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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to the medical diagnostic imaging and
minimally invasive stereotactic surgery arts. It finds particular
application in conjunction with an integrated CT scanner and mechanical
arm guided minimally invasive surgical tools and will be described with
particular reference thereto. It is to be appreciated, however, that the
invention is also applicable to guiding interventional surgical tools in
conjunction with magnetic resonance imaging and other imaging systems
capable of generating volumetric images. The system is also applicable to
other surgical tools used in conjunction with real time imaging systems
capable of monitoring a region of the patient during a minimally invasive
surgical procedure.
Heretofore, several surgical instrument guidance devices have been proposed
for use in conjunction with a CT scanner to allow a user to accurately
place a catheter, drainage tube, or biopsy probe within a patient's body.
U.S. Pat. No. 4,733,661 describes a hand held guidance device including a
planar base with a bubble level to maintain the base in a horizontal
position. Needle guides are provided on a support arm pivotally secured to
the base, the guides slidingly supporting a catheter at a desired angle as
the catheter into the patient's body. The guidance device includes a
reference line formed upon the base adapted to be aligned with a
transverse light beam projected by the CT scanner apparatus. Although it
may be possible for the device to be used to accurately insert a biopsy
needle within a patient's body without damage to any unintended targets,
one major disadvantage of the device is its reliance upon an accurate
human alignment between the reference line defined on the base of the
device and the transverse light beam projected by the CT scanner. It
would, therefore, be desirable to provide a surgical instrument guidance
device which is not dependent upon a manual alignment step.
U.S. Pat. No. 4,583,538 proposes a free standing biopsy guide that is
adapted to hold needles or probes at various selectable calculated angles.
In using the device proposed in that patent, a reference point on the
patient's body is found that exactly correlates to a point on the CT scan.
This is accomplished by means of a localization device placed on the
patient's skin which can be identified in cross section on the CT scan.
Measurements of the localization device on the CT scan are then correlated
to the device on the patient. The free standing biopsy guide is then
adjusted according to those calculations. One disadvantage of the device
taught by this patent is the time required to correlate the patient body
reference point with selected points on the CT scan. In addition, certain
inaccuracies may be introduced during the point correlation step and while
adjusting the free standing guidance device. Accordingly, it would be
desirable to provide a biopsy or other surgical instrument guide that is
rigidly affixed to the CT scanner apparatus whereby precise and automatic
correlation between the coordinate systems of the guidance device, patient
table, and patient image volume are automatically established.
U.S. Pat. Nos. 5,628,327 and 4,651,732 propose various devices for
supporting a laser apparatus for use in laser guided biopsies or other
interventional procedures. However, neither of these apparatus provide for
a combined laser and cannula guidance system. Further, neither of these
teachings suggest an interchangeable surgical instrument guidance device.
The present invention provides a new and improved interchangeable surgical
instrument guidance device and method for using same which overcomes the
above-referenced problems and others.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, an interchangeable
surgical instrument guidance device is provided. The guidance device is
used with a stereotactic arm member having a base end rigidly connected to
a CT scanner device and a second free end movable relative to the CT
scanner device for guiding the entry of a probe into a patient's body. The
guidance device includes a first and second end effector member disposed
on the free end of the stereotactic arm. The first end effector member
carries a guide channel defining a probe insertion path. The second end
effector includes a light source generating a light guide beam along the
probe insertion path. The light guide beam together with the guide channel
facilitate simultaneous mechanical and laser guided interventional
procedures.
In accordance with another aspect of the present invention, the first and
second end effector members are selectively releasably attached to the
free end of the stereotactic arm member.
Still further in accordance with the present invention, the end effectors
are interchangeable and may include such tools as orthopedic drill
attachments, ultrasound probes, and the like.
Still further, yet another aspect of the present invention, each of the
first and second end effector members forming the surgical instrument
guidance device are selectively pivotally attached to the free end of the
stereotactic arm member.
According to still yet another aspect of the present invention, the guide
channel disposed on the bottom end effector member of the guidance device
is retractable relative to the probe insertion path to facilitate the
entry of the probe into the patient's body.
In accordance with another aspect of the present invention, the guide
channel provided on the bottom end effector member is retractable relative
to the probe insertion path following a substantially arcuate path.
Still other advantages and benefits of the invention will become apparent
to those skilled in the art upon a reading and understanding of the
following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may take physical form in certain parts and arrangements of
parts, a preferred embodiment of which will be described in detail in this
specification and illustrated in the accompanying drawings which form a
part hereof, and wherein:
FIG. 1 is a diagrammatic illustration of a CT scanner and interchangeable
surgical instrument guidance device in accordance with the present
invention;
FIG. 2 is a perspective view of a mechanical arm assembly carrying a
guidance device formed in accordance with the present invention;
FIG. 3 is a diagrammatic illustration of the planning image processing
performed with the apparatus of FIG. 1;
FIG. 4 is a side view in partial cross section of a surgical instrument
guidance device formed in accordance with a first preferred embodiment of
the present invention;
FIGS. 5a and 5b illustrate respective extended and retracted positions of
the lower arm portion of the guidance device shown in FIG. 4;
FIG. 6 is a side view of an interchangeable surgical instrument guidance
device formed in accordance with a second preferred embodiment of the
present invention;
FIG. 7 is a "C" shaped surgical instrument guidance according to an
alternative embodiment of the present invention;
FIG. 8 is a perspective view of an interchangeable surgical instrument
guidance device according to yet another alternative embodiment of the
present invention;
FIG. 9 is a perspective view of an interchangeable surgical instrument
guidance device according to yet another alternative embodiment of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings wherein the showings are for the purposes of
illustrating the preferred embodiments of the invention only and not for
purposes of limiting same, with reference first to FIG. 1, a patient table
or support 10 includes a patient supporting surface 12 that is mounted for
longitudinal movement relative to a base portion 14. The base portion 14
includes a motor for raising and lowering the patient support surface 12
and for moving the patient support surface longitudinally. Position
encoders are also provided for generating electrical signals indicative of
the height and longitudinal position of the patient support. The patient
support includes a calibration marker 16 disposed at a known, fixed
location.
A planning, preferably volumetric diagnostic imaging apparatus 18 is
disposed in axial alignment with the patient table such that a patient or
subject on the patient support surface 12 can be moved into and through a
bore 20 of the volumetric imager. In the illustrated embodiment, the
volumetric imager is a CT scanner which includes an X-ray tube mounted for
repeated circular travel within a preselected plane. The X-ray tube
projects a fan-shaped beam of radiation through a ring 22 of radiation
translucent material, through the patient support 12, through a region of
interest of the subject, and to a ring or arc of radiation detectors
positioned opposite the X-ray tube. As the X-ray tube rotates within the
plane, a series of data lines are generated, which data lines are
reconstructed into at least a slice image by a reconstruction processor
included in a control console 26. The control console is typically
remotely located in a shielded room adjacent the scan room containing the
imaging apparatus 18. More specifically to the preferred embodiment, the
patient support 12 moves longitudinally as the X-ray tube is rotating
around the subject such that a selected volume of the patient is scanned
along a spiral path or a series of slices. The position of the X-ray tube
is monitored by a rotational position encoder, and the longitudinal
position of the patient support is monitored by a longitudinal position
encoder within the table 10. The reconstruction processor reconstructs a
volumetric image representation from the generated data lines. The control
console 24 typically includes one or more monitors 26 and various standard
operator input devices, such as a keyboard, trackball, mouse, or the like.
An interventionist control console 28 is supported from overhead on a
track atop the CT scanner as shown.
A mechanical arm assembly 30 is supported from overhead by a support
carriage 32 movable on an oval track system 34 affixed to the top of the
volumetric diagnostic imaging apparatus 20 as generally shown. The support
carriage is preferably lockable in one or more predetermined fixed
locations on the oval track so that a minimally invasive surgical
instrument 36 carried on an interchangeable surgical instrument guidance
device 100 formed in accordance with the present invention can be
positioned in monitored positions and orientations by an interventionist
in preparation for and in carrying out a surgical procedure. The surgical
instrument illustrated in the FIGURE includes a laser guided biopsy needle
38 carried by a combined laser and cannula guidance device 102 formed in
accordance with a first preferred embodiment of the present invention
which will be described below. Overall, however, the position and
orientation of the guidance device and the surgical instrument carried
thereon are determined by the position of the mechanical arm assembly 30
and the location of the support carriage 32 on the oval track system 34.
The frameless stereotactic mechanical arm assembly 30 is shown generally in
FIG. 2 and includes a plurality of arm segments which are interconnected
by pivot members forming joints between the arm segments. In that way, a
free end 40 of the arm is selectively movable in multiple orientations as
necessary to position the surgical instrument 36 into various desired
positions over the patient support 12. A base member 42 is rigidly
connected to the gantry 32 using suitable fasteners, epoxies, or the like.
A base joint 44 permits rotation of a primary support carriage 46 in a
direction marked A. Similarly, from the immovable base end of the arm, a
shoulder joint 48 permits rotation of an upper arm member 50 in a
direction marked B, an elbow joint 52 permits rotation of a lower arm
member 54 in a direction marked C, a forearm joint 56 permits rotation of
a knuckle member 58 in a direction marked D, and, lastly, a wrist joint 60
permits rotation of a wrist member 62 in a direction marked E.
In order to determine the position and orientation of the wrist member 62
with respect to the imaging apparatus reference frame and the volumetric
image representation obtained by the imaging apparatus, at least one
position resolver (not shown), preferably an optical incremental encoder,
is provided at each joint of the mechanical arm assembly 30 to monitor
increment articulation and rotation of the arm segments relative to each
other. The optical incremental encoders generate feedback pulses
indicative of the movement and relative position of the various arm
members in a well known manner. The feedback pulses are carried back to an
imaging apparatus control circuit using suitable wires or flexible
shielded cables extending through the multiple members of the arm
assembly.
In addition to the above, according to the present invention, in order to
determine the position and orientation of the surgical instruments
relative to the imaging apparatus reference frame and the volumetric image
representation obtained by the imaging apparatus, each interchangeable
surgical instrument guidance device 100 is adapted to provide a unique
identification signal. The signal is used by the imaging apparatus control
circuit to index a look up table for retrieving various physical
dimensional and other functional parameters corresponding to the one or
more guidance devices connected to the wrist member 62. In this manner,
the physical dimension and other functional parameters, together with the
mechanical interconnection which is measured by the resolvers and
encoders, provides an accurate indication of the position and orientation
of the guidance device 100 relative to the CT scanner and, hence, relative
to the image acquired by the CT scanner.
An imaging apparatus home position docking port 64 is provided on a forward
side of the base member 42 of the stereotactic arm assembly 30. In the
orientation shown in the FIGURE, the support carriage 32 and the arm
assembly carried thereon is accurately positioned in a known predetermined
relationship with respect to the calibration marker area 16 on the patient
supporting surface 12 of the imaging apparatus 18. Preferably, the
mathematical relationship between the calibration marker area 16 and the
home position docking port 64 is permanently established during a
calibration procedure using a calibration phantom typically performed by a
service technician during initial installation of the imaging apparatus. A
specialized arm docking connection member (not shown) is adapted to
connect the mechanical arm assembly to the home position docking port 64
between each interventional procedure. Appropriate software within the
imaging apparatus ensures that new interventional procedures are not
initiated until the arm is returned to the home position docking port 64.
As an extra precautionary measure to verify the relative orientation and
position of the guidance device 100 relative to the patient support, a tip
of the surgical instrument or pointer may be touched to the calibration
marker area 16 and an assessment made whether the electronic signal is
indicative of patient support location and surgical instrument location,
in fact, placing both at the same point in space.
Other mechanisms for monitoring the guidance device 100 type and the
position of the mechanical arm assembly 30 are also contemplated. For
example, a plurality of first transmitters, such as light emitting diodes,
are mounted in a fixed, known relationship to the mechanical arm assembly
30. A plurality of second transmitters, such as light emitting diodes, are
mounted to the guidance device 100. The plurality of second transmitters
includes at least one transmitter adapted to generate an identification
signal unique to each guidance device. An array of receivers is mounted in
a fixed relationship to the CT scanner, preferably affixed to the ceiling
of the room. Each time a different type of guidance device 100 is attached
to the mechanical arm assembly 30, the diode emitters are actuated and the
emitted signals received by the receivers. The guidance device type and
the position and orientation of the mechanical arm assembly and the
guidance device on the arm are accurately and quickly calculated by
decoding the identification signal and using geometric triangulation
techniques for the position signals. By positioning the guidance device on
a plurality of markers, preferably three or more, e.g., the several
markers in the calibration marker area 16 which are mounted in a fixed,
known relationship to the coordinate system of the CT scanner, the
guidance device coordinate system, and hence the surgical instrument
coordinate system can be readily correlated with the CT scanner coordinate
system and the coordinate system of the patient table.
With reference now to FIG. 3, an instrument coordinate circuit 72
determines the position and trajectory of the surgical instrument 36 in
instrument space, particularly a coordinate system of the instrument. The
instrument coordinate circuit includes a guidance device identification
circuit 74 and a mechanical arm assembly position circuit 76. The guidance
device identification circuit 74 receives the device identification signal
from the one or more guidance devices connected to the mechanical arm and
indexes a look up table 78 to retrieve dimensional and functional
information. The mechanical arm assembly position circuit 76 is connected
with the increment resolvers on the mechanical arm assembly 30 to receive
signals indicative of changes of position and orientation of the
mechanical arm in instrument space. An instrument-planning scanner
correlating processor 80 determines the correlation or transform between
the surgical instrument 36 and the volumetric scanner 18 coordinate
systems. The correlation or transform is normally described in terms of
offset, particularly offset along the axis of the patient support, angular
offset or rotation, and scaling. In one embodiment, a calibration
instrument is touched to a set of spaced apart markers, preferably eight,
which are disposed in a known relationship to the volumetric scanner
coordinate system. The markers are preferably in the form of a calibration
phantom located in the calibration marker area 16 on the patient support
table. By measuring the coordinates of the calibration instrument in the
instrument coordinate system while touching each marker, six or more
common points in the two coordinate systems are determined. By determining
a barrycenter, centroid, or other characteristic point of the common
points, the offset between the two coordinate systems is determined. By
determining the angular difference between the rays from the barrycenter
to each point in each coordinate system, the angular offset is determined.
By determining a difference in physical displacement between the
barrycenter and the corresponding points in each coordinate system, the
scaling factor is determined. Of course, in a system such as the
illustrated embodiment in which the instrument and the volumetric scanner
are mechanically linked, the transform or relationship between the
volumetric scanner and the instrument coordinate system needs only to be
calibrated once and, thereafter, is predetermined from the mechanical
interconnection between the component parts. The touching of the markers
need only be performed once and subsequently used merely to confirm that
the instrument and the CT scanner coordinates have not become misaligned
between interventional procedures.
Using analogous mathematics or known mechanical relationships as above, an
instrument to patient table correlating processor 82 determines the
correlation or transform between the patient table and the surgical
instrument. Preferably, the calibration phantom described above having the
plurality of markers is positioned in a known position on the table to
provide a large number of corresponding points in both coordinate systems
for the correlating process. Images of the phantom can be utilized to
derive transforms between patient table space and planning or real time
image coordinate systems.
Table resolvers 84 located in the patient table contribute vertical and
longitudinal offsets to the correlation between the surgical instrument
and the patient table when the table is raised or lowered and when the
patient support 12 is moved axially. An instrument to patient correlation
processor 86 determines a correlation between the surgical instrument
system and a patient coordinate system. Preferably, this is done by
placing the surgical instrument on three or more known reference points on
the patient. Such points might include readily identifiable anatomical
structures such as the tip of the nose, distinctive points of bones,
fiducial markers that are aligned during the volumetric imaging process,
or the like.
An instrument to volumetric image coordinate system transform processor 88
receives the correlation or transform from the surgical instrument to
planning image processor 80. The instrument to volumetric image processor
operates on input position and orientation coordinates in arm space to
transform them into volumetric image data space and visa versa. Knowing
the position of the surgical instrument in volumetric or planning data
space enables the instrument position and orientation to be superimposed
on the volumetric planning image data.
During a medical procedure, the patient is positioned in the volumetric
planning scanner and a volumetric image is generated. The volumetric image
is stored in a volumetric or planning data memory 90. The position of the
patient table during the generation of the planning data, particularly as
the table moves to generate spiral or slice data, is stored in conjunction
with the volumetric planning data such that the data is correlated with
the patient table coordinate system. The position of the free end of the
arm relative to the patient's body controls the volume planning image data
memory or a video processor 92 such that selected slices, projection
images, surface renderings, or other conventional displays of the data are
generated for display on a planning image display 94. Preferably, the
planning image display includes corresponding sagittal coronal axial and
oblique slices through a common point of intersection.
Because the planning image display is generated before the surgical
procedure, the planning movement of the surgical instrument is preferably
displayed in the planning image. The coordinates and trajectory of the
surgical instrument are conveyed to the instrument to planning image
transform processor 88 for conversion into the planning image coordinate
system. The location and trajectory of the instrument in the planning
image coordinate system is communicated to the video processor 92 which
superimposes the surgical instrument position and trajectory on the CT
data display. The position and orientation of the stereotactic arm
assembly 30 is communicated to the interventionist control 28, which
generates cursor position signals and virtual needle displays which are
transformed into the planning image coordinate system 94 and communicated
to the video processor 92 to generate a movable cursor point and a virtual
needle representation on the planning image display 94. Preferably, the
cursor is positioned at the point of intersection of concurrently
displayed transverse, coronal, and sagittal views on the volumetric image
display 94. As the operator moves the free end of the stereotactic arm
assembly through volumetric image data space and as the surgical
instrument 36 on the mechanical arm assembly 30 is moved over target areas
on the patient, the sagittal, coronal, and transverse views automatically
change correspondingly.
Turning once again to FIG. 2, an interchangeable surgical instrument
guidance device 100 formed in accordance with a first preferred embodiment
of the present invention is shown attached to the free end 40 of the
mechanical arm assembly 30. The interchangeable surgical instrument
guidance device illustrated is a combined laser and cannula guidance
device 102 including an upwardly disposed top end effector member 104
carrying a laser light emitting source 108 and a downwardly disposed
bottom end effector member 106 carrying a pair of opposing cannula needle
guide elements 110, 112. The opposing needle guide elements are biased
together into the position illustrated by a retractable tweezer unit 114
which will be described in greater detail below. The top and bottom end
effectors 104, 106 are adapted to each individually provide a distinct
identification signal to the instrument coordinate circuit 72 through
respective electromechanical connectors 116, 118 which adapt the top and
bottom end effectors for connection to the wrist member 62 of the
mechanical arm assembly 30.
FIG. 4 illustrates the combined laser and cannula guidance device 102 in
greater detail. With reference now to that FIGURE, the top end effector
member 104 is formed of a rigid hollow tube member 120 adapted to carry
multiple power supply wires 122 within the tube between the laser light
source 108 and a first set of electrical pins 124 arranged in an
intermateable plug portion 126 of the first electromechanical connector
116. According to the preferred embodiment of the invention, the wrist
member 62 includes a pair of first and second intermateable socket
portions 130, 132 which carry respective sets of electrical connection
pins 134, 136. The first set of electrical connection pins 134 on the
wrist member 62 are adapted to electrically and mechanically connect with
the first set of electrical pins 124 formed in the intermateable plug
portion 126 when the top end effector member 104 is connected to the wrist
member. Preferably, an internally threaded nut 138 is provided on the top
end effector member 104 for engaging corresponding external threads
provided on the wrist member 62.
In addition to the supply of power to the laser light source 108 through
the power supply wires 122, the first set of electrical pins 124 are
connected to an identification resistor 140 disposed within the rigid
hollow tube 120. In accordance with the present invention, the
identification resistor 140 provides a unique analog identification value
to the instrument coordinate circuit 72 for use as an index into the look
up table 78 in a manner described above. Further in accordance with the
present invention, each of the interchangeable surgical instrument
guidance devices 100 are provided with an identification resistor having
an analog resistance value unique to each guidance device. Other
equivalent schemes may be used equally to uniquely identify the guide
devices such as contact closures, DIP switches, or the like.
With continued reference to FIG. 4, but turning attention next to the
bottom end effector member 106, an elongate rigid hollow tube 142 adapts
the cannula pair 110, 112 for connection to the wrist member 62. For
reasons which will subsequently become apparent, the tube 142 is
preferably hollow in order to accommodate lateral retraction of the
tweezer unit 114 in a leftward direction as viewed in the FIGURE.
In a manner similar to that described above in connection with the top end
effector member, an identification resistor 144, preferably having an
analog resistance value unique to the bottom end effector member, is
connected to a set of electrical pins 146 provided on the intermateable
plug portion 128 of the bottom end effector member. The electrical pins
146 are adapted to engage corresponding intermateable electrical
connection pins 136 provided on the intermateable socket portion 132 of
the wrist member 62. An internally threaded nut 148 is adapted to engage
corresponding external threads formed on the wrist member in a well known
manner to securely fasten the bottom end effector member 106 to the wrist
member.
With continued reference to FIG. 4, but with additional references to FIGS.
5a and 5b, the laser light source 108 is preferably oriented on the top
end effector member 104 in a manner to direct a coherent light beam 150
through a needle guide 152 formed on opposing faces of the cannula pair
110, 112. According to well known laser guided surgery techniques, the
needle guide 152 and the light beam 150 are oriented on the top and bottom
end effector members in precise alignment with each other. In that regard,
in order to ensure that the needle guide does not become worn after
repeated use during interventional procedures thereby degrading the
precision of the surgical guidance device, the cannula pair are preferably
disposed after each use. Preferably, the cannula pair members 110, 112 are
formed of resilient lexan or polycarbonate and are releasably connected to
first and second spring members 160, 162 of the tweezer unit using
suitable fasteners such as the set of mushroom-shaped rivets 164 as shown.
The rivets are preferably permanently affixed to the first and second
spring members 160, 162. According to the preferred embodiment, after each
interventional procedure, the used cannula pairs are removed and disposed
and, thereafter, a new cannula pair is slid into releasable engagement
with the set of rivets 164. Also in accordance with the present invention,
the spring constant of the first and second spring members is selected so
that the cannula pair are adapted to be separable in the event of
unexpected patient movement. Preferably, the spring constant is selected
to be both rather stiff to accurately guide surgical instruments and to be
somewhat flexible to release the surgical instrument in response to
unexpected gross patient movement.
FIG. 5a illustrates the retractable tweezer unit 114 in an extended
position, and FIG. 5b illustrates the tweezer unit in its retracted
position. A pair of opposing registration holes 166, 168 are formed in the
hollow tube 142 of the bottom end effector member 106 generally as shown.
The opposed registration holes are adapted to receive a corresponding pair
of locking pins 170, 172 respectively affixed to the first and second
spring members 160, 162. The locking pins are easily manually operated
against the force of the resiliently biased opposing first and second
spring members 160, 162 to dislodge the locking pins out of engagement
with the corresponding opposed registration holes 166, 168 formed in the
tube 142. As the locking pins are squeezed together, the cannula pair
members 110, 112 carried on the first and second spring members 160, 162
separate, releasing a needle or biopsy probe which may be aligned with a
target site in the patient. A guide shuttle 174 is adapted to connect the
first and second spring members together and to guide the lead edges
thereof within the hollow tube 142 as the tweezer unit 114 is retracted
into the bottom end effector member 106 to a position shown in FIG. 5b.
FIG. 6 shows a second preferred embodiment of the laser and cannula
guidance device 102' formed in accordance with the present invention to
illustrate the interchangeabilit | | |
