Video-based systems for computer assisted surgery and localisation

• US 5,792,147 A
• Filed: 07/21/1997
• Issued: 08/11/1998
• Est. Priority Date: 03/17/1994
• Status: Expired due to Fees

• Current Assignee: King's College London
• Original Assignee: ROKE Manor Research Limited (Chemring Group PLC), United Medical & Dental Schools
• Inventors: Harris, Christopher George, Colchester, Alan Charles Francis, Evans, Richard John
• Primary Examiner(s): Hafer, Robert A.
• Assistant Examiner(s): YU, JUSTINE ROMANG
• Application Number:
  US08/897,670
• Time in Patent Office: 386 Days
• Field of Search: 606/130, 606/129, 378/901
• US Class Current: 606/130
• CPC Class Codes: A61B 2017/00725 Calibration or performance testing
• CPC Class Codes: A61B 2034/2057 Details of tracking cameras
• CPC Class Codes: A61B 2034/2065 Tracking using image or pattern recognition
• CPC Class Codes: A61B 2090/363 Use of fiducial points
• CPC Class Codes: A61B 2090/366 using projection of images directly onto the body
• CPC Class Codes: A61B 2090/373 using light, e.g. by using optical scanners
• CPC Class Codes: A61B 2090/3916 Bone tissue
• CPC Class Codes: A61B 2090/3937 Visible markers
• CPC Class Codes: A61B 2090/3983 Reference marker arrangements for use with image guided surgery
• CPC Class Codes: A61B 34/10 Computer-aided planning, simulation or modelling of surgical operations
• 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 90/10 for stereotaxic surgery, e.g. frame-based stereotaxis
• CPC Class Codes: A61B 90/36 Image-producing devices or illumination devices not otherwise provided for
• CPC Class Codes: A61B 90/39 Markers, e.g. radio-opaque or breast lesions markers
• CPC Class Codes: G16H 20/40 relating to mechanical, radiation or invasive therapies, e.g. surgery, laser therapy, dialysis or acupuncture
• CPC Class Codes: G16H 30/40 for processing medical images, e.g. editing
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass

Abstract

The apparatus comprises video cameras for viewing part of a patient'"'"'s body and a slide projector for projecting a predetermined pattern of light onto the patient'"'"'s body which is viewed by the cameras. A workstation and video frame grabber performs controlling and processing functions and are arranged to process said images from the cameras using image processing algorithms. The images from the cameras are superimposed upon prestored images which are generated from X-ray or CT scans. A passive pointer, having a predetermined pattern thereon which is recognisable by the controlling and processing means is used by the surgeon. The pattern is used to identify the exact position of a tip of the pointer in relation to the patient'"'"'s body and is displayed on a monitor with the superimposed images.

Claims

1. An apparatus for computer assisted surgery comprising:

camera means for viewing a part of a patient'"'"'s body,

projector means for projecting a predetermined bar pattern of light onto the part of the patient'"'"'s body being viewed by said camera means,

processing and controlling means connected to said camera means for generating three-dimensional intra-operative images of the part of the patient'"'"'s body from signals generated by the camera means representative of a view of said predetermined bar pattern projected onto the part of the patient'"'"'s body, said processing and controlling means operating to combine said three-dimensional intra-operative images with pre-operative three-dimensional images generated by a scanner and pre-stored in said processing and controlling means into a combined image, and display means, coupled to said processing and controlling means, for displaying said combined image, wherein said processing and controlling means operates to combine the intra-operative and pre-operative images in accordance with the following steps;

(i) defining, with respect to a scanner based co-ordinate system and from analysis of said pre-operative images, a representation of measured shape and position of the part of the patient'"'"'s body,

(ii) identifying features of interest in said pre-operative images with reference to the scanner based co-ordinate system,

(iii) defining, with respect to an intra-operative camera based co-ordinate system and from analysis of said intra-operative images in dependence upon said predetermined bar pattern, a further representation of measured shape and position of the part of the patient'"'"'s body,

(iv) calculating a co-ordinate transformation between said intra-operative camera based co-ordinate system and said scanner based co-ordinate system by matching said pre-operative and intra-operative images,

(v) calculating positions of said features of interest with respect to said intra-operative camera based co-ordinate system depending upon said co-ordinate transformation and said features of interest, and

(vi) combining said pre-operative and intra-operative images to provide localization for frameless stereotaxy without performing manual registration of features of the patient.

2. An apparatus as claimed in claim 1, and further including a passive pointer having a predetermined acquisition pattern attached thereto, which passive pointer is viewed by said camera means, wherein the processing and controlling means operates to recognize a position and an orientation of the pointer relative to said intra-operative camera based co-ordinate system from said acquisition pattern, to calculate the position of said passive pointer within said scanner based co-ordinate system in accordance with said co-ordinate transformation, and to superimpose, on said combined image, the position and the orientation of the passive pointer.

3. An apparatus as claimed in claim 2, wherein the processing and controlling means further operates to track movement of the pointer with respect to said intra-operative camera based co-ordinate system as the pointer correspondingly moves within a field of view of the camera means, and to accordingly display movement of the pointer in said combined image.

4. An apparatus as claimed in claim 2, wherein the predetermined acquisition pattern has a binary acquisition target, said passive pointer includes a handle extending from said pointer, and said binary acquisition target is disposed on said handle to facilitate recognition of said passive pointer by the processing and controlling means.

5. An apparatus as claimed in claim 2, wherein said camera means comprises at least two video cameras to provide intra-operative measurement data which are representative of a three-dimensional image.

6. An apparatus as claimed in claim 5, and further comprising calibration means for calibrating the intra-operative measurement data provided by said at least two video cameras.

7. An apparatus as claimed in claim 1, wherein calculating said co-ordinate transformation includes using an algorithm.

8. An apparatus as claimed in claim 1, wherein said projector means is a slide projector provided with a slide, said slide comprising a pattern of broken bars to generate the predetermined bar pattern.

9. An apparatus as claimed in claim 1, wherein the pre-operative images are formed from any of X-ray images, MR scan images and CT scan images.

10. An apparatus as claimed in claim 1, wherein intra-operative markers are attached to the part of the patient'"'"'s body and used by said processing and controlling means to compensate for movement by the patient.

11. An apparatus as claimed in claim 10, wherein each of the intra-operative markers comprises a base section for screwing into a bone of the patient, a post secured to said base section and a head attached to said post and opposite to said base section, said head being easily recognized by said processing and controlling means.

12. An apparatus as claimed in claim 11, wherein said head includes a pattern which is viewed by the camera means and the processing and controlling means recognizes said pattern for determination of a position of the head with respect to the combined image.

13. A method for use in computer aided surgery comprising the steps of:

using a scanner to generate pre-operative three-dimensional images relating to a part of a patient'"'"'s body,

projecting a predetermined bar pattern of light onto the part of the patient'"'"'s body,

viewing said predetermined bar pattern,

generating intra-operative three-dimensional images in accordance with captured intra-operative images and the predetermined bar pattern projected on the part of the patient'"'"'s body,

defining, with respect to a scanner based co-ordinate system and from analysis of said pre-operative images, a representation of measured shape and position of the part of the patient'"'"'s body,

identifying features of interest in said pre-operative images with reference to the scanner based co-ordinate system,

defining, with respect to an intra-operative camera based co-ordinate system and from analysis of said intra-operative images in dependence upon said predetermined bar pattern, a further representation of measured shape and position of the part of the patient'"'"'s body,

calculating a co-ordinate transformation between said intra-operative camera based co-ordinate system and said scanner based co-ordinate system by matching said pre-operative and intra-operative images,

calculating positions of said features of interest with respect to said intra-operative camera based co-ordinate system depending upon said co-ordinate transformation in combination with positions of said features of interest,

combining said pre-operative and intra-operative images into a combined image to provide localization for frameless stereotaxy without a requirement for performing manual registration of the part of the patient'"'"'s body, and

displaying said combined image.

14. A method as claimed in claim 13, and further comprising the steps of:

providing at least two cameras,

disposing a calibration tile in view of said at least two cameras,

calibrating said cameras in accordance with captured images so that each camera captures the same image for viewing said predetermined bar pattern depending upon a view of said calibration tile, and

calculating a relative position and orientation of said at least two cameras.

15. A method as claimed in claim 13, and further comprising the steps of:

using a passive pointer having a predetermined acquisition pattern,

determining a position of said pointer with respect to said intra-operative camera based co-ordinate system from said acquisition pattern,

calculating the position of said pointer within said scanner based co-ordinate system, and

creating the combined image and showing the position and orientation of the passive pointer.

16. A method as claimed in claim 15, and further comprising the steps of tracking movement of the pointer with respect to said intra-operative camera based co-ordinate system as the pointer correspondingly moves, and displaying said movement in said combined image.

17. A method as claimed in claim 13, and further comprising the steps of positioning intra-operative markers on the patient'"'"'s body, measuring movement of the part of the patient'"'"'s body in accordance with relative movement of the intra-operative markers, and compensating for the movement of the part of the patient'"'"'s body by correspondingly adapting said combined image in accordance with said movement.