Apparatus for neurosurgical stereotactic procedures

What is claimed is:

1. A stereotactic system comprising:

an imaging display system for displaying images;

an image fiducial selector coupled to said imaging system for selecting fiducials on an image displayed on said display system;

a target selector coupled to said imaging system for selecting a target on an image displayed on said display system;

an articulated arm terminating with a probe and coupled to said imaging system, said articulated arm providing spatial coordinates for said probe with reference to said imaging system so that a position associated with said probe is displayed on said displayed image;

a patient fiducial selector coupled to said imaging system and said articulated arm for selecting fiducials on a patient that correspond to said fiducials selected by said image fiducial selector;

a coregistration processor for coregistering said selected patient fiducials to said selected image fiducials so that said coordinates provided by said articulated arm may be matched to said displayed images whereby a path from said displayed probe position to said selected target may be displayed on said displayed image; and

a holder separate from the articulated arm and located at a desired position in proximity to a patient, said holder supporting said probe and being pivotable at said desired position with respect to said patient to allow a surgeon to evaluate and establish a desired path as displayed on said displayed image between said desired position and said selected target, said holder being lockable to fix said holder supporting said probe at a desired orientation directing said probe along said desired path, and thereafter, upon removing said probe, said holder adapted to receive an instrument, said holder providing independent of said imaging system, support and guidance for said instrument so that said instrument follows said desired path.

2. The system of claim 1, said image fiducial selector providing operator selection of said fiducials on said displayed image.

3. The system of claim 2, said image fiducial selector further comprising:

a menu presenting a predetermined number of image fiducial point identifiers; and

an activation icon for selectively activating a selected image fiducial point.

4. The system of claim 1, said patient fiducial selector further comprising:

an operator activated selector for identifying a patient fiducial, said operator activated selector enabling said image display system to accept coordinate data from said articulated arm and probe to identify a patient fiducial.

5. The system of claim 1 further comprising a patient support adapted to support a patient.

6. The system of claim 5 wherein said holder includes a ball and socket mechanism.

7. The system of claim 5 wherein said holder further includes a stereotactic system for selectively positioning the probe and the instrument proximate the patient.

8. The system of claim 7, said stereotactic system comprising:

an arc carrier rod, said arc carrier rod being mountable within said holder so that said rod points to a selected target within a patient's head;

a support arm rotatably mounted about said arc carrier rod; and

an arc slidably mountable to said support arm so that said arc defines a circle centered about said selected target within said patient's head.

9. The stereotactic apparatus of claim 8 wherein the holder further includes a collar connectable to the arc at different locations, the collar having a receptacle for selectively supporting the probe and the instrument at a second selected position and orientation, thereby defining a second path between the second selected position and the target point within the patient to facilitate an evaluation and operation along the path.

10. The stereotactic apparatus of 7 wherein the stereotactic system is removably attachable to patient at the desired position.

11. The system of claim 10, said stereotactic system comprising:

a skull ring for mounting to a patient's head; and

a transfer plate having a receptacle located therein for receiving said probe.

12. The system of claim 11, said holder further comprising a ball adapted to fit within said receptacle, said ball being lockable within said receptacle.

13. The system of claim 5 wherein said holder comprises:

a first member located at the desired position;

a second member supported by and movable with respect to the first member and selectively supporting the probe and the instrument; and

a clamp disposed with respect to the first and second members for locking the second member in the desired orientation.

14. The stereotactic apparatus of claim 13 wherein the patient support comprises a head support.

15. The stereotactic apparatus of claim 14 wherein the head support further comprises a skull clamp.

16. The system of claim 5 further comprising a base coupled between the opposite end of the articulated arm and the patient support.

17. The stereotactic apparatus of claim 16 wherein the patient support has a first connector, and the base has a connector connectable with the first connector on the patient support.

18. The stereotactic apparatus of claim 17 wherein the base further includes a releasable clamp for receiving and holding a shaft connected to the opposite end of the articulated arm.

19. The stereotactic apparatus of claim 18 wherein the base further includes a bore for receiving and holding the probe to facilitate a probe initialization process.

20. The stereotactic apparatus of claim 17 wherein the base and the first connector have a key system so that the base is connected to the first connector in a predetermined orientation.

21. The system of claim 1, said image display system further comprising:

a display of said probe and articulated arm position so that operation of said articulated arm and probe may be verified.

22. The system of claim 1, wherein said coregistration processor implements an iterative algorithm for coregistering said selected patient fiducials with radiological data used to generate said displayed radiological images.

23. The stereotactic apparatus of claim 1 wherein the articulated arm further comprises encoders operatively connected to the articulated arm for providing the spatial coordinate representations of the probe.

24. The system of claim 5 wherein the holder is adjustably supported with respect to the patient support to allow the holder to be moved in proximity to the patient.

25. The system of claim 24 wherein the holder comprises:

a first arm adjustably supported with respect to the patient support; and

a receptacle mounted to one end of the first arm and movable to the desired position with respect to the patient, the receptacle selectively receiving the probe and the instrument and holding the respective probe and instrument at the desired orientation.

26. The system of claim 25 wherein the holder further comprises a second arm coupled to the first arm to provide relative motion therebetween, the second arm being connected to the patient support.

Description Submit all comments and votes

FIELD OF THE INVENTION

This invention relates to neurosurgical apparatus generally, and more particularly, to stereotactic systems for use in neurosurgery.

BACKGROUND OF THE INVENTION

During the 1970's radiological imaging systems were developed to assist surgeons in ascertaining the internal condition of a patient in greater detail. Specifically, computer assisted tomography (CAT) systems were developed to enhance images generated from data produced during a radiological scan of a patient. The patient is placed within a gantry, and a radiation source and radiation detectors are positioned opposite one another to be rotated about a portion of the patient's body. The data generated by the radiation detectors are utilized by a computer to generate radiographic images or "slices" of the body position to give a doctor greatly enhanced views through the area of interest.

Later radiographic imaging systems included magnetic resonance (MRI) and positron emission tomography (PET) imaging which generate images from energy sources that do not use x-rays or the like. These devices are useful because they provide different or additional information about organs or tissues than CAT scan images. In this application the term scanners refers to imaging devices regardless of the technique utilized to generate the images.

Neurosurgery may be performed to investigate, repair, or remove anomalies located within the brain of a patient. The environment of such surgeries is challenging in that the organ of interest, the brain, is surrounded by relatively thick bony structure, the skull. The only presurgery access to the brain available to a surgeon is through images generated by an imaging system.

Because of the inaccessibility, size, and roughly hemispherical shape of the brain, specifying the locus of a point inside the brain generally requires reference to some fixed external reference system. To provide a surgeon with sufficient information to locate an area of interest on an image, such as a tumor or lesion, a variety of systems have been developed to provide a reference point or points which may be used to match the patient's anatomical structure with the structures displayed in the images. These systems typically require that a frame be rigidly fixed to a patient's head to provide a reference point or points. Once the reference structure is attached to the patient, the image data is generated with the reference frame fixed in relation to the imaging device, That is, there is typically a mechanical coupling between the reference structure and the imaging device, After the data is collected, the patient may be removed from the scanner but the reference frame must remain attached to the patient's head. The reference frame remains attached throughout surgery so the surgeon can correlate image information about patient anatomical structures to a position within the patient's skull located with reference to the frame.

While such systems provide surgeons with a remarkable ability to locate areas of interest within a patient's brain based upon the data acquired by radiological scanners, the required reference frames are cumbersome and complicate the acquisition of radiological data. To preserve the location of the reference frame, it must remain attached to the patient's head throughout the scanning procedure and the surgical procedure. Because the reference frames may weigh several pounds and must be securely fastened to the head, they can be uncomfortable to the patient. The distances the frames extend from the patient's head also present difficulties in maneuvering the patient. Additionally, patients with larger than normal heads often cannot be fitted with stereotactic frames.

In an effort to reduce the awkwardness of the reference structure and the discomfort it causes a patient, a stereotactic system using a skull ring which may be mounted to a patient's skull was developed. The ring is a relatively small metallic circle that is attached to a patient's head using cancellous screws. Once the ring is in place, a transfer plate having two openings, one of which has a rotatable ball and socket mechanism mounted therein, is secured within the ring. The transfer plate is also provided with a radiological opaque marker which may be discerned in the radiological images generated by the scanner. The patient is then placed inside a scanner and a member extending from the ball and socket is coupled to the machine. Once the patient has been oriented within the scanner for the collection of image data, the ball and socket is locked in a fixed orientation.

Following the collection of image data, the member extending from the ring and patient which was coupled to the scanner is disconnected so the patient may be removed. The ball and socket remains locked in its orientation so the orientation of the transfer ring on the patient's skull may be later duplicated for locating a target.

After removing the transfer plate holding the ball and socket from the skull ring attached to the patient's head, the plate is attached to a member extending above a frame table to duplicate its position and orientation on the patient's head. The images generated by the scanner are viewed and the coordinate data of a selected target, such as a lesion or tumor, and the radiological marker of the transfer plate are determined. Using this coordinate data and the indicia marked on the frame table, a target marker is maneuvered on the frame table so it identifies the target position with respect to the radiological marker. A second ball and socket mechanism is placed in the second opening of the transfer plate. Thereafter, an instrument such as a biopsy probe may then be extended through the second ball and socket to the target point to define a distance and path to the target. The second ball and socket is then locked into place to preserve the orientation to the target and the distance to the target is marked on the probe.

The transfer plate bearing the second ball and socket mechanism may then be removed from the member above the frame table and reattached to the skull ring on the patient's skull with the second locked ball and socket defining a path to the selected target. Thereafter, a biopsy probe may be used to mark the patient's skull and a craniotomy performed at that point to provide an opening in the patient's skull. The biopsy probe may then be extended through the opening in the second ball and socket to the depth marked on the probe to place the biopsy probe within the lesion or tumor. In this manner, the surgeon is able to accurately place the biopsy probe without unnecessary searching to locate the tumor or lesion prior to performing the biopsy. A further description of the above technique and apparatus is given in U.S. Pat. Nos. 4,805,615 and 4,955,891 to which reference may be had.

The above-described manner for performing the biopsy facilitates the collection of image data in a number of ways. First, the reference structure attached to the patient's skull is small in comparison to the reference frames previously used. Second, the removable plate with the ball and socket openings permit accurate location of a target area within a patient's brain prior to performing a craniotomy. Third, the removable plate with the ball and socket mechanisms ensures correct placement of the plate on the patient's skull and preserves the accuracy of the path to the target identified on the frame table. While this method greatly facilitates locating the target area within a brain, it fails to provide the surgeon with information regarding the intervening tissue area between the craniotomy opening in the skull and the target area, which lies within and possibly deeply within the brain. Furthermore, the image data generated by a scanner is not necessarily oriented transversely to the location of the opening of the ball and socket of the reference ring and thus does not provide image data at various depths between the craniotomy opening and the target area to assist the surgeon in evaluating the path to the target. Thus, while the surgeon need not search to locate the target, the surgeon does need to carefully retract the brain tissue along the path to reach the target. Otherwise, damage to any sensitive areas that may lie along the pathway is possible. The reference systems discussed above do not assist a surgeon in identifying the exact location of any such sensitive areas prior to performing the craniotomy and traversing the path to the target.

In addition to identifying the locus of the lesion or injury within the brain it is often critical to determine a suitable pathway through the brain to access that locus, in order to minimize damage to the intervening tissue. Thus, identifying the pathway to the site may be almost as critical as identifying the site itself. The above-described system has been inadequate in this respect.

In an effort to provide more automatic matching between image data and the patient as placed in surgery, systems have been developed that perform "coregistration". Coregistration is a process by which a computer matches fiducials associated with image data to fiducials associated with the patient's body. The image fiducials are typically selected by using a mouse and cursor to identify on a displayed image points that lie on a patient's skin. An articulated arm and probe are coupled to the computer to provide coordinate data for points external to the computer. Using the arm and probe, the user selects points on the patient that correspond to the selected image fiducials and the computer executes a program that matches the corresponding points. After a sufficient number of points have been selected (usually at least 8), the computer may identify the point in the displayed images that corresponds to the position of the probe proximate the patient's head. Such a system is made by Radionics of Brookline, Mass. and is identified by its product name The Operating Arm.

Such a system provides "navigational" information to a surgeon, that is, the surgeon may bring the probe to a particular location on or within a patient's head and have that location identified on the displayed image. In this way, the surgeon may view areas on the displayed image and determine their proximity to the probe location. In that manner, the surgeon may confirm the surgical approach to a target.

While these systems provide confirming navigational information they still do not project a stabilized image of the surgical path on a displayed radiological image prior to a craniotomy being performed. Such systems cannot project a stabilized path because the surgeon cannot consistently orient an