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Description  |
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BACKGROUND AND SUMMARY OF THE INVENTION
There are many neurological procedures which require the accurate placement
of a neurological instrument, including for biopsy, radioactive seed
placement, and lesion generation. One of the most common neurological
procedures requiring accurate placement is a ventriculostomy procedure in
which a cerebral ventricle drain or shunt is installed. Such a drain or
shunt is utilized for ventricular drainage when a patient manifests
hydrocephalus resulting from congenital brain malformations, acute or
chronic infections, tumors, intraventricular hemorrhage, or normal
pressure hydrocephalus.
Conventional procedures for the placement of ventricular drains or shunts
rely heavily on the skill of the neurosurgeon, and/or are relatively
expensive and time consuming. After a CT scan, or other imaging, the
neurosurgeon forms a burr hole in the skull, and then the neurosurgeon
guides a catheter through the burr hole toward landmarks on the opposite
side of the patient's head. It is necessary that the neurosurgeon be able
to completely accurately visualize the internal tomography of the brain
when performing this procedure, and it is presumed that the catheter is
properly located when the surgeon obtains fluid returned through the
catheter. In some circumstances, the neurosurgeon feels it advisable to
check the location of the catheter, and for that purpose the patient must
be subjected to another CT scan of the brain in order to verify proper
location of the catheter. Since each separate, individual, CT scan is
expensive, and since the prior art procedures are time consuming both for
the neurosurgeon and the anaesthesiologist, there has long been a need for
procedures more regularly and inexpensively accurately placing ventricular
drain or shunt catheters, which will result in longer shunt patency and
decreased morbidity due to shunt malposition.
According to one aspect of the invention of the parent application, a
stereotactic neurological instrument placement guide is provided that may
be utilized in numerous different types of neurological procedures, and
which has ideal suitability for use in ventriculostomy procedures. The
guide according to the invention is simple to construct and to utilize,
and can readily enhance accuracy, reduce time, increase confidence, and
reduce cost for a given level of confidence, in ventriculostomy procedures
and other neurological treatment methods.
The stereotactic guide of the parent application has only first and second
skull engaging point members, which have a common central axis. A frame
mounts the skull engaging point members for controlled movement with
respect to each other along the central axis. Means are provided defining
a linear guide passage in the first point member, a straight line
extension of the linear guide passage extending along a common central
axis, and the linear guide passage is large enough for the passage of a
neurological instrument (e.g. catheter or shunt) through it. The
termination of the first point member coaxial with the linear passageway
and common central axis provides for stabilizing the first point member in
a burr hole; for example the termination may comprise a truncated cone.
The point members may be attached to arms, which in turn are attached to a
guide sleeve and a guide element (bar or rod) which are movable with
respect to each other. A locking screw can lock them in a position to
which they have been moved, or they may be biased toward each other by an
elastic band, spring loading, or the like. The means defining a linear
passage may comprise a slotted sleeve rigidly fixed to the frame arm, with
a slotted tubular element received within the sleeve and rotatable from
one position in which the slots of the sleeve and tubular member are not
aligned, to a second position in which the slots are aligned. When the
slots are not aligned, the guide passage is closed and provides positive
guiding of the catheter therethrough. When the slots are aligned, the
placement guide may be removed from contact with the patient's skull, and
the catheter.
According to the parent application, the key to proper utilization of the
stereotactic neurological instrument placement guide is the proper
location of the fixing point on the opposite side of the patient's skull
from the burr hole. The positive location of the fixing point, which will
receive the second point member of the placement guide, opposite the
proposed site for the burr hole is determined utilizing a CT scan,
magnetic resonance imaging (MRI), or another type of coordinate
multiplanar tomographic imaging of the patient's skull. Utilizing X, Y,
and Z coordinates for the burr hole (marked by a nipple marker or the
like), and determining the coordinates of the particular portion of the
ventricle, or other location within the brain, desired to be acted upon by
the neurosurgeon, the data from the imaging can be used to calculate the
loci of points along a straight line between the burr hole and the target
area, which loci can be extended to the patient's skull on the opposite
side thereof from the burr hole, and that part of the patient's skull can
be marked with a nipple marker, oil, or the like. The calculations are
preferably provided by vector parameterization, utilizing a programmable
scientific calculator, and the gantry angle of the imaging equipment can
be automatically accommodated.
Desirably the distance of the target point from the burr hole is also
calculated according to the invention, so that the neurosurgeon can use
indicia on the catheter to determine when the catheter has been inserted
the distance necessary to properly position it at the target. Practicing
the method according to the invention, since the placement of the fixing
point is accurately determined, there is no necessity for a second CT
scan, or the like.
While the invention will be described herein primarily with respect to
ventriculostomy procedures, it is to be understood that both the apparatus
and procedures according to the invention may be applied to a wide variety
of neurological practices. In fact, the basic positioning facilitating
features of the parent application are applicable not just to
neurosurgery, but in general to determining the position of a line between
two points on or within a human patient's body utilizing data normally
determined from a coordinate multiplanar tomographic imaging (CT, MRI,
etc.) of the patient's body during which the patient is disposed at an
angle, and is incrementally advanced between images. Utilizing the present
invention it is possible to practice procedures not heretofore
contemplated, or to maximize the accuracy of present procedures, since
according to the invention it is possible to accurately locate and
determine the coordinates of two or more points on or within a human body
(e.g. within the brain).
Also according to the present invention, the utility of the stereotactic
neurological instrument placement guide described above is improved by
utilization of a cerebral instrument guide frame and supporting computer
programs. The cerebral instrument guide frame, and related procedures,
according to the invention allow the neurosurgeon to mark the burr hole
site and fixing point on the patient in the operating suite prior to
applying the stereotactic instrument guide described above. This
eliminates the need to mark these sites on the patient in the multiplanar
tomographic imaging (CT scanning) suite. In this way it is possible to
avoid accidental erasure or movement of identifying marks or markers
placed by the radiologist. Further, instead of having a mark on the scalp,
the neurosurgeon can directly mark the patient's skull, improving accuracy
of the stereotactic instrument guide described above.
The cerebral instrument guide frame according to the present invention is
preferably mounted in the patient's ears and on the bridge of the
patient's nose. In addition to allowing--in association with the computer
programs described hereafter--accurate location of the burr hole and
fixing point, the cerebral instrument guide frame can serve as a fixing
point for the stereotactic instrument guide described earlier. The
cerebral instrument guide frame according to the invention thus provides a
neurosurgeon a simple stereotactic method for catheter placement, or for
other neurological procedures, and expands the utility of the stereotactic
instrument guide described above.
A cerebal instrument guide frame for use with a live human patient
according to the present invention comprises the following elements: A
first arcuate member having first and second ends, and a radius. A second
arcuate member having first and second ends and a radius, (the radius of
the second arcuate member being greater than the radius of the first
arcuate member). Aligned first and second openings provided adjacent each
of the first and second ends of each of the first and second arcuate
members. First and second rigid ear fixator rods mounted in the aligned
openings, the first in the openings adjacent the first ends of the first
and second arcuate members, and the second in the openings adjacent the
second ends of the first and second arcuate members, the rods mounted for
movement with respect to the first and second arcuate members along a
common axis passing through the openings, and the arcuate members mounted
for pivotal movement with respect to each other about the common axis. An
abutment mounted on one of the arcuate members for engaging a portion of a
patient's head to preclude movement of the arcuate member past that
portion of the patient's head. And an instrument guide mounted on the
other of the arcuate members for guiding an instrument aligned therewith
into contact with the patient's head, the guide directed to the midpoint
of the common axis.
The abutment preferably comprises a nasal bridge fixation element for
engaging the bridge of a patient's nose, and the instrument guide
comprises a tubular element mounted to one of the arcuate elements for
movement with respect to that element along the arcuate extent thereof.
The abutment is mounted on the first arcuate element and the instrument
guide on the second arcuate element. A pair of orbit pads also may be
mounted on the first arcuate element on opposite sides of the nasal bridge
fixation element for engaging the patient's orbits. The tubular instrument
guide element has an internal diameter slightly greater than the external
diameter of a needle. The first and second arcuate members each preferably
comprise a hemicircle, or semicircle, and the nasal bridge fixation
element is mounted for radial movement with respect to the first arcuate
element (that is, along the radius thereof). The first and second arcuate
members preferably are made of aluminum, a rigid durable sterilizable
medical-grade structural plastic, or the like.
The cerebral instrument guide frame according to the invention may be used
in combination with the stereotactic neurological instrument placement
guide as described above, with one of the point members of the skull
engaging elements of the stereotactic neurological instrument guide
engaging the tubular instrument guide element, and in alignment therewith.
When the guide frame according to the present invention is combined with
the stereotactic neurological instrument placement guide described above,
typically the second point member comprises the "one of the point
members", and the first and second arcuate members make an angle of about
160.degree.-180.degree. with respect to each other with the second point
member in alignment with the tubular instrument guide element.
According to another aspect of the present invention, a cerebral instrument
guide for use with a live human patient is provided which comprises the
following elements: A first frame element having first and second ends,
and a central portion. A nasal bridge fixation mounted on the first frame
element at the central portion, and movable with respect to the first
frame element. A second frame element having first and second ends, and a
central portion. Pivot means for mounting the first and second frame
elements for pivotal movement with respect to each other about a common
axis. An instrument guide mounted on the second frame element, and movable
with respect thereto and directed toward the midpoint of the common axis.
And means for positively locating the pivot means with respect to the
patient's head so that the axis remains stationary with respect to a
predetermined portion of the patient's head.
Typically, the pivot means and the positively locating means comprise first
and second ear fixation rods adapted to be inserted into the patient's
ears and received within aligned openings in the first and second ends of
the first and second frame elements. The rods may be slidable with respect
to the frame elements to move toward and away from the patient's ears. The
frame elements preferably comprise first and second hemicircles with the
second frame element hemicircle having a larger radius than the first
element hemicircle. The ear rods preferably have some covers--where they
engage the patient's ears--of a soft material, such as soft rubber, to
allow seating of the rod ends into the external auditory meatia.
The computer program utilized with the present invention accepts data from
computed tomographic images representing five separate points: a target
point in a cerebral ventricle, a point representing the intended burr hole
site on the skull, a point at the right external auditory meatus, a point
at the left external auditory meatus, and a point representing the
interior superior edge of either bony orbit. The program corrects for CT
scanner gantry tilt and then calculates an angle at which to separate and
set the first and second arcs of the cerebral instrument guide frame, and
an angle between a line containing the midpoint of the line in space (the
common axis of the arcuate members) and the skull point, and a line in
space connecting the ends of the arcs. The sliding instrument guide
mounted on the second arcuate member is set at this calculated angle, and
directed toward the skull.
When the apparatus described above is utilized, the patient first has a CT
scan (or other multiplanar tomographic imaging) of the brain and skull.
Neither the cerebral instrument guide frame nor the stereotactic
instrument guide is mounted on the patient's head during the acquisition
of the CT data, but following the CT scan procedure, the target, burr
hole, right and left auditory meatia, and orbital ridge points are entered
into the computer program to calculate the angles necessary. In the
operating room, with or without the patient under general anesthesia, the
cerebral instrument guide frame is then applied to the patient's head by
symmetrically advancing the rods connecting the arc centrally toward and
into the external ear canals, and then by seating the mid-line U-shaped
nasal bridge onto the nasion. The angle between the first and second
arcuate members and the position of sliding guide along the first arc are
set, and the neurosurgeon can then pass a long needle down the sliding
guide through the scalp and onto the skull at the skull point where a
distinguishing mark for the burr hole can be made, and later for the
fixing point. The cerebral instrument guide frame may then be removed and
the stereotactic instrument guide used as a described above, or the
cerebral instrument guide frame can be left in placed and repositioned to
accept the fixing point of the stereotactic instrument guide.
According to another aspect of the present invention, a method of
positively locating a burr hole site on a patient's skull during a
neurological procedure on a human patient, using a guide comprising first
and second frame members mounted for pivotal movement with respect to each
other about a common axis defined by ear fixators, one of the frame
members having a nasal bridge fixation, and the other having an instrument
guide, is provided. The method comprises the steps of: (a) Effecting
coordinate multiplanar tomographic imaging of the patient's head. (b)
During the practice of step (a) determining locations of the target in the
patient's head, the burr hole site on the patient's skull, the patient's
left and rights auditory medati, and at least one of the patient's orbital
ridges. (c) With a computer, calculating from the data determined in step
(b) the angular positions of the frame members of the guide to mark the
burr hole site and fixing point on the patient's skull, and the proper
position of the instrument guide along the second frame member. Then (d)
moving the ear fixations of the guide into positive contact with the
patient's ears, and the nasal bridge fixation into positive contact with
the patient's nasal bridge. And (e) moving the second frame member of the
guide frame with respect to the first frame member to have the proper
orientation to mark the burr hole site, and moving the instrument guide to
the proper position along the second frame member, and then marking the
burr hole site using the instrument guide.
The method can also be for positively locating a fixing point on the
patient's skull in which case there is the further step of (f) moving the
second frame member of the guide with respect to the first frame member to
have the proper orientation to mark the fixing point on the patient's
skull, and then marking the fixing point site using the instrument guide.
Also, there may be the still further step, with the guide in place with
the relative positions of the components as provided in step (f), of
moving a stereotactic neurological placement guide having end point
members into operative association with the burr hole site and the
instrument guide on the second frame member; effecting formation of a burr
hole; and passing an instrument through one of said stereotactic
neurological placement guide point members engaging said burr hole, to
pass the instrument to the target within the patient's skull.
Alternatively, the guide is removed from the patient's ears and nose, a
burr hole is formed at the burr hole site, and the end point members of a
stereotactic neurological placement guide having end point members is
moved into operative association with the burr hole site and a fixing site
opposite the burr hole site on the patient's skull. The neurlogical
instrument is inserted through the burr hole and placement guide into
operative association with the target within the patient's skull.
Step (c) may be practiced in part by using vector parameterization, and
step (a) is practiced using a non-zero angle of inclination between
imaging equipment and the patient while there is an incremental advance
between images, the computations in step (c) taking into account the angle
of inclination and the increment of advance between images.
In general, the invention facilitates and provides a method of performing a
neurological procedure on a human patient utilizing a scanner, a Cerebral
instrument guide frame, and an operating room, that is greatly simplified
with respect to the prior art, allowing the scanning to be done without a
frame on the patient's head, and avoiding the expense and time delay of
moving a patient from the operating room back to the scanner, and running
a second scan on the patient with a frame attached to the patient's head.
This aspect of the method of the invention comprises the steps of
substantially sequentially: (a) Effecting coordinate multiplanar
tomographic imaging of the patient's head with the scanner while the
patient's head is free of frame attachments, to obtain data necessary for
performing a neurological procedure. (b) Moving the patient to the
operating room. (c) In the operating room, utilizing the data from step
(a), fixing the cerebral instrument guide frame on the patient's head; and
(d) substantially immediately after step (c), in the operating room,
without transporting the patient back to the scanner to effect a second
imaging, performing the neurological procedure on the patient, utilizing
the cerebral instrument guide frame to guide one or more medical
instruments (e.g. catheter, light pipe, laser, etc.).
It is a primary object of the present invention to provide an accurate,
effective, and simplified manner of performing neurlogical procedures on a
human patient. This and other objects of the invention will become clear
from an inspection of the detailed description of the invention and from
the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of an exemplary stereotactic neurological instrument
placement guide according to the invention;
FIG. 2 is a side exploded view, partly in elevation and partly in
cross-section, of the components associated with the first skull engaging
point member of the stereotactic neurological instrument placement guide
of FIG. 1;
FIG. 3 is an end view of a second embodiment of the second skull engaging
point member of the stereotactic neurological instrument placement guide
of FIG. 1;
FIG. 4 illustrates a pair of nipple markers that may be utilized in the
practice of the method of the invention, one shown in top perspective and
the other in bottom perspective; .
FIG. 5 is a schematic view showing the stereotactic neurological instrument
placement guide of FIG. 1 in use on a patient's head with a catheter
having been placed by the stereotactic neurological instrument placement
guide;
FIG. 6 is a schematic view of conventional coordinate multiplanar
tomographic imaging equipment utilized in the practice of the method
according to the invention;
FIG. 7 is a schematic view of a screen of the apparatus of FIG. 6 at one of
the slice locations;
FIG. 8 is a top plan view of a programmable calculator and record keeping
pad mounted in a manner facilitating its utilization in a practice of the
method according to the invention;
FIG. 9 is a top perspective view of an exemplary cerebral instrument guide
frame according to the present invention;
FIG. 10 is a side view of a patient's head with the cerebral instrument
guide frame of FIG. 9 shown in operative association therewith to mark a
burr hole site;
FIG. 11 is a front view like that of FIG. 10; and
FIG. 12 is a view like that of FIG. 10 only showing the stereotactic
neurlogical instrument placement guide of FIG. 1 mounted in association
with the cerebral instrument guide frame and the burr hole site on the
patient's skull, for insertion of a catheter.
DETAILED DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 5 illustrate an exemplary stereotactic neurological instrument
placement guide according to the invention, shown generally at reference
numeral 10. The guide 10 preferably is made of lightweight, rigid
material, such as aluminum, titanium, hard plastic, or the like. It
includes only two skull engaging elements, that is the skull engaging
elements consist of a first skull engaging point member shown generally by
reference numeral 11, and a second skull engaging point member shown
generally by reference numeral 12. A frame mounts the members 11, 12 for
movement toward and away from each other along a common central axis,
preferably so that they move linearly with respect to each other along the
linear axis 13. The frame preferably comprises a first arm 14, which
preferably is rigidly connected to the first point member 11, and a second
arm 15 which preferably is rigidly connected to the second point member
12. Movement of the arms 14, 15 with respect to each other, with the
members 11, 12 along the axis 13, is preferably provided by a sleeve 16
rigidly attached to the first arm 14, and a guide element, such as a rod
or bar, 17 rigidly connected to the second arm 15. The portions 15, 17 can
be formed integrally (as by molding), as can the portions 14, 16.
In most circumstances, it is desirable to either be able to lock the frame
of the device 10 so that the members 11, 12 are positioned at a specific
distance from each other (corresponding to the dimension of the patient's
skull at the operative area of use), or means are provided for biasing the
arms 14, 15 toward each other, or for biasing the first member 11 toward
the second member 12. Where locking is desired, a thumbscrew 18 may be
provided threaded through an opening in the guide sleeve 16 and releasably
engaging the guide element 17. When the guide element 17 is tightly
engaged, relative movement between the arms 14, 15 is not possible, but
when the thumbscrew 18 is loosened relative movement in a dimension
parallel to the axis 13 is possible. Instead of, or in conjunction with,
the thumb locking screw 18, an elastic band 19 may be provided, which
exerts a force pulling the arms 14, 15 toward each other. Alternatively
(not shown) a spring loading can be provided for the first point member 11
itself, the spring loading operating between the arm 14 and the end, skull
engaging, termination 20 of the member 11, so that it is biased into
contact with the patient's skull.
It is very desirable to be able to remove the guide 10 from contact with
the patient's skull, and from contact with the neurological instrument
(e.g. catheter), once the stereotactic device 10 has been utilized to
properly guide the neurological instrument into place. This may be
accomplished by the means most clearly illustrated in FIG. 2.
FIG. 2 illustrates the first point member 11 as a slotted sleeve 22 which
is rigidly attached to the arm 14, with the slot 23 therein preferably on
the opposite face of the sleeve 22 as the arm 14. Disposed within the
sleeve 22 is the slotted tubular element 24, having a slot 25 in one face
thereof along the length thereof, both the slots 23 and 25 having a width
which is great enough so that a catheter 26, or other neurological
instrument, may be removed therethrough. Also, the internal diameter of
the tubular element 24 is such that it provides a relatively tight fit for
the catheter 26, but so that the catheter can move longitudinally
therethrough. If the arm 14 is made of metal, it is desirable to make the
slotted sleeve of a similar metal, while it is desirable to make the
tubular member 24 of nylon, or a similar relatively rigid, durable plastic
with lubricity characteristics.
The position of the tubular element 24 within the slotted sleeve 22 can be
fixed by tightening the thumbscrew 27 which passes through the side wall
of the sleeve 22, perpendicular to the dimension of elongation of the
interior passageway, and the slot 23, therein. End termination 20 of the
tubular element 24 actually engages a burr hole in the skull, and is
preferably shaped in a manner so as to stabilize the first point member
within the burr hole. This can be accomplished, as illustrated in FIGS. 1
and 2, by forming the termination 20 as a truncated cone.
Note that the catheter 26 preferably has indicia 28 formed along the length
thereof. The position of those indicia with respect to a fixed point on
the device 10 (typically on the tubular element 24) can be used as a guide
by the neurosurgeon for insertion of the catheter 26 to make sure that it
has been inserted to the proper position, i.e. so that the lead tip 29
thereof is at the target location in the brain ventricle or other target
area.
It is preferred that the second skull engaging point member 12 merely
comprise a conical element terminating in a tip 30, which is integral with
or rigidly affixed to the arm 15. However, under some circumstances it may
be desirable to form the termination of the second point member 12 so that
it can surround a nipple marker, to facilitate accurate placement. Such a
second skull engaging point member is shown generally by reference numeral
12' in FIG. 3, the member 12' being formed as a hollow truncated cone,
with means defining an interior surface 31 which is circular and has a
diameter approximately equal to the outside diameter of a nipple marker 32
(see FIG. 4).
FIG. 4 illustrates conventional nipple markers that may be utilized with
the device 10 to ensure proper positioning thereof in the surgical
procedures according to the invention. The conventional nipple markers 32
are discs of plastic, or like material that is not clearly visible in a
CT, MRI, or other imaging procedure, with a small cylinder of lead (or
like radiopaque material) 33, having a diameter of about one-two
millimeters, on the top face 34, concentric therewith. The top face 34 is
smooth and uncoated, while the bottom face 35 has adhesive affixed thereto
(it may have a release paper covering). In use, when a nipple marker 32 is
in place, a scribe mark on the skull can be provided by passing a trocar
or screw around disc 34. Alternatively, an entire nipple marker 32 may be
used for placement, for example with respect to the second point member
12' of FIG. 3.
FIG. 5 illustrates utilization of the device 10 in the placement of a
ventricular drain or shunt. Nipple markers 32 are placed where a burr hole
37 is to be formed in the patient's skull at a location determined to be
acceptable for the particular patient and procedure involved by the
neurosurgeon, and at a fixing point 38 on the opposite side of the
patient's skull from the burr hole 37. The manner in which the fixing
point 38 is precisely located will be described hereafter.
The neurosurgeon moves the first arm 14 so that it is widely spaced from
the second arm 15, and then moves the second point member 12 into
operative contact with the fixing point 38. Then the arm 14 is moved
toward the arm 15, with the members 11, 12 moving along a common linear
axis 13, until the termination 20 of the member 11 is stabilized within
the burr hole 37. During this initial phase, the position of the arm 14
with respect to the arm 15 may be fixed, and the tubular element 24 may
slide with respect to the slotted sleeve 22, or vice versa.
Once the termination 20 has properly stabilized within the burr hole 37,
either the thumbscrew 18 can be tightened to lock the relative positions
of the arms 14, 15 in place (with the thumbscrew 27 likewise tightened),
or the elastic band 19 can be placed around the arms 14, 15 to bias them
together. When the device 10 is in this position, it is necessary to be
sure that the slots 23, 25 are misaligned with each other so that when the
catheter 26 is passed therethrough it cannot move sidewardly out of the
guide provided by the slotted sleeve 22 and tubular element 24.
With the device 10 thus so positioned, the neurosurgeon then moves the
catheter 26 into the guide provided by the sleeve 22 and element 24,
inserting it into the skull until the appropriate indicia 28 is reached
(e.g. at the top surface 39 of the element 24) indicating that the
catheter 26 has been inserted a distance calculated to be the distance of
the ventricle area to be drained from the burr hole 37.
Once the catheter 26 has been thus properly positioned it is desirable to
be able to remove the device 10 from operative engagement with the
patient's head, and the catheter 26. This is accomplished by loosening the
thumbscrew 27, then rotating the tubular member 24 so that the slot 25
therein is aligned with the slot 23 in the sleeve 22, the slots 23, 25
providing a channel which is open, and then--with the termination point 20
pulled away from the burr hole 37 (either by moving the tubular element
24, or by moving the entire arm 14)--moving the device 10 in the direction
of the guide element 17 (that is away from the patient's head) so that the
catheter passes through the channel defined by the slots 23, 25. Thus the
catheter 26 remains in place while the device 10 is completely detached.
It is to be understood that a wide variety of modifications may be made in
the stereotactic placement guide 10. For example, the tubular element 24
could be continuous, rather than slotted, and it could be removed from
engagement with the catheter 26 by pulling it out over the top of the
catheter 26, along the length thereof, and then the catheter 26 moved out
through the slot 23. Also the sleeve 22 could be pivotally connected to
the arm 14, or detachably connected thereto, and a wide variety of other
modifications are also possible.
According to the present invention, it is necessary to accurately position
the fixing point 38, otherwise the goals of accurate placement of the
neurological instrument (e.g. catheter 26) will not be achieved. Accurate
placement of the nipple marker 32, or the like, at the fixing point 38 is
accomplished utilizing conventional coordinate multiplanar tomographic
imaging equipment, shown schematically generally by reference numeral 40
in FIG. 6, and by utilizing a programmable calculator 41 (see FIG. 8), or
a like computer.
The coordinate multiplanar tomographic imaging equipment 40 preferably is
CT or MRI equipment, but other coordinate multiplanar tomographic imaging
techniques and equipment may also be utilized. Such equipment 40 typically
cooperates with a table 42 on which the patient rests, and the equipment
40 is disposed at a tilt or gantry angle 43 with respect to table 42 to
ensure proper imaging. A computer control 44 controls the equipment 40,
and desired information is viewable on the screen 45. During the imaging
operation, the table 42 is incrementally advanced in the Z dimension
illustrated in FIG. 6.
When the patient is placed in the equipment 40, a nipple marker 32 or the
like for the burr hole 37 is in place (being shown in an exaggerated size
in FIG. 6). Utilizing the equipment 40, the operator determines the X, Y,
and Z (Z being the position along the table 42) coordinates of that
location, which is a first point. The equipment 40 operator will have
already been instructed by the neurosurgeon as to what the target location
in the brain has been decided upon. For example the target location may be
a particular second point 47 (see FIG. 7, a representation of an image of
the patient's skull on the screen 45 at one particular slice) within the
ventricle 48. The coordinates of the second point 47 are also determined
by the operator as is conventional.
The operator operates the equipment 40 to conduct a conventional imaging
operation, e.g. CT scan. On the screen 45 all of the data associated with
each slice of the imaging operation is recorded, including the position
along the table 42 (the dimension Z) and the table moves an increment
between each slice, the increment typically being about 5 to 10
millimeters.
Utilizing the coordinates of the first point 32, 37 and the second point 47
(the X, Y and Z coordinates of each), the angle of inclination 43 of the
scanning equipment 40 with respect to the table 42 (the gantry angle), and
the incremental advancement (the incremental advance in dimension Z,
typically 5 millimeters), the distance between the first and second points
can be calculated, and the loci of points along a line containing the
first and second points can be determined, the line being shown
schematically at 50 in FIG. 7. This calculation is performed utilizing the
programmable calculator 41 or like computer, utilizing vector
parameterization. FIG. 7 illustrates the points 32, 47, 38 all on the same
screen only for | | |
