U.S. patent application number 10/091742 was filed with the patent office on 2002-11-14 for simulation system for image-guided medical procedures.
This patent application is currently assigned to Johns Hopkins University School of Medicine. Invention is credited to Anderson, James H., Brody, William R., Cai, Yiyu, Chui, Chee-Kong, Ma, Xin, Nowinski, Wieslaw L., Wang, Yaoping.
Application Number | 20020168618 10/091742 |
Document ID | / |
Family ID | 26956404 |
Filed Date | 2002-11-14 |
United States Patent
Application |
20020168618 |
Kind Code |
A1 |
Anderson, James H. ; et
al. |
November 14, 2002 |
Simulation system for image-guided medical procedures
Abstract
This invention provides a system and method for computer
simulation of image-guided diagnostic and therapeutic procedures
such as vascular catheterization, angioplasty, stent, coil and
graft placement, embolotherapy and drug infusion therapy. In a
particularly preferred aspect, the system is configured to resemble
a cardiovascular catheterization laboratory where interventional
radiology procedures are performed. A first user can interactively
manipulate therapeutic catheters, guidewires and other medical
devices in real-time while viewing patient-specific medical image
data sets in a manner similar to that encountered in a clinical
procedure.
Inventors: |
Anderson, James H.;
(Columbia, MD) ; Brody, William R.; (Baltimore,
MD) ; Chui, Chee-Kong; (Singapore, SG) ; Ma,
Xin; (Singapore, SG) ; Wang, Yaoping;
(Singapore, SG) ; Cai, Yiyu; (Singapore, SG)
; Nowinski, Wieslaw L.; (Singapore, SG) |
Correspondence
Address: |
DIKE, BRONSTEIN, ROBERTS AND CUSHMAN,
INTELLECTUAL PROPERTY PRACTICE GROUP
EDWARDS & ANGELL, LLP.
P.O. BOX 9169
BOSTON
MA
02209
US
|
Assignee: |
Johns Hopkins University School of
Medicine
Baltimore
MD
|
Family ID: |
26956404 |
Appl. No.: |
10/091742 |
Filed: |
March 5, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60273733 |
Mar 6, 2001 |
|
|
|
60273734 |
Mar 6, 2001 |
|
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Current U.S.
Class: |
434/262 |
Current CPC
Class: |
A61F 2002/067 20130101;
G09B 23/285 20130101; Y10S 623/901 20130101; A61F 2/07 20130101;
G16H 50/50 20180101 |
Class at
Publication: |
434/262 |
International
Class: |
G09B 023/28 |
Claims
What is claimed is:
1. A system for simulating movement of a medical device in a body
cavity or lumen of a patient, comprising: (a) a medical device
comprising a first end for manipulation by a user and a portion
comprising a second end insertable into a simulated body cavity or
body lumen in a manikin; (b) a manikin comprising an interface for
receiving the portion comprising the second end and for interfacing
with a simulated body cavity or lumen within the manikin, wherein
the interface comprises a directional force feedback mechanism for
exerting a directional force on the medical device in response to a
feedback signal received by the force feedback mechanism.
2. The system according to claim 1, wherein the directional force
feedback mechanism provides resistance to forward motion but
enables free reverse motion in response to the feedback signal.
3. The system according to claim 1, wherein the directional force
feedback mechanism comprises a rolling element coupled to the
portion of the device comprising the second end and wherein an
internal surface of the simulated cavity or lumen in the manikin
comprises an oblique slot for receiving the rolling element.
4. The system according to claim 3, wherein, in response to a
feedback signal, forward movement of the second end causes the
rolling element to be received by the slot, thereby causing
resistance to further forward motion.
5. The system according to claim 4, wherein a motor controls
movement of the rolling element.
6. The system according to claim 1, further comprising a tactile
feedback mechanism.
7. The system according to claim 6, wherein the tactile feedback
mechanism provides continuous vibrational feedback to a user
holding the medical device.
8. The system according to claim 8, wherein continuous vibrational
feedback is provided through a continuously rotating motor in
communication with the portion of the device comprising the second
end.
9. The system according to claim 1, wherein a position of at least
the second end of the medical device relative to the manikin is
continuously tracked.
10. The system according to claim 9, wherein the medical device
comprises an encoder for tracking the translation of the device and
an encoder for tracking the rotation of the device.
11. The system according to claim 9, wherein the system further
comprises a tracking unit comprising a light source, a signal
processing circuit, and one or more optical sensors, wherein the
tracking unit is placed within the interface in optical
communication with the device when it is inserted into the cavity
or lumen.
12. The system according to claim 11, wherein light from the light
source reflects on the device when inserted and wherein the
reflected light is received by the one or more optical sensors.
13. The system according to claim 12, wherein changes in reflected
light received by the one or more sensors is detected by the
system, and wherein, in response to this detection, the system
simulates movement of the device in real-time on the user
display.
14. The system according to claim 12, wherein two optical sensors
are provided which are perpendicular to one another.
15. The system according to claim 12, wherein the tracking unit is
configured in the form of a rail along which the device can
move.
16. The system according to claim 10, wherein one or more
additional medical devices comprising a first end for manipulation
by a user and a portion comprising a second end for insertion into
the simulated body cavity or body lumen, are inserted into the
interface and wherein the position of each medical device is
independently monitored.
17. The system according to claim 16, wherein the one or more
medical devices are selected from the group consisting of a
catheter, guidewire, endoscope, laparoscope, bronchoscope, stent,
coil, balloon, a balloon-inflating device, a surgical tool, a
vascular occlusion device, optical probe, a drug delivery device,
and combinations thereof.
18. The system according to claim 1, further comprising a table for
placing the manikin thereon, wherein the table comprises a
processor connectable to the network.
19. The system according to claim 18, wherein the system further
comprises at least one first user device connectable to the
network, the first user device comprising a first display interface
for displaying a three-dimensional representation of a simulated
body cavity or lumen of a patient.
20. The system according to claim 19, wherein the first display
interface further displays a three-dimensional representation of a
medical device corresponding to a medical device which is
interfaced with the manikin and wherein the system simulates on the
display the movement of the medical device within the simulated
body cavity or lumen of the manikin in real-time when a first user
manipulates the medical device interfaced with the manikin.
20. The system according to claim 19, further comprising a
simulated scanning display for displaying a two-dimensional image
of the simulated body cavity or lumen.
21. The system according to claim 20, wherein the simulated
scanning display is part of a simulated scanning device.
22. The system according to claim 21, wherein the simulated
scanning device is simulating an x-ray imaging system.
23. The system according to claim 21, wherein the simulated
scanning device and scanning display are coupled to a movable C-arm
within scanning distance of the manikin.
24. The system according to claim 1, further comprising a
re-configurable control panel for performing one or more of: image
acquisition selection; image display; manipulating a table on which
the manikin is placed; manipulating the position of a simulated
scanning device relative to the manikin; and control of one or more
shutter devices for limiting a field of view of a scanning device
placed within scanning distance of the manikin.
25. The system according to claim 1 or 20, further comprising a
monitoring station, the monitoring station comprising a second user
device connectable to the network and comprising a second display
interface for enabling a second user to monitor the movement of the
medical device within the simulated body cavity or lumen.
26. The system according to claim 25, wherein the second display
interface of the monitoring station displays selectable options
enabling the second user to select or change one or more anatomical
and/or physiological parameters of the simulated body cavity or
lumen, and wherein the selection causes the three-dimensional image
of the simulated body cavity or lumen displayed to the first user
to change to reflect the changed anatomical and/or physiological
parameters.
27. The system according to claim 20, wherein the system is
connectable to a database of patient images and/or medical
data.
28. The system according to claim 25, wherein the system is
connectable to a database of patient images and/or medical
data.
29. The system according to claim 27, wherein the patient images
comprise images of a body cavity or lumen from a patient affected
by a pathology.
30. The system according to claim 28, wherein the patient images
comprise images of a body cavity or lumen from a patient affected
by a pathology.
31. The system according to claim 21, further comprising at least
one foot-activation switch for activating or collimating the
simulated scanning device, image display or table movement
33. The system according to claim 27, wherein the first user
display interface provides access to the database and wherein, in
response to accessing, the system displays an image and/or medical
data on the first user display interface.
34. The system according to claim 27, wherein the second user
display interface provides access to the database and wherein, in
response to accessing, the system displays an image and/or medical
data on the second user display interface.
35. The system according to claim 33, wherein the second user
display interface provides access to the database and wherein, in
response to accessing, the system displays an image and/or medical
data on the second user display interface.
36. The system according to claim 35, wherein the second user
display interface provides a selectable option enabling a second
user to display the image displayed on the second user display
interface, on the first user's display interface.
37. The system according to claim 1, wherein the device is selected
from the group consisting of a catheter, guidewire, endoscope,
laparoscope, bronchoscope, stent, coil, balloon, a
balloon-inflating device, a surgical tool, a vascular occlusion
device, optical probe, a drug delivery device, and combinations
thereof.
38. A syringe for simulating fluid delivery, comprising: a housing
defining a lumen comprising an opening for delivering a fluid; a
pushing element for pushing the fluid through the opening; a
friction-producing element in communication with the pushing
element; and a motor in communication with the friction-producing
element and comprising a signal-receiving element, wherein the
friction-producing element causes friction between the pushing
element and a surface of the lumen of the housing upon activation
by the motor in response to a signal received by the
signal-receiving element.
39. The syringe according to claim 38, wherein the motor, when
activated, causes motion of the friction-producing element, thereby
causing the friction-producing element to contact the surface of
the lumen of the housing, creating friction between the pushing
element and the surface of the lumen and resistance to the motion
of the pushing element.
40. The syringe according to claim 38, wherein the
friction-producing element comprises one or more rubber pads.
41. The syringe according to claim 40, wherein each rubber pad is
coupled to an arm whose movement is controlled by the motor.
42. The syringe according to claim 41, wherein each arm is coupled
to the motor through a gear attached to the motor.
43. The syringe according to claim 38, wherein the amount of
friction produced by the friction-producing element is adjusted by
controlling a rotation angle of the motor.
44. The system according to claim 1, further comprising the syringe
of claim 38, wherein opening of the syringe is connectable to a
connecting piece having a first end for receiving fluid from the
opening and a second end for delivering fluid to a simulated body
cavity or body lumen in the manikin.
45. A balloon-inflating device for simulating deployment of a
balloon within a body cavity or lumen of a patient, comprising: a
delivery mechanism for controlling delivery of fluid through the
balloon-inflating device to the balloon; a pressure sensor for
monitoring pressure of a fluid delivered to the balloon by the
balloon-inflating device; an electrical pressure meter for reading
pressure determined by the pressure sensor, the electrical pressure
meter being connectable to a processor and for transmitting a
signal corresponding to a pressure value to the processor.
46. The system according to claim 1, further comprising the
balloon-inflating device of claim 45.
47. The system according to claim 20, wherein the system simulates
deformation of the body cavity or lumen by the medical device.
48. The system according to claim 20, wherein the system simulates
an operation of a medical device selected from the group consisting
of: a surgical procedure, inflation or deflation of a balloon,
injection of a radioopaque material into the body cavity or lumen,
and combinations thereof.
49. The system according to claim 20, wherein the system simulates
the movement of the device within a blood vessel.
50. The system according to claim 49, wherein the blood vessel is
in the brain.
51. The system according to claim 50, wherein the blood vessel is
in the heart.
52. A method for simulating the movement of a medical device in the
body cavity or lumen of a patient, comprising: providing a medical
device comprising a first end for manipulation by a user and a
portion comprising a second end inserted into a simulated body
cavity or body lumen in a manikin, wherein the simulated body
cavity or lumen in the manikin comprises a directional force
feedback mechanism, and wherein, in response to a feedback signal,
the directional force feedback mechanism creates resistance to
forward motion of the medical device but allows free reverse
motion.
53. The method according to claim 52, further comprising: providing
a system comprising: a processor in communication with the
directional force feedback mechanism, the processor connectable to
the network; and a first user device in communication with the
processor, the first user device comprising a first display
interface for displaying a representation of a body cavity or
lumen; and for providing access to a database of three-dimensional
images of body cavities and lumens from a plurality of different
patients; and enabling a user to select from the database a
representation, wherein in response to the selection, the
representation is displayed on the first display interface.
54. The method according to claim 52, wherein the first display
interface a displays a three-dimensional representation of the
medical device and wherein the system simulates the movement of the
medical device within the body cavity or lumen in real-time as a
first user manipulates the medical device which is interfaced with
the manikin.
55. The method according to claim 52 or 53, further comprising
providing a monitoring station comprising a second display
interface in communication with the processor and the first display
interface, and wherein the second display interface provides a
second user with access to the database.
56. The method according to claim 54, wherein when a second user
selects a representation from the database, the representation is
displayed on both the first and second display interface.
57. The method according to claim 53, wherein the system simulates
the deformation of a body cavity or lumen in response to movement
of the medical device by the first user and displays the
representation of the deformation on the first display
interface.
58. The method according to claim 53, wherein the medical device
performs an operation on the simulated body cavity or lumen and the
first display interface displays a simulation of the operation.
59. The method according to claim 58, wherein the operation is
inflation or deflation of a balloon within the simulated body
cavity or lumen.
60. The method according to claim 58, wherein the operation is
injection of a radioopaque fluid within the body cavity or
lumen.
61. The method according to claim 52, wherein the device is
selected from the group consisting of a catheter, guidewire,
endoscope, laparoscope, bronchoscope, stent, coil, balloon, a
balloon-inflating device, a surgical tool, a vascular occlusion
device, an optical probe, a drug delivery device, and combinations
thereof.
62. The method according to claim 54, wherein a first user inserts
one or more additional medical devices into the simulated body
cavity or lumen, and the movement of each medical device is
independently monitored.
63. The method according to claim 52, wherein the simulated body
cavity or lumen in the manikin further comprises a tactile feedback
mechanism, providing continuous vibrational feedback to a first
user manipulating the device.
64. A method for simulating fluid delivery into a body cavity or
lumen of a patient comprising: (a) providing a syringe for
simulating fluid delivery, the syringe comprising: a housing
defining a lumen comprising an opening for delivering a fluid; a
pushing element for pushing the fluid through the opening; a
friction-producing element in communication with the pushing
element; and a motor in communication with the friction-producing
element and comprising a signal-receiving element, wherein the
friction-producing element causes friction between the pushing
element and a surface of the lumen in response to a signal received
by the signal receiving element; and (b) providing a signal,
thereby causing friction between the pushing element and the
lumen.
65. A method for simulating deployment of a balloon within a body
cavity or lumen of a patient, comprising: (a) providing a
balloon-inflating device, comprising: a delivery mechanism for
controlling delivery of a fluid through the balloon-inflating
device to the balloon; a pressure sensor for monitoring pressure of
a fluid delivered to the balloon by the balloon-inflating device;
an electrical pressure meter for reading pressure determined by the
pressure sensor and for transmitting a signal corresponding to a
pressure value to a processor; (b) providing a system comprising: a
processor for receiving the signal, the processor connectable to
the network; and a user device comprising an interface displaying a
representation of the balloon within a simulated body cavity or
lumen; and (c) delivering the fluid to the balloon; wherein
deployment of the balloon in response to the delivering is
displayed on the user device.
66. The method according to claim 65, wherein the fluid is air.
67. The method according to claim 65, wherein the method is used to
simulate balloon angioplasty.
68. The method according to claim 65, further comprising providing
the system according to claim 1, inserting a balloon catheter into
the simulated body cavity or lumen to simulate navigating to a
target region of the body, and simulating positioning the balloon
deployment device in proximity to the balloon catheter to inflate
or deflate the balloon.
69. The method according to claim 67, further comprising inserting
a catheter and guidewire into the body cavity or lumen to navigate
the balloon cavity to the target region.
70. The method according to claim 67, further comprising inserting
a stent catheter to navigate to a target region and using the
balloon to deploy the stent, thereby simulating stent deployment in
the body cavity or lumen.
71. The method according to claim 68, further comprising inserting
a catheter or guidewire into the body cavity or lumen to navigate
the stent catheter to the target region.
72. A method for simulating coil embolization in a body cavity or
lumen of a patient, comprising: providing a catheter, guidewire and
coil wire comprising a coil to navigate to a target region of the
body; providing the system according to claim 19, wherein the
re-configurable control panel provides a selectable option for
detaching the coil from the coil wire, and wherein selecting the
selectable option triggers the release of the coil from the coil
wire.
73. The method according to claim 72, wherein an electrical current
triggers release of the coil from the coil wire.
Description
RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn.
119(e) to U.S. Provisional Application 60/273,733, and to U.S.
Provisional Application Serial No. 60/273,734, both filed Mar. 6,
2001, the entireties of which are incorporated by reference
herein.
FIELD OF THE INVENTION
[0002] The invention relates to a system and method for simulating
image-guided medical procedures, particularly those relying on
interventional and/or diagnostic devices such as catheters.
BACKGROUND OF THE INVENTION
[0003] Interventional radiology provides an alternative to open
field surgery. Interventional radiology began as a discipline for
diagnosing and treating vascular disease (e.g., such as narrowing
of the arteries). The interventional radiologist typically uses a
catheter inserted into a blood vessel through a puncture in the
skin to gain internal access to the vascular system. Using medical
imaging guidance, the catheter is navigated to a target site (e.g.,
such as the site of a diseased tissue) where it can be used as a
conduit through which to pass therapeutic devices. Minimally
invasive procedures relying on interventional radiology, including
lapraroscopic surgery, cardiovascular interventional radiology, and
neurointerventional radiology, have tremendous potential to reduce
patient discomfort, complications, hospital stays, post-procedural
recovery time and total medical costs.
[0004] However, despite the advantages described above, minimally
invasive procedures also pose risks. Failure to properly navigate,
orient or position catheters and/or other devices within a patient,
or failure to properly recognize an anatomic area or pathology to
be treated may result in serious injury to a vein, artery, organ,
or other internal tissue structure.
[0005] Interventional radiologists must perform the delicate
eye-hand coordinated movements needed to navigate catheters and
therapeutic devices while viewing scanned images of the patient's
body cavities or lumens on a flat TV screen. The images are
obtained from X-rays, CAT scans, MRI scans, and the like. Depth
perception is lacking and it is difficult to learn to control the
instruments through the spatially arbitrary linkage. A mistake in
this environment can be dangerous. Without performing the procedure
often, there is no way for practitioners to maintain the high
degree of skill needed to perform these procedures. It is also
impractical to implement new methods, operations, and procedures on
live individuals.
[0006] U.S. Pat. No. 6,038,488 discloses a catheter simulation
device for surgery and interventional radiology procedures.
Translation and rotation of the simulated catheter can be tracked
and a computerized control system and recording device are employed
to provide a programmed procedure which provides a realistic "feel"
to a user of a surgical procedure.
[0007] WO 99/16352 describes using graphical representations of a
surgical instrument and area of the body in which a procedure is
being performed to aid an operator using the surgical
instrument.
[0008] WO 99/39315 describes a vascular access simulation system
with a tracking system for monitoring the movements of a simulated
catheter needle assembly and a skin traction mechanism. The system
receives measurements from the tracking system to update simulation
and display of representations of the catheter while providing
control signals to a force feedback device to enable the
application of force to the catheter needle assembly.
[0009] WO 98/03954 describes a system for simulating operating
conditions during minimally invasive surgical procedures. Data
regarding the movements of a simulated surgical instrument are
interpolated by a computer processor, which utilizes a database of
information representing a patient's internal landscape to create a
computer model of the internal landscape of the patient.
[0010] U.S. Pat. No. 6,106,301 describes a radiology interface
apparatus and peripherals, such as mock medical instruments, for
simulating performance of a medical procedure on a virtual patient.
The interface measures manipulations of system peripherals and
transfers these measurements via a processor to a medical procedure
simulation system.
SUMMARY OF THE INVENTION
[0011] There is a need to have a highly realistic simulation
environment for training and pretreatment planning of image-guided,
medical procedures such as vascular catheterization, angioplasty,
embolotherapy, drug infusion therapy and stent and coil
deployment.
[0012] This invention is designed to assist physicians in their
training and in preplanning of diagnostic and therapeutic
procedures performed in the vascular cardiovascular catheterization
laboratory. In addition to providing realistic visual feedback and
interacting with essential devices, such as are found in a
cardiovascular catheterization laboratory, the simulator also
provides active haptic force and tactile feedback components to
enhance the total hand-eye coordinated experiences encountered by
physicians during actual interventional procedures. To simulate
various types of procedures, the invention also provides a novel
solution to easily configure or customize the training or
pretreatment planning environment to meet the needs of the user or
trainer.
[0013] In one aspect, the invention provides a system for
simulating the movement of a medical device in a body cavity or
lumen of a patient. The system comprises a medical device
comprising a first end for manipulation by a user and a portion
comprising a second end insertable into a simulated body cavity or
body lumen in a manikin. The manikin comprises an interface for
receiving the portion comprising the second end and for interfacing
with the simulated body cavity or lumen. The manikin further
comprises a directional force feedback mechanism for exerting a
directional force on the medical device in response to a feedback
signal.
[0014] Preferably, the directional force feedback mechanism
provides resistance to forward motion but enables free reverse
motion in response to the feedback signal. In one aspect, the
directional force feedback mechanism comprises a rolling element
coupled to the portion of the medical device comprising the second
end. An internal surface of the simulated cavity or lumen in the
manikin comprises an oblique slot for receiving the rolling
element. In response to a feedback signal, forward movement of the
second end will cause the rolling element to be received by the
slot, thereby causing resistance to further forward motion. A
motor, such as a servo motor, can be used to control movement of
the rolling element.
[0015] In another aspect, the system further comprises a tactile
feedback mechanism which can provide continuous vibrational
feedback to a user holding the medical device. Tactile feedback can
be provided through a continuously rotating motor in communication
with the portion of the medical device comprising the second end.
The tactile feedback mechanism can simulate such parameters as
blood flow, respiration and the like.
[0016] Preferably, the position of at least the second end of the
medical device relative the simulated body cavity or lumen is
continuously tracked. In one aspect, the medical device comprises
an encoder for tracking the translation of the device and an
encoder for tracking the rotation of the device. In another aspect,
the system comprises a tracking unit comprising a light source, a
signal processing circuit, and one or more optical sensors which
are placed within the interface. Light from the light source
reflects on the device when it is inserted into the interface and
reflected light from the device is received by the one or more
optical sensors of the tracking system, enabling the movement of
the device to be tracked. In response to detection of changes in
reflected light, the system will simulate movement of the device in
real-time on a user display.
[0017] In one aspect, two optical sensors are provided which lie in
two different planes which are perpendicular to each other. In
another aspect, the tracking unit is configured in the form of a
rail along which the device can move.
[0018] More than one medical device can be inserted into the
interface and the position of each medical device can be
independently monitored. Suitable medical devices for use with the
system include, but are not limited to: a catheter, guidewire,
endoscope, laparoscope, bronchoscope, stent, coil, balloon, a
balloon-inflating device, a surgical tool, a vascular occlusion
device, optical probe, a drug delivery device, and combinations
thereof.
[0019] In one aspect, the system comprises a table on which the
manikin is placed. The table can comprise a processor connectable
to the network. Additional ancillary equipment can include, but are
not limited to, foot and hand activation switches, radioopaque
contrast dye injectors, hand operated balloon inflation devices,
and monitors displaying various simulated electrophysiological
parameters.
[0020] The system comprises at least one first user device
connectable to the network which comprises a first display
interface for displaying a three-dimensional representation of a
simulated body cavity or lumen of a patient. Preferably, the first
display interface further displays a three-dimensional
representation of a medical device corresponding to a medical
device which is interfaced with the manikin. The system simulates
the movement of the medical device within the simulated body cavity
or lumen of the manikin in real-time on the display, when a first
user manipulates the medical device interfaced with the manikin.
For example, the system can be used to simulate the movement of a
catheter through a blood vessel (e.g., such as a blood vessel in
the heart or brain or another organ). In one aspect, the system
further simulates deformation of the body cavity or lumen by the
medical device.
[0021] The system also can comprise a simulated scanning display
for displaying a two-dimensional image of the simulated body cavity
or lumen. In one aspect, the scanning display is part of a
simulated scanning device. For example, the simulated scanning
device can simulate an x-ray imaging system. Both the simulated
scanning device and scanning display can be coupled to a movable
C-arm within scanning distance of the manikin.
[0022] To enhance the realism of the simulation, a re-configurable
control panel (e.g., a touch screen) can be provided for performing
one or more of: image acquisition selection; image display;
manipulating a table on which the manikin is placed; manipulating
the position of a simulated scanning device relative to the
manikin; and control of one or more shutter devices for limiting a
field of view of a scanning device placed within scanning distance
of the manikin. The system also can comprise at least one
foot-activation switch for activating or collimating the simulated
scanning device, image display and/or for controlling table
movement.
[0023] The system can be adapted for use by multiple users, for
example, as part of a training environment. In one aspect, the
system comprises a monitoring station comprising a second user
device connectable to the network and comprising a second display
interface for enabling a second user to monitor the movement of the
medical device within the simulated body cavity or lumen.
Preferably, the second display interface displays selectable
options (e.g., a drop down menu, action buttons, check buttons,
radio buttons, dialog boxes, command lines and the like), enabling
the second user to select or change one or more anatomical and/or
physiological parameters of the simulated body cavity or lumen.
Selection of a selectable option causes the three-dimensional image
of the simulated body cavity or lumen displayed to the first user
to change to reflect the changed anatomical and/or physiological
parameters selected by the second user.
[0024] In one aspect, the first user display interface provides
access to a database and in response to this accessing, the system
displays an image and/or medical data of a patient on the first
user display interface. In another aspect, the second user display
interface provides access to the database and the system displays
an image and/or medical data on the second user display interface.
In a further aspect, the second user display interface provides a
selectable option enabling a second user to display the image which
is displayed on the second user display interface, on the first
user's display interface.
[0025] The invention additionally provides a syringe for simulating
fluid delivery, comprising: a housing defining a lumen comprising
an opening for delivering a fluid, a pushing element for pushing
the fluid through the opening, a friction-producing element in
communication with the pushing element, and a motor in
communication with the friction-producing element and comprising a
signal-receiving element. The friction-producing element will cause
friction between the pushing element and a surface of the lumen of
the housing when the motor is activated. Activation of the motor is
responsive to a signal received by the signal-receiving
element.
[0026] When activated, the motor causes motion of the
friction-producing element, causing the friction-producing element
to contact the surface of the lumen of the housing. This creates
friction between the pushing element and the surface of the lumen
and causes resistance to the motion of the pushing element, thus
simulating injection of a fluid through a syringe into the body of
a patient.
[0027] The friction-producing element can comprise one or more
rubber pads, each rubber pad being coupled to an arm whose movement
is controlled by the motor, e.g., such as through a gear attached
to the motor. In one aspect, the amount of friction produced by the
friction-producing element is adjusted by controlling a rotation
angle of the motor.
[0028] The syringe can be used with the system described above. For
example, the opening of the syringe can be connectable to a
connecting piece having a first end for receiving fluid from the
opening and a second end for delivering fluid to a simulated body
cavity or body lumen in the manikin, e.g., via the manikin
interface.
[0029] The invention also provides a method for simulating fluid
delivery into a body cavity or lumen of a patient comprising
providing a syringe as described above and providing a signal to
the syringe, thereby causing friction between the friction
producing element and the pushing element. Delivery of fluid to a
body cavity or lumen can be viewed in real-time on the screen of a
first and/or second user interface.
[0030] The invention also provides a balloon-inflating device for
simulating deployment of a balloon within a body cavity or lumen of
a patient. In one aspect, the device comprises a delivery mechanism
for controlling delivery of fluid (e.g., such as air) through the
balloon-inflating device to the balloon, a pressure sensor for
monitoring pressure of fluid delivered, and an electrical pressure
meter for reading pressure determined by the pressure sensor.
Preferably, the electrical pressure meter is connectable to a
processor and can transmit a signal corresponding to a pressure
value to the processor. The balloon inflating device can be used
with the system; for example, the system can simulate the
deployment of a balloon (e.g., inflation or deflation) within the
lumen of a patient; i.e., the system can be used to simulate a
balloon angioplasty procedure.
[0031] The system also can be used to simulate other operations of
medical devices, such as a surgical procedure (e.g., such as
removal or repair of a tissue structure), injection of a
radioopaque isotope and the like.
[0032] The invention further provides methods for using the system
described above. In one aspect, the invention provides a method for
simulating the movement of a medical device in the body cavity or
lumen of a patient, comprising: providing a medical device
comprising a first end for manipulation by a user and a portion
comprising a second end inserted into a simulated body cavity or
body lumen in a manikin. The simulated body cavity or lumen in the
manikin comprises a directional force feedback mechanism and in
response to a feedback signal, the directional force feedback
mechanism creates resistance to forward motion of the medical
device but allows free reverse motion, allowing a first user to
experience the sensation of using the device in the body of a
patient. In a preferred aspect, the user experiences tactile
feedback as well as directional feedback.
[0033] The first user of the system can access a database of
three-dimensional images of body cavities and lumens from a
plurality of different patients. For example, the first user can
request a representation of a selected image to be displayed on the
display interface of his or her user device in response to this
accessing. For example, the user can select a suitable hyperlink
displayed on the interface, or can input a query into a command
line or dialog box, or can select a selectable option provided on
the interface in response to the user's accessing the database.
[0034] In one aspect, the system also superimposes a
three-dimensional representation of the medical device on the
representation of the body cavity or lumen. Preferably, the system
simulates the movement of the medical device within the body cavity
or lumen in real-time on the display interface as the user
manipulates the medical device which is interfaced with the
manikin. More preferably, the system also simulates deformation of
the body cavity or lumen as the first user simulates navigating
and/or deploying the medical device. The user can experience one or
more simulated operations of the device, such as a surgical
procedure, injection of a radioopaque dye, balloon deployment, and
the like.
[0035] The first user can manipulate a plurality of medical devices
using the interface of the manikin. In response, the system will
simulate the movement of each of these devices on the first user's
display interface. For example, the system can simulate the can
simulate navigating a first catheter to a target region of the
body, then a balloon catheter, and then positioning a balloon
deployment device (e.g., such as the one described above) in
proximity to the balloon catheter to inflate or deflate the
balloon.
[0036] In another aspect, the system also simulates inserting a
stent catheter, navigating the stent catheter to the target region,
and using the balloon deployed by the balloon catheter to deploy
the stent. In a further aspect, the system simulates coil
embolization in a body cavity or lumen of a patient. As a first
user interacts with the manikin by inserting a catheter, guidewire,
and coil wire into the simulated body cavity or lumen, the system
simulates movement of each of these devices in the simulated body
cavity or lumen on the first user's display interface. A selectable
option on a control interface provided as part of the system (e.g.,
a re-configurable control panel or touch screen) provides the user
with a selectable option for detaching the coil from the coil wire.
When the user selects the selectable option, the coil is released
from the coil wire in the manikin and on the screen of the first
user's display interface.
[0037] A second user also can interact with the first user by using
the monitoring station described above. For example, the second
user can display a particular image selected by the second user
from the database on the first user's display interface. The second
user can alter parameters of the simulation displayed to the first
user, for example, as part of a training exercise, to document the
progress of one or more first users, and/or to introduce procedural
variables that can be used to test or evaluate the response and
decision-making abilities of one or more first users.
[0038] In a particularly preferred aspect, the system is configured
to resemble a cardiovascular catheterization laboratory where
interventional radiology procedures are performed. A first user can
interactively manipulate therapeutic catheters, guidewires and
other medical devices in real-time while viewing patient-specific
medical image data sets in a manner similar to that encountered in
a clinical procedure.
BRIEF DESCRIPTION OF THE FIGURES
[0039] The objects and features of the invention can be better
understood with reference to the following detailed description and
accompanying drawings.
[0040] FIG. 1 is the block diagram of a simulation system according
to one aspect of the invention.
[0041] FIG. 2 illustrates a perspective view of a system according
to the invention. A simulated patient (6) or manikin houses
tracking and force feedback assemblies. Simulated medical devices
are introduced into the simulated patient via a user interface box
embedded within the patient/manikin (e.g., through the groin or
axillary area, in the case of a simulated catheterization lab). A
first user (1) navigating and/or deploying simulated devices can be
monitored by a second user (19) according to one aspect of the
invention.
[0042] FIG. 3 is a block diagram showing various components of a
system processor according to one aspect of the invention.
[0043] FIG. 4 is a block diagram showing various system inputs
according one aspect of the invention, such as touch screens,
footswitches, syringes, C-arm, hand-operated balloon device,
feedback structures, and their connections with the system
processor.
[0044] FIG. 5A illustrates the mechanical structure of a tracking
system and active force feedback structure according to one aspect
of the invention. More than one set of catheters and guidewires can
be used in a given simulation. The translation and rotation of each
device are measured using incremental encoders. For example,
encoder A and encoder B measure the translation and rotation of a
catheter, respectively.
[0045] FIG. 5B is a block diagram illustrating components of the
tracking system and active force feedback system and their
interactions with the system processor.
[0046] FIG. 6A illustrates a different tracking system according to
one aspect of the invention comprising one or more optical
sensors.
[0047] FIG. 6B shows a tracking unit and catheter device configured
as a loop which can be used to simulate pushing, pulling, or
twisting.
[0048] FIGS. 7A and B show more detailed views of a directional
force feedback mechanism according to one aspect of the invention.
As shown in FIG. 7A, a wheel coupled to a motor directs forward
movement of a simulated catheter through a shutter connected to the
simulate catheter. Forward and downward motion of the shutter,
forces a rolling element coupled to the catheter into an oblique
slot which creates resistance to further forward motion. A
discontinuously rotating hand provides a sensation of vibration.
FIG. 7B shows a close up of the rolling element (e.g., a shaft) and
a cross-section through the oblique slot.
[0049] FIGS. 8A1-3 and B shows the structure of a simulated syringe
with a force feedback mechanism according to one aspect of the
invention. FIG. 8A shows a cross-section through the longitudinal
axis of the device while FIG. 8B shows a cross-section through the
tranverse axis of the device.
[0050] FIG. 9 shows a simulated hand-operated balloon-inflating
device according to one aspect of the invention. A pressure sensor
is used to measure the pressure of inflation of a balloon attached
to a catheter. The sensor signal is processed and transmitted to
the system processor. A user can read the pressure value from a
display monitor or from a piezometer as shown in the upper portion
of the Figure. A user also can feel pressure transmitted back from
a catheter port from the balloon during the inflation process.
[0051] FIGS. 10A-D show re-configurable control panels according to
different aspects of the invention.
[0052] FIG. 11 shows a scaled-down simulation system according to
one aspect of the invention.
[0053] FIG. 12 shows a desktop simulation system for pretreatment
planning comprising a re-configurable control panel.
[0054] FIG. 13 is a flow chart showing the steps of a simulation
process according to one aspect of the invention.
[0055] FIG. 14 illustrates the time/realism requirements of a
simulation system according to the invention.
[0056] FIG. 15 shows a physical model of vascular data and device
data which can be inputted into a system processor according to the
invention.
[0057] FIG. 16 illustrates creation of a physical model of a body
cavity or blood vessel according to one aspect of the
invention.
DETAILED DESCRIPTION
[0058] The invention provides a system for the simulation of
image-guided medical procedures and methods of using the same. The
system can be used for training and certification, pre-treatment
planning, as well therapeutic device design, development and
evaluation.
[0059] Definitions
[0060] The following definitions are provided for specific terms
which are used in the following written description.
[0061] As used herein, "coupled to" refers to direct or indirect
coupling of one element of a system to another. An element may be
removably coupled or permanently coupled to another element of the
system.
[0062] As used herein, "within scanning distance" refers to a
distance which is close enough to the manikin to permit display of
an image of the simulated body cavity or lumen on the scanning
display of the system.
[0063] As used herein, "a re-configurable control panel" refers to
a display interface comprising one or more selectable options
(e.g., in the form of action buttons, radio buttons, check buttons,
drop-down menus, and the like) which can be selected by a user and
which can direct the system to perform operation(s). Preferably,
the one or more options can be selected by touch. The control panel
can be modified by a user (e.g., by implementing a system program
which alters the display, causing it to display different
selectable options) thereby "re-configuring" the control panel.
[0064] As used herein, "providing access to a database" refers to
providing a selectable option on the display of a user device
which, when selected, causes the system to display images or data
stored within the database, or causes one or more links to be
displayed which, when selected, causes the system to display the
images or data. In one aspect, the system displays images or data,
or links to images or data, in response to a query of the system by
a user. In one aspect, the display interface provides a "query
input field" into which the user can input a query and the
selectable option is an action button for transmitting the query to
the system.
[0065] As used herein, the term "in communication with" refers to
the ability of a system or component of a system to receive input
data from another system or component of a system and to provide an
output response in response to the input data. "Output" may be in
the form of data or may be in the form of an action taken by the
system or component of the system.
[0066] As used herein, "deployment of a balloon" refers to either
inflation or deflation of the balloon.
[0067] As used herein, a pathology "affecting the structure of the
body cavity or lumen" is one which measurably alters at least one
physical property of the body cavity or lumen..
[0068] As used herein, "a physical property" refers to a property
which relates to the structure or anatomy of a body cavity or lumen
which is measurable, generally without the aid of a labeled
molecular probe; for example, physical properties of a blood vessel
include, but are not limited to: elasticity, thickness, strength of
ventricular contractions, vascular resistance, fluid volume,
cardiac output, myocardial contractility, and other related
parameters.
[0069] As used herein, "a volume image" is a stack of
two-dimensional (2D) images (e.g., of a body cavity or lumen)
oriented in an axial direction.
[0070] As used herein, a device for "accessing a body cavity or
lumen" refers to a device which can be maneuvered in the body
cavity or lumen. "Maneuvering" refers to the ability of at least
about 50% of the external surface of the device to fit within a
cavity or lumen while retaining rotational or forward translational
freedom of movement.
[0071] As used herein, an "interventional medical device" includes
a device for treatment (e.g., stents, stent-grafts, balloons,
coils, drug delivery devices), for diagnosis (e.g., imaging
probes), and for placement of other medical devices (e.g.,
guidewires). Some devices, such as catheters, can have multiple
functions. In general, the terms "an interventional medical device"
and "device for accessing a body cavity or lumen" are used
interchangeably.
[0072] As used herein, a "knowledge base" is a data structure
comprising facts and rules relating to a subject; for example, a
"vascular properties knowledge base" is a data structure comprising
facts relating to properties of blood vessels, such as elasticity,
deformation, tissue and cellular properties, blood flow, and the
like and rules for correlating facts relating to vascular
properties to interactions with one or medical devices.
[0073] As used herein, a "rule" in a knowledge base refers to a
statement associated with a certainty factor. Rules are generally
established by interviewing human experts or by obtaining data from
databases or other knowledge bases.
[0074] As used herein, an "expert system" comprises a program for
applying the rules of one or more knowledge bases to data provided
to, or stored within the knowledge base(s), thereby enabling the
knowledge base(s) to be queried and to grow. Preferably, an expert
system comprises an inference engine which enables the system to
manipulate input data from a user to arrive at one or more possible
answers to a question by a user. More preferably, an expert system
also comprises a cache or dynamic memory for storing the current
state of any active rule along with facts relating to premises on
which the rule is based.
[0075] As used herein, a system which "simulates a path
representing at least a portion of a body cavity or lumen" is a
system which displays a three-dimensional representation of the
internal surface of the at least a portion of the body cavity or
lumen on the interface of a user device in communication with the
system.
[0076] As used herein, to "determine the best fit between the
geometry of the device and the geometry of the path" refers to
displaying a representation of at least a portion of the device and
simulating its placement within at least a portion of the body
cavity or lumen.
[0077] As used herein, a "device parameter" refers to a physical
property of a device, e.g., such as flexibility, memory, material,
shape, and the like.
[0078] As used herein, "a physical model of a device" is a
combination of a recommended geometrical model, topology, and
material. It is also the basis for making the first design of a
medical device based on patient-specific data.
[0079] As used herein, a "software suite" refers to a plurality of
interacting programs for communicating with an operating
system.
[0080] As used herein, "clinical data" refers to physical,
anatomical, and/or physiological data acquired by medical image
modalities such as X-ray, MRI, CT, US, angiography, video camera,
or by direct physical and/or electronic measurements.
[0081] As used herein, "a best fit" between a simulated path for a
simulated body cavity or lumen and a simulated medical device
refers to one which requires the minimum amount of deformation in
the simulated surgical process that takes into consideration the
patient-specific vasculature and composite materials of the
device.
[0082] As used herein, an "FEM engine" refers to a program or set
of programs for performing finite element analysis focusing on
vasculature finite element models and analysis of the interaction
between vasculature models and devices.
[0083] Intervention Simulation System
[0084] FIG. 1 is a block diagram of a simulation system according
to one aspect of the invention. Input into the system executes a
particular simulation to be enacted. Generally, a simulation
includes images of a patient and also can include a display of
patient-specific information (e.g., such as clinical information
and medical history). The patient images can be obtained from a
database of patient-specific images or images relating to a
population of demographically similar patients (e.g., such as
patients sharing a pathology). Preferably, the system also accesses
data relating to various interventional devices. For example, the
system can include data files relating to the shape and physical
properties of one or more medical devices. Preferably, the
simulation system also includes a manikin (6) (i.e., representing a
patient) for interfacing with one or more simulated medical devices
(see, e.g., as shown in FIG. 2).
[0085] Users interact with the simulation system by observing
various rendered displays (2), such as fluoroscopic images of blood
vessels, and manipulate the one or more simulated devices in
response to data received by these display (2). The invention can
simulate the anatomy of a specific patient on which the one or more
devices will be used.
[0086] Simulated Patient Interface
[0087] In one aspect, the intervention simulation system comprises
a medical device with a first end for manipulation by a user and a
portion comprising a second end which is insertable into a
simulated body cavity or body lumen in a simulated patient
interface. Preferably, the simulated patient interface is part of a
manikin (6) which simulates the physical features of a human
patient. The manikin (6) comprises an interface (5) for receiving
the portion comprising the second end and for interfacing with a
simulated body cavity or lumen within the manikin.
[0088] The interface also comprises a directional force feedback
mechanism for exerting a directional force on the candidate medical
device in response to a feedback signal received by the force
feedback mechanism. This provides a user with a feeling that he/she
is interacting with a real patient. Preferably, the directional
force feedback mechanism provides resistance to forward motion but
enables reverse motion in response to the feedback signal. The
medical device can be one which is commercially available, a device
being tested for use or not otherwise commercially available, or
can be a candidate device based on a simulated design selected to
suit the characteristics of a particular patient. Methods and
systems for designing customized medical devices are disclosed in
U.S. Provisional Application Serial No. 60/273,734, filed Mar. 6,
2001.
[0089] As shown in FIGS. 7A and B, in one aspect, the directional
force feedback mechanism comprises a rolling element (e.g., such as
a shaft) coupled to the portion of the candidate device comprising
the second end. An internal surface of the simulated cavity or
lumen in the manikin in turn comprises an oblique slot for
receiving the rolling element. In response to a feedback signal,
forward movement of the second end causes the rolling element to be
received by the slot, causing resistance to further forward motion.
Preferably, a motor, such as a servo motor, controls movement of
the rolling element. This embodiment is shown in more detail in
FIG. 7A. When a force feedback control signal is generated, the
servo motor rotates clockwise, causing a wheel to rotate, pushing a
shutter forward and downward. The forward and downward movement of
the shutter pushes the rolling element down into the slot. Because
of friction between the slot and the rolling element, the rolling
element moves upward along the slot, and any further forward
movement is resisted. If the user wishes to pull back the device,
the rolling element will move downward and can be released from the
slot.
[0090] In a most preferred embodiment, the interface comprises both
a directional force feedback mechanism and a tactile feedback
mechanism. The tactile feedback mechanism provides vibrational
feedback to a user holding the candidate medical device. In one
aspect, continuous vibrational feedback is provided through a
continuously rotating motor (e.g., such as the servo motor) in
communication with the portion of the device comprising the second
end. A discontinuously rotating motor controlling the movement of a
hand (see, e.g., FIG. 7A) also can be used to simulate intermittent
forces experienced by a body cavity or lumen. For example, in a
clinical situation, when a catheter is inserted into the
cardiovascular system, cardiovascular function and activity may
cause the catheter to vibrate. The servo motor and the rotating
hand are designed to simulate this kind of vibration. The servo
motor rotates continuously and but has an adjustable rotating
frequency. . The rotating hand pushes the catheter discontinuously,
i.e., simulating blood flow and respiration.
[0091] Haptic "display" serves at least two purposes in the
intervention simulator: kinesthetic and cognitive. First, it
provides the sensation of movement to the user and therefore it
greatly enhances surgical performance. Second, it is used to enable
a user to learn to distinguish between tissues by testing their
mechanical properties. Deformation models are used to compute the
effect of force on the biomechanics of an interventional device and
on the deformation of a cavity or lumen through which the device is
navigating and/or being deployed, and feedback signals to the force
feedback and tactile feedback mechanisms can be used to mimic
actual forces that might be experienced during an interventional
procedure.
[0092] However, although the system is capable of providing
physically meaningful forces that realistically mimic those
encountered during an interventional procedure, there may be
instances where a less realistic simulation is satisfactory. For
example, a user may want to feel that he or she has reached an
obstruction during catheterization. However, the user may not need
to experience all the various contacts he or she could feel while
maneuvering a catheter prior to experiencing a single large
resistance. The present invention provides a mechanism to stop a
user from advancing past an obstruction and yet permits the user to
pull back a simulated device.
[0093] The manikin interface can be encased in a housing comprising
one or more openings for receiving medical devices, and means for
interfacing with tracking unit(s), feedback mechanism(s) and a
system processor (described further below). Additional devices such
as syringes and balloon inflating devices can be provided as part
of the interface, e.g., simulating balloon angioplasty
proceedings).
[0094] The interface housing can be displaceable for some distance
from the manikin itself or can project from the manikin (e.g.,
being an integral part of the manikin). To further enhance realism,
only the opening(s) of the housing may visible from the manikin
(e.g., the interface "housing" can be part of the manikin).
Preferably, the interface is an embedded system as shown in FIG. 2,
with openings into areas of the manikin simulating areas of medical
intervention.
[0095] System Input Devices
[0096] The simulation system can obtain input of various types to
more closely mimic an intervention procedure. For example, as shown
in FIG. 1, input to the simulator can consist of patient medical
history and diagnostic data including, but not limited to, data
obtained from X-ray, MRI, MRA, CT or ultrasound images. Data can
relate to a specific patient, e.g., where a user is training to
perform a procedure on a specific patient using a customized
device. Alternatively, data can relate to a "symbolic patient", for
example, representing a particular demographic group of closely
related patients, such as patients having a type of pathology.
[0097] FIG. 2 shows an example of various system inputs that can be
provided. The simulated patient (6) in the Figure is a manikin that
also houses the tracking and force feedback assemblies. A physician
(1) simulates navigation of a catheter by manipulating catheters
and guidewires (5). These catheters and guidewires are inserted
into the manikin at the manikin interface. One or more monitors (2)
can be used to display simulated fluoroscopic and vascular images
simulating the internal anatomy of a patient represented by the
manikin. In one aspect, 2-D fluoroscopic views are displayed at the
same time that 3D geometric models are displayed by system user
interfaces. Preferably, the user has the option to adjust
fluoroscopic images by one or more of zooming, collimation,
rotation, and the like. In combination with 3D volume-rendered
images generated using display interfaces described further below,
a user can view the vasculature from various positions or angles
along x-, y-, and x-axes. This option can be of major value in
pre-treatment planning, since a physician can use the system to
evaluate different treatment approaches prior to performing actual
intervention in a patient.
[0098] A simulated scanning device (4) additionally can be
provided, e.g., in the form of a mock C-arm equipped with an x-ray
emitter. Preferably, the mock C-arm can move along the long side of
an operating table (8) on which the patient/manikin is placed and
can rotate around the table to simulate capturing a patient's
images at various lateral and angular positions.
[0099] For example, as shown in FIG. 2, two footswitches (7) can be
used to simulate activation of a simulated x-ray device as well as
vascular image acquisition and storage. In response to this
activation, one or more monitors (2) simulate fluoroscopic images
obtained. A footswitch is preferred for scanning and image
processing, since user(s) generally have their hands occupied with
other equipment, in actual practice
[0100] Preferably, the system provides a re-configurable control
panel (9) (e.g., a touch screen) to enable a user to simulate
patient table manipulation, vascular image acquisition selection
and display, and the use of shutter devices to limit the extent of
the field of view provided by a scanning device (4). The panel also
can be used to implement functions such as machine-activated
radioopaque dye injection (e.g., activating the simulated syringe)
and/or deployment of a balloon via a balloon-inflating device (18)
interfaced with the manikin.
[0101] FIGS. 10A-D show re-configurable control panels according to
different aspects of the invention. Preferably, the display is
programmable and has a large storage area for bitmaps, display
lists, and screens. Users can easily set up complex image control
panels according to their own requirements. FIG. 10A shows the
typical controls associated with patient table manipulation.
Manipulating these controls result in a corresponding motion of a
C-arm that carries a simulated X-ray emitter. FIG. 10B shows
controls associated with image acquisition for manipulating the
sharpness and clarity of the rendered images. FIG. 19C shows
controls for machine activated balloon inflation and deflation, and
shuttering. FIG. 10D shows controls for collecting images for
creating a roadmap.
[0102] In a preferred aspect, the invention additionally provides
one or more interventional devices interfaced with the manikin for
simulating common procedures such as an injection, balloon
deployment, and/or stent deployment.
[0103] In one aspect, therefore, the system comprises a syringe for
simulating fluid delivery. The simulation syringe comprises a
housing defining a lumen comprising an opening for delivering a
fluid, a pushing element for pushing the fluid through the opening,
a friction-producing element in communication with the pushing
element, and a motor in communication with the friction-producing
element which further comprises signal receiving element. The
simulation syringe can be interfaced with the manikin and the
signal-receiving element preferably receives signals from the
system processor, e.g., to execute contrast injection at a
particular flow rate and volume.
[0104] The friction-producing element will cause friction between
the pushing element and a surface of the lumen of the housing when
the motor is activated in response to a signal received by the
signal-receiving element. When activated, the motor causes motion
of the friction-producing element, causing the friction-producing
element to contact the surface of the lumen of the housing. This
creates friction between the pushing element and the surface of the
lumen and causes resistance to the motion of the pushing element,
thus simulating injection of a fluid through a syringe into the
body of a patient.
[0105] The friction-producing element can comprise one or more
rubber pads, each rubber pad being coupled to an arm whose movement
is controlled by the motor, e.g., such as through a gear attached
to the motor. In one aspect, the amount of friction produced by the
friction-producing element is adjusted by controlling a rotation
angle of the motor.
[0106] FIGS. 8A1-3 and B show the structure of a simulated syringe
(3) with force feedback structure according to one aspect of the
invention. In the embodiment shown in FIGS. 8A-B, a servo motor and
two arms are installed in front of the pushing element (e.g., a
handspike). These two arms are connected through two meshed gears.
Gear 1 is installed on the servo motor as is the driver of the
motor. When a force feedback signal is communicated to the servo
motor, the Gear 1 will contrarotate and Gear2 will rotate
clockwise. Arm 1 and Arm 2 splay and the rubber pads on the two
arms will touch the wall of the syringe. Because of the friction,
the surgeon will feel resistance when he or she tries to push or
pull the pushing element. The value of the friction can be adjusted
by controlling the rotation angle of the servo motor. When the
servo motor rotates clockwise, the two arms will close and the user
can move the handspike freely again.
[0107] The simulated syringe (3) can be used to simulate the
injection of radioopaque dye, to simulate fluoroscopic imaging, or
the delivery of a therapeutic agent or drug. Control parameters
such as contrast injection volume and rate can be controlled by a
user through a control interface such as a touch screen, enabling a
user to choose the rate and total volume of injection. The
injection process can be captured, and selected images of the
process saved, to provide a roadmap image on a separate
monitor.
[0108] As discussed above, the manikin also can be interfaced with
a balloon-inflating device for simulating such operations as
balloon and stent deployment. FIG. 9 shows a simulated
hand-operated balloon-inflating device. A pressure sensor is used
to measure the pressure of a fluid, such as air, being delivered to
a balloon catheter, which has been navigated to a target site. The
signal of the sensor is processed and transmitted to the system
processor through the microprocessor M1. A user is able to read
pressure values from a display monitor or from an electrical
pressure sensor, such as the piezometer shown in the upper portion
of FIG. 9. Additionally, the user is able to feel pressure
delivered by the balloon-inflating device. Preferably, the
inflating device can provide up to about at least 20 Bar of
compressed liquid to a balloon.
[0109] In one aspect, compressed liquid is provided within a
compressed liquid generator in communication with a piston. A user
can trigger delivery of compressed fluid from the generator by
imparting linear force on the piston, thereby triggering inflation
of a balloon. Preferably, the compression stroke is approximately 2
inches and can be delivered when a user twists a handle of the
balloon-inflating device, causing a screw bar to force the piston
forward. A release button or switch is provided enable rapid
release of compressed fluid, thereby triggering deflation of the
balloon. In a further aspect, an automatic control system inside
the device is used to control the forward or backward movement of a
handwheel for controlling the amount of pressure actually delivered
to the balloon, in steps of a minimum of 0.01 Bar. Pressure values
can be read from a screen of the pressure meter (e.g., such as an
LCD screen) or can be displayed on the display of a user
device.
[0110] Preferably, the system enables a user to program parameters
such as maximum pressure delivered to the balloon. In one aspect,
the user starts to increase pressure delivered to the balloon by
means of a button on a handheld remote control and monitors
pressure values on a pressure display. The system may trigger an
alarm when balloon pressure increases past a selected threshold. In
an "auto mode" the system analyzes pressure data automatically to
automatically adjust pressure and increase/decrease speed of
inflation or deflation as appropriate.
[0111] Signals from simulated devices such as the simulated syringe
and/or hand operated balloon inflation device generally are
processed by an A/D converter first and then inputted to the system
processor. Preferably, signals from footswitches are digital and
inputted directly to the microprocessor and then to the system
processor.
[0112] The system can include additional input devices to simulate
an interventional procedure. For example, one or more monitors can
be included to simulate display of electrophysiological signals
such as ECG and blood pressure.
[0113] The system is designed to allow use by multiple users (see,
e.g., FIG. 2). For example, a second user (19) can be introduced to
alter the simulation parameters that a first user (1) is
experiencing. In one aspect, therefore, the system further
comprises one or more monitors (13-17) comprising one or more
second user display interfaces for a enabling a second user (e.g.,
a trainer) (19) to monitor a simulation that a first user (1) is
experiencing. The second user/trainer (19) is provided with
selectable options on the display of his or her user interface to
enable the second user (19) to alter or introduce variables (e.g.,
anatomical or physiological variables) in order to test or evaluate
the responses or decision-making abilities of one or more first
users (1).
[0114] In one aspect, processor interface (13) is used to connect a
monitor (15), keyboard (16) and mouse (17) of a first user device
to a system processor connectable to the network. In one aspect,
the system processor communicates with a microprocessor (M1) which
resides inside an operating table which receives the manikin. Using
a floppy disk driver (10) and/or CD-ROM drive (12), and/or other
memory devices, new patient cases can be loaded into the simulation
system. Because the processor is connectable to the internet or
intranet, remote observation or training is possible. A user (1 or
19) can upload relevant patient images or other medical data or can
upgrade software using the monitor (15), keyboard (16) and mouse
(17).
[0115] FIG. 3 is a block diagram highlighting the features of the
system processor, according to one aspect of the invention. In the
aspect shown in FIG. 2, the processor is a CPU installed inside a
patient table (8) which controls data and control flow among
various system components such as a hard drive, memory, display
monitors, manikin interface, and one or more simulated medical
devices.
[0116] FIG. 4 is a block diagram showing interactions between the
system processor and various system inputs according to one aspect
of the invention. A microprocessor (M1) is used for data
acquisition. Tracking information from an optical tracking unit in
optical communication with one or more simulated medical devices is
provided to the M1 through a signal processing circuit. A mock
C-Arm moves in response to a control signal from a touch screen
connected to the microprocessor through a serial port. Preferably,
the control signal is processed by the microprocessor prior to
being received by the C-arm.
[0117] Preferably, manipulations of a device by a user in an
interface provided in the manikin are coordinated with a simulation
of the device on the user display, such that motion of the device
in the manikin is simulated on the user display in real-time.
[0118] Therefore, in one aspect, the simulation device provides a
mechanism to continuously track a position of at least the second
end of the medical device relative to the manikin. For example, the
system can comprise one or more encoders for tracking translation
and/or rotation of the device (see, e.g., FIGS. 5A and B). FIG. 5B
is a block diagram illustrating the components of the tracking
system and the active force feedback mechanism. Using rolling
spherical objects coupled to a simulated catheter and guidewire,
respectively, four incremental encoders can pick up the motions of
the simulated devices. The rolling elements also serve as part of
the directional force feedback mechanism described above.
[0119] In a currently preferred aspect, as shown in FIGS. 6A and B,
the system comprises a tracking unit which tracks the movement of
the candidate medical device. The tracking system comprises a light
source (e.g., a point light source), a signal processing circuit,
and one or more optical sensors, and is placed within the interface
in optical communication with the device and the simulated cavity
or lumen through which the device is being navigated. The candidate
device will reflect light to it from the light source and reflected
light will be received by the optical sensor(s). Changes in
reflected light picked up from the sensor(s) indicate movement of
the candidate device as a result of manipulation.
[0120] In one aspect, two optical sensors are provided within the
tracking unit, each perpendicular to the other.
[0121] As shown in FIG. 6A, the tracking unit can be in the form of
a rail along which the device can move. Alternatively, the
simulated interventional device can be looped around the tracking
device and can be manipulated by pushing, pulling, and/or twisting
the loop. Preferably, tracking systems enable the intervention
system to independently track the movement of two or more medical
devices, for example, a catheter and guidewire.
[0122] Being an embedded system with detachable components, the
simulation system is flexible and can be easily configured to suit
the customized needs of its users. FIG. 11 shows a possible
configuration that reduces the size of simulation system to one
which can be placed on a normal desktop. FIG. 12 is a desktop
system intended for pretreatment planning by interventional
radiologists.
[0123] System Processor
[0124] The intervention simulation system further comprises at
least one first user device (e.g., a computer or wireless device
connectable to the network) comprising a graphical user interface
and connectable to a system processor and/or the network.
Preferably, the processor comprises one or more programs for
generating a geometric model of a body cavity or lumen of a patient
from stored or collected volume-rendered images obtained from one
or more patients. In one aspect, the user can access a database of
such images using the user interface, either by inputting text into
a command box or dialog box and implementing a search function of
the system or by selecting one or more selectable options
reflecting files and/or images stored in the database (e.g., a
hyperlink designated by the name of the file).
[0125] The system generally operates by means of a software suite
that operates on a general purpose computer such as a PC or
IBM-compatible device. Preferably, the system comprises a processor
(e.g., as CPU), memory, graphics adaptor, printer controller, hard
disk and controller, mouse controller, and the like. The processor
should comprise a minimum of about 8 MB of RAM. Preferably, the
first user display interface is part of a monitor which is
connected to a keyboard, mouse, and, optionally, printer and/or
scanning device. The software suite of the system comprises a
program (e.g., a C language program) that controls the system's
user interface and data files, e.g., providing one or more of
search functions, computation functions, and
relationship-determining functions. In a preferred aspect, the
system comprises a geometric modeling system for modeling a
three-dimensional representation of a body lumen or cavity; a
device modeling system for modeling a three-dimensional
representation of one or more medical devices, and at least one
knowledge base for modeling interactions between a simulated body
cavity or lumen and a simulated medical device.
[0126] Geometric Modeling System
[0127] In one aspect, optical data relating to the internal
contours of a body cavity or lumen are obtained and provided to the
intervention simulation system. The optical data can be displayed
directly on one or more user interfaces or can be stored in a
system database as described above. Because the system user devices
and processors are connectable to the network, patient data also
can be accessed from remote databases.
[0128] To generate a volume-image, a stack of two-dimensional (2D)
images is collected by a scanning device in an axial direction and
is used to form a three-dimensional (3D) structure (see, e.g., as
shown in FIGS. 3A and 3B). Almost all medical scanners can produce
these axial images or can produce images that can be converted
easily to axial images. Suitable scanning devices include, but are
not limited to, x-ray devices, magnetic resonance imaging (MRI)
devices, ultrasound (US) devices, computerized tomography (CT)
devices, rotational angiography devices, gadolinium-enhanced MR
angiograph devices, or other imaging modalities. For example,
rotational CT scanners capture patient data in the form of
projection images. By using a Filtered Back Projection technique or
Arithmetic Reconstruction Technique (ART), volumetric images can be
constructed.
[0129] The system may be directly connected to the output of one or
more scanning devices, e.g., collecting optical data from such
devices as these are acquired. However, in another aspect, the
system may include a means for extracting features from individual
scanned images (e.g., communicated to the system through a scanner
or provided as a pdf file) to construct a 3D volume image. The
geometric modeling arm of the system can be implemented remotely by
a user to determine one or more of: the geometry/topology of the
body cavity or lumen, measurements relating to any pathological
features of the body cavity or lumen, and such parameters as tissue
wall thickness, elasticity and the like.
[0130] In creating a geometric model of a body cavity or lumen
(e.g., such as a blood vessel), a user of the system (e.g., a
biomedical professional with knowledge of human anatomy and
pathology) performs image processing tasks on a plurality of
scanned images to create geometrical structures and a topology
which corresponds to the contours of a body cavity or lumen
belonging to a patient being analyzed.
[0131] Volume rendering techniques such as ray casting and
projection techniques have traditionally been used in the
visualization of volume images. Ray casting methods shoot rays
through a volume object from each pixel in an image and employ
algorithms that trilinearly interpolates samples along each ray,
providing complex shading calculations and color assignments at the
sample points which are then accumulated into final pixel colors
(see, e.g., Kaufman, In Volume Rendering, IEEE Computer Science
Press, Las Alamitos, Calif., 1990). Real-time volume rendering with
hardware texture mapping (e.g., SGI) for UNIX platform or with
board card (e.g., Mitsubishi VolumePro) for PC platforms are
commercially available.
[0132] Commercially available image processing tools, such as
Photoshop.TM. can be used to manually draw out the shape of the
structure from each scanned image. Various imaging-processing
tasks, as are known in the art, can be performed by the system; for
example, segmentation can be used. Several improved algorithms
using iso-surfacing or volume-rendering techniques to visualize
vascular trees also can be used and have been described in Ehricke,
et al., Computer & Graphics 18(3): 395-406, 1994; Cline, et
al., In Magnetic Resonance Imaging (Pergamon Press) 7: 45-54, 1989;
and Puig, et al., Proc. Of Visualization '97, pp 443-446, for
example.
[0133] Projection-originated methods reconstruct 3D geometries from
two or more images (See, e.g., Solbach, et al., Computer Biomedical
Research 27(3): 178-198, 1994; Nguyen and Sklansky, IEEE
Transactions on Medical Imaging 13(3): 178-198, 1994;
Longuet-Higgens, Nature 293(10): 133-135, 1981). Thinning methods
such as "active-contour", "medial axis transformation", and
"simulated annealing", and the like, can be employed to determine
information in projection planes (see, e.g., Kass, et al.,
International Journal of Computer Vision 1: 321-331, 1987; Lee, et
al., CVGIP: Graphical Models and Image Processing 56(6): 462-478,
1994; Arcelli and di Baja, Image and Vision Computing 11(2):
163-173, 1993; Pellot, et al., IEEE Transactions Medical Imaging
13(1): 48-60, 1994; Brandt and Algazi, CVGIP: Image Understanding
55(3): 329-337, 1992). The advantage of projective reconstruction
lies in its capability to handle tiny tube-like systems such as
vascular, neural and lymphatic vessels that could be lost with
iso-surfacing algorithms.
[0134] "Piece-by-piece cylinder representation" or "generalized
cylinder representation" is widely used in vascular modeling (see,
e.g., Brown et al., Proceedings of EUROGRAPHY '87, pp 113-124;
Barillot et al., IEEE Transactions on Computer Graphics and
Applications, December 1985, pp 13-19). Polygonal tessellation,
e.g., triangulation, also can be applied to model 3D tube-like
shapes as is known in the art (see, e.g., Sederberg, et al.,
International Journal on Computational Geometry and Applications
8(4): 389-406; Choi and Park, Visual Computer 10: 372-387, 1994).
Ferley, et al., Computer Graphics Forum 165(5): 283-293, 1997,
additionally describes an implicit surface method for
reconstruction of branching shapes.
[0135] Accurate modeling of a 3D vascular network relies on good
representations of vascular segments and bifurcations. Ideally, a
vascular model should be visually smooth and the detail of the
display should be adaptable to fit application requirements. In one
aspect, a constructive approach is used to model visually smooth
vascular networks. In this approach, vascular segments are modeled
using sweeping operations while vascular bifurcations can be
modeled using blending operations (i.e., sweeping plus hole-filling
operations) (Gregory and Zhou, Computer Aided Geometric Design 11:
391-410, 1994; Ye, et al., Computer Aided Geometric Design 27:
875-885, 1995). Based on GC conditions for boundaries and
cross-boundary derivatives (see, e.g., Schreiner and Buxbaum, IEEE
Transactions on Biomedical Engineering 40(5): 482-491, 1993),
constructive algorithms for segmental sweeping and bifurcation
blending can be designed as described in Cai et al., "Constructive
Algorithms for GC1 Generation of Vascular Network," Submitted to
IEEE Biomedical Engineering, March 2001. See, as shown in FIGS. 5
and 6.
[0136] Yet another method of obtaining a volume model or a
geometric model of a body cavity or lumen is the technique of
volumetric meshing. Meshes which represent a 3D or volumetric form
can be generated from scanned images using a standard Windows
operating system such as NT. Software for generating 3D mesh images
are commercially and publicly available. Sources for such software
are described at http://www-users.informatik.rw-
th-aachen.de/.about.roberts/software.html#Commercial, and include,
for example, Altair.RTM.HyperMesh.RTM.5.0 (available from Altair
Engineering, Inc., Maplelawn, Troy, Mich. 48084).
[0137] In a preferred aspect, a volume image of a blood vessel is
obtained to construct a physical or geometric model which comprises
information relating to both shape and material of tissue forming
the blood vessel. Generally, construction of geometric models
entail dividing a 3D modeling process into a series of 2D
cross-sectional segmentation operations from which the 3D surface
of the structure is reconstructed. An image processor is used to
draw out the shape of the desired vascular structure from each
image. Segmentation methods relying on intensity thresholding or
region-growing can be used, as are known in the art, to facilitate
the process (see, e.g., Wang, et al., IEEE Engineering in Medicine
and Biology, November/December 1999, pp 33-39; Moore, et al., J.
Biomechanics 31: 179-184, 1998). Finite element modeling also can
be used for blood flow modeling, as described in, for example,
Taylor, et al., Computer Methods in Applied Mechanics and
Engineering 158: 155-196; Hughes et al., Computer Methods in
Applied Mechanics and Engineering 73(2): 173-189, 1989; Shephard
and Georges, Int. J Numerical Methods in Engineering 32: 709-749,
1991.
[0138] Surface sweeping is a powerful tool for creating tube-like
shapes, i.e., simulating blood vessels. The sweeping operation
requires a smooth trajectory and cross-sectional shapes. To form a
tube-like surface, a closed cross-sectional contour must be used. A
cubic Bzier curve is used to represent the central trajectory or
path. With .gamma. (t) representing any of G.sup.J paths, a local
coordinate system (T (t), N(t), B(t)) can be defined along the
curve (see, e.g., FIG. 5). This triplet (T (t), N(t), B(t)), also
known as a "Frenet frame", is the tangent, normal and bi-normal
defined along the trajectory of the curve. Assuming r(t) is a
contour function defined in the cross-sectional plane perpendicular
to the curve at a given point along the trajectory, the sweeping
surface can be represented as
.GAMMA.(t, .theta.)=.gamma.(t)+r(t) (cos .theta. N(t)+sin .theta.
B(t)),
[0139] as described by Piegl and Tiller, In The NURBS Book,
Springer, Berlin, 1995, where .theta. is the cross-sectional angle
and t.epsilon.[0, 1] is a parameter defined along the curve. A
bi-cubic Bzier form for the sweeping tube can therefore be
developed using a tensor-product operation (see, e.g., Piegl and
Tiller, 1995, supra).
[0140] To model bifurcation, the same sweeping operation can be
applied. In order to avoid self-intersection, only half of the
tubular surface can be used (FIG. 6). This, however, leads to
missing two triangular patches (front and back) at the joint.
Bifurcation modeling therefore requires triangular hole filling. An
analytic approach described in Gregory and Zhou, Computer Aided
Geometric Design 11: 391-410, 1994, can be used to fill triangular
holes with given neighboring surfaces. To generate G.sup.J smooth
bifurcations, however, additional modifications of hole boundaries
and hence the surrounding surfaces are desirable. The procedures
for bifurcation modeling are summarized as follows:
[0141] (i) A bifurcation is first generated by sweeping three
semi-tubular surfaces in bi-cubic Bzier form.
[0142] (ii) Two triangular holes are formed by three surrounding
semi-tubular surfaces. Each hole is initially "filled" with three
bi-cubic Bzier patches using the method described in Gregory and
Zhou, 1994, supra.
[0143] (iii) The boundaries of the semi-tubular surfaces are
changed to quintic Bzier form. The modifications are determined
from the cross-boundary tangential continuity, twist-compatibility
and unique existence of tangent planes at hole comers.
[0144] (iv) Three semi-tubular surfaces are then degree-elevated
into quintic Bzier patches and modified based on the new hole
boundaries. The next row of control points of the hole boundaries
are modified accordingly to ensure that the semi-tubular surfaces
having cubic cross-boundary derivatives along the hole
boundaries.
[0145] (v) The vector-valued cross-boundary derivative in a quintic
form along the hole boundaries is generated for the filling hole
patches.
[0146] (vi) The hole boundaries are split into two at the middle
point of the parameter, so are the associated vector-valued
cross-boundary derivatives. The star-lines and their associated
vector-valued cross-boundary derivatives are degree-elevated to
quintic as well.
[0147] (vii) Three final filling rectangular patches are generated
based on the updated starlines, split hole boundaries, and the
vector-valued cross-boundary derivatives along the star-lines and
the split hole boundaries. The remaining 3.times.3 interior control
points are determined by taking a Coons-Boolean sum approach as
described in Ye, Computer Aided Design 27: 875-885; 1995.
[0148] From the segmented medical images, a central line model of a
vasculature can be constructed. This model is represented in
hierarchical structure consisting of vessel topology (using a
parent-child relationship to represent the topological connectivity
among a list of a vascular segments), vessel geometry (coordinates
and radii), and vessel material property. The 3D model of the
vessels is then reconstructed based on the central line geometry.
Visual smoothness is achieved by employing operations like sweeping
and blending. A variational modeling approach is implemented for
vasculature segments. An advantage of such method is that it
provides flexibility in changing 3D structure. Where a pathology is
identified and measured, a vascular model can be modified to
account for the pathology.
[0149] Preferably, deformable models are used to detect structures
in images. Such models can be used to define a geometry which
minimizes the energy of a simulated structure to account for
topological change, e.g., due to factors such as blood flow
dynamics and even interactions between the device and the body
lumen or cavity. For example, catheter tip shape deforms in a
predictable manner when straightened with a guide wire, when
advancing through tortuous vessels, and when encountering vascular
constraints such as lumen narrowing, branch point bifurcations, and
the like. These events can be modeled using the simulation
system.
[0150] In one aspect, a deformation law is applied to a geometric
model obtained from a hierarchical central line model to construct
a 3D model. This 3D model can be used to model linear deformation,
linear forces, non-linear deformation, and non-linear forces. The
application of deformation laws to a geometric model is described
in, for example, Wang, et al., 1999, supra, Mallaldi, et al., J.
Mathematical Imaging and Vision 6(2-3): 269-289, 1996; Caselles et
al., Numerische mathematik 66: 1-31, 1993; Osher and Sethian, J.
Computational Physics 79: 12-49, 1988; Sethian, In Level Set
Methods, Cambridge University Press, Cambridge, England, 1996,
Caselles et al., Int. J. Vis. 22(1): 61-79; Kichenassamy et al,
Proc. 5.sup.th Int. Conf. Computer Vision, pp. 810-815, 1995).
[0151] In a further aspect, the system comprises a knowledge base,
relating to the physical and/or biological properties of a
patient(s)' body cavity or lumens. Facts within this "vascular
material knowledge base" can be derived in part from the geometric
modeling arm of the simulation system as well as from public
databases (e.g., such as PubMed.RTM.) (see, as shown in FIG. 1). In
one aspect, the property of elasticity can be established from the
relationship between image density (determined from a volume image)
of a portion of a body cavity or lumen and the stiffness of a
particular tissue. In another aspect, the diameter of a
cavity/lumen can be determined.
[0152] For example, plaque can be distinguished from vessel walls
by evaluating the image intensity of a volume image. Preferably, as
volume images of body cavities or lumens are acquired from patients
having a disease, data relating to these images are provided to one
or more of the knowledge base systems described above. Preferably,
the knowledge base system(s) include data from images are obtained
from patients having atherosclerosis, coronary vascular lesions,
carotid bifurcation stenosis, carotid bifurcation stenosis,
abdominal aortic aneurysms, peripheral vascular disease,
cerebrovascular disease, cancer, trauma, and congenital
malformations that may cause or display vascular manifestations,
and the like.
[0153] Quantitative measures of a pathology can be obtained. For
example, a quantity module which is part of the system can be used
to measure the size of a blockage (e.g., a plaque).
[0154] In yet another aspect, at least one knowledge base comprises
clinical information related to a specific patient for which a
device is being designed. This database can include such
demographic information as age, sex, drug history, medical history,
medical billing information, and the like. This portion of the
system can be encrypted so that while information can be
continually added to other knowledge bases (e.g., by remote system
users), information within the patient-specific knowledge base
cannot be tampered with. However, preferably, even information
provided by remote system users will be stored in temporary data
files until a system operator enables the system to accept the
information. Information relating to populations of patients also
can be stored for comparison with information relating to the
specific patient.
[0155] Device Modeling System
[0156] Preferably, the first display interface also displays a
three-dimensional representation of the medical device which is
interfaced with the manikin. A simulation of the device can be
obtained from a database of images of stored devices (e.g., where
these are known and/or commercially available) or from a simulation
of a device, for example, as described in U.S. Provisional
Application Serial No. 60/273,734, filed Mar. 6, 2001. A volume
scanned image of the device also can be generated using techniques
similar to those described above.
[0157] Preferably, a physical model is used to simulate a device
based on the quantitative analysis of volume-rendered images,
followed by a derivation of the geometry, topology, and physical
properties of the device. Suitable medical devices which can be
simulated include, but are not limited to: a catheter, guidewire,
endoscope, laparoscope, bronchoscope, stent, coil, balloon, a
balloon-inflating device, a surgical tool, a vascular occlusion
device, optical probe, a drug delivery device, and combinations
thereof. The system is able to model the interactions of multiple
devices with each other. For example, the system can model the
simultaneous movements of a catheter, guidewire, therapeutic device
and the like.
[0158] Navigation Modeling System
[0159] Preferably, the system simulates the movement of the
simulated device within the simulated body cavity or lumen in
real-time when a first user manipulates the medical device
interfaced with the manikin. This can be realized by performing
virtual device navigation inside a simulated body cavity or lumen
using an incremental FEM engine. Such a simulation system is
described in U.S. Provisional Application 60/273,733, filed Mar. 6,
2001, the entirety of which is incorporated by reference. For
example, the embedded FEM engine of the system can provide a
real-time simulation of catheter/guide-wire interactions with blood
vessels. This enables the first user to develop the eye-hand
coordination necessary to implement a particular interventional
procedure.
[0160] Depending on the realism or deformation accuracy required,
the underlying assumption of physical modeling is adapted to
simulate navigation and/or deployment of a particular medical
device in a body cavity or lumen.
[0161] In a preferred aspect of the invention, the system simulates
a path which represents at least a portion of a patient's body
cavity or lumen and determines fit between the geometry of the
device (with or without functional and information attribute
layers) and the geometry of the path. The system simulates the
design of the device in stages; first providing a simulation based
on optimal shape (e.g., using the device shape database), then
optimal function, then optimal information parameters.
[0162] Basic Models for Catheter Navigation
[0163] In a preferred aspect, an incremental Finite Element Method
(FEM) is applied to the analysis of catheter navigation. In this
basic FEM analysis, blood vessels are assumed to be rigid circular
tube-structures with varying radii, or with arbitrary
cross-sections and deformabilities. However, it is commonly
accepted that because most of the blood vessels within the human
body are well stretched by surrounding muscles, the vasculature
network is only minimally deformed by catheter navigation.
Generally, also the tip of a guidewire or navigating catheter is
very soft in order to prevent damage to a blood vessel when in
contact. The vessel wall is therefore relatively stiffer than the
catheter itself and therefore, it is quite reasonable to simulate a
rigid blood vessel wall when simulating navigation and/or
deployment of a catheter.
[0164] Typical catheters/guidewires are generally cylindrical in
shape, with curved or uncurved geometries (e.g., the cross-sections
of catheters/guidewires are generally circular or ring-shaped). A
catheter/guidewire can be conceptualized as comprising a plurality
of discrete 3D beam elements or segments. Thus, they can be
represented as an aggregate of multiple, flexible bodies connected
to each other at nodes capable of simulating extension,
compression, bending and torsion (i.e., modes of deformation).
Thus, catheter navigation can be considered as a sequence of
movements of flexible multibody systems comprising a plurality of
segments inside the rigid tube-structures (e.g., corresponding to
blood vessels).
[0165] In one aspect, a simulated catheter is subjected to a
simulated force such as pushing, pulling, twisting, or combinations
thereof. The movement of the catheter is represented as the sum of
rigid-body displacements and deformations at each step with the
deformations being relatively small compared to displacements.
Generally, the elements of the catheter system are treated as rigid
bodies first and then deformations are calculated for individual
nodes of elements at their equilibrium position.
[0166] A different principle can be employed which is based on a
virtual work method or multibody dynamics method (MDM). The MDM
models the kinematics (rigid body displacements) of a multibody
system. In contrast, the FEM models the deformations of flexible
bodies to analyze catheter navigation. Generally, the deformation
of a medical device such as a catheter is relatively small relative
to the rigidity of a lumen, such as a blood vessel and Hooke's law
is applied. However, where the deformation of a lumen is large (for
example, when biomaterials fail), nonlinear FEM should be
applied.
[0167] The Governing Equation
[0168] Consider a catheter represented by multiple, discrete
elements, each with a deformed configuration. This flexible
multibody system is in dynamic equilibrium with applied forces
(e.g., contact traction and internal forces) at time t. An example
of an internal force is a hyper-viscoelastic force in an isotropic
constitution model (see, e.g., The Biomedical Engineering Handbook,
Editor-In Chief, Joseph D. Bronzino, CRC Press+IEEE Press,
1995).
[0169] Two coordinate systems can be used to describe the movement
and the deformations of the catheter system. The coordinate system
XYZ is the inertial (global) reference frame and xyz is the body
(local) reference frame at time t.
[0170] The variational equations of motion of the catheter system
are given as
.intg..sub.S.delta.{overscore (u)}.sup.T{overscore
(T)}dS-.intg..sub.V.del- ta.{overscore (u)}.sup.T(.rho.{overscore
(u)}-{overscore (f)})dV=.intg..sub.V.delta.{overscore
(.epsilon.)}({overscore (.sigma.)}-{overscore (.sigma.)}.sup.0)dV
(1)
[0171] where
[0172] S denotes the boundary surface,
[0173] V denotes the volume of the catheter,
[0174] {overscore (u)} denotes the displacement vector of a
catheter point at time t,
[0175] {overscore (.epsilon.)} and {overscore (.sigma.)} denote the
strain vector and stress vector, respectively,
[0176] {overscore (.sigma.)}.sup.0 denotes the residual stress
vector due to the accumulation of the previous deformations which
can be reduced through a process of energy release (shape
recover),
[0177] .delta.{overscore (u)} denotes the virtual displacement
vector that is consistent with the constrain conditions,
[0178] .delta.{overscore (.epsilon.)} denotes the corresponding
virtual strain vector,
[0179] .rho. denotes the mass density of the catheter,
[0180] {overscore (f)} denotes the body force vector,
[0181] {overscore (u)} denotes the acceleration vector (second
order differentiation of variables with respect to time t), and
[0182] T is the traction vector and can be expressed in terms of
the external force applied at the boundary S and the contact force
between the catheter and the walls of the vessels.
[0183] The displacement vector can be defined as a summation of two
terms, a term representing rigid body displacement and a
deformation term, in order to derive an explicit equation which can
be solved to simulate catheter movement. Because rigid displacement
of the catheter results in no strain or stress, the final two
variational equations from (1) can be formulated as
.intg..sub.S.delta.{overscore (u)}.sub.r.sup.T({overscore
(T)}.sub.a+{overscore (T)}.sub.c)dS-.intg..sub.V.delta.{overscore
(u)}.sub.r.sup.T(.rho.{overscore (u)}.sub.r-{overscore (f)}(dV=0
(2)
[0184] representing the movement of catheter/multibody system, with
each element moving as a rigid object and
.intg..sub.S.delta.{overscore (u)}.sub.f.sup.T({overscore
(T)}.sub.a+{overscore (T)}.sub.c)dS-.intg..sub.V.delta.{overscore
(u)}.sub.f.sup.T(.rho.{overscore (u)}.sub.r-{overscore
(f)})dV=.intg..sub.V.delta.{overscore (.epsilon.)}.sub.f({overscore
(.sigma.)}.sub.f-{overscore (.sigma.)}.sup.0)dV (3)
[0185] where {overscore (u)}.sub.r, , denotes the rigid
displacement; {overscore (u)}.sub.f represents the deformation,
{overscore (T)}.sub.a and {overscore (T)}.sub.c represent the
external force and contact force, respectively; and {overscore
(.epsilon.)}.sub.f and {overscore (.sigma.)}.sub.f represent the
strain and stress corresponding to the deformation. It is assumed
here that deformations are generally smaller than the rigid
displacements. The deformation can then be assumed to be time
independent during navigation. Because of this, the acceleration of
deformation is not taken into consideration in this formula.
[0186] FEM Analysis
[0187] Three-dimensional (3D) beam elements can be used to derive
equations for FEM analysis of catheter movement. Equations (2) and
(3), above, can be rewritten for a catheter with N elements, where
1 n = 1 N S n u r T ( T a + T c ) S - n = 1 N V n u r T ( u - r f )
V = 0 ( 4 )
[0188] represents the rigid body displacement of the beam elements
and 2 n = 1 N S n u f T ( T a + T c ) S - n = 1 N V n u f T ( u - r
f ) V = n = t N V n f T ( f - 0 ) V ( 5 )
[0189] represents the deformations of the elements. S.sub.n and
V.sub.n denote the boundary and volume of the nth element,
respectively.
[0190] Equations (4) and (5) can be solved using routine FEM
methods to derive the matrix equations:
{overscore (M)}{overscore ()}={overscore (T)}.sub.a+{overscore
(T)}.sub.c+{overscore (f)} (6)
{overscore (K)}{overscore (u)}={overscore (T)}.sub.a+{overscore
(T)}.sub.c-{overscore (M)}{overscore ()}+{overscore (f)}+{overscore
(.delta.)}.sup.0 (7)
[0191] providing a multidynamic analysis of rigid body
displacements and for an FEM analysis of deformations for a
simulated catheter. The rigid body displacement vector {overscore
(u)} is represented by three translations and three rotations at
each FEM node, while the deformation vector {overscore (U)} is also
expressed in the same way, with a total of six degrees of freedom
at an FEM node. Matrices {overscore (M)} and {overscore (K)} denote
the global mass matrix and the global stiffness matrix,
respectively. Note that equations (6) and (7) are coupled to each
other and can be solved using a semi-implicit iteration method
(see, e.g., Rao, In The Finite Element Method in Engineering,
2.sup.nd Edition, New York: Pergamon Press, 1989).
[0192] Advanced Models
[0193] In one aspect, vessels are not treated as rigid cylindrical
structures but as deformable structures. This is particularly
useful when modeling the interaction of catheterization devices,
such as balloon and stents, with diseased arteries. These vessels
vary in cross-sectional diameter due to the presence of a
pathology, such as stenosis. Further, the deformation properties of
diseased vessels are different from the deformation properties of
normal vessels. Additionally, it may be desirable to model one or
more physiological parameters such as the effect of blood flow on
navigation of a medical device such as a catheter. Therefore, in
one aspect, the simulation process uses a hemodynamic model
describing the blood flow phenomenon. Preferably, the hemodynamic
model accounts for the affects of such variables, as disease, age,
obesity, and the like.
[0194] For a more realistic and accurate analysis of the
interaction between a device and a pathology such as coronary
stenosis, the device materials and vessels are treated as
nonlinear. Blood flowing through the vessels is modeled by treating
the blood as a homogeneous incompressible Newtonian fluid. The
vessels and associated stenosis are modeled as layered structures,
using a 3D space FEM model. Physiological influences on a body
cavity or lumen also can be considered in particular anatomic
locations in which these influences may be important concerns. For
example, when modeling coil deployment in the head, the system can
take blood flow dynamics into account, since a coil may be swept
away if incorrectly placed.
[0195] Preferably, FEM analysis occurs in real-time, in order to
simulate real-time movement of a representation of a device while a
user is manipulating a model device in the manikin. Such training
is important to developing eye-hand coordination. Preferably, this
is implemented using a fully nonlinear 3D finite element model
combined with hemodynamic analysis. This requires extensive
computer power. A multiprocessor system with at least about four
processors, with each processor having computing power equal to a 2
GHz Intel Pentium 4 CPU is one example of a system that might be
used.
[0196] Preferably, the system models interactions between the
physiology and anatomy of a patient and one or more medical devices
using physical modeling. FIG. 16 is a block diagram illustrating
the various steps in such a simulation process and how these
interact with each other. Preferably, the system accounts for
physiological responses to an intervention procedure. For example,
in simulating damage to a vessel wall through excessive pushing of
a device against the wall, the system also can simulate the effect
such an action will have on blood pressure. Similarly, a simulation
of a tumorous lesion in a blood vessel include modeling the effects
of such a lesion on local mechanical properties of tissues.
[0197] In a preferred aspect, the system includes a patient
database comprising stored volume images and files relating to
optical data obtained from body cavities and lumens of one or more
patients. Preferably, the database comprises data from a population
of patients, such as a population of normal patients, a population
of patients with coronary artery disease, peripheral vascular
disease, stenosis, and the like. In one aspect, the database
comprises vascular data from patients obtained through one or more
of a 3D Rotational XR scanner, an MRI scanner, an MRA scanner, or
any scanning device suitable for collecting scanned images for
generating volume images. Data so obtained generally is segmented.
By having two rounds of scanning using the same scanning, but with
only one round revealing the vasculature, segmented vessels can be
obtained by subtracting images of the former scan from the
corresponding images in the latter scan.
[0198] FIG. 15 illustrates the creation of a physical model for a
patient's vasculature. Based upon segmented volume images, nodes
are extracted, along with position and contour information. This
data defines the central line of a vessel. Preferably, nodes are
labeled according to the direction of blood flow as this aids in
the deformation analysis process. After a 3D geometric model is
reconstructed from the medical images, using the geometric modeling
system as described above, a deformation law is implemented using
FEM.
[0199] Deployment Models
[0200] In one aspect, in addition to modeling movement of a device
through a body cavity or lumen, the system models one or more
operations of the device. Such operations include, but are not
limited to: a surgical procedure (e.g., such as removing, cutting,
or repairing a tissue), inflation or deflation of a balloon,
injection of a radioopaque material into the body cavity or lumen,
and the like.
[0201] In one aspect, the system models interactions between an
angioplasty device and a blood vessel having one or more lesions.
For example, the system can model the deployment of a balloon
angioplasty device at a lesion site and can model inflation and
deflation of the balloon at the site. Preferably, a visual
simulation is implemented at the same time that a user manipulates
a balloon-inflating device. In one aspect, the balloon-inflating
device comprises a delivery mechanism for controlling delivery of
fluid (e.g., such as air) to a balloon, a pressure sensor for
monitoring pressure of a fluid delivered to the balloon, and an
electrical pressure meter for reading pressure determined by the
pressure sensor. The electrical pressure meter transmits a signal
corresponding to a pressure value to the system processor and, in
response, the system simulates deployment of the balloon both on
the screen of the first user device and within the manikin.
[0202] Injection of contrast medium also can be simulated. In one
aspect, the first user (or a second user training the first user)
can select an injection volume and rate from selectable options
displayed on the first user interface (or second user interface).
When these injection parameters are set, injection can be triggered
using a simulated syringe or button on the control panel. The
appearance of contrast filling the vessels (opacity) is modeled to
reflect the rate of injection relative to the blood flow rate in
the vessel. This provides a realistic impression of the injection.
Preferably, diastolic and systolic flow pattern and washout of
contrast through the vasculature also are modeled using the
contrast injection function. Roadmapping capabilities additionally
can be made available. The value of roadmapping is enhanced when it
is combined with simultaneous 3D display of the vasculature.
[0203] Simulation Methods
[0204] In one aspect, the system provides a haptic interface for
providing an interventional radiologist with the sense of touch
during pretreatment planning and training. The system can be used
in preparation for catheterization procedures with cerebral
vascular pathologies such as intracranial aneurisms, stenosis,
arteriovenous malformations, and the like. Other simulations which
can be performed using the system include, but are not limited to,
angioplasty, catheter navigation in the abdominal aorta, peripheral
intravenous catheterization, venipuncture, interventional
cardiology, and the like.
[0205] FIG. 13 is a flow diagram illustrating a simulation
according to one aspect of the invention. Preferably, the
simulation is event driven, i.e., responding to discrete actions
from one or more users. Computation of interactions between the
body cavity or lumen and one or more medical devices is implemented
by the FEM engine described above. FEM has been used widely to
compute deformations under mechanical constraints in engineering;
however, the instant invention applies FEM analysis to various
physical models of blood vessels, blood flow dynamics and medical
devices.
[0206] Any input from users comes in the form of device
manipulations, such as pushing, pulling, twisting a catheter;
deploying a coil; inflating a balloon with a balloon catheter. Each
of these inputs affects the finite element structure modeled by the
system. By solving equations representing this structure through an
iterative process as described above, an equilibrium state
representing the interaction between the device and cavity/lumen
can be obtained. At the equilibrium state, the interacting devices
and vessels are at their final deformable forms. The forces
computed at each node of the interaction between a medical
device/body cavity or lumen are then fed back to one or more users
using simulated instruments interfacing with the system. System
outputs include real-time representations of medical devices as
they navigate and/or deploy in simulated body cavities or
lumens.
[0207] Real-time interaction is an important feature of the instant
invention. The immersion of a user, and therefore, his or her
ability to learn from the simulation system, is directly linked to
the bandwidth of various components of the simulation system. An
acceptable bandwidth for visual display is in the range of about
20-60 Hz while an acceptable bandwidth for haptic display is in the
range of about 300-1000 Hz (where 300 Hz is the free hand gesture
frequency).
[0208] Two parameters that are particularly important for accurate
perception by a user are latency and computation time. Latency
measures the time between sensor acquisition (e.g., acquiring the
position of a simulated medical device relative to a simulated body
cavity/lumen) and system action (e.g., haptic rendering or force
feedback). Computation time is that amount of time needed to
determine the equilibrium state of a structure (e.g., a
representation of a device and cavity/lumen) and to update the
resulting models.
[0209] There are several contributing causes of latency, including,
but not limited to: time required for communication between input
devices and the system processor, time for communication between
the haptic display and the system processor, time for communication
between the visual display (e.g., the 2D display) and the
processor, time to compute collision detection, time for force
feedback, and time for computing deformation models. Latency
depends greatly on hardware and preferably the system comprises an
at least about 16-bits bus for internal transmission within the
embedded system (e.g., manikin interface), and a combination of
serial and USB transmissions to create external links between
simulated devices and the system processor.
[0210] Realism is also important. Very often, real-time interaction
and realism are correlated. For example, FIG. 14 shows the
relationship between response time and realism. Preferably, the
simulation system according to the invention provides a visual
feedback of 12-15 frames per second.
[0211] Visual feedback is the most powerful perception channel. The
quality of visual rendering greatly influences user immersion and
therefore the effectiveness of the simulation system. The system
provides a library of 3D representations of medical devices and a
library of 3D representations of normal or pathological patient
anatomy. In one aspect, the user can select an entry point for
insertion of a medical device into a simulated patient (e.g., at
either a radial or femoral site) and in response to the user's
manipulation, a haptic display will display the navigation of the
device through a selected body cavity or lumen. The system can be
used to direct the navigation of the device towards or away from
the heart, allowing a user to choose where navigation will begin to
be tracked. The user interface can comprise direction buttons,
enabling a user to maneuver the device in particular
directions.
[0212] Preferably, a current position of a navigating catheter
within a body cavity/lumen is overlaid on a fluoroscopic view. When
required, especially, during a course of training, a user has the
option to adjust a fluoroscopic image in a manner similar to that
employed in a CathLab. For example, the user can zoom in/out of a
particular view of a catheter-guidewire entry site for a closer
look of the position and orientation of the catheter and guidewire.
The user also can improve image quality by collimating the field of
view using the shutter function of a simulated scanning device. The
shutter function provides both lateral and vertical collimation to
recreate a clinical setting. The contrast of the fluoroscopic image
also can be modified. In addition, moving patient table control
levers can change the position of the fluoroscopic field of view.
These levers control the movement of the image in the X and Y-axes
as well as rotation and skew. They correspond to patient table
control levers used in the clinical setting.
[0213] As discussed above, the motion of one or more medical
devices relative to a body cavity or lumen is tracked and updated
simultaneously in fluoroscopic and 3D displays. The user can change
the transparency of 3D rendered vessels to better compliment the
geometry presented in the fluoroscopic view. The user also has the
option of overlapping a representation of the device with a
representation of a surface-rendered vasculature. 3D-rendered
vessels can be rotated in the x-, y-, and z-axis to better
appreciate the position of the catheter/guidewire tip relative to
the vascular anatomy. This feature is very useful in teaching
selective vessel catheterization techniques. Besides 3D views, a
fluoroscopic image can be viewed in stereo mode with the stereo
image projected onto a split screen alongside the 2D image of a
vessel. Users see the stereo virtual image on the screen of their
user devices wearing a pair of stereo glasses (e.g., such as
StereoGraphic Crystal Eyes). The stereo virtual objects consist of
vessels, associated volume data, and the one or more interventional
devices being navigated and/or deployed through the vessels.
[0214] Besides providing stereo and 3D views of the catheterization
process, the simulator has the capability of locating catheter tip
position within multi-planar images of a body region. The system
will highlight tip position relative to anatomical structures on
the display of one or more user devices. Preferably, images of the
tip are viewable in any of an axial, coronal, sagittal or combined
mode, representing images of scanned anatomical structures (e.g.,
such as obtained from CT, MRI or actual cross-anatomical color
images). It is an important aspect of the system to provide
multi-functional views for teaching complex techniques, such as
those used in interventional procedures. In one aspect, an
endoscopic view is provided of the tip of the catheter within the
enclosing vessels of the cardiovascular system.
[0215] In another aspect, the system provides a haptic system for
providing a neuroradiologist with the sense of touch during
pretreatment planning and training. Preferably, the system
comprises a database of angiographic information and a vascular
model can be extracted from a database comprising data relating to
geometry and topology of the cerebral vasculature (e.g., using a
knowledge base). Physical properties of vessels can be obtained
from outside sources such as the literature or from various
experts. A library of devices suitable for use with vessels in the
brain is included in the system. In one aspect, the library
comprises data files relating to the geometry and/or physical
properties of interventional devices, such as catheters,
guidewires, stents, and coils. A device shape and material
knowledge base can be provided as described in U.S. Provisional
Application Serial No. 60/273,734, filed Mar. 6, 2001.
[0216] In one aspect, the system simulates an intracranial blood
vessel with an aneurysm. Intracranial aneurysms are berry-like
blisters in cerebral arteries that are caused by a weakness of all
vessel wall layers. If rupture of an aneurysm occurs, hemorrhage
can cause serious damage to the brain. To prepare for an
interventional proceeding, a clear understanding of the anatomy
surrounding an aneurysm is critical, such as the location and size
of the neck, or connection between the aneurysm and vessel which
feeds into it. An aneurysm is usually clearly visible in volume and
surface-rendered images.
[0217] Preferably, the system displays a representation of the
aneurysm and surrounding blood vessels and models the interactions
of a simulated device being maneuvered in proximity to the
aneurysm. In one aspect, the system is used to simulated the
placement of one or more coils to treat the aneurysm. In one
aspect, aneurysm coiling is simulated by navigating a medical
device such as a coilwire to the aneurysm and replacing the wire
with a coil. The coil is deployed by detaching the coil from the
wire. Multiple coils can be deployed by repeating the detachment
process with new coil wires. Each of these actions can be simulated
on the haptic display using the system according to the
invention.
[0218] In other aspect, a user can simulate other interventional
procedures such as contrast fluid injection, inflation or deflation
of a balloon, stent deployment, injection of a drug or therapeutic
-agent. The system provides both haptic and visual feedback to the
user to enable the user to develop the eye-hand coordination
necessary to become skilled in these procedures.
[0219] As described above, the invention produces a highly
realistic simulation environment for preplanning image-guided
medical device delivery procedures and for training individuals who
perform such procedures. In addition to its application in
biomedical engineering, component parts of this invention may be
applied to many other fields, for example, such as the field of 3D
computer games. It should be apparent to those of ordinary skill in
the art that variations, modifications, and other implementations
of what is described herein will occur to those of ordinary skill
in the art without departing from the spirit and scope of the
invention and the claims.
[0220] All of the references, patents, and applications identified
above, are expressly incorporated herein in their entireties.
* * * * *
References