U.S. patent application number 10/807047 was filed with the patent office on 2005-09-29 for vascular-access simulation system with receiver for an end effector.
Invention is credited to Feygin, David, Ho, Chih-Hao.
Application Number | 20050214726 10/807047 |
Document ID | / |
Family ID | 34963573 |
Filed Date | 2005-09-29 |
United States Patent
Application |
20050214726 |
Kind Code |
A1 |
Feygin, David ; et
al. |
September 29, 2005 |
Vascular-access simulation system with receiver for an end
effector
Abstract
The illustrative embodiment is a simulation system for
practicing vascular-access procedures without using human subjects.
The simulator includes a data-processing system and a haptics
interface device. The haptics device provides the physical
interface at which an end effector (e.g., medical instrument, such
as a needle, catheter, etc.) is manipulated to simulate needle
insertion, etc. In accordance with the illustrative embodiment, the
haptics device includes a receiver. The receiver receives the end
effector when it's inserted by a user into the haptics device.
Sensors that are associated with the receiver monitor the motion
and position of the end effector, generate signals indicative
thereof, and transmit the signals to the data processing system.
The signals are processed to determine the effects of manipulation
of the end effector. In some embodiments, the signals are processed
to determine the various resistive forces that would arise if the
user were manipulating a needle/catheter through actual human
anatomy. Responsive to this determination, the receiver generates
forces that the user experiences as a resistance to continued
advance (insertion) of the end effector. Simulated results are
displayed by the computer system.
Inventors: |
Feygin, David; (Washington,
DC) ; Ho, Chih-Hao; (Reston, VA) |
Correspondence
Address: |
DEMONT & BREYER, LLC
SUITE 250
100 COMMONS WAY
HOLMDEL
NJ
07733
US
|
Family ID: |
34963573 |
Appl. No.: |
10/807047 |
Filed: |
March 23, 2004 |
Current U.S.
Class: |
434/262 |
Current CPC
Class: |
G09B 23/285
20130101 |
Class at
Publication: |
434/262 |
International
Class: |
G09B 023/28 |
Claims
We claim:
1. An apparatus comprising a receiver, wherein: said receiver has
at least three degrees of freedom, wherein axes of said three
degrees of freedom intersect; and said receiver receives an end
effector, wherein said end effector removably couples to said
receiver.
2. The apparatus of claim 1 further comprising said end effector,
wherein said end effector comprises a catheter.
3. The apparatus of claim 1 wherein two of said three degrees of
freedom are rotational and one of said three degrees of freedom is
translational.
4. The apparatus of claim 1 further comprising pseudo skin, wherein
said receiver is disposed beneath said pseudo skin.
5. The apparatus of claim 4 further comprising said end effector,
wherein said pseudo skin lies in a plane between said end effector
and said receiver, and wherein to simulate a vascular access
procedure, said end effector crosses said plane to couple with said
receiver.
6. The apparatus of claim 1 further comprising: a plurality of
sensors, wherein said sensors: monitor movement of said receiver
with respect to said degrees of freedom, wherein said movement is
indicative of the position and orientation of said end effector;
and generate signals indicative of said monitored movement; and a
data processing system, wherein said data processing system
receives signals generated by said sensors.
7. The apparatus of claim 6 and further wherein said data
processing system determines a position and orientation of said end
effector based on said received signals.
8. The apparatus of claim 1 wherein said receiver comprises a
force-feedback assembly, wherein said force-feedback assembly
generates a resistance to movement of said end effector.
9. The apparatus of claim 8 wherein said force-feedback assembly
comprises a motor.
10. An apparatus comprising: an end effector; and a movable member,
wherein: said end effector reversibly couples to said movable
member to simulate a vascular access procedure; and said movable
member moves along a linear path in response to manipulation of
said end effector.
11. The apparatus of claim 10 wherein said movable member is
coupled to a cable.
12. The apparatus of claim 11 wherein said cable is coupled to a
motor.
13. The apparatus of claim 12 wherein, responsive to a control
signal, said motor generates a resistance to movement of said
movable member.
14. The apparatus of claim 11 further comprising a plurality of
pulleys disposed on a frame, wherein: said pulleys engage said
cable; and said pulleys are arranged so that a tension in said
cable aligns with said linear path along which said movable member
moves.
15. The apparatus of claim 11 wherein said movable member comprises
a pulley, wherein said movable member is coupled to said cable via
said pulley.
16. The apparatus of claim 10 wherein said movable member comprises
a magnet, and wherein said end effector couples to said movable
member via said magnet.
17. The apparatus of claim 10 further comprising a housing, wherein
said movable member is disposed within said housing and said end
effector is disposed outside of said housing.
18. The apparatus of claim 17 further comprising pseudo skin,
wherein said pseudo skin is substantially co-planar with a surface
of said housing.
19. An apparatus comprising a receiver for an end effector, wherein
said receiver comprises: a frame; an arrangement for providing two
orthogonal axes of rotation for said frame, wherein said frame is
coupled to said arrangement; and a movable member, wherein: said
movable member receives an end effector during a vascular access
procedure; said movable member moves along a linear path in a
region defined by said frame; and said linear path intersects said
two orthogonal axes of rotation of said frame.
20. The apparatus of claim 19 further comprising a force-feedback
assembly, wherein said force-feedback assembly is coupled to said
movable member, and wherein said force-feedback assembly imparts a
force that resists forward motion of said movable member by said
end effector.
21. The apparatus of claim 20 wherein said force-feedback assembly
comprises: a motor; and a cable, wherein said cable is coupled to
said motor.
22. The apparatus of claim 21 wherein said movable member includes
a rolling-contact element, wherein said cable is coupled to said
rolling-contact element.
23. The apparatus of claim 21 further comprising a counterbalance,
wherein said counterbalance is coupled to said frame.
24. An apparatus comprising: pseudo skin; and a receiver for
coupling to an end effector, wherein: said receiver is disposed
beneath said pseudo skin; and said receiver has no offset degrees
of freedom.
25. The apparatus of claim 24 wherein a magnetic force is used for
coupling said end effector to said receiver.
26. The apparatus of claim 24 wherein said end effector is selected
from the group consisting of a catheter, a needle, and a combined
catheter and needle.
27. The apparatus of claim 24 wherein said receiver has three
degrees of freedom.
28. The apparatus of claim 27 wherein two of said three degrees of
freedom are rotational and one of said three degrees of freedom is
translational.
29. The apparatus of claim 24 wherein said receiver comprises a
movable member, and wherein said movable member is movable along a
linear path.
30. The apparatus of claim 24 wherein said receiver comprises a
movable member, and wherein said movable member is physically
adapted for rolling contact during movement.
31. The apparatus of claim 24 wherein said receiver is
gravitationally balanced.
32. The apparatus of claim 24 further comprising said end effector,
wherein, until coupled to said receiver by a user, said end
effector is disposed above said pseudo skin.
33. The apparatus of claim 24 wherein said receiver further
comprises: a movable member, wherein said movable member couples to
said end effector; and a force-feedback assembly, wherein said
force-feedback assembly is coupled to said movable element.
34. An apparatus comprising: pseudo skin; and a receiver for
coupling to an end effector, wherein: said receiver is disposed
beneath said pseudo skin; and said receiver comprises a
force-feedback assembly.
35. The apparatus of claim 34 wherein said receiver further
comprises a movable member, and wherein: said movable member is
coupled to said force-feedback assembly; said movable member
couples to said end effector; when said movable member is coupled
to said end effector, movement of said end effector causes said
movable member to move.
36. The apparatus of claim 35 further comprising a data processing
system, wherein, responsive to a signal from said data processing
system, said force-feedback assembly generates a force that opposes
movement of said movable member and said end effector, in at least
a first direction.
37. An apparatus comprising: an end effector, wherein said end
effector is a pseudo medical instrument; pseudo skin, wherein said
pseudo skin is physically adapted to enable said end effector to
pass through it to a first region beneath said pseudo skin; a data
processing system, wherein said data processing system: receives
information indicative of a position of said end effector in said
first region; determines a position of a virtual end effector in a
virtual anatomy based on said received information; determines a
resistive force that would arise if said virtual end effector were
present at said position in said virtual anatomy; and a
force-feedback system, wherein said end effector is coupled to said
force-feedback system when said end effector is in said first
region, and wherein said force-feedback system generates said
resistive force, and wherein said resistive force opposes movement
of said end effector in said first region in at least some
directions.
Description
STATEMENT OF RELATED CASES
[0001] This case is related to U.S. patent applications Ser. No.
______ (Atty. Dkt. No. 115-001), Ser. No. ______ (Atty. Dkt. No.
115-003), Ser. No. ______ (Atty. Dkt. No. 115-004), and Ser. No.
______ (Atty. Dkt. No. 115-005), all of which are incorporated by
reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates generally to systems that
simulate medical procedures for the purposes of training or
accreditation. More particularly, the present invention relates to
a system, apparatus and subsystems for simulating vascular-access
procedures.
BACKGROUND OF THE INVENTION
[0003] Medical practitioners, such as military medics, civilian
emergency-medical personnel, nurses, and physicians, routinely
perform vascular-access procedures (e.g., IV insertion, central
venous-line placement, peripherally-inserted central catheter,
etc). It is desirable for a practitioner to be proficient at
performing these procedures since the proficient practitioner is
far less likely to injure a patient and is almost certain to reduce
the patient's level of discomfort.
[0004] Becoming proficient in vascular-access procedures requires
practice. In fact, the certification and re-certification
requirements of some states mandate a minimal number of needle
sticks, etc., per year per provider. Historically, medical
practitioners practiced needle-based procedures on live volunteers.
More recently, simulation techniques and devices have been
developed to provide training in vascular-access procedures without
the use of live volunteers. U.S. Pat. No. 6,470,302 ("the '302
patent") surveys the art of medical-simulation devices and also
discloses a vascular-access simulation system.
[0005] The vascular-access simulation system that is disclosed in
the '302 patent includes an "interface" device and a computer
system. To practice a vascular-access procedure, a user manipulates
an "instrument," referred to in the patent as a "catheter unit
assembly," which extends from the device and serves as a
catheter-needle. Potentiometers and encoders within the interface
device track the motion and position of the instrument and relay
this information to the computer system. The computer system
performs a simulation of the surface and subsurface anatomy of
human skin, and determines the effect of the instrument's motion on
the skin's anatomy. Simulated results are displayed by the computer
system. Using the motion information from the interface device, the
computer system also generates a control signal that controls a
force-feedback system that is coupled to the instrument. The
force-feedback system generates various resistive or reactive
forces that are intended to simulate the forces that are
experienced by a medical practitioner during an actual
vascular-access procedure. The user senses these forces during
manipulation of the instrument.
[0006] The simulation system that is disclosed in the '302 patent
has many shortcomings that substantially limit its utility as a
training or accreditation tool. A few of these shortcomings are
discussed below.
[0007] One shortcoming of that simulation system is that forces
that are sensed by a user during manipulation of the catheter unit
assembly are generally unrealistic. There are several reasons for
this. One reason is that the linear axis along which the catheter
unit assembly moves is offset from the rotational axes of a
sensing/force-feedback assembly to which it's coupled. This results
in an unrealistic torque sensation about the "insertion point" of
the catheter unit assembly. A second reason for the unrealistic
forces and force sensations that are experienced by a user is
excessive friction. Specifically, the various tension members and
bearings that couple the catheter unit assembly to the
sensing/force-feedback assembly introduce a substantial amount of
dynamic and static friction to the system. This is problematic
because the interface device cannot present a force that is less
than the friction that is inherent in the system. This excessive
friction therefore limits the dynamic range of the system. Also,
the presence of static friction (i.e., stiction) in the device
hampers smooth motion of the catheter unit assembly. Stiction is
not experienced during an actual vascular-access procedure.
[0008] A third reason for the unrealistic forces that are
experienced during use of the device that is disclosed in the '302
patent is that the device has relatively high inertia. In
particular, the large catheter unit assembly and the offset pulley
used in the force-feedback mechanism introduce substantial mass
into the system. This is undesirable because the catheter unit
assembly will not feel as "light" as it should when little or no
force feedback is being applied.
[0009] A second shortcoming of the '302 is that the end effector
(i.e., the catheter unit assembly) is permanently coupled to the
force-feedback system. Although not atypical for this type of
system (i.e., haptics devices) due to the difficulty of de-coupling
an end effector from its force-feedback system, this is very
undesirable because to truly mimic most "actual" systems,
de-coupling is necessary.
[0010] For example, in the case of an actual vascular-access
procedure, a medical practitioner experiences "force-feedback"
during insertion of a needle or catheter (i.e., an end effector)
into a patient's arm. That is, the anatomy of the arm presents a
resistance that is sensed (feedback) by the practitioner. In the
actual procedure, the needle or catheter is not, of course,
"coupled" to the arm until it is inserted by the practitioner. But
in the system that is disclosed in the '302 patent, the catheter
unit assembly is coupled to the force-feedback system and extends
from interface device at all times. A user, therefore, does not
actually insert the catheter unit assembly (i.e., the end
effector); there is no coupling and de-coupling.
[0011] The inability of prior-art vascular-access simulation
systems to realistically simulate a vascular-access procedure
limits their usefulness as a training or accreditation tool.
SUMMARY
[0012] The illustrative embodiment of the present invention is a
simulation system that provides realistic training and practice for
performing vascular-access procedures without using human subjects.
Unlike most prior-art simulation systems, some embodiments of the
present system provide a realistic simulation of the resistive
forces that a medical practitioner would experience if the
simulated procedure were an actual procedure that was being
performed on a real anatomy (e.g., human arm, etc.). Furthermore,
in accordance with the illustrative embodiment of the present
invention, the end effector (e.g., medical instrument, such as a
needle, catheter, etc.) is not coupled to a force-feedback system
until a user does so.
[0013] The illustrative embodiment of a vascular-access simulator
includes a data-processing system and an interface device, referred
to herein as a "haptics device." The haptics device provides the
physical interface for performing vascular-access procedures. More
particularly, a user inserts an end effector into the haptics
device and manipulates it to simulate needle insertion,
cannulation, etc. In some embodiments, the simulator is capable of
sensing the orientation of the end effector. For example, in some
embodiments in which the end effector is a needle or catheter or
both, the simulator is capable of sensing the orientation of a
beveled end of the needle or catheter.
[0014] In accordance with the illustrative embodiment, the haptics
device includes a receiver that receives the end effector when it
is inserted into the haptics device. In some embodiments in which
the end effector is a needle-catheter module, the receiver is a
needle-stick module.
[0015] In some embodiments, the needle-stick module provides one
linear degree of freedom and two, independent, rotational degrees
of freedom (i.e., pitch and yaw). In the illustrative embodiment,
the linear degree of freedom enables a user to advance the
needle/catheter module into the haptics device. This mimics the
insertion of a needle/catheter into a patient's arm. The rotational
degrees of freedom enable a user to move an engaged needle/catheter
module up or down and left or right. This mimics the freedom of
movement that a user has during an actual vascular-access
procedure.
[0016] Sensors within the haptics device monitor the motion and
position of the needle/catheter module (e.g., by measuring the
insertion depth and pitch and yaw angles of the needle-stick
module, etc.). The sensors generate signals indicative of the
monitored activity and transmit the signals to the data processing
system.
[0017] The data processing system processes the information
acquired by the sensors and, in conjunction with an anatomical
model, determines the effects (e.g., deformation, entry into a
vein, etc.) of a user's manipulation of the needle/catheter module
on the surface and subsurface features of the virtual body part on
which the simulated vascular-access procedure is being performed.
Results are displayed by the computer system. The results include,
for example, a three-dimensional rendering of the body part of
interest, a visual indication of the position of the
needle/catheter relative to the body part, and a visual indication
of how the needle/catheter affects that body part.
[0018] Furthermore, in some embodiments, using the anatomical model
and the information obtained from the sensors, the data processing
system determines the various resistive forces that would arise if
the user were manipulating a needle or catheter through an actual
anatomy (e.g., human arm, etc.). Based on this determination, the
data processing system or an associated device generates a control
signal.
[0019] The control signal is ultimately received by the
needle-stick module and, responsive thereto, the needle-stick
module provides "force feedback" to a user. The force-feedback is
sensed by a user as a resistance to continued advance (insertion)
of the needle/catheter module. The resistance is intended to
simulate penetration or contact with various surface and subsurface
features of human anatomy (e.g., the skin, a vein, harder
structures such as ligaments, bones, etc.) The resistance
advantageously varies with insertion depth and the pitch and yaw of
the needle/catheter module (since the resistance is determined
based on the estimated position of needle/catheter module in a
portion of the human anatomy).
[0020] As previously mentioned, it is typical, although
undesirable, for an end effector to be permanently coupled to a
force-feedback system. In accordance with the illustrative
embodiment of the present invention, the needle/catheter module
(i.e., an end effector) is not coupled to the needle-stick module
(which includes a force-feedback assembly) until a user couples
them during a simulated vascular-access procedure. And when the
simulated procedure is over, the user decouples the needle/catheter
module from the needle-stick module. A user's interactions with
simulators described herein therefore more closely simulate a real
vascular-access procedure than simulators in the prior art. This
more realistic simulation is expected to result in a more useful
training experience.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 depicts vascular-access simulation system 100 in
accordance with the illustrative embodiment of the present
invention.
[0022] FIG. 2 depicts functional elements of haptics device 102,
which is a part of vascular-access simulation system 100.
[0023] FIG. 3 depicts a top view of haptics device 102.
[0024] FIG. 4A depicts the salient elements of vascular-access
simulation system 100, wherein the end effector is not yet inserted
into a receiver within haptics device 102.
[0025] FIG. 4B depicts vascular-access simulation system 100
showing the end effector coupled to the receiver within haptics
device 102.
[0026] FIG. 5 depicts an illustrative embodiment of the
needle/catheter module.
[0027] FIG. 6 depicts the pseudo needle of the module depicted in
FIG. 5.
[0028] FIG. 7 depicts the pseudo catheter of the module depicted in
FIG. 5.
[0029] FIG. 8 depicts an embodiment of vascular-access simulation
system 100 wherein said system includes a data processing system,
pseudo skin, an end effector, and a receiver having a sensor and a
force-feedback system.
[0030] FIG. 9 depicts the needle/catheter module coupled to a
movable member in the receiver.
[0031] FIGS. 10A-10C depict an illustrative embodiment of the
needle-stick module, including a receiving module.
[0032] FIGS. 11A-11D depict further detail of the receiving
module.
[0033] FIG. 12 depicts an embodiment of the movable member.
DETAILED DESCRIPTION
[0034] The terms and phrases listed below are defined for use in
this specification as follows:
[0035] "End Effector" means a device, tool or instrument for
performing a task. The structure of an end effector depends on the
intended task. For example, in the illustrative embodiment, the end
effector is intended to be used to simulate a vascular access
procedure, and is therefore implemented as a catheter-needle
module. Those skilled in the art will recognize that term "end
effector" is borrowed from robotics, where it has a somewhat
different definition: a device or tool connected to the end of a
robot arm.
[0036] "Imitation" means an artificial likeness that is intended to
be substantially similar to an item being imitated; a copy. For
example, "imitation skin," which is used in conjunction with the
illustrative embodiment of the present invention, is intended to
mimic or copy genuine skin via appropriate selection of color,
appearance, feel, and overall presentation.
[0037] "Mock" means "representative;" a stand-in for a genuine
article, but not intended to closely imitate the genuine article. A
mock article will never be confused with the genuine article and
typically does not promote a suspension of disbelief that the mock
article is the genuine article. For example, "mock skin" is not
intended to mimic genuine skin, and typically departs from it in
terms of color, appearance, feel or overall presentation.
[0038] "Pseudo" is an inclusive term that means "imitation" or
"mock." For example, pseudo skin is meant to encompass both
imitation skin and mock skin.
[0039] "Skin" means genuine skin.
[0040] Additional definitions are provided later in this Detailed
Description.
[0041] This Detailed Description continues with an overview of a
vascular-access simulator in accordance with the illustrative
embodiment. Following the overview, specific embodiments of several
elements of the simulator are described in greater detail.
[0042] Overview
[0043] The illustrative embodiment of the present invention
pertains to a simulation system that provides realistic training
and practice for vascular-access procedures without using human
subjects. As depicted in FIG. 1, vascular-access simulator 100
includes haptics device 102 and data-processing system 104.
[0044] Haptics device 102 provides the physical interface for
performing any of several simulated vascular-access procedures
(e.g., intravenous catherization, central venous-line placement,
sternal intraosseous insertion, etc.).
[0045] The term "haptics" (as in "haptics device 102" ) relates to
touch (i.e., the sense of touch). A fundamental function of haptics
device 102, and indeed any haptics interface, is to create a means
for communication between users (i.e., humans) and machines. This
"communication" is possible since humans are capable of
"mechanically" interfacing with their surroundings due, at least in
part, to a sense of touch. This "sense of touch" includes
sensations of pressure, texture, puncture, thermal properties,
softness, wetness, friction-induced phenomena, adhesions, etc.
Furthermore, humans also experience vibro-tactile sensations, which
include the perception of oscillating objects in contact with the
skin and kinesthetic perceptions (i.e., awareness of one's body
state, including position, velocity, and forces supplied by the
muscles). As will become clear later in this Detailed Description,
our ability to perceive a variety of these sensations is exploited
by haptics device 102.
[0046] To the extent that some embodiments of simulator 100 are
intended for use as a practice and training tool, it is
advantageous for haptics device 102 to simulate vascular-access
procedures as realistically as possible and provide a quantitative
measure of the user's performance of the simulated procedure. To
this end, haptics device 102 possesses one or more of the following
attributes, in addition to any others:
[0047] It possesses sufficient degrees-of-freedom to simulate the
relatively free movement of a needle/catheter during an actual
vascular-access procedure.
[0048] It offers the opportunity to perform all steps of a
vascular-access procedure, including, for example, needle
insertion, skin interactions (e.g., palpation, skin stretch, etc.),
catheter threading, etc.
[0049] It generates appropriate skin- and venous-puncture
forces.
[0050] It measures or otherwise quantifies the effects of user
actions on simulated anatomy.
[0051] It generates appropriate haptic feedback (i.e., feel) during
skin-interaction steps.
[0052] It is configured to provide ergonomically-correct hand
position during simulated vascular-access procedures.
[0053] It is small enough so that it can be positioned in front of
a computer monitor so that the haptics device and the monitor are
inline with a user's forward-looking field of view.
[0054] It is at least subtly suggestive of human anatomy and does
not present any substantial departures therefrom so as to support a
user's ability to suspend disbelief during a simulated
vascular-access procedure.
[0055] Data-processing system 104, which includes processor 106,
monitor 108, keyboard 110, mouse 112, and speakers 114, supports
the visual aspects of the simulation and other functions described
below. Processor 106 is a general-purpose processor that is capable
of receiving and processing signals from haptics device 102,
running software for the visual portion of the vascular-access
simulation including an anatomy simulator, running calibration
software for calibrating the various sensing elements used in
haptics device 102, and sending control signals to haptics device
102 to support closed-loop force feedback, among other
capabilities. Processor 106 comprises memory, in which the software
described above is stored. In the illustrative embodiment,
processor 106 is a personal computer.
[0056] Monitor 108 displays a rendering that is generated by
processor 106, in conjunction with the above-referenced software.
The rendering, which in some embodiments is three-dimensional, is
of a region of the body (e.g., isolated arm, thorax, neck, etc.) on
which a simulated vascular-access procedure is being performed. The
rendering advantageously depicts visual aspects such as, without
limitation, the anatomical structures that underlie skin, local
deformation of the skin in response to simulated contact, and
tracking of a "virtual" instrument (e.g., a needle, etc.) through
anatomical structures that underlie the skin.
[0057] Haptics device 102 is now described in further detail. For
pedagogical purposes, haptics device 102 is depicted in FIG. 2 as
comprising several functional modules or elements. These
include:
[0058] End effector or Needle/catheter module 218;
[0059] Pseudo skin 220;
[0060] Palpation module 222;
[0061] Skin-stretch module 224;
[0062] Receiver or Needle-stick module 226; and
[0063] Electronics/communications interface 228.
[0064] The functional elements of haptics device 102 listed above
that relate to human anatomical features or are otherwise intended
to generate resistive forces that would be sensed when penetrating
such anatomical features (elements 222-228) are advantageously
contained within housing 216 or otherwise located "underneath"
pseudo skin 220. In an actual vascular-access procedure, the needle
or catheter, of course, remains outside of the body until inserted
during the procedure. Likewise, in accordance with the illustrative
embodiment, the end effector-needle/catheter module 218--remains
outside of housing 216 and pseudo skin 220 until a portion of it is
inserted during a simulated vascular-access procedure. In some
embodiments, housing 216 is subtly shaped like a portion of a human
arm, yet is nondescript enough to avoid creating a discontinuity
between what is seen and what is felt.
[0065] Pseudo skin 220 is a membrane that is used in conjunction
with the simulation of skin-interaction techniques, such as
palpation, occlusion, and skin stretch techniques. Pseudo skin 220
is advantageously, but not necessarily, imitation skin (i.e.,
skin-like in appearance). In embodiments in which pseudo skin 220
is imitation skin, it possesses any one of a number of natural
flesh tones. In some embodiments, pseudo skin 220 is at least
somewhat resilient to enable a user to perform skin-interaction
techniques. In some embodiments, pseudo skin 220 comprises a
thermoplastic elastomer such as Cawiton.RTM., which is available
from Wittenburg, B.V., Hoevelaken, Netherlands. The use of
imitation skin, as opposed to mock skin, is desirable because it
helps a user to "suspend disbelief," which contributes to making
simulator 100 more useful as a training tool.
[0066] As depicted in FIG. 3, pseudo skin 220 is accessed for
insertion and skin-interaction techniques (e.g., palpation,
occlusion, skin stretch, etc.) through openings 330 and 332 in
housing 216. Opening 330 defines palpation/occlusion region 331
(i.e., the site at which palpation and occlusion techniques are
performed) and opening 332 defines skin-stretch region 333 (i.e.,
the site at which the skin-stretch technique is performed) and
includes insertion point 334 for the end effector (e.g.,
needle/catheter module 218).
[0067] The ability to perform skin-interaction techniques provides
a more realistic simulation of vascular-access procedures. In some
embodiments, this ability is provided in conjunction with palpation
module 222 and skin-stretch module 224. These modules, and
illustrative embodiments thereof, are described in further detail
applicant's co-pending U.S. patent application Ser. No. ______
(Atty. Dkt. 115-001).
[0068] Pseudo skin 220 is disposed adjacent to the inside surface
of housing 216 so that it appears to be nearly co-extensive (i.e.,
co-planar) with housing 216 at openings 330 and 332. This is
intended to create a subtle suggestion that the surface of housing
216 is "skin" at regions other than where pseudo-skin 220 is
accessed for skin-interaction techniques. Consistent with human
anatomy, the remaining functional elements of haptics device 102
(elements 222-228), with the exception of needle/catheter module
218, are "hidden" beneath pseudo skin 220.
[0069] The end effector (e.g., needle/catheter module 218, etc.) is
inserted into haptics device 102 at insertion point 334 in opening
332. In some embodiments, simulator 100 is capable of sensing
orientation of the end effector, such as to determine the
orientation of a feature of a needle or catheter. In some
embodiments, the feature is a bevel. This is an important aspect of
the real insertion technique, since proper bevel orientation
reduces a patient's discomfort during needle/catheter insertion. In
some embodiments, needle/catheter module 218 is configured to be
very similar to a real needle and catheter.
[0070] Once inserted into haptics device 102, the tip of
needle/catheter module 218 engages receiver 226, which, for the
illustrative embodiment of a vascular access simulator, is referred
to as a "needle-stick module." Needle-stick module 226 supports the
continued "insertion" of the needle/catheter module 218. In
particular, in some embodiments, needle-stick module 226 is
configured to provide one linear degree of freedom and two
rotational degrees of freedom (i.e., pitch and yaw). The linear
degree of freedom provides a variable insertion depth, enabling a
user to advance needle/catheter module 218 into the "patient's arm"
(i.e., haptics device 102). The rotational degrees of freedom
enable a user to move (an engaged) needle/catheter module 218 up or
down and left or right. In some embodiments, needle-stick module
226 measures insertion depth, and pitch (up/down) and yaw
(left/right) angles.
[0071] In some embodiments, needle-stick module 226 provides "force
feedback" to a user, whereby the user senses a variable resistance
during continued advance (insertion) of needle/catheter module 218.
The resistance is intended to simulate penetration of the skin, a
vein, and harder structures such as ligaments, bones, and the like.
The resistance advantageously varies with insertion depth and the
pitch and yaw of needle/catheter module 218, as described further
below.
[0072] It will be understood that the "measurements" of angle,
position, etc. that are obtained by the functional elements
described above are obtained in conjunction with various sensors
and data-processing system 104. In particular, most of the
functional elements described above include one or more sensors.
The sensors obtain readings from an associated functional element,
wherein the readings are indicative of the rotation, displacement,
etc., of some portion of the functional element. These readings
provide, therefore, information concerning the manipulation of
needle/catheter module 218 in addition to any parameters.
[0073] Each sensor generates a signal that is indicative of the
reading, and transmits the signal to electronics/communications
interface 228. Sensors used in some embodiments include, without
limitation, potentiometers, encoders, and MEMS devices. Those
skilled in the art will know how to use and appropriately select
sensors as a function of their intended use in conjunction with the
functional elements described above.
[0074] Electronics/communications interface 228 receives the
signals transmitted by the various functional elements of haptics
device 102 and transmits them, or other signals based on the
original signals, to data-processing system 104. Furthermore,
electronics/communications interface 228 distributes power to the
various functional modules, as required.
[0075] As described later below, electronics/communications
interface 228 also receives signals from data processing system 104
and transmits them to needle-stick module 226, among any other
modules within haptics device 102, as part of a closed loop
force-feedback system. In some embodiments, the signals received
from data processing system 104 are amplified before they are
transmitted to needle-stick module 226, etc. As an alternative to
having electronics/communications interface 228 transmit the
signals that are received from data processing system 104, in some
embodiments, the electronics/communications interface generates new
signals based on the received signals. This approach, which is
typically referred to as embedded control, is well known in the
art. It disadvantageously requires a substantial increase in
processing power and data management (relative to simply
transmitting the received signals, or simply amplifying the
received signals) and is generally a less-preferred approach.
[0076] Data-processing system 104 receives the measurement data
and, using the simulation software, calculates the forces that are
being applied by the user during the skin-interaction procedures.
Furthermore, using an anatomical model, data-processing system 104
calculates the position and angle of a virtual needle within a
simulated anatomy (e.g., arm, etc.). Data-processing system 104
displays, on monitor 108, a rendering of the appropriate anatomy
(e.g., arm, etc.) and displays and tracks the course of a virtual
needle within this anatomy.
[0077] Furthermore, based on the position and course of the virtual
needle (as calculated based on the position and orientation of
needle/catheter module 218), data-processing system 104 generates
control signals that are transmitted to needle-stick module 226.
These control signals vary the resistive force presented by
needle-stick module 226 to account for various anatomical
structures (e.g., vein, tissue, tendons, bone, etc.) that
needle/catheter module 218 encounters, based on the simulation. As
a consequence, the resistance to continued needle/catheter
insertion that is experienced by a user of simulator 100 is
consistent with the resistance that would be sensed by a
practitioner during an actual vascular access procedure.
[0078] Having completed the overview of vascular-access simulator
100 and haptics device 102, the end effector (in the illustrative
embodiment needle/catheter module 218) and receiver (in the
illustrative embodiment needle-stick module 226) will be described
in further detail.
[0079] FIGS. 4A and 4B depict haptics device 102 and data
processing system 104 of simulator 100. In the embodiment depicted
in these Figures, haptics device 102 includes needle/catheter
module 218, needle-stick module 226 and electronics/communications
interface 228. It will be appreciated that in other embodiments,
other functional modules (such as those described previously) in
addition to or instead of needle-stick module 226 and
electronics/communications interface 228 are typically present
within haptics device 102.
[0080] The needle-stick module and the electronics/communications
interface are disposed within housing 216. Both needle/catheter
module 218 and needle-stick module 226 are electronically coupled
to electronics/communications interface 228, and through it coupled
to data processing system 104. As previously described,
electronics/communication- s interface 228 provides power to these
and other modules, receives signals from these and other modules as
well as data processing system 104, and sends signals to
needle-stick module 226 and data processing system 104.
[0081] Needle-stick module 226 is disposed substantially beneath
pseudo skin 220 and is accessible to needle/catheter module 218 via
insertion point 334. In some embodiments, a portion (i.e., guide
1089, see .paragraph.0086 and FIGS. 10A-10C) of needle-stick module
226 is raised slightly above the plane of pseudo skin 220 to simply
the process of engaging needle/catheter module 218 to the
needle-stick module. In the illustrative embodiment, insertion
point 334 is an opening in pseudo skin 220. In some other
embodiments, the needle/catheter module penetrates pseudo skin 220.
FIG. 4A depicts the simulator before a user has inserted
needle/catheter module 218 into needle-stick module 226. FIG. 4B
depicts the simulator after a user has inserted the needle/catheter
module into the needle-stick module.
[0082] FIGS. 5-7 depict an illustrative embodiment of
needle/catheter module 218 and its constituent parts. In the
illustrative embodiment, needle/catheter module includes needle
portion 536 and catheter portion 554, which can be coupled to or
decoupled from one another. FIG. 5 depicts the needle portion and
catheter portion coupled to one another. FIG. 6 depicts only needle
portion 536 and FIG. 7 depicts only catheter portion 554. When
needle portion 536 is coupled to catheter portion 554, needle 650
(FIG. 6) is received by catheter 758 (FIG. 7).
[0083] As depicted in FIG. 5, needle/catheter module 218 includes
sensor 538. In the illustrative embodiment, sensor 538 is disposed
in needle portion 536. In some embodiments, sensor 538 provides
data that is indicative of the orientation of the bevel, such as
bevel 760 of catheter portion 554 (see, FIG. 7). Those skilled in
the art will know how to select and use a device to function as
sensor 538. In some embodiments, sensor 538 is one or more
micro-electromechanical system (MEMS) devices. As is well known in
the art, MEMS devices typically have a size within a range of about
100 nanometers to a millimeter, and are created using surface
micro-machining techniques (e.g., depositing mechanical and
sacrificial layers, selectively etching to pattern, etc.)
[0084] In the illustrative embodiment that is depicted in FIG. 6,
needle portion 536 includes needle housing 640, needle 650, and
wire 652. Housing 640 includes surface features such as ergonomic
grip 642 and ridge 644. Needle portion 536 and catheter portion 554
are configured for locking engagement, such as by inserting ridge
644 into a complementary slot (not depicted) in coupler 756 of
catheter 554.
[0085] Needle housing 640 contains sensor 538, which in the
illustrative embodiment depicted in FIG. 6 comprises two MEMS
accelerometers 646 and 648. The accelerometers are electrically
coupled to wire 652, which is, in turn, coupled to
electrical/communications interface 228. The accelerometers are
oriented orthogonal to one another so that they detect motion along
orthogonal axes. Each of accelerometers 646 and 648 is capable of
generating a signal that is indicative of motion along two
orthogonal axes. It is notable that while MEMS accelerometers 646
and 648 can detect motion along two orthogonal axes, this is not
necessary for resolving the orientation of, for example, the bevel.
This can be done by detecting motion along only one axis. This
information obtained by the accelerometers is ultimately
transmitted to data processing system 104 and used by it to resolve
the orientation of housing 640 or anything rigidly coupled to it
(such as catheter portion 554) in two dimensions. MEMS
accelerometers suitable for use as sensor 538 include, for example,
dual-axis accelerometers with duty cycle output, such as model
ADXL202E available from Analog Devices, Inc. of Norwood, Mass.
[0086] In the illustrative embodiment, needle portion 536 is
connected via wire to electrical/communications interface 228. But
in some other embodiments, needle-catheter module 218 is a wireless
device. In these other embodiments, needle portion 536 communicates
wirelessly with either electrical/communications interface 228 or
(directly) with data processing system 104. In such embodiments,
needle portion 536, electrical/communications interface 228, and
data processing system 104 include a transceiver, receiver, or
transmitter, as appropriate. In embodiments in which
needle/catheter module 218 operates wirelessly, it advantageously
includes its own power source, such as one or more lithium-ion
batteries, etc. Those skilled in the art will know how to make and
use embodiments of the present invention in which needle/catheter
module 218 is configured for wireless operation.
[0087] In the illustrative embodiment, bevel 760 is formed on
catheter 758. Those skilled in the art of vascular-access
techniques will recognize that in an authentic instrument (i.e.,
authentic needle and catheter) the bevel is typically formed in the
needle rather than the catheter. Bevel 760 is formed on catheter
758, rather than needle 650, as a preferred location in view of
other design decisions (in particular, the manner in which needle
650 is coupled to needle-stick module 226, which is described in
detail later in this specification). In other embodiments, the
bevel is formed on needle 650. In such other embodiments, it will
be advantageous to suitably modify the way in which needle 650
couples to needle-stick module 226.
[0088] FIG. 8 depicts further detail of an illustrative embodiment
of needle-stick module 226. In this embodiment, needle-stick module
includes force-feedback assembly 862 and sensor 864. In FIG. 8,
needle 650 or catheter 758 is shown "penetrating" pseudo skin 220
at insertion point 334 and is received by needle-stick module
226.
[0089] Sensor 864, which can be one or more sensors, senses the
position of needle 650/catheter 758. In some embodiments, sensor(s)
864 obtains information indicative of the extent of penetration of
the needle/catheter into needle-stick module 226. In some other
embodiments, sensor(s) 864 also measures the orientation of the
needle/catheter, assuming that needle/catheter module 218 is free
to move in other directions. In other words, sensor(s) 864 monitor
movement along axes that align with one or more available degrees
of freedom.
[0090] Sensor(s) 864 generates signal(s) indicative of the
monitored movement. The sensor(s) are directly or indirectly
coupled to data processing system 104. The signals, or other
signals derived therefrom, are transmitted from sensor(s) 864 and
are ultimately received by data processing system 104. Using the
data contained in the signal(s), and in conjunction with anatomical
model 866 and force-calculation software 868, the data processing
system:
[0091] determines the anatomical features that the needle/catheter
would encounter (skin, vein, ligaments, bone, etc.), based on its
position, were it moving through an actual anatomy; and
[0092] calculates the resistive forces that would arise as the
needle/catheter encounters these various anatomical features.
[0093] A control signal(s) is generated by controller 870 based on
the force calculations. The control signal(s) is transmitted to
haptics device 102 and is ultimately received by force-feedback
assembly 862.
[0094] Responsive to the control signal(s), force-feedback assembly
862 generates force F.sub.R that opposes movement of the
needle/catheter. In some embodiments, force F.sub.R only opposes
"forward" movement (i.e., movement in the direction of continued
insertion) of the needle/catheter through needle-stick module 226.
In some other embodiments, forces are generated that oppose
movement of the needle/catheter both in the forward and reverse
direction (i.e., insertion and removal).
[0095] FIG. 9 depicts further detail of an embodiment of
needle-stick module 226. In the embodiment that is depicted in FIG.
9, needle-stick module 226 includes movable member 972. When
needle/catheter module 218 is inserted into haptics device 102,
needle 650 or catheter 758 couples to movable member 972. The
movable member is capable of moving forward or backward along
translational axis A-A; for example, as a user manipulates
needle/catheter module 218 into or out of haptics device 102. In
some embodiments, sensor 864A monitors translational motion of
movable member 972 and, hence, the translational motion of
needle/catheter module 218.
[0096] It is desirable for movable member 972 to move with very low
friction. In some embodiments, this is implemented via an
arrangement that provides "rolling contact." In other words, to the
extent that movable member 972 contacts a surface, the contact
involves a rolling member (e.g., pulleys against a cable, ball
bearings against a surface, etc.) Rolling contact is to be
distinguished, for example, from sliding contact, the latter
typically associated with greater friction.
[0097] FIGS. 10A-10C, 11A-11D and 12 depict an embodiment of
needle-stick module 226. In particular, FIGS. 10A-10C depict an
embodiment of needle-stick module 226 via exploded view (FIG. 10A),
side view (FIG. 10B) and top view (FIG. 10C). FIGS. 11A-11D depict
an illustrative embodiment of receiving module 1076, which includes
force-feedback assembly 862 and movable member 972. And FIG. 12
depicts an illustrative embodiment of movable member 972.
[0098] Referring now to the exploded view depicted in FIG. 10A,
needle-stick module 226 comprises receiving module 1076, base and
gimbal assembly 1078, and counterweight assembly 1080. Receiving
module 1076 couples to secondary-gimbal bracket 1083, counterweight
holder 1081 rigidly couples to pitch potentiometer shaft 1084, and
link 1086 couples, at one end, to receiving module 1076 (via to
ball-joint ball 1090) and at the other end to counterweight holder
1081 (see also, FIGS. 10B, 10C). Base 1079 of needle-stick module
226 is disposed on the bottom inside surface of housing 216 in the
manner depicted in FIGS. 4A and 4B.
[0099] The illustrative embodiment of needle-stick module 226
provides three degrees of freedom--one translational and two
rotational--as follows. Movable member 972 moves within receiving
module 1076 along translational axis 1-1. This provides the
"translational" degree of freedom. (See also, FIG. 10C,
translational movement is movement in the directions indicated by
path A-A.) Secondary gimbal bracket 1083 and receiving module 1076
rotate about pitch axis 2-2. (See also, FIG. 10B, pitch is movement
in the directions indicated by path B-B.) Primary-gimbal bracket
1088 and receiving module 1076 rotate about yaw axis 3-3. (See
also, FIG. 10C, yaw is movement in the directions indicated by path
C-C.) Rotation about the pitch and yaw axes provide the two
"rotational" degrees of freedom of needle-stick module 226.
[0100] In the illustrative embodiment, pitch and yaw of receiving
module 1076 are tracked by potentiometers. More particularly, pitch
is evaluated using pitch potentiometer 1092 and yaw is evaluated
using yaw potentiometer 1094, as described further below.
Potentiometers 1092 and 1094 are, therefore, specific embodiments
of generic sensor(s) 864 of FIG. 8.
[0101] With continuing reference to FIG. 10A, pitch potentiometer
1092 is coupled to the obscured side of potentiometer holding plate
1096. As receiving module 1076 swings up or down (i.e., pitches),
link 1086 forces counterweight holder 1081 to rotate about an axis
that aligns with pitch potentiometer shaft 1084 (see also, FIG.
10B). Since counterweight holder 1081 is rigidly attached to
potentiometer shaft 1084, that shaft turns as the counterweight
holder rotates. Rotation of the potentiometer shaft and, hence,
pitching of receiving module 1076 is therefore "sensed" by pitch
potentiometer 1092. Pitch potentiometer 1092 is electrically
coupled to electronics/communications interface 228 (not depicted
in FIG. 10A, see, e.g., FIGS. 4A and 4B). Pitch potentiometer 1092
generates a signal indicative of the sensed movement and transmits
it to electronics/communications interface 228 and, through it, to
data processing system 104. It is notable that since counterweight
1082 moves along with counterweight holder 1081, the weight of
receiving module 1076 is counterbalanced through its full range of
motion.
[0102] Still referring to FIG. 10A, yaw potentiometer 1094 is
disposed beneath yaw potentiometer shaft 1097 and is coupled to an
obscured surface of base 1079. Primary-gimbal bracket 1088 is
mechanically coupled to yaw potentiometer shaft 1097 by links 1098
and 1099 (see also, FIG. 10C). Yaw potentiometer shaft 1097 is
coupled to yaw potentiometer 1094 in known fashion. Rotation of yaw
potentiometer shaft 1097 and, hence, yawing of receiving module
1076 is therefore "sensed" by yaw potentiometer 1094. The yaw
potentiometer is electrically coupled to electronics/communications
interface 228 (not depicted in FIG. 10A, see, e.g., FIGS. 4A and
4B). Yaw potentiometer 1094 generates a signal indicative of the
sensed movement and transmits it to electronics/communications
interface 228 and, through it, to data processing system 104.
Potentiometers suitable for use as potentiometers 1092 and 1094 are
commercially available from Clarostat Sensors and Controls, Inc. of
El Paso, Tex., among others.
[0103] In use, the catheter and or needle of needle-catheter module
218 is inserted into guide 1089. Once inserted into guide 1089, the
tip of the catheter or needle and movable member 972 couple to one
another. In the illustrative embodiment, magnet 973 is disposed at
the forward end of movable member 972 (see, FIGS. 10A and 12). The
magnet is used as a means to readily and reversibly couple the tip
of needle 650 or catheter 758 to movable member 972.
[0104] It was previously disclosed that in some embodiments,
movable member 972 is coupled to a force-feedback system, referred
to earlier as force-feedback assembly 862. As previously described,
force-feedback assembly 862 generates a resistance to continued
insertion of needle-catheter module 218 into receiving module 1076.
An illustrative embodiment of force-feedback assembly 862 and
additional description of receiving module 1076 is now provided in
conjunction with FIGS. 11A-11D.
[0105] FIG. 11A depicts an exploded view of an embodiment of
receiving module 1076. In the illustrative embodiment, receiving
module 1076 includes frame 1149, which comprises lower plate 1150
and upper plate 1152. The receiving module also includes movable
member 972 and force-feedback assembly 862, which comprises motor
1156, motor encoder 1158, motor pulley 1160, pulleys 1162, and
cable 1164 (shown in FIG. 11D only).
[0106] Movable member 972 is disposed between upper and lower
plates 1150 and 1152 and is positioned between centrally-located
openings 1154 in the plates. Referring to FIG. 11B, movable member
972 is suspended at pulleys 1274A and 1274B (see also, FIG. 12) by
cable 1164, which is depicted as a dashed line for clarity. Cable
1164 is fixed at one end by holder 1166 and fixed at the other end
by holder 1168. Holders 1166 and 1168 are coupled to one another by
tensioning screw 1170, which adjusts the tension in cable 1164.
Cable 1164 is supported at a variety of intermediate locations by
pulleys 1162 (i.e., 1162A-1162D). The cable also wraps around motor
pulley 1160, thereby coupling movable member 972 to motor 1156.
[0107] FIGS. 11C and 11D depict a bottom view of receiving module
1076. These Figures depicts sequential "snap shots," wherein needle
650/catheter 758 is inserted deeper into receiving module 1076
(e.g., by a user practicing a vascular-access technique with
needle/catheter module 218, etc.). Since the needle/catheter is
coupled to movable member 972 (e.g., by magnet 973, etc.), the
movable member is also moved "deeper" into receiving module 1076.
Indeed, once coupled, any movement of needle/catheter module 218
causes movable member 972 to advance or retreat along axis 1-1
within region 1154 of plates 1150 and 1152.
[0108] As described above, motor 1156 is coupled to movable member
972 via cable 1164 (FIG. 11B). Any movement of the movable member
therefore causes the motor to move. For example, as movable member
972 moves forward or "deeper" into receiving module 1076, motor
pulley 1160 turns in a clockwise direction (for the particular
arrangement depicted in FIG. 11B). Movement of the motor pulley
causes the motor to turn and this movement is captured by encoder
1158 (FIG. 11A) in known fashion. As a consequence, translational
motion of movable member 972, and, therefore, the position of
needle/catheter module 218, is sensed by encoder 1158. The encoder
is therefore an embodiment of sensor(s) 864 of FIG. 8. The encoder
is electrically coupled to electronics/communications interface 228
(see, e.g., FIGS. 4A and 4B). Encoder 1158 generates a signal
indicative of the movement of motor 1156 and transmits it to
electronics/communications interface 228 and, through it, to data
processing system 104.
[0109] In addition as functioning as a means for tracking the
position of movable member 972 (and needle/catheter module 218),
motor 1156 also functions as a key element of force-feedback
assembly 862.
[0110] In particular, responsive to a control signal (e.g.,
generated by controller 870 of FIG. 8, etc.), which is based on
calculations performed by data processing system 104, the motor
engages with a specified amount of torque in a counterclockwise
direction (for the particular arrangement depicted in FIG. 11B).
This generates a force, F.sub.R, which opposes or counters the
force applied by a user during continued insertion of
needle/catheter 218. As previously described, force F.sub.R is
intended to simulate the resistance that would be presented by
various anatomical features, were the simulated vascular-access
procedure an actual procedure that was being performed on a real
anatomy.
[0111] It is notable that in the arrangement that is depicted in
FIG. 11B, the insertion force applied by a user is aligned with the
tension in cable 1164 and with the translational degree of freedom.
As a consequence, no unusual or unrealistic torque sensations are
experienced by a user as needle/catheter module 218 is inserted
into receiving module 1076.
[0112] A motor suitable for use in conjunction with the present
invention is a coreless brushed DC motor, such as is commercially
available from Maxon Precision Motors, Inc. of Fall River, Mass. In
some embodiments, cable 1164 is made from stainless steel and the
pulleys 1162 are nylon pulleys. In such embodiments, the
force-feedback assembly has very low inertia, very low friction,
and is very stiff. As will be appreciated by those skilled in the
art, these are all attributes of a good haptics design.
[0113] It is to be understood that the above-described embodiments
are merely illustrative of the present invention and that many
variations of the above-described embodiments can be devised by
those skilled in the art without departing from the scope of the
invention. For example, in this specification, numerous specific
details are provided in order to provide a thorough description and
understanding of the illustrative embodiments of the present
invention. Those skilled in the art will recognize, however, that
the invention can be practiced without one or more of those
details, or with other methods, materials, components, etc.
[0114] Furthermore, in some instances, well-known structures,
materials, or operations are not shown or described in detail to
avoid obscuring aspects of the illustrative embodiments. It is
understood that the various embodiments shown in the Figures are
illustrative, and are not necessarily drawn to scale. Furthermore,
the particular features, structures, materials, or characteristics
can be combined in any suitable manner in one or more embodiments.
It is therefore intended that such variations be included within
the scope of the following claims and their equivalents.
* * * * *