U.S. patent application number 16/738125 was filed with the patent office on 2020-07-16 for system, method, and apparatus for configuration, design, and operation of an active cannula robot.
The applicant listed for this patent is Vanderbilt University. Invention is credited to Jessica BURGNER, David B. COMBER, Hunter B. GILBERT, Ray LATHROP, Philip J. SWANEY, Kyle WEAVER, Robert J. WEBSTER, III.
Application Number | 20200222079 16/738125 |
Document ID | / |
Family ID | 53773915 |
Filed Date | 2020-07-16 |
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United States Patent
Application |
20200222079 |
Kind Code |
A1 |
SWANEY; Philip J. ; et
al. |
July 16, 2020 |
SYSTEM, METHOD, AND APPARATUS FOR CONFIGURATION, DESIGN, AND
OPERATION OF AN ACTIVE CANNULA ROBOT
Abstract
The present invention relates to a system and apparatus for
implementing a method for identifying tube parameters of a curved
tube of an active cannula for operating on a target in a patient.
The method includes the step (a) of acquiring a model of the
patient anatomy including the target. The method also includes the
step (b) of selecting a set of parameters characterizing a curved
tube. The method also includes the step (c) of computing a
workspace for an active cannula having the selected curved tube
parameters. The method also includes the step (d) of comparing the
workspace to the anatomical model to determine the degree to which
an active cannula having the selected curved tube parameters covers
the target. The method also includes the step (e) of repeating
steps (b) through (d) through a defined number of curved tube
parameter sets. The method also includes the step (f) of
identifying the curved tube parameters that provide an active
cannula with an optimal degree of target coverage.
Inventors: |
SWANEY; Philip J.;
(Nashville, TN) ; LATHROP; Ray; (Nashville,
TN) ; BURGNER; Jessica; (Hannover, DE) ;
WEAVER; Kyle; (Thompson Station, TN) ; GILBERT;
Hunter B.; (Nashville, TN) ; WEBSTER, III; Robert
J.; (Nashville, TN) ; COMBER; David B.;
(Nashville, TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Vanderbilt University |
Nashville |
TN |
US |
|
|
Family ID: |
53773915 |
Appl. No.: |
16/738125 |
Filed: |
January 9, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14177864 |
Feb 11, 2014 |
10548630 |
|
|
16738125 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2017/3443 20130101;
A61B 2017/00331 20130101; A61B 2017/003 20130101; A61B 2090/103
20160201; A61B 17/3421 20130101; A61B 2017/00991 20130101; A61B
90/11 20160201; A61B 2034/105 20160201; A61B 34/10 20160201; A61B
2034/301 20160201; A61B 34/30 20160201; A61B 34/20 20160201 |
International
Class: |
A61B 17/34 20060101
A61B017/34; A61B 34/30 20060101 A61B034/30; A61B 34/10 20060101
A61B034/10 |
Goverment Interests
GOVERNMENT RIGHTS
[0002] This invention was made with government support under grant
number 11S1054331 awarded by the National Science Foundation. The
government has certain rights in the invention.
Claims
1. An active cannula robot system for performing a surgical
treatment on a target in a patient, the system comprising: an
active cannula robot comprising an outer cannula tube and an inner
cannula tube that extends coaxially within the outer cannula tube,
the inner cannula tube having a distal curved end portion
terminating at a tip, the robot being operable to cause
translational movement of the outer and inner cannula tubes along
the axis and to cause rotational movement of the inner cannula tube
about the axis relative to the outer cannula tube to apply the
treatment to the target; and a controller configured to select a
configuration of the curved end portion of the tube based on image
data related to the target so that the tip can reach at least a
threshold portion of the target through the translational and
rotational movement.
2. The system recited in claim 1, wherein the target comprises a
clot resulting from an intracerebral hemorrhage, wherein the image
data related to the clot is mapped to image data related to the
patient's skull so that the position and orientation of the clot in
the skull is known, the controller being configured to select the
configuration of the curved end portion of the tube on the basis of
the image data related to the clot.
3. The system recited in claim 2, wherein the controller is
configured to select the configuration of the curved end portion of
the tube on the further basis of a surgical robot entry point on
the patient's skull and a predetermined trajectory along which the
outer and inner cannula tubes are inserted through the patient's
skull into the patient's brain.
4. The system recited in claim 3, further comprising a trajectory
stem and an image guidance system that is operative to align the
trajectory stem along the predetermined trajectory, wherein the
controller is configured to select the configuration of the curved
end portion of the inner cannula tube on the further basis of the
trajectory.
5. The system recited in claim 2, wherein the image data related to
the clot and the image data related to the patient's skull
comprises CT image data.
6. The system recited in claim 1, wherein the robot is operable to
retract the inner cannula tube into the outer cannula tube, the
outer cannula tube having a straight configuration, the curved end
portion deforming elastically and conforming to the straight
configuration of the outer cannula tube when retracted into the
outer cannula tube and returning resiliently to its curved
configuration when extended from the outer cannula tube, the inner
cannula tube being constructed so that the curved end portion when
extended from within the outer cannula tube after being retracted
within the outer cannula tube resumes its curved configuration.
7. The system recited in claim 6, wherein the robot is operable to
deliver the active cannula robot to the target in an axial
direction with the inner cannula tube retracted into the outer
cannula tube, the robot, thereafter extending the curved end
portion of the inner cannula tube from the outer cannula tube into
the target to treat the target.
8. The system recited in claim 2, further comprising an aspirator
operatively connected to the inner cannula tube, the aspirator
being operable to apply suction via the inner cannula tube to
evacuate the clot.
9. The system recited in claim 1, wherein the controller is
operable manually to control movement of the active cannula robot
in combination with image guidance to move the tip of the inner
cannula tube within the target.
10. The system recited in claim 1, wherein the controller is
operable automatically though open loop control to control movement
of the active cannula robot to move the tip of the inner cannula
tube within the target.
11. The system recited in claim 1, further comprising a manual
actuator comprising a first manual actuator operable to cause
translational movement of the outer cannula tube along the axis, a
second manual actuator operable to cause translational movement of
the inner cannula tube along the axis, and a third manual actuator
operable to impart rotation of the inner cannula tube about the
axis.
12. The system recited in claim 1, wherein the controller is
configured to select a configuration of the curved end portion of
the tube by: (a) acquiring an anatomical model of the patient
anatomy including a target model of the target; (b) selecting a set
of curved tube parameters characterizing the curved end portion of
the inner cannula tube; (c) computing a workspace for the active
cannula robot in which the inner cannula tube has the selected
curved tube parameters; (d) comparing the workspace to the target
model to determine the degree to which an active cannula robot with
an inner cannula tube having the selected curved tube parameters
can cover the target; (e) repeating steps (b) through (d) through a
defined number of different curved tube parameter sets; and (f)
identifying curved tube parameter sets that, in combination, allow
the active cannula robot to provide an optimal degree of target
coverage.
13. The system recited in claim 12, wherein the controller is
configured to perform step (c) of computing a workspace by: mapping
the joint space parameters of the active cannula robot to
configuration space parameters in order to define a forward
kinematic model for the active cannula robot; discretizing the
joint space of the active cannula robot to produce a discrete set
of joint positions of the active cannula robot; and solving the
kinematic model for each discrete combination of joint positions to
compute the workspace of the active cannula robot.
14. The system recited in claim 13, wherein the controller is
configured to perform step (d) of comparing the computed workspace
to the clot model by: converting the target model to a discrete set
of voxels; computing an inner cannula tube tip position for each of
the joint positions of the active cannula robot; and evaluating
each computed inner cannula tube tip position to determine whether
it lies within a voxel of the target model.
15. The system recited in claim 12, wherein the controller is
configured to perform step (d) of comparing the workspace to the
model by determining the degree to which the workspace overlaps the
model.
16. The system recited in claim 12, wherein the target comprises a
clot resulting from an intracerebral hemorrhage in a patient,
wherein the controller is configured to perform step (a) of
acquiring a target model by acquiring a model of the clot mapped
relative to a model of the patient's skull.
17. The system recited in claim 16, wherein the controller is
configured to perform the step of comparing the workspace to the
model by determining a trajectory at which to advance the active
cannula robot through the patient's skull and into the patient's
brain to access the clot, and orienting the computed workspace
within the clot according to the determined trajectory.
18. The system recited in claim 12, wherein the defined number of
curved tube parameter sets correspond to actual curved tube
parameter sets for inner cannula tubes in a pre-existing set of
tubes, wherein the controller is configured to select the curved
tube parameter set identified in step (f) from the pre-existing set
of tubes.
19. The system recited in claim 12, wherein the defined number of
curved tube parameter sets are theoretical parameter sets that are
incremented sequentially through a predetermined range of discrete
values, wherein the controller is configured to identify the curved
tube parameters identified in step (f) as being parameters for
subsequently constructing and configuring a curved tube of the
active cannula robot.
20. The system recited in claim 12, wherein the controller is
configured to perform the steps of determining for each joint
position whether the entire curve of the active cannula robot is
positioned within the target model, and discarding joint positions
in which any portion of the curve is positioned outside the target
model.
Description
RELATED APPLICATION DATA
[0001] This application is a Divisional of U.S. Non-Provisional
application Ser. No. 14/177,864, which was filed on Feb. 11,
2014.
FIELD OF THE INVENTION
[0003] The invention relates to active cannula robots. More
particularly, the invention relates to a system, method, and
apparatus for configuring, designing, and operating an active
cannula robot to perform a surgical operation. According to one
aspect, for an active cannula robot has a straight outer tube and a
retractable, curved inner tube, the system performs a method for
designing and configuring the curved tube based on the target of
the surgical operation. In one particular aspect, the surgical
operation is the image guided evacuation of a hematoma resulting
from an intracerebral hemorrhage.
BACKGROUND
[0004] Minimally invasive surgical techniques are less invasive
than open surgery techniques used for the same purpose and are
therefore desirable due to their offering reduced trauma, reduced
pain & scarring, more rapid recovery, and reduced post-surgical
complications. Some of these techniques can be performed
robotically. In neurosurgery, attempts have been made at a
needle-based minimally invasive robotic approach to treating some
conditions. These systems are generally stereotactic robotic
systems that use straight needle trajectories with image guidance
to hit specific targets at a specific worksite within the brain, in
a manner similar to that of a standard brain biopsy. This
needle-based approach results in less damage to the surrounding
brain tissue during delivery, at the expense of offering no
appreciable dexterity once the target is reached. One particular
condition that would benefit to a needle based approach that offers
dexterity at the worksite is an intracerebral hemorrhage.
[0005] Approximately 1 in 50 people will have an intracerebral
hemorrhage (ICH) at some point in their lives, and the one-month
mortality rate is approximately 40%. ICH occurs when a blood vessel
in the brain ruptures and a collection of blood, referred to herein
as a "clot" or "hematoma," accumulates within the cranial cavity
and compresses the brain. The clot can be treated with drugs or
surgical evacuation via open craniotomy to help remove the clot and
decompress the brain. While one would expect decompression via clot
removal to result in improved patient outcomes, there is no
clinical data supporting this for the majority of ICH patients.
Benefits of various treatments have only been shown in select
patients with small, superficial lesions and a good preoperative
performance status. There remains no treatment of proven clinical
benefit for typical ICH patients. In standard open surgical
procedures, the brain substance is cut with electrocautery and
tubular retraction systems, with or without endoscopic assistance,
and Archimedes screw-type devices are applied to remove the clot.
These current ICH treatments, however, provide only minimal
improvement in outcomes.
[0006] Some of the ineffectiveness of the current ICH treatments
can be attributed to permanent brain injury that is caused by the
hemorrhage and is irreversible even with clot removal.
Neurosurgeons, however, generally believe that there is a volume of
at-risk brain tissue that can be salvaged and returned to
pre-injury function if its condition is optimized through
decompression. The ability to restore brain tissue to pre-injury
function does not necessarily depend on complete removal of the
clot. For example, by some estimates, clinically meaningful
decompression can begin when approximately 25-50% of the clot is
removed.
[0007] Decompression through removal of the clot resulting from the
ICH, referred to herein as "evacuation" or "debulking," is known to
help optimize the condition of the brain. Decompression, however,
can be challenging for certain clot locations and shapes,
particularly those resulting from deep hemorrhages. For many clots,
an operative trajectory of any significant dimension would result
in a volume of tissue disruption that is greater than that which
would be saved by its evacuation. As a result, only superficial
clots are candidates for evacuation using current operative
approaches.
SUMMARY
[0008] The present invention relates to a robotic active cannula,
or active cannula robot, comprising robotically actuated concentric
tubes. According to one aspect, the concentric tubes include a
straight outer tube that can he actuated for translational movement
along an axis and an inner tube that can be actuated for rotation
about the axis relative to the outer tube and for insertion from
and retraction into the outer tube. The inner tube has an elastic
curved end portion that can be retracted into the outer tube.
Through extension, retraction, and rotation relative to the outer
tube, the end portion of the inner tube can be articulated
throughout a workspace that is defined by the curved configuration
of the inner tube.
[0009] According to another aspect, the active cannula robot is
configured to be customized by incorporating multiple inner tubes
with various curvatures and/or stiffnesses selected on the basis of
the desired workspace. For instance, the curvatures and/or
stiffnesses of one or more inner tubes can be selected to treat a
surgical target at a known worksite location and having a known
shape and extent determined by scanned image data. These multiple
inner cannulas can be hot-swapped during the surgical procedure
while the outer tube remains in-situ at the worksite. According to
this aspect of the invention, the hot-swappable configuration of
the inner tubes can allow the aggregate workspace of the active
cannula to cover the target at the worksite through the
implementation of what amounts to multiple concentric tube robots,
used sequentially.
[0010] According to this aspect, a kinematicmodel for the inner
tube is evaluated to determine the workspace of a tube having a
given set or parameters. The determined workspace is then compared
to the scanned image data of the target to determine the extent to
which the tube can cover the target. In making this determination,
the location and orientation of the target, i.e., the trajectory at
which the inner tube accesses the target, is taken into account.
This process is repeated through a discrete set of tube parameters,
and the tube configuration that offers the optimal workspace for
covering the target is selected for the surgical procedure. Through
this process, it may be determined that more than one tube, used in
succession, can offer an aggregate workspace that is optimally
tailored to the target.
[0011] One particular neurosurgical operation to which the present
invention is particularly well-suited relates to the treatment of
an ICH. Thus, according to this aspect, the active cannula robot of
the invention can be a 3 degree-of-freedom (DOF) concentric tube
robot that can be used to perform image-guided evacuation of clots
resulting from an ICH. The robotic system incorporating the robotic
active cannula is no more invasive than a standard brain biopsy,
yet enables ICH clots to be evacuated via articulation of the
curved tip. To perform the evacuation, the inner tube can be
configured as an aspiration cannula. The robotic system can thus
provide a straight needle trajectory to enter the brain and access
the location of the clot in combination with an articulated robotic
cannula that can maneuver within the clot at the site of the ICH.
According to this aspect, the system can be used to select the
inner tube(s) of the active cannula robot so that the robot
workspace conforms to the location, shape, and orientation of the
ICH clot, as determined from scanned image data.
[0012] The present invention relates to a method for identifying
tube parameters of a curved tube of an active cannula for operating
on a target in a patient. The method includes the step (a) of
acquiring a model of the patient anatomy including the target. The
method also includes the step (h) of selecting a set of parameters
characterizing a curved tube. The method also includes the step (c)
of computing a workspace for an active cannula having the selected
curved tube parameters. The method also includes the step (d) of
comparing the workspace to the anatomical model to determine the
degree to which an active cannula having the selected curved tube
parameters covers the target. The method also includes the step (e)
of repeating steps (b) through (d) through a defined number of
curved tube parameter sets. The method also includes the step (f)
of identifying the curved tube parameters that provide an active
cannula with an optimal degree of target coverage.
[0013] According to one aspect of the invention, the step (c) of
computing a workspace includes the step of mapping the joint space
parameters of the active cannula to configuration space parameters
in order to define a forward kinematic model for the active
cannula. The step (c) also includes the step of discretizing the
joint space of the active cannula to produce a discrete set of
joint positions of the active cannula. The step (c) includes the
further step of solving the kinematic model for each discrete
combination of joint positions to compute the workspace of the
active cannula.
[0014] According to another aspect of the invention, the step (d)
of comparing the computed workspace to the clot model comprises the
step of converting the target model to a discrete set of voxels.
The step (d) also includes the step of computing a tip position for
each of the joint positions of the active cannula. The step (d)
includes the further step of evaluating each computed cannula tip
position to determine whether it lies within a voxel of the target
model. According to another aspect of the invention, the step (d)
of comparing the workspace to the model can include determining the
degree to which the workspace overlaps the model. According to
another aspect of the invention, the method can include the further
steps of determining for each joint position whether the entire
curve of the active cannula is positioned within the target model,
and discarding joint positions combinations in which any portion of
the curve is positioned outside the target model.
[0015] According to another aspect of the invention, the target can
include a clot resulting from an intracerebral hemorrhage in a
patient, wherein the step (a) of acquiring a model of the target
comprises acquiring a model of the clot mapped relative to a model
of the patient's skull. The step of comparing the workspace to the
model can include the steps of determining a trajectory at which to
access the clot through the patient's skull, and orienting the
computed workspace within the clot according to the determined
trajectory.
[0016] According to another aspect of the invention, the defined
number of curved tube parameter sets can be actual parameter sets
for cannula tubes in a pre-existing set of tubes, and the active
cannula identified in step (f) is one selected from the
pre-existing set of tubes.
[0017] According to another aspect of the invention, the defined
number of curved tube parameter sets can also be theoretical
parameter sets that are incremented sequentially through a
predetermined range of discrete values, and the curved tube
parameters identified in step (f) are for subsequently constructing
and configuring a curved tube of the active cannula.
[0018] The present invention also relates to an active cannula
robot system for performing a surgical treatment on a target in a
patient. The system includes an active cannula robot including an
outer tube and an inner tube that extends coaxially within the
outer tube. The inner tube has a distal curved end portion
terminating at a tip. The robot is operable to cause translational
movement of the outer and inner tubes along the axis and to cause
rotational movement of the inner tube about the axis relative to
the outer tube to apply the treatment to the target. A controller
is configured to select a configuration of the curved end portion
of the tube based on image data related to the target so that the
tip can reach at least a threshold portion of the target through
the translational and rotational movement.
[0019] According to one aspect, the target comprises a clot
resulting from an intracerebral hemorrhage. The image data related
to the clot is mapped to image data related to the patient's skull
so that the position and orientation of the clot in the skull is
known. The controller is configured to select the configuration of
the curved end portion of the tube on the basis of the image data
related to the clot. The controller is configured to select the
configuration of the curved end portion of the tube on the further
basis of a surgical robot entry point on the patient's skull.
According to another aspect, the system includes a trajectory stein
and an image guidance system operative to align the trajectory stem
along a predetermined trajectory into the patient's brain. The
controller is configured to select the configuration of the curved
end portion of the tube on the further basis of the trajectory. The
image data related to the clot and the image data related to the
patient's skull can be CT image data.
[0020] According to another aspect, the robot is operable to
retract the inner tube into the outer tube, the inner tube being
constructed so that the curved end portion when extended from
within the outer tube after being retracted within the outer tube
resumes its curved configuration. The robot is operable to deliver
the active cannula to the target in an axial direction with the
inner tube retracted into the outer tube, the robot thereafter
extending the curved end portion of the inner tube from the outer
tube into the target to treat the target. An aspirator can be
operatively connected to the inner tube. The aspirator is operable
to apply suction via the inner tube to evacuate the clot.
[0021] According to another aspect, the controller can be operable
manually to control movement of the active cannula in combination
with image guidance to move the tip of the inner tube within the
target. The controller can be operable automatically though open
loop control to control movement of the active cannula to move the
tip of the inner tube within the target. The robot can include a
manual actuator including a first manual actuator operable to cause
translational movement of the outer tube along the axis, a second
manual actuator operable to cause translational movement of the
inner tube along the axis, and a third manual actuator operable to
impart rotation of the inner tube about the axis.
[0022] The present invention also relates to an active cannula
robot for performing a surgical operation on a patient. The robot
includes an outer tube and an inner tube that extends coaxially
with the outer tube. The inner tube includes a curved end portion
that is retractable into the outer tube, the curved end portion
deforming elastically and conforming to the straight configuration
of the outer tube when retracted into the outer tube. The robot is
actuatable to cause extension and retraction of the outer tube
along the axis. The robot is further actuatable to cause extension
of the inner tube from the outer tube, retraction of the inner tube
into the outer tube, and rotation of the inner tube relative to the
outer tube. A retainer for securing the inner tube to the robot is
manually releasable to permit removal and replacement of the inner
tube during a surgical operation without retracting the outer
tube.
[0023] According to one aspect, the robot includes a frame having a
front end and an opposite rear end. An outer tube carrier is
coupled to the frame. The outer tube carrier is movable along the
frame to cause the translational movement of the outer tube along
the axis. An inner tube carrier is coupled to the frame. The inner
tube carrier is movable along the frame to cause translational
movement of the inner tube along the axis. The inner tube carrier
includes a tube mount for supporting the inner tube for rotation
about the axis. The retainer secures the inner tube in the tube
mount. A motor assembly is coupled to the rear end of the frame.
The motor assembly includes a first motor operable to move the
outer tube carrier along the frame, a second motor operable to move
the inner tube carrier along the frame, and a third motor operable
to impart rotation of the inner tube about the axis. The retainer
permits removal and replacement of the inner tube without
disturbing the remaining components of the robot. The outer tube
carrier includes emergency release mechanisms that are manually
operable to decouple the outer tube carrier from the first motor
and to decouple the inner tube carrier from the second motor to
permit the tube carriers to he moved manually along the frame in
order to retract the inner and outer tubes.
[0024] According to one aspect, a trajectory stem guides the outer
tube along a predetermined trajectory. A base coupled to the
trajectory stem includes a locking mechanism for fixing the
position of the trajectory stem at a desired orientation relative
to the patient. The base is to the patient. The front end of the
frame is configured to be coupled with the trajectory stem that, is
secured to the patient so that the trajectory stein guides the
trajectory of the outer tube when extended from the frame into a
patient.
[0025] According to another aspect, the outer tube carrier includes
a driver block through which a shaft rotatable by the first motor
extends. Rotation of the shaft acts on the driver block to impart
movement of the outer tube carrier along the frame. The driver
block includes an emergency release mechanism that is manually
operable to decouple the driver block from the outer tube carrier
and thereby decouple the outer tube carrier from the first motor.
The inner tube carrier comprises a driver block through which a
shaft rotatable by the second motor extends. Rotation of the shaft
acts on the driver block to impart movement of the inner tube
carrier along the frame. The driver block includes comprising an
emergency release mechanism that is manually operable to decouple
the driver block from the inner tube carrier and thereby decouple
the inner tube carrier from the second motor.
[0026] According to another aspect, the motors of the motor
assembly are operable to actuate the inner and outer tubes to
perform a surgical operation to evacuate a clot resulting from an
intracerebral hemorrhage through the inner tube. The first motor is
operable to deliver the outer tube to the clot in an axial
direction with the inner tube retracted into the outer tube. The
second motor is operable to extend the curved end portion of the
inner tube from the outer tube into the clot to evacuate the clot.
The second and third motors are operable to translate and rotate
the curved end portion of the inner tube within the clot to
evacuate the clot. The second and third motors are operable to move
the position the tip thorough a predetermined path within the clot
to evacuate the clot. An aspirator is operatively connected to the
inner tube and is operable to apply suction via the inner tube to
evacuate the clot.
[0027] According to another aspect, a second retainer secures the
outer tube to the robot. The second retainer is manually releasable
to permit removal and replacement of the outer tube during the
surgical operation. The second retainer is manually releasable to
permit removal and replacement of the outer tube without disturbing
the remaining components of the robot.
[0028] According to another aspect, a transmission tube assembly
includes concentric transmission tubes arranged coaxially with the
inner and outer tubes and configured to transmit at least one of
translational and rotational movement from an actuator assembly to
the inner and outer tubes.
[0029] According to another aspect, a transmission tube assembly
includes an outer transmission tube and an inner transmission tube
that extend coaxially with each other and with the outer and inner
tubes. The outer transmission tube is coupled to the outer tube and
the inner transmission tube is coupled to the inner tube. The robot
is actuatable to cause extension and retraction of the outer
transmission tube along the axis. The robot is also actuatable to
cause extension of the inner transmission tube from the outer
transmission tube, retraction of the inner transmission tube into
the outer tube, and rotation of the of the inner tube relative to
the outer transmission tube, the extension, retraction, and
rotation of the inner and outer transmission tubes producing
corresponding movements of the inner and outer tubes. The tubes of
the transmission tube assembly have torsional stiffnesses that are
greater than torsional stiffnesses of the outer and inner
tubes.
[0030] According to another aspect, the robot includes a frame
having a front end and an opposite rear end. An outer tube carrier
is coupled to the frame, the outer tube carrier is movable along
the frame to cause the translational movement of the outer tube
along the axis. An inner tube carrier is coupled to the frame. The
inner tube carrier is movable along the frame to cause
translational movement of the inner tube along the axis. The inner
tube carrier includes a tube mount for supporting the inner tube
for rotation about the axis. The retainer secures the inner tube in
the tube mount. A manual actuator is coupled to the rear end of the
frame. The manual actuator includes a first manual actuator
operable to move the outer tube carrier along the frame, a second
manual actuator operable to move the inner tube carrier along the
frame, and a third manual actuator operable to impart rotation of
the inner tube about the axis.
[0031] According to another aspect, an active cannula robot for
performing a surgical operation on a patient. The robot includes an
active cannula comprising an outer tube and an inner tube that
extends coaxially within the outer tube. A frame supports the
active cannula. An actuator actuates the active cannula to cause
translational movement of the outer and inner tubes along the axis.
An emergency release mechanism is manually operable to decouple the
outer and inner tubes from the actuator to permit manual retraction
of the tubes.
[0032] According to a further aspect, an active cannula robot for
performing a surgical operation on a patient includes an active
cannula comprising an outer tube and an inner tube that extends
coaxially within the outer tube. A frame supports the active
cannula. An actuator actuates the active cannula to cause
translational movement of the outer and inner tubes along the axis.
A retainer is manually operable to permit swapping inner tubes
during the surgical operation without disturbing the remaining
components of the robot.
DRAWINGS
[0033] The invention may be best understood by reference to the
following description taken in conjunction with the accompanying
drawing figures in which:
[0034] FIG. 1 is a schematic illustration of an active cannula
robot system, according to an aspect of the invention.
[0035] FIGS. 2 and 3 are perspective views of an active cannula
robot that forms a portion of the system of FIG. 1.
[0036] FIG. 4 is a side elevation view of the active cannula
robot.
[0037] FIG. 5 is a top plan view of the active cannula robot.
[0038] FIGS. 6 and 7 are partially exploded perspective views of
the active cannula robot.
[0039] FIGS. 8-10 are detail views illustrating a sterilization
feature of the active cannula robot.
[0040] FIG. 11 is a perspective view illustrating an emergency
release feature of the active cannula robot.
[0041] FIG. 12 is a schematic illustration of the system of FIG. 1
illustrating an alignment feature of the system.
[0042] FIGS. 13A-13F illustrate a torque transmitting feature of
the active cannula robot.
[0043] FIGS. 14A and 14B are schematic illustrations that depict
certain parameters of the active cannula robot.
[0044] FIGS. 15A-15C are schematic illustrations that depict an
alignment feature of the active cannula robot system.
[0045] FIGS. 16A and 16B illustrate an embodiment of the active
cannula robot system incorporating manual controls.
[0046] FIGS. 17A-17C illustrate methods according to the
invention.
DESCRIPTION
[0047] The invention relates generally to concentric tube robots.
According to one aspect, the invention relates to a system, method,
and apparatus for configuring, designing, and operating an active
cannula robot to perform a surgical operation. The active cannula
robot has a straight outer tube and a retractable, curved inner
tube. The system is operable to perform a robotic surgical
operation on a target at a work site in a patient. The system is
also operable to design and configure the curved inner tube of the
robot to have a workspace tailored to the target of the surgical
operation based on scanned image data related to the target. In one
particular implementation of the invention, the system designs and
configures the robot to have a workspace tailored to the shape,
location, and orientation of an ICH clot, and operates the robot to
perform the image guided evacuation of the ICH clot.
[0048] Through the invention, an active cannula configuration that
provides optimal coverage for a particular target, such as an ICH
clot, can be identified and implemented. By "optimal," it is meant
to describe the identification of the configuration that is
best-suited under the given circumstances to provide the required
therapy. Thus, the optimal configuration may not necessarily be the
one that provides the best coverage of the target. Other factors,
such as patient risk can affect the determination of what is
"optimal" under the circumstances. For example, a neurosurgeon may
determine that a configuration that covers the largest portion of a
target may pose too large a risk to warrant its use and therefore
could opt for a different configuration that lessens the risk but
that also reduces coverage of the target. In the ICH clot removal
scenario, choosing a configuration that may not cover the largest
possible area of the clot not in order to reduce the risk of
damaging adjacent brain tissue could nonetheless be considered the
optimal configuration.
[0049] The active cannula robot system of the invention can be used
to perform a wide variety of surgical operations on a target at a
worksite in a patient. Therefore, any characterization of the robot
herein as an ICH clot evacuation robot is not meant to be limiting,
but instead merely illustrative of one particular implementation
selected from the wide variety of implementations to which the
system is applicable. In this description, the term "clot" is used
to refer to the collection of blood resulting from an ICH, which
can also be referred to interchangeably as a "hematoma." Also, in
this description, the term "debulking" is used to refer to the
removal of the clot, which can also be referred to interchangeably
as "evacuating" the clot.
Concentric Tube Robot System
[0050] FIG. 1 illustrates an example of a robotic system 10 that
can be used to treat a target at a worksite in a patient 12. In an
example implementation, the system 10 can be used in a
neurosurgical implementation in which the target is a clot 116
resulting from an ICH. The system 10 includes a concentric tube
robot 20 mounted on a passive articulated support arm 22. For the
example neurosurgical implementation described herein, a trajectory
guide 24 is attached to the patient's skull 14 and is used to guide
the robot 20 along a desired trajectory. A reference frame 26 is
rigidly attached to the robot 20 and is used to track movement of
the robot relative to the patient 12 via an image guidance and
monitoring system. 38. The support arm 22, trajectory guide 24 and
reference frame 26 help maintain the robot 20 at a specific
predetermined position and orientation relative to the target, e.g.
the ICH clot 16, in the patient 12. The position and orientation
are determined through image mapping of the patient 12, and the
position, orientation, and shape of the target in the patient, to
place the robot 20 in a position relative to the patient suited to
treat the clot with the robot 20.
[0051] The system 10 includes a controller 66 that performs two
basic functions: 1) performing cannula tube design/selection
algorithms, and 2) controlling the operation of the robot 20 to
perform a surgical operation. For simplicity, the controller 66
described herein performs both of these functions. In one
implementation, the controller 66 includes a computer 66a and a
motor controller 66b (see FIG. 1). The computer 66a alone can
perform the tube selection algorithms described herein, and can
interface with the motor controller 66b to control operation of the
robot as described herein. These functions could be separated,
however, and the system 10 could, for example, include one computer
for performing the tube design/selection algorithms and another
different computer for controlling operation of the robot 20.
[0052] The computer 66a can be any suitable computerized device
having processing and memory capabilities sufficient to perform the
functions described herein. For instance, the computer 66a can be a
desktop computer, notebook computer, or an application specific
machine that, combines the computer and motor control functionality
of the system 10. The components of the controller 66, i.e., the
computer 66a and the motor controller 66b, can be adapted for wired
or wireless communication.
[0053] In an example implementation, the computer 66a is a personal
computer (e.g., an Intel.RTM. Pentium-based PC) and a standard
motor controller that the computer interfaces. The motor controller
66b can be a standard motor controller or amplifier, such as a
Galil.RTM. DMC Series motor controller/amplifier, which is
manufactured by and commercially available from Galil Motion
Control, Inc. of Rocklin, Calif. In this implementation, the
computer 66a can be connected motor controller 66b via a wired
Ethernet connection.
[0054] In this arrangement, the high-level motor control
calculations are performed by the computer 66a using custom
software applications generated using commercially available
software, such as Matlab.RTM. (Mathworks, Inc. of Natick, Mass.)
and/or a compilable programming language such as C or C++. These
high-level algorithms generate robot control instructions in the
form set points, indicating desired motor positions, that are sent
to the controller 66b. The controller 66b can perform low-level
control functions (e.g., closed loop PID control) and generate
amplified signals to drive the motors to the set points received
from the computer 66a.
[0055] Those skilled in the art will appreciate that the
design/selection calculations and robot control algorithms
described herein can be implemented in a wide variety of manners
incorporating the use of various computer and motor control
equipment. These description of the controller 66, the computer
66a, and the motor controller 66b are meant in no way to limit
those options.
[0056] Referring generally to FIGS. 2-7, according to one aspect of
the invention, the robot 20 includes two concentric tubes--an outer
tube 40 and an inner tube 50 which, together, can be referred to
herein as an active cannula 30. The outer tube 40 is a straight,
stiff tube made of stainless steel. The outer tube 40 can act as a
needle and therefore can be referred to as a "needle tube" or
"straight needle" component of the active cannula 30. The inner
tube 50 has a precurved distal end portion 52 and is made of a
superelastic material, such as a nickel-titanium alloy ("nitinol").
The inner tube 50 can be operatively connected to an aspirator 28
and therefore can serve as and be referred to as an "aspiration
tube" of the active cannula 30.
[0057] The inner tube 50 is retractable into the outer tube 40. As
the curved end 52 of the inner tube 50 enters and passes through
the outer tube 40, it straightens as it conforms to the shape of
the outer tube. Due to the superelastic characteristics of its
nitinol construction, the curved end 52 returns to its curved
configuration as it exits the from the distal end of the outer tube
50. The active cannula 30 has a tip 32 defined by the terminal
distal end or tip of the inner tube 50. In its use for ICH
evacuation, the tip 32 can be referred to as an aspiration tip.
[0058] The robot 20 can be capable of controlling three degrees of
freedom ("3 DOF") of the active cannula 30 through individual
control of the concentric tubes 40 and 50. For instance, the robot
20 can control insertion, retraction, and rotation of the inner
tube 50. Since the outer tube 40 is a straight needle, the ability
to control its rotation is not important, so the robot 20 may be
configured to control only its translational movement (i.e., its
insertion and retraction) along the longitudinal axis 18 of the
robot 20 and active cannula 30. In the example implementation, the
outer tube 40 is configured to act as a needle and proceed along a
straight path to deliver its tip to the location of the ICH. Once
the outer tube 40 is positioned at the ICH location, the inner tube
can be systematically inserted, retracted, and rotated robotically
to move the tip 32 through the clot so that the clot can be
debulked via suction applied by the aspirator 28.
[0059] The robot 20 includes an actuation unit 60 in which the
active cannula 30 is mounted and an actuation unit in the form of a
motor assembly or pack 150 that is connectable with the actuation
unit at a rear or "motor" end 62 thereof. The motor pack 150 is
operable to apply the motive force for individually actuating the
concentric tubes 40, 50 to control movement of the active cannula
30, which extends outward from an opposite front or "robot" end 64
of the actuation unit 60.
[0060] The actuation unit 60 includes a frame 70 that has a
generally box-shaped configuration. A rear plate 72 defines the
rear end of the frame 70 and the motor end 62 of the actuation unit
60. A front plate 74 defines the front end of the frame 70 and the
robot end 64 of the actuation unit 60. First and second rails 76,
78 extend between and interconnect the front and rear plates 72, 74
to thereby form the frame 70. The longitudinal axis 18 of the robot
20 extends longitudinally through the actuation unit 60, parallel
to the rails 76, 78 and coaxially through the concentric tubes 40,
50 of the active cannula 30.
[0061] The outer tube 40 includes a hollow tubular structure that
forms an inner lumen of the straight needle in through which the
inner tube 50 extends. A hub 44 is secured to a proximal end
portion of the outer tube 40 opposite the distal surgical end. 48
of the tube. The inner tube 50 includes a hollow tubular structure
that forms the cannula tube. A gear 58 is sandwiched between two
hubs 56, all of which are secured to a proximal end portion of the
inner tube 50 opposite the distal, surgical curved end portion 52
of the tube.
[0062] The actuation unit 60 includes an outer tube carrier 80 that
is attached or otherwise connected to the first rail 76 for sliding
movement along the first rail in opposite directions parallel to
the axis 18. The movement of the outer tube carrier 80 along the
first rail 76 can be facilitated by a suitable bushing or bearing
structure. The outer tube carrier 80 includes a driver block 82
through which a first shaft 84 extends. The first shaft 84 has
opposite end portions that are mounted or otherwise secured to the
end plates 72, 74 by means, such as bushings or bearings, that
permit the shaft to rotate. A portion of the first shaft 84 has
outer (male) threads that cooperate with inner (female) threads on
the driver block 82 so that rotation of the shaft imparts linear
movement of the driver block, and thus the outer tube carrier 80,
along the first rail 76. The direction that the outer tube carrier
80 travels is dictated by the direction in which the first shaft 84
rotates.
[0063] The outer tube carrier 80 includes a transversely extending
support plate 90 that includes a tube mount 92 for receiving and
supporting the outer tube 40. In the example embodiment of FIGS.
2-7, the tube mount 92 includes a recess 94 for receiving the hub
44 of the outer tube 40 and a retainer plate 96 for securing the
hub in the recess. The retainer plate 96 can be secured by known
means, such as threaded fasteners. When secured in the tube mount
92, the outer tube 40 is positioned extending along the axis 18.
The outer tube 40, secured to the outer tube carrier 80 is thus
moveable with the carrier along the axis 18 in response to
rotational movement of the first shaft 84.
[0064] The actuation unit 60 also includes an inner tube carrier
100 that is attached or otherwise connected to the second rail 78
for sliding movement along the second rail in opposite directions
parallel to the axis 18. The movement of the inner tube carrier 100
along the second rail 78 can be facilitated by a suitable bushing
or bearing structure. The inner tube carrier 100 includes a driver
block 102 through which a second shaft 104 extends. The second
shaft 104 has opposite end portions that are mounted or otherwise
secured to the end plates 72, 74 by means, such as bushings or
bearings, that permit the shaft to rotate. A portion of the second
shaft 104 has outer (male) threads that cooperate with inner
(female) threads on the driver block 102 so that rotation of the
shaft imparts linear movement of the driver block, and thus the
inner tube carrier 100, along the second rail 78. The direction
that the inner tube carrier 100 travels is dictated by the
direction in which the second shaft 104 rotates.
[0065] The inner tube carrier 100 includes a pair of spaced,
parallel, transversely extending support plates 110, each of which
include a tube mount 112 for receiving and supporting the inner
tube 50. The tube mounts 112 are axially aligned with each other.
Each mount 112 includes a recess 114 for receiving one of the hubs
56 of the inner tube 50. One or both of the mounts 112 includes a
retainer 116, such as a plate, for securing its associated hub 56
in the recess. One such retainer plate 116 can be sufficient to
secure the inner tube 50 to the inner tube carrier 100. The
retainer plate 116 can be secured by known means 118, such as
threaded fasteners, e.g., screws. When the inner tube 50 is secured
in the tube mounts 112, the gear 58 is positioned between the
support plates 110.
[0066] When the inner tube 50 is secured in the tube mounts 112, it
is also positioned extending along the axis 18 and can thereby be
positioned coaxially within the inner lumen of the outer tube 40.
The inner tube 50, secured to the inner tube carrier 100, is thus
moveable with the carrier along the axis 18 in response to
rotational movement of the second shaft 104. The inner tube 50 is
also rotatable relative to the inner tube carrier 100 when secured
in the tube mounts 112. The inner tube 50 can thus be rotated via
the gear 58. The outer tube carrier 80 and inner tube carrier 100
together carry the active cannula 30.
[0067] A third shaft 120 has opposite end portions that are mounted
or otherwise secured to the end plates 72, 74 by means, such as
bushings or bearings, that permit the shaft to rotate. The third
shaft 120 extends through the support plates 110, adjacent the
inner tube 50. The support plates 110 include guides 122, such as
bearings, through which the third shaft 120 extends. The guides 122
receive stabilize the third shaft 120 radially, while permitting
rotation of the shaft relative to the support plates 110 and also
permitting the support plates to move linearly relative to the
shaft along its length. To accomplish this, the third shaft 120
can, for example, have a non-circular (e.g., square) cross-section,
and the guides 122 can have a bearing structure in which their
inner rings have a corresponding non-circular opening through which
the third shaft extends. In this configuration, the guides 122 can
slide freely over the third shaft 120 when the support plates 110
move longitudinally, while their bearing structures simultaneously
support the shaft for rotation.
[0068] The third shaft 120 includes a gear 124 that is positioned
between the support plates 110 and that engages the gear 58 of the
inner tube 50. Rotation of the third shaft 120 thus imparts
rotation to the inner tube 50. The gear 124 is fixed to the third
shaft 120 in a manner such that it rotates with the shaft while at
the same time is free to slide axially along the length of the
shaft. The gear 124 can, for example, have a non-circular (e.g.,
square) opening that corresponds with the aforementioned
non-circular cross-section of the third shaft 120 without being
fixed to the shaft. Due to this configuration, the gear 124 can
slide freely along the length of the third shaft 120, which allows
it to maintain its engagement with the gear 58 as the inner tube
carrier 100 moves along the length of the actuation unit 60. By
maintaining this engagement, the gear 124 can impart rotation to
the gear 58 to rotate the inner tube 50 at any axial position of
the inner tube carrier 100. In fact, this configuration can allow
the third shaft 120 to maintain its ability to impart rotation to
the inner tube 50 even while the inner tube carrier 100 and the
inner tube 50 itself is moving axially.
[0069] The motor pack 150 includes a first motor 152 for actuating
the first shaft 84, a second motor 154 for actuating the second
shaft 104, and a third motor 156 for actuating the third shaft 120.
The motors can be of any desired configuration, such as a brushless
DC stepper motor configuration. The motors 152, 154, 156 are
mounted on one side of a motor plate 210, and each include a
respective motor coupling 160 that extends through and protrudes
from an opposite side of the plate. A mechanism 164 such as latch,
lock, or fastener(s), secure the motor pack 150 to the actuation
unit 60 by interconnecting the motor plate 210 to the rear plate
72. Connecting the motor pack 150 to the actuation unit 60 engages
the motor couplings 160 with their respective shafts to thereby
couple the motors 152, 154, 156 to the shafts 84, 104, 120. In one
example, the motor couplings 160 can be respective portions of
Oldham couplings, which are well known in the art as being shaft
couplings that are simple, secure, and reliable.
[0070] The motor pack 150 is operable to actuate the active cannula
30. The first motor 152 is operable to control insertion and
retraction of the outer tube 40. The second motor 154 is operable
to control insertion and retraction of the inner tube 50. The third
motor 156 is operable to control rotation of the inner tube 50.
[0071] The actuation unit 60 is designed to be both sterilizable
and biocompatible. The actuation unit 60 is constructed entirely
from autoclavable and biocompatible components. All of the
materials used to construct the actuation unit 60 are either
biocompatible polymers (e.g., Ultem.RTM. or PEEK.RTM.), stainless
steel (which would be passivated before clinical use), aluminum
(which would be anodized before clinical use), or nitinol (in the
case of the inner tube 50). The hubs 46, 56 and the gear 58 are
secured to their respective tubes 40, 50 using a biocompatible and
autoclavable bonding agent or glue (e.g., Loctite.RTM., M-21 HP
medical device epoxy agent). All of these materials can withstand
sterilization in an autoclave.
[0072] Referring to FIGS. 8-10, the motor pack 150 also includes a
bag ring 130 for securing a sterile bag 132 to the motor plate 210.
With the sterile bag 130 connected as shown in. FIG. 8, the shafts
84, 104, 120 are left exposed for connection with the motor
couplings 160. As shown in FIG. 10, cover plates 166 can be slid
over the motor couplings 160 and secured to the motor plate 210 so
as to create a tortuous path P (see FIG. 10) between the
non-sterile motor pack 150 in the sterile bag 132 and the sterile
actuation unit 60.
[0073] The sterile bag 132 in combination with the tortuous path P
created by the cover plates 166 can provide a sterility barrier
that is sufficient to permit use of the robot 20 in a surgical
environment such as an operating room. To set up the robot 20 in
the operating room. The actuation unit 60, including the robot
tubes 40, 50, are first autoclaved to sterilize the unit. The
sterile bag 132 is attached to the motor pack 150 using the bag
ring 130, the motor couplings 160 are coupled to the shafts 84,
104, 120, the motor pack 150 is attached via the motor plate 210,
and the cover plates 166 are installed. The sterile bag 132 is then
pulled over the motor pack 150 and sealed using means, such as
sterile tape. The motor pack 150 is thereby isolated from the
sterilized actuation unit 60.
Inner Tube Hot-Swap Feature
[0074] According to one aspect, the robot 20 includes a
quick-release "hot-swap" feature that allows for interchangeably
installing inner tubes 50 having different features, such as
curvature, radius, stiffness, or a combination of these features,
during a robotic surgical procedure without dismantling or
de-constructing the robot 20 and without disturbing the arrangement
of the system 10 and the position/orientation of the robot with
respect to the patient 12. Owing to the configuration of the inner
tube carrier 100, specifically the tube mounts 112, the inner tube
50 can be released for removal and replacement by removing a
fasteners 118 and pivoting or removing the retainer plates 116. The
inner tube 50 can first be retracted fully so that the tube can
flex as it is removed from the outer tube 40.
[0075] To insert another inner tube 50, its curved end 52 is
inserted into the inner lumen 44 of the outer tube 40 from the
proximal end adjacent the gear 56 and advanced until the hubs 56
come into alignment with the mounts 112 in the support plates 110.
The hubs 56 are placed in the mounts 112, the retainer plates 116
are placed back into position, and the fasteners 118 are
reinstalled to secure the inner tube 40 in the mounts. In a
configuration where the fasteners 118 are thumb screws, the removal
of the retainer plates 116 is provides convenient and expedient.
Alternative means, such as a manually actuated latching mechanism,
could also be used.
Emergency Release Feature
[0076] Referring to FIG. 11, according to another aspect, the robot
20 includes an emergency release feature that allows for the quick
removal of both the inner tube 50 and the outer tube 40. The driver
block 82 is secured to the outer tube carrier 80 by releasable
fastening means 88, such as a thumb screw. The driver block 102 is
secured to the inner tube carrier 100 by releasable fastening means
108, such as a thumb screw. The thumb screws 88, 108 provide a
convenient and expedient means by which to disengage the driver
blocks 82, 102 from the carriers 80, 100. The thumb screws 88, 108
could have alternative configurations, such as alternative threaded
fasteners or a manually actuated latching mechanism. In an
emergency situation where the robot 20 needs to be retracted from
the patient 12 quickly, the thumb screws 88, 108 are operated to
disengage the driver blocks 82, 102 from the carriers 80, 100. This
decouples the tube carriers 80, 100 from the shafts 84, 104, which
allows the carriers to slide freely along the rails 76, 78. The
tubes 40, 50 can then be retracted manually from the patient 12 in
a quick and efficient manner simply by manually sliding the
carriers 80, 100 along the rails 76, 78.
Image Guided Positioning
[0077] The system 10 can incorporate an image guidance system 38 to
position the robot 20 relative to the patient 12. This positioning
is described herein as it relates to the example implementation in
which the system 10 is used to evacuate an ICH clot. Those skilled
in the art will appreciate that similar procedures can be performed
where the system 10 is used to perform other procedures.
[0078] Prior to the ICH clot removal procedure, computed tomography
(CT) medical images of the patient and the ICH are acquired.
Registration is accomplished using a surface scan of the patient's
face, which is then matched to the corresponding surface in the CT
image volume. A reference frame 42 mounted to the patient's skull
allows the image guidance system 38 to monitor the position and
alignment of the patient 12, specifically the patient's head and
the clot 16. Since the active cannula 30 is introduced onto the
patient's brain with the inner tube 50 retracted, the delivery of
the straight needle tube 40 is essentially identical to delivery of
a biopsy needle. This being the case, known conventional image
guided neurosurgical systems presently used to align and introduce
straight biopsy needles can also be used to align and introduce the
active cannula robot 20. One example of a known image guidance
system 38 that can be used to align and monitor the active cannula
robot 20 is a StealthStation.RTM. system using Navigus.RTM. biopsy
hardware, which is available commercially from Medtronic, Inc.,
USA. Other commercially available image guidance systems can be
used. The reference frame 26, which is attached to the robot 20,
can be adapted to work with the chosen image guided neurosurgical
system in order to facilitate monitoring the position and alignment
of the robot.
[0079] Referring to FIG. 1, the trajectory guide 24 includes a
trajectory stein 170 that is mounted on the patient's skull and
through which the active cannula 30 extends. The trajectory stem
170 is selected to work in conjunction with the image guidance
system 38 and therefore can be in the form of custom or proprietary
hardware specifically designed for use with the image guidance
system. The trajectory stem 170 can, for example, be one that is
included. In the aforementioned Navigus.RTM. line of neurosurgical
biopsy hardware. The trajectory stein 170 defines the path or
trajectory along which the active cannula 30 extends from the robot
20 through the skull and into the brain.
[0080] in use, the robot 20 is positioned relative to the patient
12 so that the active cannula 30 extends along the axis 18 through
the trajectory stem 170 (see FIG. 1). The trajectory stem 170 is
configured to connect with a base 172 that is connectable with the
patient's skull, e.g., via screws. A locking ring 174 facilitates
the connection between the trajectory stein 170 and the
skull-mounted base 172 so that the trajectory stem can direct the
active cannula 30, with the inner tube 50 retracted into the outer
tube 40 through the base and into the patient's skull along the
desired trajectory.
[0081] To set up and align the system 10, the surgeon first creates
a hole in the skull, opens the dura to expose the brain, and
attaches the base 172 to the skull, e.g., using screws. The
trajectory stem 170 is then snapped into the base 172 and loosely
secured with the locking ring 174. An alignment probe 178, which
enables visualization of the insertion trajectory via the chosen
image-guidance system, is inserted into the trajectory stem 170.
Image guidance is used to align the trajectory stem 170 by pivoting
the stem in the base 172 until the trajectory of the stein is
aligned with the desired. ICH clot target 16. The locking ring 174
is then tightened to fix the position of the trajectory stem 170,
after which the alignment probe can be removed.
[0082] Next, the robot 20, attached to the support arm 22, is moved
into the surgical field, and the front plate 74 of the actuation
unit 60 is coupled to the trajectory stein 170 by means, such as a
bracket/clamping mechanism 54. The robot 20 can then be operated to
move the active cannula 30 through the trajectory stem 170 along
the desired trajectory into the brain. The robot 20 can be
operated, for instance, to first insert the outer tube 40 into the
brain to position its tip at the ICH location or in the ICH itself.
Then, the robot 20 can be operates to insert and/or rotate the
inner tube 50 in the ICH to remove the clot. During operation of
the robot 20, the insertion, retraction, and rotation of the tubes
40, 50 can be monitored using CT medical imaging via the reference
frame 26.
Active Trajectory Maintaining Configuration
[0083] The trajectory stern 170 can have an alternative
configuration that facilitates maintaining the alignment of the
robot 20 with the skull-mounted base 172. The weight and size of
the robot 20 is large enough that a misalignment between the
trajectory stem 170 and the base 172 could result in the
application of excessive forces to the bone screws 190 which mount
the base to the skull. Referring to FIGS. 15A-15D, the trajectory
stem 170 and the base 172 can include an active alignment system
180 that ensures proper alignment between the stem and base without
applying undue stress to the bone screws 190.
[0084] This active alignment system 180 could replace the locking
ring with a predetermined number of sensors 182 spaced radially
about the axis 18 and connected to the trajectory stem 170. For
example, the alignment system 180 could include three sensors 182,
spaced at 120.degree. intervals about the robot axis 18. The
sensors 182 are configured to deflect in response to a misalignment
between the robot 20 and the trajectory stem 170. In the embodiment
illustrated in FIGS. 15A-15C, the sensors 182 comprise plunger
elements 184 that engage a flange 186 that extends radially outward
from and perpendicular to the trajectory stem 170. Each sensor 182
is configured to produce a signal representative of the deflection
of the sensor, in this case the plungers 184. The plungers 184
could, for example, include a strain gauge having a resistance
changes in response to strain and therefore can be used to produce
a signal representative of the amount of deflection undergone by
the sensor 182. Alternatively, the plungers 184 could actuate a
variable resistance element, e.g., a rheostat, having a resistance
changes in response to strain and therefore can be used to produce
a signal representative of the amount of deflection undergone by
the sensor 182.
[0085] When the robot 20 and the trajectory tube 170 are correctly
aligned (see FIG. 15A), the plungers 184 engage the flange 186 and
deflect to an equal extent, producing similar or identical
deflection signals. The differential between the sensor signals is
indicative of any misalignment (see FIG. 15B). If three sensors 182
are used, these signal differentials can be used to
calculate/triangulate the direction and magnitude of the
misalignment. This misalignment magnitude and direction can be
displayed visually, e.g., via the controller 66 (computer 66a) in
real time, so that adjustments can be made with visual
feedback.
[0086] Once a misalignment is identified measures should be made to
relieve the stresses on the interface of the base 172 with the
skull due to the misalignment. One possible solution would be a
robotic base (replacing the support arm 22) which could actively
move or position the robot 20 to prevent or remedy a misalignment.
Instead of mounting the robot 20 on a rigid, fixed, passive support
arm 22, the robot could itself' be mounted on an active positioning
mechanism 184 that can adjust the position of the robot to maintain
the trajectory of the active cannula 30, e.g., via servo motors.
The sensors 182 could be used as inputs to a controller that is
configured to control the operation of the positioning mechanism
184. In use, the robot 20 could be initially aligned via manual
control of the positioning mechanism 184. The inputs from the
sensors 182 could then be used as a setpoint that the controller
could maintain via closed loop control of the positioning mechanism
184. In this manner, the proper trajectory can be maintained
without compromising the connection of the base 174 to the skull
14.
[0087] An alternative solution is shown in FIG. 15C. In this
alternative, the robot 20 includes a would be a set of padded arms
192 extending from the robot to the skull 14. These padded arms 192
would stabilize the robot 20 with respect to the skull 14. The
padded arms 192 could be anchored to the skull 14 via a series of
straps 194 that extend around the skull. In this manner,
misalignment forces between the robot and skull would be
distributed over a large area of the skull 14 by the padded arms
192 instead of the small area of the bone screws 190 that attach
the base 172 to the skull. The axial position of the padded arms
192 can be adjustable to control the misalignment detected via the
sensors 182. These adjustments could be active, i.e., computer
controlled via the controller 66 operatively connected to
appropriate servo motors 196 to minimize the stress/maintain proper
robot alignment in response to the sensor 182 signals, or
adjustable manually, e.g., via knobs.
Alternative Torque Transmission Configuration
[0088] In certain scenarios, it may be necessary to position the
actuation mechanism 60 a significant distance from the work space.
The inner tube 50 can be considered to include two basic sections:
a working end that performs the ICH evacuation and a transmission
section that translates and rotates the working end. The working
end of the inner tube 50 is the curved end portion 52, which is
purposely constructed of an inherently flexible material due to
manner in which it is utilized in the operation of the active
cannula 30. The transmission section is simply the portion of the
inner tube 50 that extends from the curved portion 52 to the
actuator assembly 60. As described previously, the transmission
section can be constructed of the same material that is used to
construct the working end and therefore has the same inherent
flexibility.
[0089] During use of the active cannula 30, inner tubes 50 with
larger curvatures of the working section produce higher torques on
the transmission section when the tube is rotated. This can lead to
torsional windup in the transmission section of the inner tube 50.
Torsional windup is undesirable because it distorts the shape of
the inner tube 50, which can introduce uncertainty in the operation
of the active cannula 30. Torsional windup can lead to a reduced
workspace for the inner tube 50 because excessive windup in the
tube limits the curvatures that can be implemented. Ideally, the
transmission section would be rigid in order to avoid these
problems.
[0090] According to one aspect of the invention, referring to FIGS.
13A-13F, a transmission tube assembly 220 couples the active
cannula 30 to the actuator assembly, i.e., the motor pack 150 via
the tube carriers 80, 100. The transmission tube assembly 220
includes an outer transmission tube 222 and an inner transmission
tube 224. The inner transmission tube 224 is positioned coaxially
within the outer transmission tube 222. An outer tube coupler 230
is fixed to the distal end of the outer transmission tube 222 and
couples the outer tube 40 to the outer transmission tube. An inner
tube coupler 232 is fixed to the distal end of the inner
transmission tube 224 and couples the inner tube 50 to the inner
transmission tube. The transmission tube assembly 220 is configured
such that the inner tube 224 can slide or telescopes axially within
the outer tube 222 and can also rotate about the axis 18 relative
to the outer tube.
[0091] In this configuration, the inner transmission tube 224 can
be adapted to include the gear 58 and hubs 56 that facilitate
connection of the inner transmission tube to the inner tube carrier
100 of the actuation unit 60. Similarly, the outer transmission
tube 222 can be adapted to include the hub 44 that, facilitates
connection of the outer transmission tube to the outer tube carrier
80 of the actuation unit 60. These connections can be facilitated,
for example, by features such as a key-receiving slot 236 or a pin
receiving hole 238 machined or otherwise formed in the proximal
ends of the outer and inner transmission tubes 222, 224.
[0092] The outer and inner transmission tubes 222, 224 can
therefore be actuated by the actuation unit 60 in the same manner
that the outer and inner tubes 40, 50 in the configuration of the
robot 20 illustrated in FIGS. 2-7. The outer and inner tubes 40, 50
of the active cannula 30, being coupled to the outer and inner
transmission tubes 222, 224, respectively, can thus be translated
and/or rotated by the actuation mechanism 60. In this
configuration, the active cannula 30, including the outer tube 40
and inner tube 50, extend from the distal end of the transmission
tube assembly 220. Thus, the robot 20 shown in FIGS. 2-7, fit with
the transmission tube assembly 220, can deliver and operate the
active cannula 30.
[0093] Robot Design and Configuration
[0094] The curved inner tube 50 can have any desired curvature, as
long as that curvature is one which can be straightened completely
with a maximum material strain that remains within the elastic
range of nitinol, i.e., approximately 8-10%. Within these
constraints, virtually any desired curvature can be achieved
through the use of known heat treatment processes. For any given
curvature, a workspace exists. The workspace associated with a
curvature of an inner tube is the space that can be reached with
the tip of that particular curved tube. The workspace of the inner
tube 50 thus corresponds to the shape of the target that the active
cannula 30 can access. In the example ICH clot removal
implementation of the robot 20, the workspace of an inner tube 50
thus corresponds with the shape of the ICH clot that can be
evacuated with that particular tube.
[0095] According to the invention, knowing the predefined curvature
of the inner tube 50, the controller 66 can compute the shape of
the workspace for that particular tube using a mechanics-based
model. This model can be evaluated for different tube
configurations to determine the workspace for that particular tube
configuration. According to one aspect of the invention, given
image data related to a surgical target, the controller 66 can
design one or more tube configurations by solving the kinematic
model systematically through a discrete set of tube parameters to
identify the parameters of the tube or set or tubes that provide a
desired or optimal degree coverage of the target. According to
another aspect of the invention given an active cannula 30 with a
finite set of inner tubes 50 each having a different pre-curved
configuration and corresponding workspace, the controller 66 can
evaluate the kinematic model and compare the calculated workspace
to the image data of the target to select, the tube or tubes from
the subset that provide a desired or optimal degree coverage of the
target.
[0096] In the illustrated implementation, the controller 66 can use
the kinematic model to determine the configuration(s) of the inner
tube(s) 50 so that the workspace of the active cannula 30 can treat
an ICH clot. For clots with complex geometries, there may not be a
combination of inner tubes 50 that offers a combined workspace
capable of complete clot removal. Because of this, two or more
inner tubes 50 with different curve configurations can be selected
so that their combined workspace covers the required area to as
complete an extent as conditions permit. For these multi-tube
scenarios, the active cannula robot 20 is ideally suited to leave
the outer tube 40 positioned "in situ" at the worksite while inner
tubes 50 are hot-swapped and used sequentially.
[0097] Regardless of the implementation, to model the active
cannula 30 the three degrees of freedom of the straight outer tube
40 and the circularly pre-curved inner tube 50 are parametrized
using the variables .rho..sub.1 and .rho..sub.2 to describe the
linear insertion distance of the outer and inner tubes,
respectively. The angle .alpha. describes the axial angle (i.e.,
the angle of rotation about the axis 18) of the inner tube 50.
Thus, the joint space of the active cannula 30 is q=(.rho..sub.1,
.rho..sub.2, .alpha.).
[0098] Referring to FIG. 14A, the inner tube 50 is composed of an
initial straight section with length Ls followed by a planar
constant curvature section with length Lc with radius r. When the
inner tube 50 is inserted into the outer tube 40, there are three
regions to model kinematically, with lengths l.sub.1, l.sub.2,
l.sub.3 see FIG. 14B). The mapping from joint space to
configuration space parameters describing the curve of the
robot(i.e., "arc parameters,") is as follows:
1 = .rho. 1 ##EQU00001## 2 = { .rho. 2 - .rho. 1 - Lc if .rho. 2 -
.rho. 1 > LC 0 else 3 = { Lc if .rho. 2 - .rho. 1 > Lc .rho.
2 - .rho. 1 else .kappa. 3 = r - 1 . ##EQU00001.2##
[0099] These parameters define a forward kinematic model for the
active cannula 30, T=T.sub..alpha. T.sub.12 T.sub.3, where:
T a = [ cos .alpha. - sin .alpha. 0 0 sin .alpha. cos .alpha. 0 0 0
0 1 0 0 0 0 1 ] ; ##EQU00002## T 1 2 = [ 1 0 0 0 0 1 0 0 0 0 1 1 +
2 0 0 0 1 ] ; and ##EQU00002.2## T 3 = [ 1 0 0 0 0 cos ( .kappa. 3
3 ) - sin ( .kappa. 3 3 ) cos ( .kappa. 3 3 ) - 1 .kappa. 3 0 sin (
.kappa. 3 3 ) cos ( .kappa. 3 3 ) sin ( .kappa. 3 3 ) - 1 .kappa. 3
0 0 0 1 ] ##EQU00002.3##
[0100] For the circularly curved inner tube configurations modeled
above, the parameters available for design are the curvature and
arc length of the inner tube 50, such that a given design is
defined as d={Lc, r}.
[0101] Medical image data, such as CT image data, can be used to
evaluate the extent to which an active cannula 30 having a given
configuration has a workspace that conforms to or covers a given
target. For example, the CT medical image data that is routinely
acquired during the diagnosis of an ICH can registered, segmented
using software such as 3D Slicer.TM. (an open-source platform
available for download at www.slicer.org). Segmentation can be used
to identify the open space between the brain and the skull and also
the boundary of the target (ICH). An image model (volume or
surface) of the patient's skull, brain and the ICH clot is thereby
obtained. The neurosurgeon can then identify on the model the
location where the cannula will enter the patient (e.g., the burr
hole in the skull) and the location on the ICH clot where the inner
tube 50 will enter the clot. The position of the ICH can be mapped
relative to the model of the skull.
[0102] The joint space of the active cannula 30 (q=(.rho..sub.1,
.rho..sub.2, .alpha.)) can be processed into discrete counterparts
and, from this, the workspace of the active cannula 30 can be
computed by evaluating or solving the kinematic model for each
discrete combination of joint positions. The computed workspace is
compared to the image data of the target (e.g., segmented ICH clot
image data) to determine the degree to which the two overlap. The
degree of overlap is indicative of the extent to which the active
cannula 30 having that particular configuration can cover the
target. Making this determination requires knowledge of the
position and orientation of the target and the accessible
trajectories through which the target can be reached. This
information is provided by the surgeon, as described above.
[0103] In the example implementation, comparing the workspace to
the image data of the target determines the extent to which the ICH
clot can be evacuated by the active cannula 30 incorporating an
inner tube 50 having the configuration evaluated by the kinematic
model. In the ICH clot removal implementation, making this
determination requires knowledge of the entry point on the
patient's skull and the trajectory of the active cannula 30, which
are determined by the surgeon as the shortest or otherwise best
path along which to reach the target ICH while compromising as
little brain structure as possible.
[0104] To evaluate the ability of an active cannula 30 having an
inner tube 50 with a particular configuration to cover a target of
a given shape, a volumetric objective tube selection function was
formulated. To formulate this function, the model of the target is
converted to a discrete set of isotropic volume elements or
"voxels". Voxels inside and outside the target are differentiated
using a binary voxel representation. The objective tube selection
function for target (e.g., ICH clot) coverage (d) is defined as the
percentage of the total clot volume that is accessible by the tip
of the active cannula 30 having that particular inner tube 50
configuration.
[0105] The portion of the cannula workspace volume that lies within
the target V(d) is generated for each d by discretizing the joint
space of the active cannula 30 robot and computing the cannula tip
position for each combination of joint values. This can be done,
for example, with 1 mm translational and 1.degree. rotational
increments. A secondary evaluation can be used to determine whether
the entire curve of the inner tube 50 is positioned within the
target, and joint value combinations in which any portion of the
inner tube 50 is positioned outside the clot can be discarded.
[0106] For example, to discretize the joint space of the active
cannula 30, the inner tube 50 can be advanced 1 mm and, at this
translational position, rotated through 360 1.degree. increments,
with the position of the tip 32 being calculated at each position.
The secondary evaluation of whether the entire curve of the inner
tube 50 is positioned within the target can be evaluated at every
position. Once all 360 tip positions are evaluated, the inner tube
50 can be advanced another 1 mm increment and the rotational
calculations and secondary evaluations repeated.
[0107] Each computed cannula tip position is evaluated to determine
whether it lies within a voxel of the target model. The voxels that
contain tip points are labeled as covered voxels, and those that
remain are labeled as uncovered. The percentage of the clot covered
can be computed by dividing the total number of target voxels by
the number of covered voxels. This process can be repeated with
different inner tubes 50 having different tip configurations to
determine which tube or combination of tubes provides the ideal
target coverage removal percentage. This process can be repeated
for various entry points, trajectories, and inner tube
configurations of the robot 20. Through this evaluation, the system
10 can be used to determine the ideal inner tube configurations for
covering the target. In the example implementation, the system 10
can be used to determine the ideal entry point, trajectory, and
combination of inner tube configurations for covering the ICH
clot.
Inner Tube Selection Method
[0108] From the above, those skilled in the art will appreciate
that, according to one aspect, the invention relates to a method
for determining the optimal design(s) or configuration(s) for the
curved inner tube of a concentric tube active cannula robot. These
optimal designs can then be shaped or otherwise manufactured and
subsequently used to perform the surgical procedure custom tailored
to the target. This method, however, requires the luxury of time,
which may not be available depending on the circumstances.
[0109] According to another aspect, the invention can also relate
to a method for selecting from an existing set of pre-configured
tubes a subset of those tubes that provides a workspace for
covering a target that is optimal given the circumstances.
According to this aspect, a predetermined set of pre-configured
inner tubes 50 (e.g., a set of 5, 10 or more tubes) that vary in
configuration is made available to the surgeon. Using the kinematic
model evaluation approach described above, one or more of the tubes
can be selected to provide an active cannula 30 with a workspace
that covers the target to the extent possible, given the
circumstances. This eliminates the need for time to shape or
otherwise manufacture the inner tubes.
[0110] According to a further aspect, in a combination of these
approaches, the set of pre-configured tubes can be identified
through a pre-surgery evaluation in which the kinematic model is
evaluated and compared to the image data of the target as described
above. Then, during surgery, the kinematic model evaluation can be
executed to determine which of the pre-configured tubes to use for
the actual procedure. In this manner, the pre-surgery evaluation
can take into account factors, such as trajectories, access (burr
hole) locations, and even slight changes in clot shape/size, that
can vary depending on changing patient conditions or unforeseen
complications.
Tube Selection Method
[0111] From the above, those skilled in the art will appreciate
that the invention relates to a method for identifying tube
parameters of a curved tube of an active cannula for operating on a
target in a patient. The methods, which can be implemented by the
controller 66, including the computer 66a, are illustrated in FIGS.
17A-17C. Those skilled in the art will appreciate that the steps
illustrated and described herein sequentially, could be performed
in different orders or simultaneously.
[0112] Referring to FIG. 17A, a method 300 for identifying tube
parameters a curved tube of an active cannula for operating on a
target in a patient includes the step 302 of acquiring a model of
the patient anatomy including the target. The method 300 also
includes the step 304 of selecting a set of parameters
characterizing a curved tube. The method 300 also includes the step
306 of computing a workspace for an active cannula having the
selected curved tube parameters. The method 300 also includes the
step 308 of comparing the workspace to the anatomical model to
determine the degree to which an active cannula having the selected
curved tube parameters can cover the target. The method 300 also
includes the step 310 of repeating steps 304, 306, and 308 through
a defined number of curved tube parameter sets. The method 300 also
includes the further step 312 of identifying the curved tube
parameters that provide an active cannula with an optimal degree of
target coverage.
[0113] FIG. 17B illustrates step 306 of method 300. The step 306 of
computing a workspace includes the step 320 of mapping the joint
space parameters of the active cannula to configuration space
parameters in order to define a forward kinematic model for the
active cannula. The step 306 also includes the step 322 of
discretizing the joint space of the active cannula to produce a
discrete set of joint positions of the active cannula. The step 306
includes the further step 324 of solving the kinematic model for
each discrete combination of joint positions to compute the
workspace of the active cannula.
[0114] FIG. 17C illustrates step 308 of method 300. The step 308 of
comparing the computed workspace to the clot model comprises the
step 330 of converting the target model to a discrete set of
voxels. The step 308 also includes the step 332 of computing a tip
position for each of the joint positions of the active cannula. The
step 308 includes the further step 334 of evaluating each computed
cannula tip position to determine whether it lies within a voxel of
the target model.
DEMONSTRATIVE EXAMPLES
[0115] To evaluate the effectiveness of the system 10 in the
example ICH clot removal implementation, a study was performed
utilizing CT data sets from seven patients previously treated for
an ICH. For each case, a neurosurgeon selected a desired entry
path, and for each path all possible aspiration tube sets were
evaluated and calculated using the objective tube selection
function described above. Tube parameters used in the objective
tube selection function were defined as follows: [0116] Inner tubes
50 were considered to have an outer diameter of 1.14 mm and an
inner diameter of 0.91 mm. [0117] A 10% recoverable strain
threshold was used. [0118] The curved section length. Lc was first
discretized in 5 mm steps starting at 10 mm. Then, the same
procedure was used with a finer resolution of 2 mm. [0119] Minimum
and maximum radii of curvature were 6.4 and 150 mm, respectively,
with 2.5 mm discretization within this range.
[0120] For selection of the optimal aspiration tube(s), four
scenarios of use were considered. For each scenario, the tables
shown below illustrate the optimal tube choice(s) selected by the
objective function across both the 5 mm and 2 mm
discretizations.
Scenario 1: Single Aspiration Tube
[0121] In this first scenario, the active cannula 30 was only
permitted to have one inner tube 50, which was required to remain
within the clot at all times. For each patient case, the tube
curvature and arc length that, maximizes coverage of the hematoma
(f)was computed as:
f*=arg max f(d);
with results summarized below in Table 1.
TABLE-US-00001 TABLE 1 SUMMARY OF OPTIMAL ASPIRATION TUBES FOR
SCENARIO 1 Case l.sub.c R f* 1 108 17.19 66% 2 85 13.53 71% 3 50
10.46 85% 4 75 11.94 68% 5 70 11.14 88% 6 55 13.75 61% 7 65 10.35
75%
[0122] For each case, Table 1 shows the ideal configuration for the
inner tube 50 given the single tube, remain totally within the clot
requirements of Scenario 1. While the single tube level of coverage
illustrated in Table 1 exceeds a 25-50% minimum coverage target,
two other scenarios of use were considered in order to provide
additional options for the neurosurgeon if increased coverage is
desired. These scenarios are described and illustrated in the
following paragraphs.
[0123] Scenario 2: Single Aspiration Tube With Brain
Deformation
[0124] In this scenario, the requirement that the entire curved
tube remains inside the clot at all times was relaxed, instead
permitting small lateral deflection of the active cannula tip 32 at
the surface of the clot up to some threshold (t.sub.d). This is
done by positioning the tip of the outer tube 40 outside of and
away from the exterior bounds of the ICH clot and then advancing
the inner tube 50 so that the tip 32 is permitted to deflect off
axis 18 up to threshold t.sub.d prior to entering the clot. By
doing this, the volume of clot accessible to a single constant
curvature aspiration tube can be increased significantly because
the volume of the clot adjacent the outer tube 40 can be evacuated.
The results of this scenario are shown below in Table 2.
TABLE-US-00002 TABLE 2 SUMMARY OF OPTIMAL ASPIRATION TUBES FOR
SCENARIO 2 Case L.sub.c R t.sub.d f* 1 120 19.10 14.90 93% 2 80
17.73 10.59 94% 3 110 17.51 9.09 99% 4 80 12.73 3.42 88% 5 80 12.73
7.02 98% 6 60 29.63 15.00 98% 7 60 44.63 15.00 100%
[0125] For each case, Table 2 shows the ideal configuration of the
inner tube 50 and the allowed deflection outside the ICH clot. Note
that, in Scenario 2, the maximum t.sub.d was limited to 15 mm. The
amount of permissible t.sub.d is in general based on the preference
of the specific surgeon using the system. If t.sub.d is set to
zero, then Scenario 2 is identical to Scenario 1. Note also that
one could also can achieve a similar result without any deflection
outside the ICH clot and therefore without cutting brain tissue by
first deploying the inner tube 50 within the clot, and then
retracting the outer and inner tubes 40, 50 simultaneously.
Scenario 3: Two Aspiration Tubes in Succession
[0126] In this scenario, a configuration of the active cannula 30
was sought that maintains the high coverage achieved in. Scenario 2
while eliminating the need for brain deflection (t.sub.d). This
configuration is achieved by selecting two inner tubes 50 with
different curvatures (d.sub.1, d.sub.2), which will be used
sequentially via the hot-swap feature. After the first inner tube
50 has evacuated all of the clot it is able to reach, it is removed
with the outer tube 40 remaining in place in the patient's brain so
that the system 10 maintains registration. The second inner tube 50
is introduced to remove additional clot material not accessible by
the first inner tube. The goal is to choose the parameters of the
two tubes simultaneously, such that the overall volume of the clot
removed is maximized, as follows:
f*=arg max(f(d.sub.1).andgate.f(d.sub.2));
with the results shown below in Table 3.
TABLE-US-00003 TABLE 3 SCENARIO 3: SEQUENTIAL USE OF TWO ASPIRATION
TUBES WITH COMBINED COVERAGE f* Case L.sub.c R f L.sub.c R f f* 1
70 16.14 67% 60 9.55 57% 86% 2 60 17.05 66% 55 8.75 62% 87% 3 45
12.16 82% 40 6.37 65% 94% 4 80 12.73 67% 45 7.16 60% 87% 5 60 12.05
87% 45 7.16 60% 87% 6 60 14.54 60% 55 8.75 49% 78% 7 40 11.37 73%
40 6.36 63% 90%
[0127] For each case, Table 3 shows the best combination of inner
tubes 50, their respective coverage percentages, and their combined
coverage percentages. The similarity in curvatures of both tubes
across all cases is noteworthy, as is the high overall volume of
clot removed. To determine how well a single set of two tubes could
work across all patients, the optimization was ran again seeking to
maximize the average coverage across all patients with a single set
of tubes. This resulted in a first tube with L.sub.c=58 mm, r=13.23
mm and a second tube with L.sub.c=40 mm, r=6.37 mm. This tube set
enables an average coverage of 79% across all patients, with a
minimum of 60% and a maximum of 95%.
Scenario 4: Discrete Tube Set
[0128] This scenario evaluated the performance of a fixed set of
five tubes (radii of curvature: 6, 8.5, 11, 13.5, and 16 mm), where
the radii were chosen to span the optimal tube curvatures of
Scenario 3. A perturbed entry path in which the path deviated from
the optimal path was also evaluated. For the optimal path, the five
tubes used in sequence were shown to be capable of removing an
average of 95%, as shown below in Table 4:
TABLE-US-00004 TABLE 4 SCENARIO 4: SEQUENTIAL USE OF FIVE
PRESELECTED TUBES AND INFLUENCE OF ENTRY PATH PERTURBATION Case
Optimal Entry Path f* Perturbed Entry Paths min f* 1 92% 60% 2 94%
85% 3 98% 97% 4 96% 57% 5 100% 95% 6 92% 32% 7 95% 95%
[0129] In the fourth scenario, a perturbation study was performed
due to the fact that there can be some uncertainty in burr hole
placement and also in targeting the desired clot entry point. In
considering the level of error that can be expected in clinical
use, it should be noted that the accuracy of the Navigus.RTM.
components used by the present system 10 to target the ICH location
in the brain has been experimentally found to be 1 mm with a
standard deviation of 0.28 mm. It should also be noted that the
surgeon will have access to image-guidance when selecting the burr
hole location and, thus, in principle should be able to place the
burr hole at the desired location approximately as accurately as
internal skull points can be targeted (i.e., the same
image-guidance system is used for both purposes).
[0130] A conservative level of error of a little over three
standard deviations was introduced with a maximum burr hole error
of 2.5 mm and a maximum clot entry point error of 2 mm. The burr
hole error was set slightly higher than the clot targeting error to
account for the fact that the surgeon may be slightly more careful
in internal point targeting than in burr hole placement. The worst
case needle angular misalignment within these bounds occurs when
both burr hole error and clot entry error simultaneously deviate
maximally from the planned locations, and do so in the worst
possible direction, i.e., worst with respect both to one another,
and with respect to clot geometry. This is a conservative worst
case scenario, considering that since the errors are likely
Gaussian in nature, it is statistically unlikely that both errors
would be maximal simultaneously, let alone in the worst possible
direction. Considering this case provides a useful lower bound on
worst case scenario clot coverage.
[0131] In this scenario, 25 perturbation cases were generated for
each of the seven patient cases by considering all combinations of
five evenly angularly distributed points at a radial distance of
2.5 mm on the skull surface around a planned burr hole location and
five evenly angularly distributed points at a radial distance of 2
mm around the planned clot entry point. Table 4 shows the minimum
clot volume coverage across all patient and perturbation cases. It
can be concluded from this study that if surgeons are correct in
their estimate that decompression benefit begins when 25-50% of the
clot is removed, it is statistically improbable that a small number
of discrete tubes will be incapable of accessing the requisite
geometry.
In Vitro Phantom Material
[0132] To further explore the practical feasibility of
robot-assisted ICH clot evacuation using a single tube with allowed
tissue deflection (see Scenario 2), an experiment was conducted in
simulated (sometimes referred to as "phantom") brain material. The
inner aspiration tube used had a straight section with Ls=260 mm
followed by a section with constant curvature of r=30.3 mm with
Lc=55 mm. The aspiration tube had an outer diameter of 1.75 mm and
a wall thickness of 0.3 mm. The outer tube had an outer diameter of
3.2 mm and a wall thickness of 1 mm.
[0133] The experiment was conducted using gelatin as both a
simulated brain tissue and ICH clot. In this experiment, simulated
brain tissue was made using 10% by weight clear Knox gelatin
(available commercially from Kraft Foods Global, Inc., USA), and
the simulated clot was made with red Jell-O gelatin. The simulated
clot was softer than the simulated brain tissue. The simulated ICH
was approximately spherical with a 63.5 mm diameter.
[0134] The trajectory stem 170 was aligned with the clot and
secured using the locking ring 174. The robot 20 was then affixed
to the passive arm 22 and attached to the trajectory stem 170. The
active cannula 30 was then inserted into the clot, with the inner
tube 50 retracted fully inside the outer tube 40, and the tubes
were then used to evacuate the clot. Motion planning was conducted
manually by the experimenter who visually observed the debulking
process through the wall of the phantom brain tissue and input new
desired target locations to the robot manually using the computer
keyboard. The robot 20 was able to remove 92% of the clot material,
determined by initially measuring the amount of red gelatin used.
The surface of the clot was visually inspected for positive margins
and none were detected. The residual simulated clot material left,
after the end of the experiment was collected and weighed. The
achieved results are similar to the 99% theoretical coverage of
this clot discussed above in regard to Scenario 2. The system 10
could have removed more of the simulated clot material at the
clot-brain interface if there had been less concern with damaging
the simulated healthy brain tissue. This could have been done, for
example, by increasing the allowable t.sub.d (see Table 2).
In Vitro Skull Experiment
[0135] An in vitro experiment was performed using an anatomically
correct skull model to experimentally demonstrate the system 10
under conditions similar to those in patient case 1 of Scenario 3.
To replicate the geometry of patient case 1, a two-piece
semi-transparent plastic skull which was filled with gelatin to
simulate brain tissue. A gelatin model of the segmented clot from
patient case 1 was suspended in the brain tissue gelatin at a
position and orientation similar to that of patient case 1. Barium
was added to the clot gelatin to enable visualization of the clot
in the CT image.
[0136] The nitinol inner tubes 50 used in this experiment were
modeled after those listed in Table 3 for patient case 1, although
the tubes relaxed slightly as they were removed from the heat
treatment fixture, so the resulting radii of curvature were 19.8
min and 12.6 mm. The robot 20 was aligned with the entry path
selected by an experienced neurosurgeon, in a manner similar or
identical to those discussed previously. Because the skull was not
completely transparent, the top of the skull was removed after the
robot was aligned to enable visualization of the tubes in the clot.
Motion planning, robot position commands, and determination of the
removed clot volume were implemented in the same or a similar
manner to that described above in the in vitro phantom
experiment.
[0137] The robot 20 was able to remove 83.1% of the clot, measured
in a manner identical to the manner described above in the in vitro
phantom experiment. Based on the curvatures of the experimental
tubes, the expected clot removal percentage was 80.6% (using the
actual 19.8 mm and 12.6 mm radii). The fact that the experimental
results slightly exceeded the theoretical prediction can be
attributed to minor tissue deformation as suction was applied.,
which brings more material within reach of the cannula tip. Note
that deformation also is likely to be present in human brain
tissue, so the theoretical percentages described herein (which
consider only rigid geometry) may be conservative.
Robot Operation and Control--Evacuating the ICH Clot
[0138] Having determined the optimal configuration for the inner
tube or tubes 50 for evacuating a particular ICH clot in accordance
with the methods described above, the system 10 can be operated to
remove an ICH clot. Because the inner tube(s) 50 are selected based
on CT image data of the ICH clot, and because the active cannula
robot 20 is registered for surgery using the image guidance system
38, the workspace of the active cannula 30 will coincide with the
shape, location, and orientation of the clot. The clot can
therefore be evacuated by applying suction to the inner tube 50 and
moving the tip 32 of the tube systematically through the workspace.
To accomplish this, the robot 20 can be operated manually by the
surgeon with real time monitoring via the image guidance system 38
or automatically by the controller 66.
[0139] Manual operation can be performed in a pure manual mode
(described below) or teleoperatively. To perform the surgery in a
teleoperative manual mode, the surgeon uses the controller 66 to
command low level movements of the robot. Through this
teleoperative manual control, the surgeon inserts the active
cannula 30 with the inner tube 50 retracted so that the outer
(needle) tube 40 can enter the brain via the trajectory guide 170
to reach the ICH location. At the ICH location, the surgeon can
operate the active cannula 30 via controller commands to
progressively insert and rotate the inner tube 50 in the clot while
applying suction to evacuate the clot, while monitoring the image
guidance system to maintain the tip 32 within the clot.
[0140] In a pure manual mode, the motor pack is replaced with
manual controls 200 as shown in FIGS. 16A and 16B. The controls 200
include manual actuators in the form of wheels 202 and 204 that are
linked to the shafts 84, 104, respectively and are thereby
rotatable to cause insertion and retraction of the outer tube 40
and inner tube 50, respectively. The controls 200 also include a
manual actuator in the form of a knob 206 that is linked to the
shaft 120 and is thereby rotatable to cause rotation of the inner
tube 50 about the axis 18.
[0141] To perform the surgery in the pure manual mode, the surgeon
uses the manual controls 200 to command movements of the active
cannula 30. Through manual manipulation of the wheels 202, 204, the
surgeon inserts the active cannula 30 with the inner tube 50
retracted so that the outer (needle) tube 40 can enter the brain
via the trajectory guide 170 to reach the ICH location. At the ICH
location, the surgeon can operate the active cannula 30 via the
manual controls 200 to progressively insert (wheel 204) and rotate
(knob 206) the inner tube 50 in the clot while applying suction to
evacuate the clot, while monitoring the image guidance system to
maintain the tip 32 within the clot.
[0142] The robot 20 can also perform the surgery automatically
under open loop control in which the controller 66 operates the
robot to actuate the cannula 30 according to instructions "learned"
by the controller during the execution of the objective tube
selection function. Since the execution of this function
necessarily determines which of the discretized positions of the
inner tubes) 50 fall inside the clot and which fall outside the
clot, these determinations can serve as a guide or map for
operating the robot 20 in an open loop control scheme to
automatically evacuate the Such automatic control can, of course,
be monitored in real time by the surgeon via the image guidance
system 38. This open loop automatic robot control can also be
broken down into steps or increments that the surgeon can initiate
manually, one step at a time, to evacuate the ICH clot.
[0143] The foregoing has described a system, method, and apparatus
for image guided evacuation of a hematoma resulting from an
intracerebral hemorrhage using a robotic active cannula. While
specific embodiments of the invention have been described, it will
be apparent to those skilled in the art that various modifications
thereto can be made without departing from the spirit and scope of
the invention. For example, while the embodiments described herein
have related to an active cannula configuration with a single
curved tube, those skilled in the art will appreciate that some or
all of these features are applicable to multi-curved tube
configurations. Accordingly, the foregoing description of the
invention is provided for the purpose of illustration only and not
for the purpose of limitation.
* * * * *
References