HK1003861A - Apparatus and method for neurosurgical stereotactic procedures - Google Patents

Description

Apparatus and method for a stereotactic procedure for neurosurgery

Technical Field

The present invention relates generally to neurosurgical devices, and more particularly to a stereotactic system for use in neurosurgery.

Background

During the seventies, radiological imaging systems have been developed to help surgeons more thoroughly ascertain the internal condition of patients. In particular, computer-assisted tomography (CAT) systems have been developed to improve the quality of images obtained from data generated during a patient's radiological scan. The patient is placed in a gantry and the source and detector are positioned relative to each other for rotation about a portion of the patient's body. The data generated by the radiation detector is used by the computer to generate a radiographic image or "slice" of the body part, giving the physician a much clearer view of the entire region of interest.

Later, radiographic imaging systems also included Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) imaging, which generated images from sources other than X-rays or the like. These devices are useful because they provide information about organs and tissues that is different from or additional to CAT scan images. In this application, the term scanner refers to an imaging device, regardless of the technique used to generate the image.

Neurosurgical procedures are performed to study, repair or remove abnormalities located in the brain of a patient. The environment of such surgery is challenging because the organ in which interest is located: the brain is surrounded by a relatively thick skeletal structure, the skull. The only way that the brain is accessible to the surgeon prior to surgery is through the images produced by the imaging system.

Due to the inaccessibility, size and generally hemispherical shape of the brain, the determination of the locus of points within the brain typically requires reference to some fixed external reference system. To provide the surgeon with sufficient information to determine a region of interest on the image, such as a tumor or lesion, various systems have been developed to provide a reference point or points that can be used to correspond the patient's anatomical results to the structures displayed on the image. These systems typically require a frame to be securely fixed to the patient's head to provide a reference point or points. Once the reference structure is attached to the patient, image data is generated according to a reference frame that is fixed relative to the imaging device. That is, there is typically a mechanical connection between the reference structure and the imaging device. After data collection, the patient can be removed from the scanner, but the frame of reference must still be attached to the patient's head. The frame of reference remains attached throughout the surgical procedure so that the surgeon can correlate image information about the patient's anatomy to a location within the patient's skull that is located relative to the frame.

While such systems provide surgeons with the surprising ability to determine the region of interest in the patient's brain based on the data acquired by the radiological scanner, the required framework is cumbersome and complicates the acquisition of radiological data. To maintain the position of the frame of reference, it must remain attached to the patient's head throughout the scanning procedure and the surgical procedure. Because the reference frames can weigh several pounds and must be securely fixed to the head, they can be uncomfortable for the patient. Frames the distance the patient's head extends can also be difficult when maneuvering the patient. In addition, patients with larger than normal heads often cannot fit the stereotactic frame.

To reduce the clumsiness of the reference frame and the discomfort it causes to the patient, a stereotactic system has been developed that uses a skull ring that can be mounted to the patient's skull. The ring is a relatively small metal ring that is mounted on the patient's head using a porous screw. Once the ring is installed, a transfer plate having two holes, one of which has a rotatable ball and socket mechanism mounted therein, is secured within the ring. The transfer plate is also provided with radiopaque markers that can be identified in the radiographic image produced by the scanner. The patient is then placed into the scanner and a piece of the member extending from the ball and socket is connected to the machine. Once the patient is oriented within the scanner to collect image data, the ball and socket are locked in a fixed orientation.

After image data is collected, the members extending from the ring and from the patient connected to the scanner are disengaged so that the patient can be removed. The ball and socket remain locked in their orientation so that the orientation of the delivery ring on the patient's skull can be later replicated to target.

After the transfer plate holding the balls and sockets is removed for mounting in the cranium ring of the patient's head, the plate is connected to a piece of member that extends from above the frame block to replicate its position and orientation on the patient's head. The images produced by the scanner are examined to determine the selected target, such as a lesion or tumor, and the coordinate data of the transfer plate radiolabel. The coordinate data and the markers marked on the gantry stage are used to manipulate the target markers on the gantry stage to identify target locations relative to the radiolabels. The second ball and socket mechanism is placed in the second hole 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 determine the distance and path to the target. The second ball and socket are then locked in place to maintain the orientation to the target, and the distance to the target is marked on the probe.

The transfer plate supporting the second ball and socket mechanism can then be removed from the component above the frame table and reinstalled onto the skull bone ring on the patient's skull bone, with the locked second ball and socket to determine a path to the selected target. Thereafter, the patient's skull may be marked using a biopsy probe and a craniotomy procedure performed at this point to provide a hole in the patient's skull. The biopsy probe may then be passed through the second ball and the hole in the socket to a depth marked on the probe to place the biopsy probe within the lesion or disease. In this way, the surgeon can accurately place the biopsy probe without having to search for a localized tumor or lesion prior to performing the biopsy. Further description of the above techniques and devices is found in U.S. patent nos.4805615 and 4955891(U.S. patent nos.4805615 and 4955891), which are incorporated herein by reference.

The above described method of performing a biopsy speeds up the collection of image data in many ways. First, the reference structure mounted to the patient's skull is small compared to previously used reference frames. Second, a movable plate with a ball and socket hole enables precise positioning of the target area within the patient's brain prior to performing the craniotomy procedure. Third, the movable plate with the ball and socket mechanism ensures that the plate is properly placed on the patient's skull and maintains the accuracy of the path to the target determined on the frame block. While this method greatly accelerates the determination of a target area within the brain, it does not provide the surgeon with information about the intervening tissue area between the craniotomy in the skull and the target area, which is located within the brain and may be located deep within the brain. Furthermore, the image data generated by the scanner is not necessarily directed across the location of the ball of the reference ring and the hole of the socket, and thus does not provide image data at different depths between the craniotomy hole and the target area to assist the surgeon in estimating the path to the target. Thus, while the surgeon does not need to search to locate the target, the surgeon does need to take care to retrieve the brain tissue along the way to the target. Otherwise, some sensitive areas extending along the path may be damaged. The above-described reference system does not help surgeons determine the exact location of such sensitive areas and traverse the path to the target prior to craniotomy.

In addition to determining the trajectory of lesions or lesions within the brain, it is often critical to determine the appropriate path through the brain to the trajectory in order to minimize damage to intervening cellular tissue. Thus, determining the path to the site is almost as critical as determining the site itself. The above system is not suitable in this respect.

To provide a more automated match between image data and a patient placed in surgery, systems have been developed that perform "mutual registration". Mutual registration is the process by which the computer pairs fiducial points associated with the image data with fiducial points associated with the patient's body. Typically, the image reference points are selected by applying a mouse and a cursor to identify points on the patient's skin on the displayed image. The articulated arm and probe are connected to a computer to provide coordinate data for points external to the computer. The user applies the arm and the probe, selects points on the patient which correspond to the selected image reference points, and the computer executes a program which pairs the corresponding points. After a sufficient number of points is selected (typically at least 8 points), the computer can identify the points on the displayed image that correspond to the probe location proximate the patient's head. Such a system is manufactured by radients o Brookline, masscusetts, and is labeled under its product name "arm".

Such systems provide "navigation" information to the surgeon, i.e., the surgeon can place the probe at a particular location on or within the patient's head, and identify that location on the displayed image. In this way, the surgeon can examine the areas on the displayed image and determine their proximity to the probe location. Thus, the surgeon can insist on the correctness of the surgical approach to the target.

While these systems provide convincing navigation information, they still fail to project an image of a stable surgical path on the displayed radiographic image prior to the craniotomy procedure. Such systems do not project a stable path because the surgeon cannot consistently orient and stabilize the probe in exactly the same position each time an inspection of the path is required. As a result, such systems cannot confirm or permanently indicate the path to the target because the probe is operated by hand. Furthermore, such systems do not ensure that the surgeon can follow any path that the surgeon chooses based on the displayed radiographic examination results.

What is needed is a system that allows a surgeon to select, evaluate, and lock in place a path to a selected target prior to performing a craniotomy procedure. What is needed is a system that can guide a surgeon during and after a craniotomy along an estimated surgical path to a target. What is needed is a way to select and maintain several selected paths to multiple targets after the paths are evaluated.

Disclosure of Invention

These and other problems of previously known systems can be overcome by a system constructed in accordance with the principles of the present invention. The system includes an imaging display system for displaying a radiographic image; an image reference point selector connected to the imaging system for selecting a reference point on the image displayed on the display system; a target selector coupled to the imaging system for selecting a target on the image displayed on the display system; the articulated arm and probe, which is coupled to the imaging system, can be referenced to the imaging system to provide spatial coordinates of the probe so that the position associated with the probe is displayed on the display image. A patient reference point selector, coupled to the imaging system and the articulated arm, for selecting reference points on the patient corresponding to the selected reference points of the displayed image. A mutual registration processor registers the patient fiducial points with the selected image fiducial points so that the coordinates provided by the articulated arm can be paired with the display image so that the position of the probe can be displayed on the display image. The probe holder holds the probe of the articulated arm in a position adjacent the patient's head, the holder being selectively lockable so as to remain adjacent the patient's head. With this system, the surgeon can estimate the path between the probe location and the selected target displayed on the display image.

A system according to the principles of the present invention allows a patient to be scanned without any flat or frame reference fixed to the patient. The system registers the image reference points with selected anatomical features of the patient so that the probe positions can be displayed on the radiographic image and the path to the selected target projected on the image. The surgeon may evaluate the path to the selected target and lock the probe position in place if the path is deemed acceptable. The surgeon may then mark the appropriate marks on the patient's head to perform the craniotomy. In a similar manner, paths to other targets may be identified and marked prior to any craniotomy.

The system also includes surgical instrument cannulas adapted to be mounted in the probe holder such that instruments can be inserted through the cannulas in the correct orientation and position along the estimated path to the selected target. Thus, the probe holder can be used to expedite surgeon selection and evaluation of a path and thereafter maintain the path and a guide instrument along the path.

The system of the present invention further includes an arcuate plate carrier bar for determining a predetermined radius to a selected target. The notched arc is rotatably mounted to the reference bar and the probe holder with the probe mounted thereon is adapted to slide within the notched arc. Thus, the notched arc can be rotated in a hemispherical fashion around the patient's head, while the probe card and holder are slid along the notched arc for evaluation by the surgeon using the radiographic display system to determine the entry points. The imaging system is also provided with a processor for data interpolation of the radiation data produced by the scanner to provide views along the probe from any entry points selected along the hemispherical stereoplanning system when it is positioned with the probe reaching the holder. Using this system, the surgeon can evaluate several entry points and select one of them that is least risky to the patient.

Another advantage of the present system is that after a target is selected and a biopsy or surgical procedure is performed on the target, the surgeon can select a second target of interest within the patient's brain. After this selection, the probe holder may be released and the probe reinserted to define a second path to a second selected target. The hemispherical stereotactic system may then be connected to provide multiple access points to a second target for evaluation, and once the appropriate path is selected, surgery may be performed on the second target. Use of this system in this manner speeds up surgery in which radioactive seeds can be implanted into various regions of the tumor with the effect that the radioactivity is substantially localized to the tumor region. Such applications may also assist surgeons in accurately placing multiple depth electrodes in a patient's brain for monitoring.

These and other advantages of the proposed system according to the principles of the present invention may be understood with reference to the drawings and the accompanying detailed description.

Brief description of the drawings

The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating the preferred embodiments and other embodiments and are not to be construed as limiting the invention.

FIG. 1 is a perspective schematic view of components of one embodiment of a system according to the principles of the present invention;

FIG. 2 illustrates a representative screen displaying image information generated by the system of FIG. 1; while

Fig. 3 is a diagram of a preferred embodiment of a stereotactic sub-system for use in the system of fig. 1.

Detailed description of the invention

Shown in fig. 1 is a neurosurgical stereotactic system 10 constructed in accordance with the principles of the present invention. The system includes an image display subsystem 12, an articulated arm and probe 18, and a stereotactic planning subsystem 16. The image display subsystem 12 displays images derived from image data generated by the scanner, or from data interpolated from such data. The subsystem 12 receives operator input for selecting a fiducial point, receives coordinate data from the articulated arm and probe, and registers the selected fiducial point on the patient 13 with the selected fiducial point of the patient's radiation image, thus indicating the position of the probe and the path to the selected target. The subsystem 12 also displays an image of the articulated arm so that the operation of the arm and probe can be verified.

The articulated arm and probe 18 provides spatial data to the display subsystem 12 through an encoder interface 20. The spatial data is preferably generated by an optical encoder 22, although other types of spatial coordinate data generating components may be used. In addition to the data provided by the arm and probe 18 for locating the position of the probe, the probe 24 may also provide rotational data as it rotates about its longitudinal axis to rotate the displayed image on the subsystem 12, as will be described in more detail below.

The stereotactic subsystem 16 stabilizes the probe 24 as the surgeon guides the probe through the patient's head. The subsystem 16 also contains components, described in greater detail below, that enable the probe to be locked in place, which is used to guide the surgical instrument to a selected target. The subsystem 16 also contains components, which will be described in greater detail below, that are operable to provide a surgical path to a target within the patient with multiple access points, all of which are aligned with the center of the selected target range. These components provide the surgeon with a reasonably good degree of reliability so that each probe position provided is with the chosen target.

The radiation display subsystem 12 includes a computer 30 to which are connected a high resolution graphics monitor 32, a mouse 34, a foot pedal 36, a keyboard 38 and a tape drive 40. The computer 12 may additionally include a 3.5 inch floppy disk drive or the like and a Digital Audio Tape (DAT) drive or the like. A magnetic tape drive 40, a floppy disk drive, and a Digital Audio Tape (DAT) drive may be used to provide radiation image data to the computer 30. These tape drives may also be used to archive data generated by computer 30 or to modify software executing on computer 30. Computer 30 may also be connected to a computer network such as ethernet using conventional techniques. Such networks may be used to provide radiation image data, software or diagnostic services.

The monitor 32 is preferably a Multi-Scan HG single gun three beam color picture tube hyperfine pitch resolution monitor (Multi-Scan HG Trinitron pitch resolution monitor) available from Sony Corporation of America (Sony Corporation of America). Computer 30 is preferably Dell 450DE/2DGX manufactured by Dell Computers of Houston, Tex. The tape drive 40 for reading the image scan Data is preferably a 9-track tape drive manufactured by the Overland Data of San Diego, Calif. The encoder Interface 20 and the articulated arm and probe 18 are manufactured by immersion human Interface corporation of San Francisco, California, San Francisco, San Interface Corp.

Computer 30 preferably executes an Atlas program developed by nomosf Pittsburgh, Pernsylvania, knomors corporation of pexiburg, pa. Astralas (Atlas) is a computer program that displays a radiation image derived from radiation scan data provided by a magnetic tape and interpolates the data to provide additional views that do not appear in the radiation scan data. The Atlas (Atlas) program in the preferred embodiment has been modified to receive data from the articulated arm and probe 18 through the encoder interface 20. The program is loaded using the resident operating system of the computer 30, which in the preferred embodiment is the Microsoft disk operating system (MS-DOS). The Alderas (Atlas) program contains its own high-level input/output programs and other computer resource functions, such that the Alderas (Atlas) program can use the basic level of input/output operations of the resident operating system of the computer 30. In the preferred embodiment, the computer 30 is also equipped with a telephone interface so that software such as diagnostics and other support functions can be provided remotely by telephone.

The articulated arm and probe 18 is mounted on a surgical cranial clamp 46, while it is mounted on an operating table 48 (which may be of a known type). The base support 50 (fig. 1) is attached to a mounting sleeve 52 which is mounted to a star explosive connector 54 of the surgical cranial clamp 46. The base support 50 is preferably mounted to the sleeve 52 by means of a hexagonal set screw or the like. The mating surfaces of the sleeve 52 and the holder 50 are preferably keyed so that the substrate holder 50 has only one possible orientation. This feature is important to maintain the accuracy of the reference point when using a sterile base support and arm for placement of the surgical drape as described in detail below. The base support 50 also includes lockable mounting screws 56 for the articulating arm at one end and a hollow tubular extension 58 at its other end for holding the articulating arm and probe 24. The screw 56 is rotatably mounted about a slot 60 cut into the base support 50 for the articulating arm and probe 18.

The articulated arm and probe 18 (fig. 1) also includes a mounting stud 62, a two piece arm member 64, and the probe 24. Hinge member 68 connects mounting stud 62, arm member 64 and probe 24 to form the arm and probe 18. At each hinge point there is a rotation in two perpendicular planes, so that each arm has two degrees of freedom. The positions of each arm member to which the respective hinges are to be made are preferably provided with optical encoders 22 which are connected to the arms in mutually perpendicular relationship at each hinge. The probe 24 is mounted within a sleeve 70 at the outermost end of the arm so that it can rotate about its longitudinal axis. This rotational movement is used by the computer 30 to rotate the radiation image displayed to the surgeon on the screen of the monitor 32. Extending from one end of the arm 18 is an interface cable 72 which terminates at the encoder interface 20. The encoder interface 20 converts data from the six optical encoders 22 of the articulated arm 18 into rotational position (angular) data for the computer 30.

The tape drive 40 may be used to provide image scan data to the computer 30. Most image scanners will scan the resulting image data for archiving by storing them on a magnetic medium such as a 9-track tape 74. The tape may then be read by the tape drive 40 and provided to the computer 30, with the computer 30 storing data on other magnetic media, such as a hard disk drive. Image data read from a magnetic tape inserted in the drive 40 may be used as generated by a scanner. However, each scanner manufacturer may format the data differently. The image data generated by each type of scanner is preferably converted to a standard format before being stored on the internal magnetic media of the computer 30. In this way, the image display program executing on the computer 30 does not require different modules or programs for each format in order to use data from different scanners.

Typically, the data generated by the scanner includes both image data and non-image data. The non-image data includes parameter definitions such as patient name, date, patient location, scan orientation, scan parameters, and other imaging details specific to each of the different scanner manufacturers. The preferred embodiment of the program executing on computer 30 extracts basic data entries common to all scanner producers and stores them in a key evaluation file using an image data file. The keyword evaluation file contains a list of keywords that identify each data field and the evaluation of that field. For example, the data field identifier for the patient's name is followed by a data expression for the patient's name for the sequential scan. For purposes of system analysis, these files are preferably human-readable, as they are generally not accessible to the user.

The image data typically comprises numerical data representing gray scale values such as (Hounsfield) units or some other luminance/contrast value, which values can be used to generate an image, as is well known. These digital values are compressed or represented as integers or real values. The preferred embodiment of the program executing on the computer 30 does not compress any compressed values and converts all numerical data to integer data. The data is then stored in an image data file. These files are preferably written to the disk in a hierarchical file structure that separates the patient data from each other, as well as in image studies and series for each patient.

Foot pedal 36, mouse 34, and keyboard 38 may be used by an operator to provide input to computer 10. For example, the mouse 34 may be used to control a cursor on the screen of the monitor 32 to select different options, as will be described in more detail below. As another example, foot pedal 36 may be used by the surgeon to activate the selection of a reference point on the patient.

In the preferred embodiment, the graphical display program executed on computer 30 includes a Graphical User Interface (GUI), an input/output (I/O) library, an articulated arm interface program, and a number of application modules. The GUI interface controls the display of data and menus on the screen of the monitor 32. The I/O library program performs various input and output functions such as reading out image data from the tape drive 40. The articulated arm interface provides a display of menus and fiducial selection points at the bottom of the monitor 32 screen of the preferred embodiment of the subsystem 12 shown in fig. 1. Finally, the application module executes software to perform conversion operations, such as interpolating data for the image and registering the image data with fiducial points of the selected patient.

Shown in fig. 1 is an alternative embodiment of a stereotactic planning subsystem 16 that attaches an articulated arm and probe 18 to a patient to enable the estimation and selection of a surgical path. The apparatus includes a skull ring 80, a transfer plate 82, a rotary socket 84, and a probe alignment ball 86. The device is applied after the patient's hair has been shaved, betadine prepared, and xylocaine injected, by securing the cranial ring 80 to the patient's head by a cancellous bone screw. After the skull ring 80 is secured, the transfer plate 82 is mounted on the skull ring by posts (not shown) extending from the skull. The rotary socket 84 is mounted to the skull bone ring by means of hexagonal set screws or the like. The swivel socket 84 includes a base 92 and an upwardly projecting sleeve 94. The probe alignment ball 86 is inserted into the sleeve 94. Probe alignment ball 86 is adapted to receive the end of probe 24, such as by using a probe alignment sleeve 193 as shown and described in FIG. 3. In this manner, the probe 24 can be inserted into the probe alignment ball 86 with the probe and ball moving together relative to the patient's scalp surface.

Once the surgeon has selected a particular orientation based on the information provided by the radiation image displayed on monitor 32, screw 98 extending outwardly from sleeve 94 may be tightened to secure probe alignment ball 86 in place. A surgical instrument cannula (not shown) of a known type may then be inserted into the probe alignment ball 86 to allow a drill bit or other instrument to be inserted through the instrument cannula to open the patient's skull. Biopsy instruments may also be inserted through the cannula to the target area. In this way, the use of the ring 80, transfer plate 82, socket 84 and ball 86 provides the surgeon with a stable platform to position the probe 24 and securely lock the estimated orientation in place, thereby providing guidance for the surgical procedure.

Also shown in fig. 1 is a hemispherical stereotactic planning system for access to site selection. The apparatus includes an arcuate plate carrier bar 100, a rotating support arm 102, an arcuate plate 104, and a variable sleeve assembly 106. After the probe alignment ball 86 has been oriented so that the probe 24 is directed at the target, the probe can be removed and the arc carrier bar 100 inserted into the probe alignment ball 86. The pivoting support arm 102 is then mounted on the arcuate plate carrier bar 100 and secured around the bar using screws 110. A tongue or wedge 112 is mounted in lockable relationship to the rotating support arm 102 and is adapted to fit within a track cut into the arcuate plate 104. The arcuate plate 104 may be secured to the arm 102 at any location along the length of the arcuate plate 104 by tightening the screw 118 that turns the support arm 102. The variable sleeve system 106 is also adapted to have an awl that is slidably mounted in the arc plate 104 such that the variable sleeve assembly 106 can be locked in place at any position along the length of the arc plate 104. The cannula assembly 106 also includes a receptacle, such as a receptacle similar to the probe holder 192 shown in FIG. 3, that receives the probe 24 so that the surgeon can evaluate the path to the selected target by observing the path displayed on the monitor 32 of the subsystem 12. Because the live weight bar 100 is pointed at the target, the support arm 102 and the curved plate 104 can rotate about the patient's head in a semi-spherical fashion centered about the target. The support arm 102 is preferably locked into position about the arc carrier bar 100 such that the central hole in the variable sleeve assembly 106 is positioned about 19 centimeters from the target distance of the arc 104 about the alignment center.

The components of the hemispherical stereotactic system allow the surgeon to manipulate the probe 24 around the patient's head with a reasonably good degree of reliability so that the socket is pointing at the previously selected target. By simply rotating the arcuate plate 104 about the rod 100 and sliding the sleeve 106 within the arcuate plate 104, the surgeon is provided with a number of fields for evaluation that can be locked in place as a surgical guide.

A preferred embodiment of the stereotactic system 16 is shown in fig. 3. The system includes a probe holder nest 180 and rigid bifurcated arms 182 that are placed between solar explosive connector 54 and casing 52. Bifurcated arms 182 terminate in a pivotal joint 184 from which an adjustable arm 186 extends. Another adjustable arm 190 extends from the pivot joint 188 at the end of the arm 186. 190 terminate in a probe gripper 192 which, as already described in connection with fig. 1, is provided with the transfer plate 82, the ball socket mechanism 84 and the adjustment ball 86, wherein the ball 86 is adapted to receive a probe alignment sleeve 193. Thus, the subsystem 16 provides a rigid adjustable arm by which the probe holder 192 and auxiliary assembly can be manipulated about the patient's head and then selectively locked in place for path estimation, surgical instrument guidance, or hemispherical system attachment.

To apply the system 10 to neurosurgery, the patient 13 is scanned in an image scanner to produce a series of images. A "series" may be a set of parallel, equally spaced images, sometimes also referred to as "slices", of a volumetric portion of the patient's body. The images constituting the series are preferably continuous. Combinations of more than one series of images, commonly referred to as "research projects" or "suites," may also be applied by the system. Examples of series are axial, coronal, rotational, and sagittal. The axial series is from the top of the patient's head to the base of the skull, the coronal series is from the face to the back of the patient's head, the rotational series is around the patient's head, and the sagittal series is from the side view of the patient's head to the other side. The axial series is preferably generated at a gantry angle of 0 deg., otherwise, distortion may occur in the data from the preferred embodiment of the Aldelas (Atlas) procedure.

After the series is generated by the scanner, it may be driven down to the magnetic medium for transport to the system 10. Typically, image data is written to a 9-track tape 74, which is readable by a 9-track tape reader 40. The user may drive the computer 30 and drive a 9-track tape interface program in an input/output (I/O) library. By employing this program, the user can read image data from the 9-track tape 74 into the computer 30, which then stores the data in an appropriate format in a hard disk drive or the like. The computer 30 may also receive data from an image scanner via a DAT reader, floppy disk drive, computer network, or the like.

After the image data is read into the computer memory, the user may execute a program that displays the image radiation data on a display window of the monitor 32. After a series is selected, the first image or sheet of the series is displayed in the display window 122 as shown in FIG. 2. the user can view each image in the series using a mouse to operate the glider 124 button on the screen.

The user may select the second series displayed in the second display window 126. After the second display window is created by clicking on the view icon 128 of the second window, the user may select the particular series displayed in the window and similarly view the different sheets by operating the glider button 130 using the mouse.

The computer 30 may also generate a second series that the scanner did not generate. The computer 30 generates this process by interpolating data from one of the series generated by the scanner to generate the second series. For example, a coronal series may be generated by a scanner and displayed in a first display window of the system. If the user chooses to display the sagittal series in the second window, which is not generated by the scanner, the system interpolates the data for the right hand edge of each coronal image, generating a sagittal view from the data. This process is repeated for parallel images of the same spacing in the coronal perspective view to establish a second sagittal series.

In the preferred embodiment, the Atlas program reformats the image data to produce data representing a stereoscopic image of the scanned area. This is done by interpolating the image data of a single slice to produce additional "slices" that the scanner did not acquire. This is preferably done by generating so-called "Voxel" values that represent image values that are cubic in scale, although other stereo shapes may be applied. For example, if the series is composed of slices representing 3mm, each pixel representing an image of 0.5mm by 0.5mm, the interpolated Voxels preferably represents a cube of 1mm by 1 mm. To interpolate the Voxel values for the Voxels in the image plane, each combination of four adjacent pixels forming a square is averaged, and the resulting average results constitute data to form the Voxels in a 1mm x 1mm plane image. For Voxels representing planes at 2mm and 3mm depth, the in-plane Voxel image is preferably combined with the underlying image plane (reference plane) at the next lower 4mm plane using linear weights proportional to the distance from the selected plane to the reference plane. Of course, other interpolation schemes may be applied as is well known in the art. After the interpolated data are generated, Aldelas (Atlas) applies these data to generate any series that the user requires.

Once the display window or windows are created and the appropriate series of images are displayed in those windows, the user can select an image reference point. This is done by clicking the mouse over an appropriate area in the image reference point identifier menu shown in FIG. 2. Upon activation of one of the image point icons, the user may manipulate a cross-line cursor across the image using the mouse 34, and after aligning it with a particular feature point, a click tap on the mouse button to cause execution of a program on the computer 30 to fit the point on the image to the selected image point representation. The user may perform this procedure for, say, 8 points, although fewer or more points may be implemented in a system according to the principles of the present invention. But at least 3 points are needed before mutual registration occurs, and preferably, about 8 to 10 points are used, which results in the best mutual registration.

The mounting sleeve 52, base mount 50, and articulating arm and probe 18 are mounted to the cranial clamp 46 which holds the patient's head. The cranial clamp 46 is preferably a cranial clamp manufactured by Ohio Medical instruments CO., Inc. of Cincinnati, Ohio and designated as a modified "MAYFIELD" clamp. The clip includes a ratchet arm 146 mounted within a sleeve arm 148 and includes a two pin retaining clip (not shown) mounted on the sleeve arm, with a torque screw and pin 150 mounted on the ratchet arm 146. The clip is adjusted to fit the patient's head by well-known procedures.

Disposed on the sleeve arms are sun explosion connectors 54 to which the mounting sleeves 52 are mounted. The base support 50 for the articulating arm and probe 18 is attached to the mounting sleeve 52 by hex set screws or the like, while the articulating arm and probe 18 are attached to the base support 50 as previously described. The user must place the articulated arm so that all of the laterally mounted optical encoders are on the same side of each arm portion. If the arm is placed in the wrong position, the computer 30 and encoder interface 20 interpret the angular data from the articulated arm as if it were in the opposite direction to its true motion and incorrectly display the position of the probe. Once the arm is in place, the probe 24 is placed in the tubular extension 58 of the substrate holder in preparation for probe initialization (shown in dotted lines in FIG. 1).

By clicking on the probe initialization graphic 154 (FIG. 2), the user causes the computer 30 to begin receiving angular data input from the articulated arm and probe 18 and to initialize the position of the probe within the extension 58 as a reference point. A display area 156 is shown in the lower left portion of the screen of monitor 32 showing the position of each arm portion and the tip of probe 24. By retracting the probe 24 from the tubular extension rod 58, the user can manipulate the articulated arm and probe tip in space and view their movement on a screen. In this way, the user can verify that the optical encoder 22 is in the correct position, for example, by observing the upward movement of the probe as it moves upward in a vertical position. If the direction of probe movement is shown to be opposite to the direction of actual probe tip movement, the user knows that the arm is not properly initialized and the arm should be brought into position and the initialization repeated.

After assuring that the probe is properly initialized, the user can then place the probe tip at a point outside of the patient's skull that corresponds to the previously selected image reference point. Typically, these points include the bridge of the nose aligned with the center of the eye socket or the like. The user first clicks on a selection button adjacent the patient point icon 158 and places the probe 24 on the patient's skull point corresponding to the image fiducial point associated with an activated patient point. By depressing foot pedal 36, the patient reference point coordinates marked by the probe position are correlated to the activated patient point. The reader should note that the selection of patient fiducials may precede the selection of image fiducials.

After the user selects at least three patient and image fiducials, the computer 30 starts executing a program to register the radiation image data with the selected patient fiducials. To perform mutual registration, the program preferably performs an iterative algorithm. An indicator window 160 is provided on the screen of the monitor 32 (fig. 2) to provide the user with information regarding the quality of the mutual registration between the radiation data and the selected patient reference points. Generally, the mutual registration improves with the number of points selected, with approximately 8 to 10 points normally providing reasonably good mutual registration between the patient and the image data.

Mutual registration is preferably accomplished by an iterative algorithm on one of the program modules executing on computer 30. The optimal algorithm selects a set of image fiducial points and corresponding patient fiducial points. The centroid of the geometric chart determined by each selected group is calculated. The coordinates of one of the centroids are then converted to the coordinates of the second centroid, and the points associated with the first centroid are converted as well. The difference in coordinates between the scaled and uncapped points in the first set is squared to determine a total error value or quality factor. The scaled points are then changed by an increment in only one direction, and the difference between their corresponding points in the first set and the second set is calculated and squared. If the error result is less than the quality factor, then the incremented value becomes the point value in the first set and the error result becomes the new quality factor.

Incremental changes are again made in the same direction and new error results are calculated. When the error result is greater than the current quality factor, the scaled point is considered to be the best fit.

The incremental change is now calculated and evaluated in the other direction. The incremental change in the second direction is made until the error result is greater than the quality factor, and the previously scaled point is considered the best fit. An incremental change is then made in the previous direction until the error result is greater than the current quality factor. Incremental changes were then tested for the second direction. This process continues until scaling in either direction does not produce an error result that is less than the current quality factor. When this occurs, incremental changes and trials are performed in the third direction with the error results and quality factors calculated as previously described. When an incremental change in either direction does not produce an error result greater than the current quality factor, the mutual registration is complete and all points in one set can be scaled to corresponding points in a second set.

Sometimes, the patient's fiducial points do not correspond exactly to the selected points in the image data, thereby potentially reducing the computation of the mutual registration. By resetting the corresponding "application" icon, undoing such points, the calculation of mutual registration may be improved. The computer 30 allows the user to selectively activate and deactivate points to determine which provide the best registration between the patient and the image data. The reader should note that the mutual registration improves as the number of fiducials increases, however, a better action is to reselect one of the image or patient fiducials so that it better corresponds to its counterpart.

The user may select the target either before or after mutual registration. This is done by activating the set target icon 162 on the screen of the monitor 32 using the mouse 34 and cross-moving the cursor to the interior region of the patient's head displayed within the image using the mouse. Typically, the region of interest may be a tumor, lesion, suspicious activity site, for which the surgeon wishes to place a deep electrode, or a region for implantation of radioactive "seeds" for radiosurgery. The coordinates of the target are established by clicking on the set target icon 162.

After the mutual registration and target selection is complete, the user can place the probe 24 at any location on the patient's skull (so long as the region is part of the scanner scan region), and the path from that point (represented by arrow 172) to the target (represented by cross-line 174) is displayed. The displayed path to the target preferably indicates whether the path does exist on the image sheet displayed at that moment. The distance between the probe position and the selected target along the displayed path for each position is shown in the lower right corner of the display window (FIG. 2). For example, the surgeon may place the probe at a point shown on the image sheet currently being displayed. However, the surgeon may also hold the probe in an orientation such that the path from the probe 24 to the target traverses one or more sheets before reaching the target. In this case, the area that does exist on the sheet being displayed is preferably represented in yellow, while the rest of the path to the target is preferably represented in red (fig. 2). Using the mouse 34 to manipulate the glider button 130, the surgeon may view each portion of the target path in the appropriate image sheet until the target is reached to evaluate the tissue traversed by the selected path. If the surgeon determines that the path is at risk and unacceptable, the surgeon may select a different orientation or different point on the patient's skull and re-examine the path.

By selecting the view "cross probe", a series is presented in a second display window, which can be manipulated using the mouse 34 to move the slider button 130 of that display window. In this way, an image across the plane of the probe 24 is displayed from the probe 24 to the target area. In this way, the surgeon can estimate the path through the patient's brain tissue to reach the target.

Once the surgeon has selected a particular path to the selected target, the skull ring 80 can be mounted to the patient's head and the transfer plate 82 mounted on the skull ring 80. The transfer plate 82 includes probe alignment balls 86 in which the probes 24 can be placed. After the probe 24 is placed in the ball 86, it can be moved to again select the path to the target area that is best according to the surgeon's opinion. When the probe 24 is held in this position, the ball 86 may be locked in place to determine the path to the target and the probe removed. The device shown in fig. 3 is preferably used to avoid the cranial ring 80 from sticking to the patient's head.

The substrate holder and probe for fiducial verification and mutual registration are preferably replaced with a second substrate holder 50 and probe 24 that can be sterilized. The substrate holder and probes that can be sterilized are preferably made of gray anodized aluminum, while the non-sterilizable substrate holder and probes are made of black anodized aluminum. The sterilizable tubular extension 58 and probe 24 are preferably shorter than their non-sterilizable counterparts to facilitate sterilization. However, the mounting sleeve 70 of the probe 24 is to be connected with the probe mounting stud extending from the outermost hinge of the articulated arm in the second position to ensure that the reference points for mutual registration are not disturbed.

After a sterile surgical drape with holes is placed over sleeve 52, a sterile substrate holder is mounted to sleeve 52. A sterile tubular drape is placed over the arm and mounting stud 62 prior to mounting the articulated arm and probe 18 to the base support 50. The probe mounting sleeve 70 is then placed over the tubular drape to secure the sterilizable probe 24 in place. The probe is then returned to the extension bar 58 and the user clicks on the gray probe icon 176 (FIG. 2) so that the Allas program can be matched against the length of the probe 24. The thickness of the surgical drape is offset in the mechanism that sterilizes the parts. That is, the bore of the mounting sleeve is appropriately enlarged to offset the surgical drape between the mounting post and the sleeve. This offset is required to ensure that the screws used to lock the probe to the column do not dislodge the probe tip from the centerline of the column. The user then clicks on a tap of the probe initialization icon 154 to check the arm movement. The mutual registration is automated using the previously selected fiducial points.

In this regard, the surgeon may open the patient's skull using a suitable drill bit and insert the instrument cannula into the transfer plate 82. The surgeon may then insert, for example, a biopsy needle directly into the target at the indicated depth, with considerable confidence that the biopsy needle is in the target area and only through the examined tissue in the image displayed in the display window. After this procedure, the surgeon may close the opening or perform further processing on the target area. Likewise, the surgeon may choose other purposes and treat them as the first.

After installing the cranial plate 80 and locking the plate 82 in place, the surgeon may decide to install an arcuate plate bar 100 to provide a hemispherical instrument positioning system that is centered about the target area. This is done by mounting an arcuate plate rod 100 to the ball 86, mounting a rotating support arm 102 to the rod 100, and connecting an arcuate plate 104 to the support arm 102. The variable assembly 106 is then mounted to the arc 104, rotating the support arm 102 about the rod 100, and sliding the arc 104 relative to the support arm 102; or moving the variable assembly 106 along the arcuate plate 104, any position around the hemisphere may be selected. At any such point, the surgeon has considerable confidence that the point he sets is centered on the target area.

While the present invention has been illustrated by description of alternative embodiments and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or at least limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. For example, both MRI and CT images may be loaded into computer 30 and registered with each other prior to registering with the patient. The MRI scan may provide the surgeon with organ details, while the CT scan may provide the surgeon with precise coordinates. Thus, in its broadest aspects, the invention is not limited to the specific details, representative imaging systems, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicants' inventive concept.

Claims (28)

1. A neurosurgical stereotactic planning system, the system comprising:

an imaging display system for displaying an image;

an image fiducial selector coupled to the imaging system for selecting a fiducial on an image displayed on the display system;

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

an articulated arm and probe connected to said imaging system, said articulated arm providing spatial coordinates of said probe with reference to said imaging system, whereby a position associated with said probe is displayed on said displayed image;

a patient fiducial point selector connected to said imaging system and said articulated arm for selecting fiducial points on the patient corresponding to said fiducial points selected by said image fiducial point selector;

a mutual registration processor for registering said selected patient fiducial point with said selected image fiducial point such that said coordinates provided by said articulated arm can be paired with said displayed image such that a path from said displayed probe position to said selected target can be displayed on said displayed image; and

a probe holder for holding said probe of said articulated arm adjacent the head of a patient, said probe holder being selectively lockable to maintain a position adjacent the skull of said patient so that a surgeon can evaluate a path displayed in said displayed image between said probe position and said selected target and secure an instrument holder so that any instrument inserted in said instrument holder can follow said displayed path.

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

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

a menu giving a predetermined number of image reference point recognizers; and

an activation icon for selectively activating the selected image reference point.

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

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

5. The system of claim 1, said probe holder being adjustable for changing the orientation of said probe within said holder relative to the patient's skull.

6. The system of claim 5, wherein the adjustable pointing probe holder is a ball and socket mechanism.

7. The system of claim 1, the probe holder further comprising:

a skull ring mounted to the head of a patient; and

a transfer plate having a receptacle thereon for receiving the probe.

8. The system of claim 7, said probe holder further comprising a ball and socket mechanism adapted to fit within said socket, said ball and socket mechanism being lockable within said socket.

9. The system of claim 1, the image display system further comprising:

display of the position of the probe and the articulated arm so that the operation of the articulated arm and probe can be verified.

10. The system of claim 1, wherein said mutual registration processor performs an iterative algorithm for mutually registering said selected patient fiducial points with radiation data used to generate said displayed radiographic image.

11. The system of claim 1 further comprising:

a stereotactic system for selectively positioning a surgical instrument adjacent a head of a patient.

12. The system of claim 11, the stereoscopic tactical system further comprising:

an arcuate plate carrier bar mountable within the probe holder such that the bar is directed toward a selected target within the patient's head;

a support arm mounted for rotation about said arcuate plate carrier bar; and

an arcuate plate slidably mounted to said support arm, whereby said arcuate plate defines a circumference centered on said selected target within said patient's head.

13. A method for estimating and fixing a surgical pathway to a selected target, the method comprising the steps of:

displaying an image generated from the scanner image data;

selecting a reference point on the displayed image;

selecting a target within the displayed image;

providing spatial coordinates of points outside the displayed image;

selecting a set of exterior points having said provided spatial coordinates;

registering said selected external point with said selected image reference point such that a path between said selected target and one of said external locations is displayable on said display image; and

selectively securing the probe adjacent the patient's head so that the surgeon can evaluate said path between one of said external locations and said selected target displayed on said displayed image, and an instrument can be inserted therethrough for advancement along said displayed path.

14. The system of claim 13, the probe positioning step further comprising:

changing the orientation of the probe relative to the patient's skull; and

selectively locking the probe in a selected orientation.

15. The method of claim 13 further comprising:

the position of the articulated arm and probe is displayed so that the operation of the articulated arm and probe can be verified.

16. The method of claim 13, said step of mutually registering further comprising:

selecting a first set of image points;

selecting a second set of exterior points;

calculating the centroid of the geometric figure determined by each group of points;

converting the first set of points to coordinate values corresponding to the first centroid to the second centroid;

calculating a quality factor according to the conversion of the first group of points;

scaling the first set of points by increments in one direction;

estimating whether said first set of points is a better fit than said unsealed points; and

converting the first set of points to the second set of points when the estimate is less than the quality factor in all directions displayed within the image.

17. A neurosurgical stereotactic planning system, the system comprising:

a cranial clamp for holding a patient's head;

an articulating arm connected at one end to the probe and connectable at an opposite end to the cranial clamp;

a probe holder located at a selected location near the patient's head for holding the probe at the selected location. The probe holder is selectively lockable to maintain the probe in a selected orientation at a selected position to define a path between the selected position and a target point in the patient's head to facilitate evaluation and manipulation along the path.

18. The neurosurgical volumetric planning system of claim 17, wherein the probe holder comprises:

a first member located at a selected position;

a second member supported by the first member and movable relative to the first member for receiving and holding the probe; and

a clip positioned relative to the first and second members for locking the second member and the probe in a selected orientation relative to the first member.

19. The neurosurgical stereoplanning system of claim 17 further comprising a base connected between the opposing ends of the articulated arm and the cranial clamps.

20. The neurosurgical stereoplanning system of claim 19 wherein the cranial clamp includes a first connector connected to an arm of the cranial clamp and the base is mounted on a second connector connectable to the first connector on the cranial clamp.

21. The neurosurgical stereoplanning system of claim 20 wherein the base further comprises releasable clips for receiving and holding the shafts connected to the opposite ends of the scarfing arms.

22. The neurosurgical stereoplanning system of claim 21, wherein the base further comprises a cylinder for positioning and holding the probe to expedite the initialization process of the probe.

23. The neurosurgical stereoplanning system of claim 22, further comprising a first non-sterile base, articulated arm and probe and a second sterile base, articulated arm and probe.

24. The extraneural and surgical stereoplanning system of claim 23, wherein each of the first and second mounts and the first connector have a keying system such that each of the first and second mounts connects with the first connector in a predetermined orientation.

25. The surgical stereoplanning system for liu of claim 17, wherein the probe holder further comprises:

a shaft having one end connected to the probe holder at a selected location and at a selected orientation; and

a socket connected to the opposite end of the shaft and movable to different positions and orientations relative to the shaft, the socket receiving the probe and holding the probe in a second selected orientation transverse to the target point.

26. The neurosurgical volumetric planning system of claim 17, wherein the probe holder further comprises:

a rod;

a rod gripper for gripping a rod in a selected orientation at a selected position;

a support arm connectable to the rod at different positions along the length of the rod;

an arcuate plate member connectable to the support arm; and

a cannula connectable to the arcuate plate member at different positions, the cannula having a receptacle for receiving and holding the probe at a second selected position and in a second selected orientation transverse to the target point.

27. A surgical stereotactic planning system, the system comprising:

means for supporting a patient;

an articulated arm connected at one end to the probe and connectable at an opposite end to a patient support device;

a probe holder located at a selected position near the patient for holding the probe at the selected position, the probe holder being selectively lockable to maintain the probe at a selected orientation of the selected position to determine a path between the selected position and a target point within the patient to facilitate evaluation and manipulation along the path.

28. A surgical stereotactic planning system, the system comprising:

means for supporting a patient;

an articulated arm having a movable end and a fixed end connectable to a patient support device;

a gripper located at a selected position proximate the patient for gripping the movable end of the articulated arm at the selected position, the gripper being selectively lockable to maintain the movable end of the articulated arm in a selected orientation at the selected position to thereby determine a path between the selected position and a target point within the patient to facilitate evaluation and manipulation along the path.