Surgery – Instruments – Stereotaxic device
Reexamination Certificate
2000-04-20
2001-07-17
Philogene, Pedro (Department: 3732)
Surgery
Instruments
Stereotaxic device
C600S417000, C600S429000
Reexamination Certificate
active
06261300
ABSTRACT:
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 t
Carol Mark
Day James L.
Miller Erik G.
Riker Robert J.
Ohio Medical Instrument Company, Inc.
Philogene Pedro
Wood Herron & Evans L.L.P.
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