MUON TOMOGRAPHY IMAGING IMPROVEMENT USING OPTIMIZED LIMITED ANGLE DATA

• US 20150287237A1
• Filed: 04/03/2015
• Published: 10/08/2015
• Est. Priority Date: 04/04/2014
• Status: Active Grant

• Current Assignee: Decision Sciences International Corporation
• Original Assignee: Decision Sciences International Corporation
• Inventors: Bai, Chuanyong, Kindem, Joel, Luo, Weidong, Sossong, Michael James, Steiger, Matthew, Simon, Sean
• Granted Patent: US 9,639,973 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01N 9/00 Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
• CPC Class Codes: G01V 5/00 Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity
• CPC Class Codes: G01V 5/22 Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays
• CPC Class Codes: G01V 5/226 using tomography
• CPC Class Codes: G06T 11/006 Inverse problem, transformation from projection-space into object-space, e.g. transform methods, back-projection, algebraic methods
• CPC Class Codes: G06T 11/60 Editing figures and text; Combining figures or text
• CPC Class Codes: G06T 15/08 Volume rendering

Abstract

Disclosed technology can provide a process for generating reconstructed muon image resolution to optimize the use of the limited angular range muon track data collected by a muon tomography system. In one aspect, a process for improving reconstructed muon image resolution for a volume of interest (VOI) imaged by a muon tomography system includes: collecting raw muon track data of cosmic ray muon tracks passing through the VOI; grouping the raw muon track data into two or more subsets of tracks based on at least one angular distribution of the muon tracks in the raw muon track data; generating a set of images of the VOI based on the two or more subsets of tracks; and combining information from the set of reconstructed images and a reconstructed image based on the full set of the raw muon track data to obtain a resulting reconstructed image of the VOI.

Claims

1. A method for generating charged particle tomography images for a volume of interest (VOI) by a charged particle tomography system, the method comprising:

collecting raw track data of tracks of cosmic-ray based charged particles passing through the VOI;

grouping the collected raw track data into subsets of the tracks based on angular distribution of the tracks in the raw track data;

generating a set of images of the VOI based on the grouped subsets of the tracks; and

combining information from at least the generated set of images to obtain an resulting image of the VOI.

2. The method of claim 1, comprising:

generating an image based on full set of the raw track data; and

wherein the combining includes combining information from the generated image based on the full set of the raw track data along with the information from the generated set of images to obtain the resulting image of the VOI.

3. The method of claim 2, wherein grouping the raw track data into the subsets of the tracks based on the angular distribution includes partitioning the raw track data into a first subset corresponding to large zenith angles and a second subset corresponding to small zenith angles.

4. The method of claim 3, wherein the first subset of tracks has a zenith angle range from 0 to X and the second subset of tracks has a zenith angle range from X to 90°

, wherein X is between 20°

to 45°

.

5. The method of claim 4, comprising:

selecting X so that percentage of the tracks in the first subset and percentage of the tracks in the second subset have a predetermined relationship.

6. The method of claim 5, wherein the predetermined relationship includes the two percentages being substantially equal to each other.

7. The method of claim 3, wherein a first image of the set of images based on the first subset of the tracks is associated with an object resolution in a horizontal direction parallel to a detector plane in the charged particle tomography system;

and

wherein a second reconstructed image based on the second subset of the tracks is associated with an object resolution in a vertical direction perpendicular to a detector plane in the charged particle tomography system.

8. The method of claim 7, wherein a third reconstructed image based on the full set of the raw track data is associated with an object resolution in the horizontal direction which is at a level between the object resolutions in the horizontal direction for the first reconstructed image and the second reconstructed image;

and

wherein the third reconstructed image based on the full set of the raw track data is associated with an object resolution in the vertical direction at a level between the resolutions in the vertical direction for the first reconstructed image and the second reconstructed image.

9. The method of claim 1, wherein grouping the raw track data into the subsets of the tracks based on the angular distribution includes:

partitioning the raw track data into a first subset corresponding to azimuthal angles in a first range which are within 45°

of an x-direction in a detector plane of the charged particle tomography system; and

partitioning the raw track data into a second subset corresponding to azimuthal angles in a second range which are within 45°

of a y-direction in a detector plane of the charged particle tomography system.

10. The method of claim 9, wherein a first image of the set of images based on the first subset is associated with an object resolution in the y-direction;

and

wherein a second reconstructed image of the set of images based on the second subset is associated with an object resolution in the x-direction.

11. The method of claim 1, wherein grouping the raw track data into the subsets of the tracks based on the angular distribution includes:

identifying a subset of the tracks which are substantially perpendicular to a direction û

in a detector plane of the charged particle tomography system.

12. The method of claim 11, wherein an image based on the identified subset of the tracks substantially perpendicular to the direction û

is associated with an object resolution in the û

-direction.

13. The method of claim 1, wherein grouping the raw track data into the subsets of the tracks based on the angular distribution includes:

partitioning the raw track data into a first subset corresponding to large zenith angles, a second subset corresponding to small zenith angles, and a third subset corresponding to azimuthal angles, wherein the large zenith angles, the small zenith angles, and the azimuthal angles for the first, second, and third subsets respectively are within 45°

of an x-direction in a detector plane of the charged particle tomography system; and

partitioning the raw track data into a fourth subset corresponding to azimuthal angles which are within 45°

of a y-direction in a detector plane of the charged particle tomography system.

14. The method of claim 1, wherein at least two of the subsets of the tracks share a common cosmic-ray based charged particle track.

15. The method of claim 1, wherein the cosmic-ray based charge particles include muons.

16. A method for generating charged particle tomography image for a volume of interest (VOI) by a charged particle tomography system, the method comprising:

collecting raw track data of tracks of cosmic-ray charged particles passing through the VOI;

generating an image of the VOI based on the raw track data;

identifying an orientation of objects in the generated image of the VOI based on the raw track data;

grouping the raw track data into subsets of the tracks based on the identified orientation;

generating a set of images of the VOI based on the subsets of the tracks; and

combining information from the generated set of images of the VOI based on the subsets of the tracks and the generated image based on the full set of the track data to obtain a resulting image of the VOI associated with a resolution along the identified orientation.

17. The method of claim 16, wherein grouping the raw track data into the subsets of the tracks based on the identified orientation includes identifying a subset of the tracks substantially perpendicular to the identified orientation.

18. The method of claim 17, wherein an image of the set of images based on the identified subset of tracks substantially perpendicular to the identified orientation is associated with an object resolution in the identified orientation.

19. The method of claim 16, wherein grouping the raw track data into the subsets of the tracks includes partitioning the raw track data into a first subset corresponding to large zenith angles and a second subset corresponding to small zenith angles.

20. The method of claim 19, wherein the first subset of the tracks has a zenith angle range from 0 to X and the second subset of the tracks has a zenith angle range from X to 90°

, wherein X is between 20°

or 45°

.

21. The method of claim 16, wherein a first image based on the first subset of tracks provides an improvement of an object resolution in a horizontal direction parallel to a detector plane in the charged particle tomography system;

and wherein a second image based on the second subset of tracks provides an improvement of an object resolution in a vertical direction perpendicular to a detector plane in the charged particle tomography system.

22. The method of claim 16, wherein grouping the raw track data into the subsets of the tracks includes partitioning the raw track data into a first subset corresponding to azimuthal angles in a first range which are within 45°

of an x-direction in a detector plane of the charged particle tomography system; and

a second subset corresponding to azimuthal angles in a second range which are within 45°

of a y-direction in the detector plane of the charged particle tomography system.

23. The method of claim 22, wherein a first reconstructed image based on the first subset of tracks is associated with an object resolution in the y-direction;

and

wherein a second reconstructed image based on the second subset of tracks is associated with an object resolution in the x-direction.

24. The method of claim 16, wherein the cosmic-ray charged particles include muons.

25. A method for performing charged particle tomography imaging of a volume of interest (VOI) by a charged particle tomography system, the method comprising:

changing an orientation of the VOI relative to a detector plane of the charged particle tomography system; and

collecting raw track data of tracks of cosmic-ray charged particles passing through the VOI at the changed orientation; and

generating an image of the VOI based on the collected raw track data at the changed orientation,

wherein changing the orientation of the VOI changes a zenith angular range of the tracks and changes a resolution of the generated image in a vertical direction perpendicular to the detector plane.

26. The method of claim 25, wherein changing the orientation includes:

rotating the VOI about a horizontal axis parallel to the detector plane of the charged particle tomography system by an angle between 0 and 90°

;

or

rotating the detector plane about the VOI by an angle between 0 and 90°

.

27. The method of claim 25, wherein the cosmic-ray charged particles include muons.

29. The tomography system of claim 27, further comprising a third set of position sensitive detectors positioned on a third position with respect to the VOI to detect horizontally propagating muons.

28. A charged particle tomography system for performing charged particle tomography imaging of a volume of interest (VOI) exposed to cosmic-ray charged particles, comprising:

a first set of position sensitive detectors located on a first position with respect to the VOI to detect events of incident charged particles that contact the first set of position sensitive detectors and enter the VOI;

a second set of position sensitive detectors located on a second position with respect to the VOI opposite to the first position to detect events of outgoing charged particles that exit the VOI and contact the second set of position sensitive detectors; and

a rotation mechanism configured to change an orientation of the VOI with respect to a detector plane of the first and second sets of position sensitive detectors by performing operations including

rotating the VOI about a horizontal axis parallel to the detector plane by an angle between 0 and 90°

, or

rotating the first and second sets of position sensitive detectors about the VOI by an angle between 0 and 90°

; and

a data collection module for collecting data of cosmic ray muon tracks passing through the VOI at the changed orientation,

wherein changing the orientation changes a zenith angular range and affects an image resolution in a vertical direction perpendicular to the detector plane.