SYSTEMS, DEVICES, AND METHODS FOR TRACKING AND COMPENSATING FOR PATIENT MOTION DURING A MEDICAL IMAGING SCAN

• US 20160073962A1
• Filed: 01/23/2014
• Published: 03/17/2016
• Est. Priority Date: 01/24/2013
• Status: Active Grant

• Current Assignee: KinetiCor, Inc.
• Original Assignee: KinetiCor, Inc.
• Inventors: Pan, Xiaojiang Jason, Yu, Jeffrey N., Lovberg, John Arthur
• Granted Patent: US 9,717,461 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2090/3937 Visible markers
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/1121 Determining geometric values, e.g. centre of rotation or angular range of movement
• CPC Class Codes: A61B 5/1127 using markers
• CPC Class Codes: A61B 5/682 Mouth, e.g., oral cavity; tongue; Lips; Teeth
• CPC Class Codes: A61B 5/702 Posture restraints
• 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 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61B 5/7485 Automatic selection of region of interest
• CPC Class Codes: A61N 2005/1059 using cameras imaging the patient
• CPC Class Codes: G01R 33/283 Intercom or optical viewing arrangements, structurally associated with NMR apparatus
• 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 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/10021 Stereoscopic video; Stereoscopic image sequence
• CPC Class Codes: G06T 2207/30204 Marker
• CPC Class Codes: G06T 7/248 involving reference images or patches
• CPC Class Codes: G06T 7/74 involving reference images or patches

Abstract

A motion compensation system for tracking and compensating for patient motion during a medical imaging scan comprises an optical marker comprising an optically visible pattern and a mounting portion; a first optical detector positioned to digitally image the optically visible pattern along a first line of sight; a second optical detector positioned to digitally image the optically visible pattern along a second line of sight; a tracking engine configured to determine a pose of the object in six degrees of freedom by analyzing images from the first and second optical detectors; and a controller interface configured to generate tracking information based on the pose and to electronically transmit the tracking information to a scanner controller to enable compensation within a medical imaging scanner for object motion.

Claims

1. A motion compensation system for tracking and compensating for patient motion during a medical imaging scan, the motion compensation system comprising:

an optical marker comprising an optically visible pattern and a mounting portion, the mounting portion configured to affix the optical marker to an object being tracked, the optically visible pattern comprising a plurality of reference point locators, each locator configured to define a single reference point of a reference shape;

a first optical detector positioned to digitally image the optically visible pattern along a first line of sight, the first optical detector configured to generate a first digital image of the optically visible pattern;

a second optical detector positioned to digitally image the optically visible pattern along a second line of sight, the second optical detector configured to generate a second digital image of the optically visible pattern;

a tracking engine configured to determine a pose of the object in six degrees of freedom by analyzing the first and second images; and

a controller interface configured to generate tracking information based on the pose and to electronically transmit the tracking information to a scanner controller to enable compensation within a medical imaging scanner for object motion;

wherein the tracking engine and controller interface comprise a computer processor and an electronic storage medium.

7. The motion compensation system of claim 1, wherein the optically visible pattern is distributed among at least two non-connected structures.

9. The motion compensation system of claim 1, wherein the plurality of reference point locators comprise alternating dark and light elliptical shapes.

10. The motion compensation system of claim 9, wherein the elliptical shapes are configured to appear circular when viewed along the first and second lines of sight when the object being tracked is in a home position.

17. The motion compensation system of claim 1, wherein each reference point is no more than 0.5 inches away from another reference point.

18. The motion compensation system of claim 1, wherein each reference point is defined by a centroid of a reference point locator.

25. The motion compensation system of claim 1, wherein the tracking engine is configured to repeatedly determine the pose of the object at a rate no slower than a scan rate of the medical imaging scanner.

26. The motion compensation system of claim 1, wherein the first and second optical detectors are configured to be affixed to the medical imaging scanner.

28. The motion compensation system of claim 1, wherein at least one of the first and second lines of sight is an indirect line of sight.

33. The motion compensation system of claim 1, wherein the tracking engine is further configured to define a region of interest for each of the digital images, the region of interest comprising a portion of the digital image within which the optically visible pattern is anticipated to appear, wherein the tracking engine is configured to analyze only the region of interest in determining the pose of the object, and wherein the tracking engine is configured to automatically move the region of interest based on anticipated future motion of the object being tracked.

35. The motion compensation system of claim 1, wherein analyzing the first and second images comprises:

determining two-dimensional positions of the reference points in coordinate systems of the optical detectors;

calculating six baseline attributes of the reference shape based on the two-dimensional positions of the reference points; and

estimating, iteratively, a pose of the object being tracked, until an amount of error is within a threshold amount, the amount of error being between the six baseline attributes and six comparison attributes, the six comparison attributes calculated by assuming the object is in an estimated pose.

36. The motion compensation system of claim 35, wherein the baseline and comparison attributes comprise at least one of the following:

a sum of displacements of the reference shape as viewed along the first line of sight and as viewed along the second line of sight;

a difference between displacements of the reference shape as viewed along the first line of sight and as viewed along the second line of sight;

a difference in distance from a first reference point to a second reference point as viewed along the first line of sight and as viewed along the second line of sight;

a sum of an apparent median tilt of the reference shape as viewed along the first line of sight and as viewed along the second line of sight; and

a difference between an apparent median tilt of the reference shape as viewed along the first line of sight and as viewed along the second line of sight.

37. The motion compensation system of claim 1, wherein the controller interface is further configured to convert the pose of the object from a tracking coordinate system to a scanner coordinate system.

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38. A system for tracking motion of an object, the system comprising:

a marker location filter for determining locations of marker reference points, the marker location filter configured to;

receive from a first optical detector a first digital image of an optical marker, the first digital image representing a view of the optical marker along a first line of sight;

receive from a second optical detector a second digital image of the optical marker, the second digital image representing a view of the optical marker along a second line of sight, the second line of sight being different than the first line of sight,

wherein the optical marker comprises a plurality of optically visible landmarks, the plurality of optically visible landmarks defining a plurality of reference points, the plurality of reference points defining a reference shape;

determine positions of the plurality of reference points in the first digital image; and

determine positions of the plurality of reference points in the second digital image;

an object orientation filter for estimating a three-dimensional pose of the object, the object orientation filter configured to;

calculate a plurality of baseline attributes related to the reference shape, the plurality of baseline attributes calculated based on the determined positions of the plurality of reference points; and

estimate iteratively the three-dimensional pose of the object, until a measure of error is within an acceptable amount, the measure of error calculated based on the plurality of baseline attributes as compared to a plurality of comparison attributes, the plurality of comparison attributes calculated by assuming the object is in an estimated pose; and

one or more computers configured to operate the marker location filter and object orientation filter, wherein the one or more computers comprises a computer processor and an electronic storage medium.

39. The system of claim 38, wherein each of the plurality of baseline attributes is calculated based on properties of the reference shape as viewed along the first line of sight and the reference shape as viewed along the second line of sight.

40. The system of claim 38, wherein each of the plurality of baseline attributes describes a different variation between the reference shape as viewed along the first line of sight and the reference shape as viewed along the second line of sight.

41. The system of claim 38, wherein the plurality of baseline attributes and the plurality of comparison attributes comprise at least one of the following:

a sum of displacements of the reference shape as viewed along the first line of sight and as viewed along the second line of sight;

a difference between displacements of the reference shape as viewed along the first line of sight and as viewed along the second line of sight;

a difference in distance from a first reference point to a second reference point as viewed along the first line of sight and as viewed along the second line of sight;

a sum of an apparent median tilt of the reference shape as viewed along the first line of sight and as viewed along the second line of sight; and

a difference between an apparent median tilt of the reference shape as viewed along the first line of sight and as viewed along the second line of sight.

45. The system of claim 38, further comprising:

a controller interface configured to;

generate motion tracking data based on the estimated three-dimensional pose of the object; and

transmit electronically to a scanner controller the motion tracking data to enable a scanner to compensate for motion of the object.

49. The system of claim 38, wherein the plurality of optically visible landmarks comprise alternative dark and light elliptical shapes.

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70. An optical marker for use in a motion tracking system, the optical marker comprising:

an optically visible pattern comprising a plurality of reference point locators, each reference point locator configured to define a single reference point of a reference shape, each reference point locator comprising alternating dark and light elliptical shapes centered on the single reference point; and

a mounting portion configured to affix the optical marker to an object being tracked.

72. The optical marker of claim 70, wherein the reference shape is a triangle.

75. The optical marker of claim 70, wherein each reference point is no more than 0.5 inches away from another reference point.

80. The optical marker of claim 70, further comprising an internal light source to illuminate the optically visible pattern.

81. The optical marker of claim 70, wherein the mounting portion is configured to rigidly affix the optical marker to the object being tracked.

82. The optical marker of claim 70, wherein the mounting portion is configured to affix the optical marker to top teeth of a patient.

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