US 5,389,101 A · Apparatus and method for photogrammetric surgical localization

Abstract

A method and apparatus for defining the location of a medical instrument relative to features of a medical workspace including a patient's body region are described. Pairs of two-dimensional images are obtained, preferably by means of two video cameras making images of the workspace along different sightlines which intersect. A fiducial structure is positioned in the workspace for defining a three dimensional coordinate framework, and a calibration image pair is made. The calibration image pair comprises two 2D projections from different locations of the fiducial structure. After the calibration image pair is made, the fiducial structure is removed. A standard projection algorithm is used to reconstruct the 3D framework of the fiducial structure from the calibration image pair. Appropriate image pairs can then be used to locate and track any other feature such as a medical instrument, in the workspace, so long as the cameras remain fixed in their positions relative to the workspace. The computations are desirably performed with a computer workstation including computer graphics capability, image processing capability, and providing a real-time display of the workspace as imaged by the video cameras. Also, the 3D framework of the workspace can be aligned with the 3D framework of any selected volume scan, such as MRI, CT, or PET, so that the instrument can be localized and guided to a chosen feature. No guidance arc or other apparatus need be affixed to the patient to accomplish the tracking and guiding operations.

Claims30

Dependent claims

Apparatus for defining a location of a medical instrument relative to features of a medical workspace including a patient's body region, comprising:

workspace imaging means positionable for producing a plurality of pairs of images of the medical workspace, each of said image pairs comprising two images made along one of each of a different one of two sightlines, said sightlines intersecting at an angle;
digitizing means operably disposed for digitizing each of said images of said image pairs to produce sets of digital image signals, one said set of digital image signals corresponding to each of said images;
fiducial means removably positionable in said workspace for providing a series of fiducial points held in fixed spatial relation to one another;
and
computing means connected to said digitizing means to receive said digital image signals therefrom, said computing means being operable to:
establish a workspace coordinate framework in three dimensions from a first selected one of said pairs of images made when said fiducial means is positioned within said workspace,
determine workspace coordinates in said workspace coordinate framework of any selected point which can be identified from both images of said first selected image pair,
receive a set of scan coordinates for each of three or more selected landmarks present in a scan made in a scan coordinate framework, and correlate said scan coordinates with the workspace coordinates of said landmarks as derived from one of said image pairs, said landmarks being selected from the group of anatomic features, surgical implants, and radiologic implants,
compute conversion functions for converting the scan coordinates of a selected feature in said scan to corresponding workspace coordinates in said workspace framework, and for converting observed workspace coordinates of a selected feature observable in both of said images of a selected one of said image pairs to corresponding scan coordinates in said scan coordinate framework, and
perform said conversion functions for user-selected features found in said scan or in a subsequent selected one of said image pairs.

7 more elements

A method of localizing a feature of interest in a workspace, comprising the steps of:

providing a fiducial structure comprising
a sufficient number of fiducial indicators arranged to define a three-dimensional coordinate system and having known 3D coordinates, and
support frame means for supporting and connecting said fiducial indicators, said support frame means constructed to hold said fiducial indicators in fixed relation to each other;
making a calibration image pair of the workspace comprising two 2D images of the workspace made along different sightlines, and with the fiducial structure positioned in the workspace such that a preset minimum number of fiducial points are visible in both images of the calibration image pair;
digitizing respective 2D images of the calibration image pair;
determining a first plurality of 2D coordinates from one member of the calibration image pair and a second plurality of 2D coordinates from the other member of the calibration image pair;
computing a 3D workspace coordinate framework from said first and second pluralities of 2D coordinates and the known 3D coordinates of the fiducial structure;
removing the fiducial structure from the workspace;
making a subsequent image pair comprising two 2D images of the workspace having a patient's body region therein, the two 2D images being made along the same respective sightlines as the calibration image pair;
digitizing the respective 2D images of the subsequent image pair;
and
determining workspace 3D coordinates of a feature of interest in the workspace from the respective 2D images of the subsequent image pair.

9 more elements

Apparatus for localizing a medical instrument relative to features of a patient's body region, comprising:

a fiducial structure removably positionable in a medical workspace, and comprising
a sufficient number of fiducial indicators arranged to define a three-dimensional coordinate system and having known 3D coordinates, and
support frame means for supporting and connecting said fiducial indicators, said support frame means constructed to hold said fiducial indicators in fixed relation to each other;
workspace imaging means positionable for producing a plurality of pairs of images of said medical workspace, each of said image pairs comprising two images made along one of each of a different one of two sightlines, said sightlines intersecting at an angle;
digitizing means operably disposed for digitizing each of said images of said image pairs to produce sets of digital image signals, one said set of digital image signals corresponding to each of said images;
and
computing means connected to said digitizing means to receive said digital image signals therefrom, said computing means being operable to:
determine a first plurality of 2D coordinates from one member of a calibration image pair and a second plurality of 2D coordinates from an other member of said calibration image pair, said calibration image pair being an image pair made with said fiducial structure positioned in said medical workspace,
compute a 3D workspace coordinate framework from measured physical 3D coordinates of said fiducial structure in combination with said first and second pluralities of 2D coordinates,
compute an algorithm for converting any 2D coordinates derived from a subsequent image pair made after said fiducial structure is removed from said medical workspace, to corresponding 3D workspace coordinates,
determine a set of 2D image coordinates reflective of a current position of a feature of interest present in both images of said subsequent image pair, and
convert said set of 2D image coordinates to a set of corresponding workspace 3D coordinates.

9 more elements

Dependencies are inferred from the claim text.

Apparatus and method for photogrammetric surgical localization

Life of this patent

Apparatus and method for photogrammetric surgical localization

Life of this patent

Abstract

Claims30