System and method for image based sensor calibration

• US 7,085,400 B1
• Filed: 06/14/2000
• Issued: 08/01/2006
• Est. Priority Date: 06/14/2000
• Status: Active Grant

• Current Assignee: Surgical Navigation Technologies, Inc. (Medtronic Plc)
• Original Assignee: Surgical Navigation Technologies, Inc. (Medtronic Plc)
• Inventors: Holsing, Troy, Goodchild, Gordon
• Primary Examiner(s): Johns, Andrew W.
• Assistant Examiner(s): Edwards, Patrick
• Application Number:
  US09/593,495
• Time in Patent Office: 2,239 Days
• Field of Search: 382/103, 382/145, 382/148, 382/151, 382/154, 382/289, 382/291, 382/319, 382/152
• US Class Current: 382/103
• CPC Class Codes: A61B 2017/00725 Calibration or performance testing
• CPC Class Codes: A61B 2090/378 using ultrasound
• 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 90/36 Image-producing devices or illumination devices not otherwise provided for
• CPC Class Codes: G06T 2207/30004 Biomedical image processing
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration

Abstract

Apparatus and methods are disclosed for the calibration of a tracked imaging probe for use in image-guided surgical systems. The invention uses actual image data collected from an easily constructed calibration jig to provide data for the calibration algorithm. The calibration algorithm analytically develops a geometric relationship between the probe and the image so objects appearing in the collected image can be accurately described with reference to the probe. The invention can be used with either two or three dimensional image data-sets. The invention also has the ability to automatically determine the image scale factor when two dimensional data-sets are used.

Claims

1. A method of calibrating a tracking device to an image, comprising:

tracking a position of a calibration jig and a position of a probe;

collecting a plurality of images of at least one calibration pattern of the calibration jig with the probe;

locating centers of intersection points in image space associated with each calibration pattern for each of the plurality of images and extracting a calibration point therefrom;

determining the position for at least one calibration point in probe space for each of the plurality of images;

relating the positions of the calibration points in image space and the positions of said calibration points in probe space;

computing an image space reference position in probe space; and

storing the image space reference position.

2. The method of claim 1 further including:

identifying an orientation of the intersection points in a first image of the plurality of images collected;

computing a position component of the calibration point in calibration jig space by comparing the distances from the center of one of the intersection points near each image edge to the centers of two other intersection points for each image; and

transforming the positions of calibration points described in calibration jig space to positions described in probe space.

3. The method of claim 2 wherein the identification of orientation is performed automatically, specified manually, or combinations thereof.

4. The method of claim 2 further including:

receiving positions of identical calibration points described in image space and described in probe space;

rotating the calibration points described in image space to align with the calibration points described in probe space;

computing centroids of the calibration points described in the rotated image space and the calibration points described in the probe space;

translating the calibration points described in the rotated image space to the calibration points described in probe space; and

adjusting the scale of the calibration points described in the rotated and translated image space to minimize the point to point error with the calibration points described in probe space.

5. The method of claim 1 wherein the plurality of images are collected utilizing a probe comprising an ultrasonic transducer generating and receiving ultrasonic signals and further utilizing a processing system which forms two dimensional images from the ultrasonic signals received by the ultrasonic transducer.

6. The method of claim 1, wherein collecting a plurality of images of at least one calibration pattern includes positioning an ultrasound probe relative to the calibration jig to image the calibration jig with the ultrasound probe;

directing ultrasound waves with the ultrasound probe into a jig space of the calibration jig.

7. A method of calibrating a tracking device to a three-dimensional volumetric image, comprising:

tracking a position of a calibration jig and a position of a probe;

collecting a volumetric image of at least one calibration pattern contained in the calibration jig;

extracting two-dimensional slices from the volumetric image;

locating centers of intersection points in slice space associated with each calibration pattern for each of the plurality of slices and extracting a calibration point therefrom;

determining the position for at least one calibration point in probe space for each of the plurality of slices;

relating the positions of the calibration points in slice space and the positions of said calibration points in probe space;

computing a reference position of the volumetric image in probe space; and

storing the reference position of the volumetric image.

8. The method of claim 7 further including:

extracting a first slice from the three-dimensional image;

identifying an orientation of the intersection points in the first slice;

computing a position component of the calibration point in calibration jig space by comparing the distances from the center of one of the intersection points near each slice edge to the centers of two other intersection points for each slice; and

transforming the positions of calibration points described in calibration jig space to positions described in probe space.

9. The method of claim 7 further including:

receiving positions of identical calibration points described in slice space and described in probe space;

rotating the calibration points described in slice space to align with the calibration points described in probe space;

computing centroids of the calibration points described in the rotated slice space and the calibration points described in the probe space; and

translating the calibration points described in the rotated slice space to the calibration points described in probe space.

10. The method of claim 7 wherein the three-dimensional volumetric image is collected utilizing a probe which is an ultrasonic transducer which generates and receives ultrasonic signals and a processing system which forms the three-dimensional image from the ultrasonic signals received by the ultrasonic transducer.

11. A system for registering a tracking device to an image, comprising:

a means for tracking a three-dimensional position of a calibration jig and a position of a probe;

a means for collecting a plurality of images of at least one calibration pattern on the calibration jig with the probe;

a means for providing the plurality of images to the tracking means;

a means for locating centers of intersection points in image space associated with each calibration pattern for each of the plurality of images and extracting a calibration point therefrom;

a means for determining the position for at least one calibration point in probe space for each of the plurality of images;

a means for relating the positions of the calibration points in image space and the positions of said calibration points in probe space;

a means for computing an image space reference position in probe space; and

a means for storing the image space reference position.

12. The system of claim 11 further including:

a means for identifying an orientation of the intersection points in a first image of the plurality of images collected;

a means for computing a position component of the calibration point in calibration jig space by comparing the distances from the center of one of the intersection points near each image edge to the centers of two other intersection points for each image; and

a means for transforming the positions of calibration points described in calibration jig space to positions described in probe space.

13. The system of claim 12 wherein the identification means is performed automatically, specified manually, or combinations thereof.

14. The system of claim 12 further including:

a means for receiving positions of identical calibration points described in image space and described in probe space;

a means for rotating the calibration points described in image space to align with the calibration points described in probe space;

a means for computing centroids of the calibration points described in the rotated image space and the calibration points described in the probe space;

a means for translating the calibration points described in the rotated image space to the calibration points described in probe space; and

a means for adjusting the scale of the calibration points described in the rotated and translated image space to minimize the point to point error with the calibration points described in probe space.

15. The system of claim 11 wherein the means for collecting images further comprises:

an ultrasonic transducer means for generating and receiving ultrasonic signals; and

a processing means for forming two dimensional images from the ultrasonic signals received by the transducer means.

16. A system for calibrating a tracking device to a three-dimensional volumetric image, comprising:

a means for tracking a position of a calibration jig and a position of a probe;

a means for collecting a volumetric image of at least one calibration pattern contained in the calibration jig, coupled to the tracking means;

a means for extracting two-dimensional slices from the volumetric image;

a means for locating centers of intersection points in slice space associated with each calibration pattern for each of the plurality of slices and extracting a calibration point therefrom;

a means for determining the position for at least one calibration point in probe space for each of the plurality of slices;

a means for relating the positions of the calibration points in slice space and the positions of said calibration points in probe space;

a means for computing a reference position of the volumetric image in probe space; and

a means for storing the reference position of the volumetric image.

17. The system of claim 16 further including:

a means for extracting a first slice from the three-dimensional image;

a means for identifying an orientation of the intersection points in the first slice;

a means for computing a position component of the calibration point in calibration jig space by comparing the distances from the center of one of the intersection points near each slice edge to the centers of two other intersection points for each slice; and

a means for transforming the positions of calibration points described in calibration jig space to positions described in probe space.

18. The system of claim 16 further including:

a means for receiving positions of identical calibration points described in slice space and described in probe space;

a means for rotating the calibration points described in slice space to align with the calibration points described in probe space;

a means for computing centroids of the calibration points described in the rotated slice space and the calibration points described in probe space; and

a means for translating the calibration points described in the rotated slice space to the calibration points described in probe space.

19. The system of claim 16 wherein the means for collecting images further comprises:

an ultrasonic transducer means for generating and receiving ultrasonic signals; and

a processing means for forming three dimensional images from the ultrasonic signals received by the transducer means.