OPTICAL GEOMETRY CALIBRATION DEVICES, SYSTEMS, AND RELATED METHODS FOR THREE DIMENSIONAL X-RAY IMAGING

• US 20170219498A1
• Filed: 02/01/2017
• Published: 08/03/2017
• Est. Priority Date: 02/01/2016
• Status: Active Grant

• Current Assignee: University of North Carolina At Chapel Hill (University of North Carolina System)
• Original Assignee: University of North Carolina At Chapel Hill (University of North Carolina System)
• Inventors: Chtcheprov, Pavel, Zhou, Otto Z., Lu, Jianping
• Granted Patent: US 10,835,199 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2034/2065 Tracking using image or pattern recognition
• CPC Class Codes: A61B 2090/367 creating a 3D dataset from 2D images using position information
• CPC Class Codes: A61B 2560/0228 using calibration standards
• CPC Class Codes: A61B 5/0037 Performing a preliminary scan, e.g. a prescan for identifying a region of interest
• CPC Class Codes: A61B 6/04 Positioning of patients; Tiltable beds or the like operating tables A61G13/00; operating chairs A61G15/00
• CPC Class Codes: A61B 6/0492 using markers or indicia for aiding patient positioning
• CPC Class Codes: A61B 6/582 Calibration
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: A61B 6/584 determining position of components of the apparatus or device using images of the phantom
• CPC Class Codes: A61B 6/585 Calibration of detector units
• CPC Class Codes: G01N 2223/301 portable apparatus
• CPC Class Codes: G01N 2223/302 comparative arrangements
• CPC Class Codes: G01N 2223/303 calibrating, standardising
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• CPC Class Codes: G01T 1/2978 Hybrid imaging systems, e.g. using a position sensitive detector (camera) to determine the distribution in one direction and using mechanical movement of the detector or the subject in the other direction or using a camera to determine the distribution in two dimensions and using movement of the camera or the subject to increase the field of view G01T1/2985 takes precedence
• CPC Class Codes: G01T 7/005 calibration techniques stabilization of spectrometer G01T1/40

Abstract

Optical geometry calibration devices, systems, and related methods for x-ray imaging are disclosed. An optical-based geometry calibration device is configured to interface with a two-dimensional (2D) imaging device to perform three-dimensional (3D) imaging. The optical-based geometry calibration device includes one or more optical cameras fixed to either an x-ray source or an x-ray detector, one or more markers fixed to the x-ray detector or the x-ray source, with each of the one or more optical cameras being configured to capture at least one photographic image of one or more corresponding optical markers when each x-ray image of the object is captured, and an image processing system configured to compute positions of the x-ray source relative to the x-ray detector for each 2D projection image based on the at least one photographic image of the one or more markers

Claims

1. An imaging system with in situ real time determination of imaging geometries by which individual two-dimensional (2D) x-ray projection images are captured for three-dimensional (3D) image reconstruction, the imaging system comprising:

an x-ray source;

a detector positioned relative to the x-ray source, the detector being configured to obtain the individual 2D x-ray projection images of an object from a plurality of spatial positions and orientations of the x-ray source and/or the detector relative to the object;

an optical-based in situ real time geometry calibration device to determine a spatial position and orientation of the x-ray source and the detector relative to the object and to each other for each of the individual 2D x-ray projection images; and

an image processing system configured to reconstruct a 3D structure of the object from the individual 2D x-ray projection images and associated imaging geometry parameters.

2. The system of claim 1, wherein the optical-based in situ real time geometry calibration device comprises an optical camera and a marker, wherein the optical camera and the marker are respectively mounted on the x-ray source and the detector or vice versa, and the optical camera has a clear view of the marker.

3. The system of claim 2, wherein the marker is an optical pattern including a black and white chessboard pattern.

4. The system of claim 2, wherein the optical camera is configured to capture at least one photographic image of the marker at each position where an individual 2D x-ray projection image of the object is taken, and wherein the image processing system is configured to compute the spatial position and orientation of the x-ray source and the detector relative to the each other based on a comparison of the at least one photographic image of the marker to prior dimensions of the marker, prior relative positions of the optical camera with respect to the x-ray source, and a relative position of the marker with respect to the detector.

5. The system of claim 1, wherein the individual 2D x-ray projection images are taken over a limited angular range to reconstruct 3D tomosynthesis images of the object.

6. The system of claim 1, wherein the detector is a flat panel detector or a multi-pixel detector.

7. The system of claim 1, wherein the x-ray source is an x-ray source array containing multiple distributed focal spots.

8. The system of claim 7, wherein the optical camera is configured to capture at least one photographic image of the marker at each relative position of the x-ray source with respect to the detector;

and

wherein the image processing system is configured to compute the spatial position and orientation of each x-ray focal spot and the x-ray source array relative to the detector based on a comparison of the at least one photographic image of the marker to prior dimensions of the marker, prior relative positions of the optical camera with respect to the x-ray source, a relative position of the marker with respect to the detector, and prior relative positions of focal spots in the x-ray source array.

9. The system of claim 1, wherein the x-ray source and the detector are manually or mechanically moved to the plurality of spatial locations and orientations relative to one another to capture the individual 2D x-ray projection images.

10. The system of claim 1, wherein the optical-based in situ real time geometry calibration device comprises multiple optical cameras and multiple markers, wherein the multiple optical cameras and the markers are mounted on either the x-ray source and the detector, and each optical camera of the multiple optical cameras is configured to capture at least one photographic image of at least one corresponding marker of the multiple markers.

11. The system of claim 1, wherein the system is configured as a portable 3D imaging system for use in the field or in an emergency vehicle.

12. A free-form x-ray imaging system for three-dimensional (3D) imaging of an object, the system comprising:

an x-ray source freely positioned on one side of the object for emitting x-ray photons;

an x-ray detector mechanically detached from the x-ray source and freely positioned substantially opposite from the x-ray source, the x-ray detector being configured to detect the x-ray photons emitted by the x-ray source;

a geometry calibration device comprising one or more optical cameras fixed to either the x-ray source or the x-ray detector and one or more optical markers fixed to the x-ray detector and/or the object, each of the one or more optical cameras being configured to capture at least one photographic image of one or more corresponding optical markers when each x-ray image of the object is captured;

an image processing system configured to determine a position of the x-ray source and the detector relative to each other and to the object being imaged for each projection image and to reconstruct a 3D structure of the object from the projection image and corresponding determined geometry parameters; and

a control unit configured to coordinate an activation of one or more of the x-ray source or the one or more optical cameras.

13. The system of claim 12, wherein the one or more optical markers is held at a position that is substantially fixed relative to the object while one or more of the x-ray source or the detector are moved to multiple locations relative to the object.

14. The system of claim 12, wherein the one or more markers comprises one or more geometrical patterns of the object such that the geometry calibration device is configured to detect the one or more geometrical patterns of the object.

15. The system of claim 12, wherein the system is a computed tomography system with a reconfigurable and flexible imaging geometry, allowing collection of projection images with variable source-detector distances and flexible source trajectory.

16. An optical-based geometry calibration device configured to interface with a two-dimensional (2D) imaging device to perform three-dimensional (3D) imaging, the optical-based geometry calibration device comprising:

one or more optical cameras fixed to either an x-ray source or an x-ray detector;

one or more markers fixed to the x-ray detector or the x-ray source, with each of the one or more optical cameras being configured to capture at least one photographic image of one or more corresponding optical markers when each x-ray image of the object is captured; and

an image processing system configured to compute positions of the x-ray source relative to the x-ray detector for each 2D projection image based on the at least one photographic image of the one or more markers.

17. A method of three-dimensional (3D) x-ray imaging of an object with real time geometry calibration using optical cameras and markers, the method comprising:

positioning one or more optical marker relative to an x-ray detector and one or more optical camera relative to an x-ray source with predetermined position and orientation;

moving the x-ray source and/or the x-ray detector into different positions relative the object being imaged;

simultaneously capturing optical images of the one or more marker by the one or more optical camera and obtaining individual two-dimensional (2D) x-ray projection images of the object from a plurality of spatial positions and orientations of the x-ray source and/or the detector relative to the object;

using the optical image of the marker to perform in situ real time geometry calibration to determine a spatial position and orientation of the x-ray source and the x-ray detector relative to each other and the object, for each of the individual 2D x-ray projection images; and

performing 3D image reconstruction of the object using the 2D x-ray projection images and associated geometry parameters.

18. The method of claim 17, wherein the 3D x-ray imaging is cone beam computed tomography imaging.

19. The method of claim 17, wherein the 3D x-ray imaging is limited angle tomosynthesis imaging.