Systems, devices, and methods for tracking and compensating for patient motion during a medical imaging scan

• US 9,734,589 B2
• Filed: 07/22/2015
• Issued: 08/15/2017
• Est. Priority Date: 07/23/2014
• Status: Active Grant

• Current Assignee: KinetiCor, Inc.
• Original Assignee: KinetiCor, Inc.
• Inventors: Alameida, Jr., William Herman, Engelmann, Michael, Yu, Jeffrey N., Lovberg, John Arthur, Pan, Xiaojiang Jason
• Primary Examiner(s): Chang, Jon
• Application Number:
  US14/806,521
• Publication Number:
  US 20160035108A1
• Time in Patent Office: 755 Days
• Field of Search: 382131
• CPC Class Codes: A61B 2034/2055 Optical tracking systems
• CPC Class Codes: A61B 2090/3937 Visible markers
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• 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 5/721 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: A61N 5/1049 for verifying the position of the patient with respect to the radiation beam
• CPC Class Codes: G06T 2207/30204 Marker
• CPC Class Codes: G06T 7/0012 Biomedical image inspection
• CPC Class Codes: G06T 7/248 involving reference images or patches
• CPC Class Codes: G06T 7/292 Multi-camera tracking
• CPC Class Codes: G06V 40/20 Movements or behaviour, e.g. gesture recognition recognition of facial expressions G06V40/16

Abstract

A motion tracking system for dynamic tracking of and compensation for motion of a patient during a magnetic resonance scan comprises a first camera positioned to view an optical marker along a first line of sight; a second camera positioned to view the optical marker along a second line of sight; and a computer system configured to analyze images generated by the first and second cameras to determine changes in position of the optical marker, and to generate tracking data for use by a magnetic resonance scanner to dynamically adjust scans to compensate for the changes in position of the optical marker, wherein the computer system is configured to dynamically adapt its image analysis to utilize images from all cameras that are currently viewing the optical marker.

Claims

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

an optical marker configured to be attached to the patient, wherein the optical marker comprises a plurality of optically visible landmarks, the plurality of optically visible landmarks defining a plurality of reference points;

a plurality of optical detectors, wherein each of the plurality of optical detectors is positioned to view the optical marker along a different line of sight;

one or more computer readable storage devices configured to store a plurality of computer executable instructions; and

one or more hardware computer processors in communication with the one or more computer readable storage devices and configured to execute the plurality of computer executable instructions in order cause the motion tracking system to;

receive a digital image from each of the plurality of optical detectors, wherein each digital image represents a view along a different line of sight;

determine, for each digital image, whether the digital image includes a view of the optical marker;

determine, for each digital image that includes a view of the optical marker, positions of the plurality of reference points in the digital image;

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

estimate iteratively a three-dimensional pose of the patient, until a measure of error is within a threshold 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.

2. The motion tracking system of claim 1, wherein the motion tracking system is further caused to repeatedly estimate the three-dimensional pose of the patient at a rate of at least 100 Hz.

3. The motion tracking system of claim 1, wherein the plurality of baseline attributes comprises a set of principal quantities, the set of principal quantities comprising values associated with the relationships between the positions of reference points.

4. The motion tracking system of claim 1, wherein determining whether each digital image includes a view of the optical marker comprises:

classifying each pixel in the digital image as one of two colors;

grouping one or more connected regions, wherein the connected regions are comprised of adjacent pixels with the some color;

filtering out one or more connected regions based on a size threshold;

computing the centroid of one or more connected regions; and

grouping together one or more connected regions by their computed centroids.

5. The motion tracking system of claim 1, wherein the motion tracking system is further caused to remap a coordinate system associated with the estimated three-dimensional pose of the patient.

6. The motion tracking system of claim 4, wherein grouping one or more connected regions comprises:

identifying connected regions with centroids occurring within one pixel of each other; and

calculating a centroid for each group of the one or more connected regions.

7. The motion tracking system of claim 4, wherein the motion tracking system is further caused to binarize each digital image before classifying each pixel in the digital image as one of two colors.

8. The motion tracking system of claim 6, wherein calculating a centroid for each group of the one or more connected regions comprises averaging the centroid for each connected region in the group of one or more connected regions.

9. The motion tracking system of claim 1, wherein the motion tracking system is further caused to generate tracking data based on the estimated three-dimensional pose of the patient and to transmit the tracking data to a medical imaging scanner controller to enable a medical imaging scanner to dynamically adjust the medical imaging scan to compensate for patient motion.

10. The motion tracking system of claim 9, further comprising:

the medical imaging scanner, wherein the medical imaging scanner is configured to dynamically adjust the medical imaging scan to compensate for patient motion based on the tracking data.

11. A motion tracking system for dynamic tracking of and compensation for motion of a patient during a magnetic resonance scan, the motion tracking system comprising:

an optical marker configured to be attached to a patient being scanned, wherein the optical marker comprises an optically visible pattern comprising a plurality of reference point locators, each reference point locator configured to define a single reference point, each reference point locator comprising alternating dark and light elliptical shapes centered on the single reference point,

wherein at least one of the plurality of reference point locators is larger than at least another of the plurality of reference point locators, and

wherein the optically visible pattern is rotationally asymmetrical about an axis normal to a plane of the optically visible pattern;

a first camera positioned to view the optical marker along a first line of sight;

a second camera positioned to view the optical marker along a second line of sight; and

a computer system configured to analyze images generated by the first and second cameras to determine changes in position of the optical marker, and to generate tracking data for use by a magnetic resonance scanner to dynamically adjust scans to compensate for the changes in position of the optical marker,

wherein the computer system is configured to dynamically determine whether the first camera, the second camera, or both cameras are currently viewing the optical marker, and

wherein the computer system is configured to dynamically adapt its image analysis to utilize images from all cameras that are currently viewing the optical marker.

12. The motion tracking system of claim 11, further comprising:

one or more additional cameras each positioned to view the optical marker along a different line of sight,

wherein the computer system is further configured to dynamically determine which of all of the cameras are currently viewing the optical marker.

13. The motion tracking system of claim 11, further comprising:

a third camera positioned to view the optical marker along a third line of sight; and

a fourth camera positioned to view the optical marker along a fourth line of sight,

wherein the computer system is further configured to dynamically determine which of all of the cameras are currently viewing the optical marker.

14. The motion tracking system of claim 11, further comprising:

one or more additional optical markers configured to be attached to the patient being scanned,

wherein the computer system is configured to analyze images generated by all cameras that are currently viewing at least one optical marker to determine changes in position of the optical markers, and to generate tracking data for use by the magnetic resonance scanner to dynamically adjust scans to compensate for the changes in position of the optical markers.

15. The motion tracking system of claim 11, further comprising:

the magnetic resonance scanner, wherein the magnetic resonance scanner is configured to dynamically adjust scans to compensate for the changes in position of the optical marker based on the tracking data.