codes: G01N 23/20 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
• CPC Class Codes: G01V 5/222 measuring scattered radiation

Abstract

Methods for characterizing an inspected object on the basis of attenuation determined from pair-wise illuminated voxels. A beam of penetrating radiation characterized by a propagation direction and an energy distribution is scanned across an object, while scatter detectors with collimated fields-of-view detect radiation scattered by each voxel of the inspected object that is intercepted by the incident beam of penetrating radiation. By calculating the attenuation of penetrating radiation between pairs of voxels of incidence of the incident beam, a tomographic image is obtained characterizing the three-dimensional distribution of attenuation in the object of one or more energies of penetrating radiation, and thus of various material characteristics.

Claims

1. A method for characterizing an object on the basis of mean-free-path of penetrating radiation, the method comprising:

generating an incident beams of penetrating radiation, the incident beam characterized by a propagation direction and an energy distribution;

disposing a plurality of detector elements about the beam of penetrating radiation each detector characterized by a field of view;

collimating the field of view of each detector;

detecting radiation scattered from a plurality of voxels lying within the inspected object, each voxel being defined as the intersection of the field of view of one of the detector elements and the propagation direction of the incident beam of penetrating radiation; and

calculating attenuation of scattered penetrating radiation between pairs of voxels, each voxel of the pair corresponding to one of at least two propagation directions of the incident beam of penetrating radiation.

2. A method in accordance with claim 1, further comprising varying the propagation direction of the incident beam of penetrating radiation so as to be incident sequentially on the inspected object at a plurality of points of incidence.

3. A method in accordance with claim 1, wherein the step of detecting radiation includes detecting specified energy components of the radiation scattered out of the incident beam of penetrating radiation.

4. A method in accordance with claim 1, further comprising:

scanning the incident beam in a pattern substantially transverse to the propagation direction so as to be incident on the inspected object at a plurality of points of incidence.

5. A method in accordance with claim 1, further comprising a step of displaying the attenuation of penetrating radiation as a function of position within the inspected object.

6. A method in accordance with claim 1, wherein the step of disposing detectors about the incident beam of penetrating radiation includes disposing arrays of scatter detectors along directions having a vector component substantially parallel to the propagation direction of the incident beam.

7. A method in accordance with claim 1, wherein the step of disposing detectors about the incident beam of penetrating radiation includes disposing detectors in a plane substantially transverse to the beam of penetrating radiation.

8. A method in accordance with claim 1, wherein calculating the attenuation of penetrating radiation includes determining a mean free path of scattered radiation as a function of position within the inspected object.

9. A method in accordance with claim 1, wherein the step of collimating includes restricting the field of view of each detector to a direction at a specified range of angles with respect to the propagation direction of the incident beam.

10. A method in accordance with claim 1, further comprising varying the energy distribution of the incident beam of penetrating radiation.

11. A method in accordance with claim 1, wherein the step of scanning includes scanning an aperture with respect to an x-ray tube.

12. A method in accordance with claim 1, wherein the step of scanning includes activating discrete elements of a source array.

13. A method in accordance with claim 1, further comprising identifying a material as a threat substance based on a comparison of a calculated mean free path with a table of measured values.

14. A method in accordance with claim 1, further comprising validating a calculated attenuation based on a repeat interrogation of a voxel with detector elements of opposing field of view.