Fluoroscopic tracking and visualization system

• US 6,490,475 B1
• Filed: 04/28/2000
• Issued: 12/03/2002
• Est. Priority Date: 04/28/2000
• Status: Expired due to Term

• Current Assignee: Stryker European Holdings I, LLC (Stryker Corporation)
• Original Assignee: GE Medical Systems Global Technology Company LLC (GE Healthcare Technologies, Inc.)
• Inventors: Kapur, Tina, Seeley, Teresa, Gregerson, Gene, Lin, Faith
• Primary Examiner(s): Lateef, Marvin
• Assistant Examiner(s): Lin, Jeoyuh
• Application Number:
  US09/560,608
• Time in Patent Office: 949 Days
• Field of Search: 600/407, 600/426, 600/425, 600/421, 600/427, 600/429, 606/130, 606/431, 250/362, 250/363.01, 250/363.02, 250/363.03, 250/363.04, 250/363.05, 250/363.07, 250/363.09, 250/368, 250/370.08, 250/370.09, 250/370.1, 250/4, 250/550, 378/6, 378/21, 378/41, 378/42, 378/44, 378/46, 378/62, 378/63, 378/68
• US Class Current: 600/426
• CPC Class Codes: A61B 2034/2055 Optical tracking systems
• CPC Class Codes: A61B 2090/367 creating a 3D dataset from 2D images using position information
• CPC Class Codes: A61B 2090/376 using X-rays, e.g. fluoroscopy
• CPC Class Codes: A61B 2562/17 Comprising radiolucent components
• 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 5/06 Devices, other than using radiation, for detecting or locating foreign bodies for removing same A61B17/50 ; determining position of probes within or on the body of the patient
• CPC Class Codes: A61B 5/062 using magnetic field
• CPC Class Codes: A61B 5/064 using markers A61B5/062 takes precedence
• CPC Class Codes: A61B 6/12 Arrangements for detecting or locating foreign bodies
• CPC Class Codes: A61B 6/4441 the rigid structure being a C-arm or U-arm
• CPC Class Codes: A61B 6/5235 combining images from the same or different ionising radiation imaging techniques, e.g. PET and CT
• CPC Class Codes: A61B 6/547 involving tracking of position of the device or parts of the device
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: A61B 90/36 Image-producing devices or illumination devices not otherwise provided for

Abstract

A system employs a tracker and a set of substantially non-shadowing point markers, arranged in a fixed pattern or set in a fluoroscope calibration fixture that is imaged in each shot. The fixture is preferably affixed to the image detector of the fluoroscope, and tracking elements secured with respect to the fixture and at least one of a tool and the patient, provide respective position data irrespective of movement. A marker detection module identifies markers imaged in each shot, and a processor applies the known marker positions to model the projection geometry, e.g., camera axis and focus, for the shot and, together with the tracked tool position, form a corrected tool navigation image. In one embodiment an inverting distortion correction converts the tracked or actual location of the tool and displays the tool on the fluoroscopic image to guide the surgeon in tool navigation. In another aspect of the invention, the fluoroscope takes a series of frames while rotating in a plane about the patient, and the camera models derived from the marker images in each frame are applied to define a common center and coordinate axes in the imaged tissue region to which all of the fluoroscope view may be registered. The processor then filters and back-projects the image data or otherwise forms a volume image data set corresponding to the region of tissue being imaged, and desired fluoro-CT planar images of a the imaged patient volume are constructed from this data set. Planes may then be constructed and displayed without requiring complex tracking and image correlation systems previously needed for operating-room management of MRI, CT or PET study image data. Further, the fluoro-CT images thus constructed may be directly registered to preoperative MRI, CT or PET 3D image data, or may obviate the need for such preoperative imaging. Preferably, the tracker employs electromagnetic tracking elements, as shown for example in U.S. Pat. No. 5,967,980, to generate and/or detect electromagnetic field components unobstructed by the patient and intervening structures, and to determine coordinates directly referenced to the patient, the tool or the camera. The calibration fixture may be implemented with BBs in a radiolucent block of structural foam, and/or may be implemented by microlithographic techniques, in which case magnetic tracking elements may be simultaneously formed in registry with the markers on a sheet that mounts to the camera, is incorporated in a radiographic support table, or otherwise positioned to be imaged in each shot.

Claims

1. A method for surgical imaging and display of the type including a fluoroscope x-ray source, imaging assembly, display and image processor, for displaying a fluoroscope image for surgical guidance, wherein the method comprises the steps of:

(i) positioning a defined set of markers disposed in a pattern so as to be imaged in each pose or view of the imaging assembly, said set of markers being fixed in pre-determined positions in a rigid carrier;

(ii) securing a first tracking element against motion with respect to the carrier so that determining position of said tracking element in a single measurement determines position of all the markers of the set;

(iii) identifying images of at least a subset of said markers in a first view;

(iv) applying said identified images and the determined marker positions to calibrate a camera model of the shot;

(v) repeating steps (i)-(iv) for each of a plurality of successive views taken in successively different fluoroscope positions; and

(vi) registering image data from the plurality of views to a common coordinate system.

2. The method of claim 1, further comprising the steps of removing the identified images of markers from the first view to form an unobstructed view and displaying the unobstructed view.

3. The method of claim 1, further comprising the steps of

securing additional tracking elements to at least one object selected from among a patient and a tool so as to determine position of said object, and

positioning an image of object in the registered view.

4. The method of claim 1, further comprising the steps of

securing an additional tracking element to a patient to determine position of the patient, wherein said common coordinate system corresponds to a common region of imaged tissue in the patient, and

back-projecting image data from the plurality of views to form a fluoro-CT data set for said common region of tissue.

5. The method of claim 4, further comprising the step of registering said fluoro-CT data set to a set of preoperative CT, MRI or PET image data for said common region of tissue.

6. A system for surgical imaging and display of tissue structures of a patient, and including a display and an image processor for displaying such images in coordination with a tool image to facilitate manipulation of the tool during the surgical procedure, the system being configured for use with a fluoroscope such that at least one image in the display is derived from the fluoroscope at the time of surgery, and characterized in that the system comprises:

a three-dimensional spatial fixture isometrically affixed to an imaging side of the fluoroscope for providing patterns of markers which are imaged in each fluoroscope image;

a tracking assembly having at least two tracking elements operative to determine position of the fixture and patient, one of said tracking elements being secured against motion with respect to the spatial fixture so that determining position of said tracking element determines position of all the markers in a single measurement,

a camera characterization module operative on data derived from images of the markers to model fluoroscopic imaging projection for each fluoroscope frame; and

a CT image module connected for receiving a determination from the tracking assembly and the camera characterization module and operatively determining a common coordinate system in a region of imaged patient tissue for a plurality of fluoroscope poses,

said CT image module being operative to form a fluoro-CT image data set representing said region of imaged patient tissue for reconstruction of image planes of tissue in said region.

7. The surgical imaging system of claim 6, wherein said system applies said tracking data and camera imaging parameters to project a representation of a tracked tool to a transformed display position on an untransformed but marker-free fluoroscope image.

8. The surgical imaging system of claim 6, wherein said CT image module applies back projection to a registered sequence of fluoroscope images to form said fluoro-CT image data set.

9. The surgical imaging system of claim 8, further comprising a module for correlating said fluoro-CT images with preoperative MRI, CT or PET image data to provide fused images for display.

10. A system for use with fluoroscope to effect registration of a preoperative 3D image data set to tissue of a patient, so as to display a preoperative image corresponding to a position of patient tissue tracked by a tracking assembly, such system comprising

a tracking assembly including at least first and second tracking elements adapted for determination of fluoroscope and of patient tissue positions, respectively, in a coordinate system

a processor operative with position information from the tracking assembly and with fluoroscope image data from a fluoroscope to construct a fluoro-CT data set representing a region of tissue in a patient, and

a display image selector configured to operatively register a preoperative image set with said fluoro-CT data set to thereby assign tracked tissue coordinates to the preoperative image set whereby preoperative images are automatically registered to tracked positions of patient tissue.