Motion tracking system for real time adaptive imaging and spectroscopy

• US 9,076,212 B2
• Filed: 09/23/2013
• Issued: 07/07/2015
• Est. Priority Date: 05/19/2006
• Status: Expired due to Fees

• Current Assignee: Medical College of Wisconsin Incorporated, Queen's Medical Center, Research Corporation of The University of Hawaii, UWM Research Foundation, Inc. (University of Wisconsin System)
• Original Assignee: Medical College of Wisconsin Incorporated, Queen's Medical Center, Research Corporation of The University of Hawaii, UWM Research Foundation, Inc. (University of Wisconsin System)
• Inventors: Ernst, Thomas Michael, Prieto, Thomas Edmund, Armstrong, Brian Stewart Randall
• Primary Examiner(s): Seth, Manav
• Application Number:
  US14/034,252
• Publication Number:
  US 20140037174A1
• Time in Patent Office: 652 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0077 Devices for viewing the surface of the body, e.g. camera, magnifying lens
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/1127 using markers
• CPC Class Codes: A61B 5/1128 using image analysis A61B5/1127 takes precedence
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/7292 Prospective gating, i.e. predicting the occurrence of a physiological event for use as a synchronisation signal
• CPC Class Codes: A61B 6/0492 using markers or indicia for aiding patient positioning
• CPC Class Codes: A61B 6/547 involving tracking of position of the device or parts of the device
• CPC Class Codes: G01R 33/28 Details of apparatus provided for in groups G01R33/44 - G01R33/64
• CPC Class Codes: G01R 33/56509 due to motion, displacement or flow, e.g. gradient moment nulling G01R33/567 takes precedence
• CPC Class Codes: G06T 7/0012 Biomedical image inspection
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80
• CPC Class Codes: G06V 10/62 relating to a temporal dimension, e.g. time-based feature extraction; Pattern tracking
• CPC Class Codes: H04N 7/18 Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast

Abstract

This invention relates to a system that adaptively compensates for subject motion in real-time in an imaging system. An object orientation marker (30), preferably a retro-grate reflector (RGR), is placed on the head or other body organ of interest of a patient (P) during a scan, such as an MRI scan. The marker (30) makes it possible to measure the six degrees of freedom (x, y, and z-translations, and pitch, yaw, and roll), or “pose”, required to track motion of the organ of interest. A detector, preferably a camera (40), observes the marker (30) and continuously extracts its pose. The pose from the camera (40) is sent to the scanner (120) via an RGR processing computer (50) and a scanner control and processing computer (100), allowing for continuous correction of scan planes and position (in real-time) for motion of the patient (P). This invention also provides for internal calibration and for co-registration over time of the scanner'"'"'s and tracking system'"'"'s reference frames to compensate for drift and other inaccuracies that may arise over time.

Claims

1. An object orientation marker for use in a motion tracking system for tracking motion of an object to which the object orientation marker is coupled, the object orientation marker comprising:

an optically transparent substrate having a front surface and a rear surface;

front artwork applied to the front surface of the substrate;

rear artwork applied to the rear surface of the substrate;

wherein at least one of the front artwork and the rear artwork comprises one or more landmarks configured to be viewable in an image of the object orientation marker; and

wherein the front artwork and the rear artwork comprise gratings configured to create moiré

patterns, the moiré

patterns being configured to be sensitive to changes in orientation.

2. The object orientation marker of claim 1, wherein the one or more landmarks comprises a starburst pattern.

3. The object orientation marker of claim 1, wherein the one or more landmarks comprises alternating spokes and interstitial spaces.

4. The object orientation marker of claim 3, wherein the alternating spokes and interstitial spaces are generally wedge-shaped.

5. The object orientation marker of claim 1, wherein the one or more landmarks comprises a circular landmark.

6. The object orientation marker of claim 1, wherein the front artwork and rear artwork are configured to enable determination of a pose of the object to which the object orientation marker is coupled by analyzing a single image of the object orientation marker.

7. The object orientation marker of claim 6, wherein the pose describes six degrees of freedom.

8. The object orientation marker of claim 6, wherein the pose describes less than six degrees of freedom.

9. The object orientation marker of claim 1, wherein the optically transparent substrate comprises glass.

10. The object orientation marker of claim 1, wherein the optically transparent substrate comprises plastic.

11. An object orientation marker for use in a motion tracking system for tracking motion of an object to which the object orientation marker is coupled, the object orientation marker comprising:

an at least partially optically transparent substrate; and

artwork applied to the substrate;

wherein the artwork comprises one or more landmarks;

wherein the artwork further comprises gratings configured to create patterns sensitive to changes in orientation;

wherein the one or more landmarks and the gratings are positioned to enable, using a single image of the object orientation marker, a determination of an orientation of the object orientation marker in six degrees of freedom.

12. The object orientation marker of claim 11, wherein the gratings are configured to create moiré

patterns.

13. The object orientation marker of claim 11, wherein the artwork further comprises a first artwork applied to a first surface of the substrate and a second artwork applied to a second surface of the substrate.

14. The object orientation marker of claim 13, wherein the first surface comprises a front surface of the substrate and the second surface comprises a back surface of the substrate.

15. The object orientation marker of claim 11, wherein the one or more landmarks comprises a starburst pattern.

16. The object orientation marker of claim 11, wherein the one or more landmarks comprises alternating spokes and interstitial spaces.

17. The object orientation marker of claim 16, wherein the alternating spokes and interstitial spaces are generally wedge-shaped.

18. The object orientation marker of claim 11, wherein the one or more landmarks comprises a circular landmark.

19. A method of estimating a pose of an object to which an object orientation marker comprising one or more landmarks and one or more regions comprising moiré

patterns is affixed, the method comprising;

imaging by an electronic detector the object orientation marker to generate a digital image of the object orientation marker;

determining by a computer system locations of the one or more landmarks of the object orientation marker by analyzing the digital image;

calculating by the computer system a first estimate of the pose based on the determined locations of the one or more landmarks;

determining by the computer system, using the first estimate of the pose, areas of the digital image corresponding to the one or more regions of the object orientation marker comprising moiré

patterns;

estimating by the computer system a phase and a frequency of each moiré

pattern within the one or more regions of the object orientation marker; and

calculating by the computer system a second estimate of the pose based on both the locations of the one or more landmarks and the phase and frequency estimates of the moiré

patterns;

wherein the computer system comprises a computer processor and an electronic memory.

20. The method of claim 19, wherein the pose describes six degrees of freedom.