U.S. patent application number 16/801117 was filed with the patent office on 2020-06-18 for deflectabe medical device.
The applicant listed for this patent is KONINKLIJKE PHILIPS N.V.. Invention is credited to Jacob Roger HAARTSEN, Maurice Hubertus Elisabeth VAN DER BEEK, Rudolf Maria Jozef VONCKEN.
Application Number | 20200187753 16/801117 |
Document ID | / |
Family ID | 52807718 |
Filed Date | 2020-06-18 |
United States Patent
Application |
20200187753 |
Kind Code |
A1 |
VONCKEN; Rudolf Maria Jozef ;
et al. |
June 18, 2020 |
DEFLECTABE MEDICAL DEVICE
Abstract
A deflectable medical device (1) includes a shape memory alloy
wire (15) integrated into a flexible elongated body (11). The shape
memory alloy wire (15) is arranged to shorten upon receiving energy
from an energy supply (2,4), thereby deflecting the medical device
(1). A rod (18) positioned in a lumen (14) of the flexible
elongated body (11) and compressed between a fixture (16) in the
proximal end (12) of the elongated body (11) and the distal end
(13) of the elongated body (11) is responsible for the shape memory
alloy wire (15) recovering its initial length upon discontinuation
of energy supply.
Inventors: |
VONCKEN; Rudolf Maria Jozef;
(EINDHOVEN, NL) ; HAARTSEN; Jacob Roger;
(EINDHOVEN, NL) ; VAN DER BEEK; Maurice Hubertus
Elisabeth; (EINDHOVEN, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS N.V. |
Eindhoven |
|
NL |
|
|
Family ID: |
52807718 |
Appl. No.: |
16/801117 |
Filed: |
February 25, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15563807 |
Oct 2, 2017 |
10575715 |
|
|
PCT/EP2016/057160 |
Mar 31, 2016 |
|
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16801117 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2017/00318
20130101; A61M 25/005 20130101; A61B 1/0058 20130101; A61B
2017/00305 20130101; A61B 18/1492 20130101; A61M 25/0147 20130101;
A61M 25/0158 20130101 |
International
Class: |
A61B 1/005 20060101
A61B001/005; A61M 25/01 20060101 A61M025/01; A61M 25/00 20060101
A61M025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 2, 2015 |
EP |
15162438.4 |
Claims
1. A deflectable medical device comprising: a flexible elongated
body comprising a longitudinal axis; a shape memory alloy wire
disposed within the flexible elongated body eccentric to the
longitudinal axis, wherein the shape memory alloy wire is
configured to shorten in an axial direction in response to
receiving energy from an energy supply such that the flexible
elongated body is deflected; and a rod disposed within the flexible
elongated body, wherein the rod is configured to provide a force in
the axial direction to lengthen the shape memory alloy wire when
the energy supply discontinues providing the energy to the shape
memory alloy wire.
2. The device of claim 1, wherein the energy supply is connected
electrically to the shape memory alloy wire, and wherein the shape
memory alloy wire is configured to convert electrical energy
provided by the energy supply into heat through electrical
resistance.
3. The device of claim 1, wherein the energy supply is connected
electrically to a resistor disposed: proximate to the shape memory
alloy wire; or coaxial with the shape memory alloy wire; or as a
coating surrounding the shape memory alloy wire; or as windings of
a material around the shape memory alloy wire.
4. The device of claim 3, wherein the resistor heats the shape
memory alloy wire when energized with energy from the energy
supply.
5. The device of claim 1, wherein the energy supply provides
alternating current to a coil surrounding the shape memory alloy
wire, and wherein the coil heats the shape memory alloy wire
through induction when energized by the alternating current.
6. The device of claim 1, wherein the energy supply is a pump for
providing fluid flow proximate to at least a portion of the shape
memory alloy wire.
7. The device of claim 6, wherein the fluid flow is hotter than the
shape memory alloy wire and provides heat energy to the shape
memory alloy wire.
8. The device of claim 6, wherein the fluid flow is cooler than the
shape memory alloy wire and removes heat energy from the shape
memory alloy wire, such that the shape memory alloy wire is induced
to lengthen in the axial direction in response to the fluid
flow.
9. The device of claim 1, wherein a control unit controls a
quantity of energy received from the energy supply by the shape
memory alloy wire.
10. The device of claim 1, further comprising a handgrip on a
proximal end of the device.
11. The device of claim 1, wherein the shape memory alloy wire
comprises an alloy of Ni--Ti, Cu--Al--Ni, Cu--Zn, or
Ni--Ti--Pd.
12. The device of claim 1, wherein the shape memory alloy wire
comprises a diameter of between about 50 micrometers and about 200
micrometers.
13. The device of claim 1, wherein the flexible elongated body
comprises a polymer.
14. The device of claim 13, wherein the polymer comprises a
thermoplastic elastomer.
15. The device of claim 14, wherein the thermoplastic elastomer
comprises PEBAX.
16. The device of claim 1, wherein the shape memory alloy wire is
incorporated into the flexible elongated body by overmolding.
17. The device of claim 1, wherein the flexible elongated body
includes through-holes in a distal portion for dispensing fluid
into a surrounding of the distal portion.
18. The device of claim 1, wherein a distal portion of the flexible
elongated body further comprises a metallic tip for providing
treatment energy to a surrounding of the distal portion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/563,807, filed Oct. 2, 2017, now U.S. Pat. No. 10,575,715,
which is the U.S. National Phase application under 35 U.S.C. .sctn.
371 of International Application No. PCT/EP2016/057160, filed on
Mar. 31, 2016, which claims the benefit of European Patent
Application No. 15162438.4, filed on Apr. 2, 2015. These
applications are hereby incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates to a medical device with
controllable deflection of a portion of the medical device, a
system comprising the medical device and a method for deflecting a
medical device.
BACKGROUND OF THE INVENTION
[0003] Minimally invasive procedures involve accessing specific
sites through anatomical structures. Examples of such procedures
are angioplasty, stenting, thrombolysis, where an interventional
device is navigated through the vasculature to access a designated
site. Navigating through branching pathways is challenging without
appropriately designed steerable medical devices.
[0004] A medical device with a steerable distal portion is
disclosed in U.S. Pat. No. 5,090,956, wherein the maneuverability
of the distal portion is achieved by a combination of a temperature
activated memory element moving in a first direction to assume a
predetermined shape when heated to a predetermined temperature and
a spring for yieldable urging the shape memory element in a second
direction away from the first direction upon cooling of the memory
element to a temperature less than the predetermined temperature,
so that the memory element is moved to assume a shape other than
the predetermined shape.
[0005] Multidirectional steering of such medical device can be
achieved by integrating multiple temperature activated memory
elements, each of them being able to assume a predetermined shape
when heated to a predetermined temperature. Deflection of a device
with such configuration occurs due to the mechanical equilibrium of
the force generated by the first temperature activated memory
element moving in a first direction to assume a predetermined
shape, the restoring force of the spring and the restoring forces
of the non-active memory elements. Such construction becomes
complex with increasing maneuverability requirements due to the
fact that the force necessary to be created by a first temperature
activated memory element in order to overcome the restoring forces
of the spring and the remaining non-activated memory elements is
significantly large, resulting in a considerably large cross
sectional area of the temperature activated memory element. This
however works against miniaturization of the device, hence when a
second temperature activated memory element is required to deflect
the device in a second direction to assume a predetermined shape of
the second temperature activated memory element, the large cross
section area of the first element creates a large restoring force
at its turn, which limits the bending radius of the device.
SUMMARY OF THE INVENTION
[0006] It is an object of the invention to provide a medical device
with improved potential for miniaturization.
[0007] According to the invention, this object is realized by a
medical device comprising:
[0008] a flexible elongated body having proximal and distal ends
and a first lumen,
[0009] a shape memory alloy wire eccentric to the longitudinal axis
and extending at least partially along the elongated body, the
shape memory alloy wire fixed at least at two distinctive points
with respect to the elongated body and arranged to receive energy
from an energy supply so as to heat the shape memory alloy
wire,
[0010] a fixture in the proximal end of the elongated body,
[0011] a rod located in the first lumen and extending at least from
the fixture to the distal end of the elongated body, the rod fixed
with respect to the elongated body between the fixture and the
distal end;
[0012] wherein the rod is compressed between the fixture and the
distal end of the elongated body,
[0013] wherein the shape memory alloy wire is arranged to shorten
upon receiving energy from the energy supply.
[0014] The benefit of using wires of shape memory alloys is the
miniaturization potential of the medical device, since the
operation of the medical device relies on the lever that is created
by the shape memory alloy wire positioned eccentric to the
longitudinal axis of the medical device, and arranged to shorten
upon receiving energy from the energy supply. There is no need of a
restoring force of a spring or that of supplementary structures
urging the shape memory element in a second direction away from the
first direction upon cooling of the memory element to a temperature
less than the predetermined temperature, since the deflection is
not created by the bending force of a shape memory element.
[0015] The shape memory alloy wire requires axial tension to regain
its initial length after discontinuing supply of energy to the
shape memory alloy wire, a process called detwinning, attributed to
the unique deformation mechanism partially responsible for the
shape memory effect in addition to phase transformation. A rod
located in a first lumen and extending from a fixture in the
proximal end of the elongated body to the distal end of the
elongated body, and arranged such that the rod is compressed
between the fixture and the distal end of the elongated body, is
responsible for detwinning the shape memory alloy wire. The rod
arranged in a compressed status creates tensile stress in the
elongated body, which brings the shape memory alloy wire back to
its initial length upon discontinuation of energy supply to the
shape memory alloy wire. A significant advantage of the invention
is that there are less stringent spatial requirements for creating
axial detwinning forces than for creating lateral restoring bending
forces. Improvement in deflection performance of the medical device
according to the invention are the smaller radius of bending with
respect to a medical device with shape memory alloy elements
bending laterally and better reproducibility of the steering
performance.
[0016] In an embodiment, the medical device is further adapted such
that the compression of the rod is adjustable through the fixture
in the proximal end of the elongated body.
[0017] In another embodiment of the medical device, the elongated
body of the medical device may comprise a second lumen, wherein the
shape memory alloy wire can be arranged. The shape memory alloy
wire may be fixed only at its both ends with respect to the
elongated body, allowing free movement of the shape memory alloy
wire along the rest of its length with respect to the elongated
body. The friction between the elongated body and the shape memory
alloy wire can significantly be reduced during operation of the
medical device, creating an even larger range of bending radii
addressable by the medical device.
[0018] Numerous principles may be used for heating the shape memory
alloy wire. In an embodiment according to the invention, the
medical device comprises a resistor connectable to an energy supply
and arranged to convert the electrical energy provided by the
energy supply in heat for heating the shape memory alloy wire. The
resistor may be a metallic wire placed in the surrounding of the
shape memory wire, or it may be a metallic structure coaxial with
the shape memory alloy wire. Alternatively, the shape memory alloy
wire may be provided with a conformal metallic coating as resistor.
The latter has that advantage that the lateral dimension necessary
for the energy source can be minimized, since the thickness of such
coating is sufficient in the micrometer range.
[0019] In another embodiment according to the invention the shape
memory alloy wire can be adapted to be connectable to the energy
supply and arranged to convert electrical energy provided by the
energy supply in heat. The benefit of directly connecting the shape
memory alloy wire to the energy supply is that no additional
internal energy source is necessary to be positioned in the
surrounding of the shape memory alloy wire, since the heating of
the shape memory alloy wire can be obtained by its own resistive
heating.
[0020] In yet another embodiment according to the invention the
medical device comprises additional lumens in the elongated body,
extending at least partially along the shape memory alloy wire. The
lumens, adapted to be connectable to a pump for providing fluid
flow, may be connected with each other at their distal ends. The
fluid flow can significantly improve the response of the medical
device by accelerating the recovery of the medical device to its
neutral position when providing energy to the shape memory alloy
wire discontinues. Alternatively, the pump can be used as energy
supply, providing fluid flow in the lumens at higher temperature
than that of the shape memory alloy wire, thereby facilitating heat
transfer from the fluid to the shape memory alloy wires so as to
heat the shape memory alloy wire.
[0021] A medical device may comprise multiple shape memory alloy
wires extending at least partially along the elongated body, having
initial lengths and being fixed at both ends with respect to the
elongated body. Deflection of the medical device in multiple
directions can be achieved when the shape memory alloy wires are
arranged to receive dissimilar quantities of energy from the energy
supply. Depending on the combination of the quantities of energies
received by the shape memory alloy wires, the radii of bending of
the medical device can practically be achieved in any direction
with respect to the longitudinal axis of the medical device.
[0022] In yet a further embodiment, the elongated body of the
medical device comprises segments with various stiffness, and the
shape memory alloy wires extend at least partially along two
adjacent segments with different stiffness. The benefit of such
configuration is the potential for deflecting a medical device in a
complex three-dimensional shape.
[0023] In a further aspect of the invention a system is presented
comprising the deflectable medical device, an energy supply and a
control unit. The control unit is arranged to control the quantity
of energy provided by the energy supply to the shape memory alloy
wire in the medical device. The control unit and the energy supply
may be integrated in one unit. The system may further comprise a
pump for circulating fluid through the lumens specifically
designated therefore in the medical device. The pump may also be
controlled by the control unit with respect to supplying fluid flow
for the medical device at required temperature and volumetric flow
rate.
[0024] In another aspect of the invention a method for deflecting a
medical device is presented, the method comprising:
[0025] providing a compression to a rod fixed between a distal end
and a fixture in a proximal end of an elongated body of a
deflectable medical device, the medical device further comprising
one or multiple shape memory alloy wires arranged eccentric to the
longitudinal axis of the elongated body, extending at least
partially along the elongated body and fixed at both ends with
respect to the elongated body,
[0026] providing energy to the one or multiple shape memory alloy
wires by an energy supply. The method according to the invention
allows lateral bending of the medical device due to the axial
stroke of the shape memory alloy wires positioned eccentric with
respect to the longitudinal axis of the medical device. The method
may further comprise a step for providing fluid flow in a third
lumen in the elongated body of the medical device, thereby
improving the response time of the medical device to
discontinuation of energy supplied to the shape memory alloy wires
and accelerate the recovery of the medical device to its neutral
position.
[0027] Additional aspects and advantages of the invention will
become more apparent from the following detailed description, which
may be best understood with reference to and in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In the drawings:
[0029] FIG. 1 shows schematically and exemplarily an embodiment of
a medical device according to the invention,
[0030] FIG. 2 shows schematically and exemplarily the medical
device with deflected distal portion,
[0031] FIG. 3 shows schematically and exemplarily an embodiment of
the medical device with deflected distal portion, the medical
device comprising heterogeneous elongated body,
[0032] FIG. 4 shows schematically and exemplarily an embodiment of
the medical device with shape memory alloy wire embedded into the
elongated body,
[0033] FIG. 5 shows schematically and exemplarily an embodiment of
the medical device with resistor positioned in the surrounding of
the shape memory alloy wire,
[0034] FIG. 6 shows schematically and exemplarily an embodiment of
the medical device with lumens in the elongated body adapted for
fluid flow,
[0035] FIG. 7 shows schematically and exemplarily an embodiment of
the medical device comprising a lumen for fluid flow and fluid
dispensing holes in the distal portion,
[0036] FIG. 8 shows schematically and exemplarily an embodiment of
the medical device with a metallic distal end,
[0037] FIG. 9a, 9b show transversal cross sections of alternative
embodiments of the medical device,
[0038] FIG. 9c, 9d show transversal cross sections of alternative
embodiments of the medical device comprising multiple shape memory
alloy wires,
[0039] FIG. 10 shows schematically and exemplarily a system for
deflection of a medical device according to the invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0040] Navigation of medical devices through branching pathways
sets stringent requirement with respect to device configuration.
Besides reduced diameter and flexibility of the medical devices,
steering of the distal portion is utmost important for the ability
of reaching designated locations within anatomical structures. FIG.
1 shows an embodiment of a medical device 1 according to the
invention. The medical device 1 is constructed from a flexible
elongated body 11 having a proximal end 12 and a distal end 13,
comprising a first lumen 14 visible in the longitudinal cross
section B-B of the medical device, wherein a rod 18 is positioned.
The rod may consist of compressible or incompressible materials.
The proximal end 12 of the elongated body 11 comprises a fixture
16, the rod 18 extending from the fixture 16 to the distal end 13
of the elongated body 11. The proximal end 12 of the elongated body
may be a handgrip. The functional designation of the fixture 16 is
fixing and/or supporting the rod directly or indirectly, such that
the rod 18 can be brought in a compression state between the
fixture 16 and the distal end 13 with respect to the elongated body
11. The position of the fixture 16 may be variable with respect to
the handgrip by sliding the fixture 16 through a slot 17. The
fixture 16 may alternatively be a spindle mechanism. Depending on
the mechanism used for the fixture, the rod 18 may extend
proximally beyond the fixture 16 or even beyond the medical device
1. The rod 18 is arranged such that it is compressed between the
fixture 16 and the distal end 13 of the elongated body 11, thereby
generating a tensile stress in the elongated body 11. The fixture
16 may further comprise a loaded spring supporting the rod 18. The
first lumen 14 may be positioned coaxially in the medical device as
shown in FIG. 1, or it may be eccentric to the longitudinal axis,
like in the FIG. 2.
[0041] A shape memory alloy wire 15, visible in the transversal
cross section A-A and in the longitudinal cross section B-B, is
arranged in a second lumen 19, extending at least partially along
the elongated body 11 and positioned eccentric to the longitudinal
axis 30 of the elongated body 11. Both ends of the shape memory
alloy wire are fixed with respect to the elongated body 11. The
shape memory alloy wire 15 is arranged to receive energy from an
energy supply through wiring 20 connected to the proximal and
distal ends of the shape memory alloy wire 15. By supplying
electrical energy to the shape memory alloy wire, its temperature
rises due to resistive heating.
[0042] The shape memory alloy wire 15, having an initial length, is
arranged to shorten upon its resistive heating, which creates a
pulling force on the elongated body 11 at the locations where both
ends of the shape memory alloy wire 15 are fixed with respect to
the elongated body 11. This creates a deflection of the portion of
the elongated body 11 associated to the position of the shape
memory alloy wire 15, due to the eccentric position of the second
lumen 19 to the longitudinal axis 30 of the medical device 1. The
longitudinal axis 30 is defined as the line connecting the centers
of the transversal cross sections along the length of the medical
device 1 in the neutral position, thus when there is no energy
provided to the shape memory alloy wire. The radius of deflection R
depends on the materials used for the manufacturing of the medical
device 1, as well as on the design configuration. Usual candidates
for the shape memory alloy wires are alloys of Ni--Ti, Cu--Al--Ni,
Cu--Zn, Ni--Ti--Pd with typical diameters of 50-200 micrometers. A
broad range of polymers can be used for fabrication of the
elongated body, from which the most known group is that of
thermoplastic elastomers (e.g. PEBAX).
[0043] The benefit of using wires of shape memory alloys is the
miniaturization potential of the medical device, since relatively
thin shape memory alloy wires create sufficiently high force in
axial stroke upon heating. The operation of the medical device
relies on the lever that is created by the shape memory alloy wire
positioned eccentric to the longitudinal axis 30 of the medical
device, therefore a restoring bending force of a spring or that of
supplementary structures, urging the shape memory element in a
second direction away from the first direction upon cooling of the
shape memory alloy wire, is not necessary. However, the shape
memory alloy wire 15 requires axial tension to regain its initial
length after discontinuing supply of energy to the shape memory
alloy wire 15. Detwinning, the particular deformation mechanism
partially responsible for the shape memory effect in addition to
phase transformation, is promoted by the axial tension generated in
the elongated body 11 due to the compression of the rod 18 between
the fixture 16 and the distal end 13. Detwinning shape memory alloy
wires in axial direction is less stringent and requires only
sufficient axial tension in the elongated body, which allows
manufacturing of medical devices with smaller diameter than those
needing detwinning of laterally bending shape memory elements.
[0044] In the embodiment of the medical device shown in FIG. 3, the
elongated body of the medical device is heterogeneous, specifically
it is constructed from two materials with different properties. The
proximal part of the elongated body 11 is made of a stiffer polymer
which can additionally be reinforced with braiding to confer higher
rigidity of the proximal portion of the medical device. The distal
part 21 of the elongated body can be made of a more flexible
polymer, as mostly the distal part of the medical device has
different requirements in order to easily be deflectable when
navigating in branching anatomical structures. The second lumen 19
extends at least partially in both segments of the elongated body,
in the stiffer proximal part 11 and in the flexible distal part 21.
The shape memory alloy wire 15, located in the second lumen 19 and
fixed at both ends with respect to the heterogeneous elongated
body, can be considerably long. A shape memory alloy wire of a
certain material, hence with a defined maximum allowable strain,
can produce a larger axial stroke for a longer segment when it is
exposed to a difference of temperature. The deflection of the
medical device due to the axial stroke created by the shortening of
the shape memory alloy wire will not have its effect in the stiffer
part, but the effect will be transferred almost entirely to the
flexible distal part, resulting in a smaller radius of deflection r
of the distal part of the medical device 1. In another embodiment
of the medical device the stiffer and flexible regions of the
elongated body may alternate repeatedly along the length of the
medical device, resulting in complex three dimensional deflection
of the medical device in operation.
[0045] The second lumen 19 in the elongated body is not directly
necessary for deflecting a medical device, therefore the shape
memory alloy wire 15 may directly be integrated in the elongated
body, as shown in FIG. 4. The requirement for deflecting the
medical device is that an axial stroke of the shape memory alloy
wire 15 is created with respect to the longitudinal axis of the
elongated body 11. Therefore, the shape memory alloy wire has to be
fixed at least in two distinctive points with respect to the
elongated body 11. Technology like overmolding allows incorporation
of the shape memory alloy wire in the elongated body. When multiple
contact points or regions exist between the elongated body 11 and
the shape memory alloy wire 15 along their overlapping length, the
friction between the two can be significant during relative motion
occurring by deflection of the medical device. This can potentially
limit the range of bending radii addressable by the medical device.
Processing steps such as covering portion of the shape memory alloy
wire with materials promoting low friction is a practical
solution.
[0046] The shape memory alloy wire may be arranged to receive
energy from an energy supply in numerous alternative ways. In an
embodiment of the medical device 1 shown in FIG. 5, the elongated
body 11 comprises a resistor connectable to an energy supply and
arranged to convert the electrical energy received from the energy
supply in heat for heating the shape memory alloy wire. The
resistor may comprise windings 22 of metallic wire around the shape
memory alloy wire 15, or it may be a metallic wire placed in the
surrounding of the shape memory alloy wire. Alternatively, the
resistor may be metallic structure coaxial with the shape memory
alloy wire. This can be realized by conformal metallic coating of
the shape memory alloy wire through various technological
procedures (e.g. evaporation, electroplating, etc.).
[0047] A coil surrounding the shape memory alloy wire may also be
used for induction heating of the shape memory alloy wire 15. Such
embodiment may be similar to that presented in FIG. 5, wherein the
induction coil 22 can be operated with a high-frequency alternative
current.
[0048] The energy supply might be a pump circulating fluid in the
surrounding of the shape memory alloy wire 15, the fluid having a
higher temperature than the shape memory alloy wire. In a medical
device with such a configuration, shown in FIG. 6, the shape memory
alloy wire 15 receives energy from the fluid through heat transfer.
A third lumen 23 and a fourth lumen 24 in the elongated body 11 are
connected with each other in the distal portion of the elongated
body, and they extend such that at least partially overlap in the
axial direction with the shape memory alloy wire 15. The third
lumen 23 is adapted to allow fluid inflow and the fourth lumen 24
to allow fluid outflow. The wiring 20 of the shape memory alloy
wire 15 is superfluous and might be absent when fluid at higher
temperature than that of the shape memory alloy is circulated for
heating the shape memory alloy wire 15.
[0049] The medical device shown in FIG. 6 can alternatively be
configured such that the shape memory alloy wire 15 receives
electrical energy through the wiring 20 from the energy supply, and
fluid at a lower temperature than that of the shape memory alloy
wire 15, flowing through the third and fourth lumens 23,24, cools
the shape memory alloy wire. The cooling fluid flow can
significantly shorten the response time of the medical device to
discontinuation of supplying energy to the shape memory alloy wire,
thereby accelerating the recovery of the medical device to its
neutral position.
[0050] In an alternative embodiment of the medical device shown in
FIG. 7, the elongated body comprises just the third lumen 23,
adapted only for fluid inflow. The third lumen 23 communicates with
through-holes 25 in the distal portion 13 of the elongated body.
The fluid flowing through the third lumen 23 is dispensed into the
surrounding of the distal end 13 via the through-holes 25. Cooling
of the shape memory alloy wire 15 with this configuration is
advantageous for medical devices where irrigation with fluid is
required (e.g. cardiac ablation).
[0051] FIG. 8 shows a medical device with distal portion ending
with a metallic tip 26 for providing energy to the surrounding. In
cardiac ablation the surrounding is heart tissue and the energy may
be radiofrequency current delivered by a platinum-iridium alloy
tip. The rod 18 can be supported by the metallic tip 26 at the
distal end 13, or it can be fixed to it. In yet a further
alternative, the rod 18 may be used as electrical connection of the
metallic tip to the external radiofrequency current source.
[0052] Combination of the aforementioned embodiments may provide
optimal solution for specific applications. The position of various
components of the medical device may also vary. In the transversal
cross section of a medical device, shown in FIG. 9a, the third and
fourth lumens 23,24 adapted for fluid flow are at equal distance to
the shape memory alloy wire 15, thereby further accelerating the
recovery of the medical device to its neutral position upon
discontinuation of supplying energy to the shape memory alloy wire.
FIG. 9b shows an embodiment with a first lumen 14 having a larger
cross section, wherein besides the rod 18 also the wiring 20 of the
shape memory alloy wire as well as the third 23 and fourth 24
lumens are placed. The main advantage is an easier manufacturing of
such a medical device.
[0053] Multiple shape memory alloy wires extending at least
partially along the elongated body may be used in a medical device
in order to increase the maneuverability of the medical device in
multiple directions and/or to deflect differentially various
segments of the medical device. In FIG. 9c a transversal cross
section of an embodiment of the medical device is shown, comprising
three shape memory alloy wires 15, allowing deflection of the
distal portion of the medical device in any direction with respect
to its longitudinal axis 30 by an appropriately harmonized
operation of the individual shape memory alloy wires with
dissimilar quantities of energy from the energy supply. In an
alternative embodiment the medical device with multiple shape
memory alloy wires 15 may have individual cooling lumens 23 for
each shape memory alloy wire 15, as shown in FIG. 9d.
[0054] The deflection of the medical device needs to be controlled
and reproducible for navigation within complex anatomical
structures. A system 10 assuring reproducible deflection
performance of the medical device is shown in FIG. 10. A control
unit 3 is regulating the quantity of energy provided by the energy
supply 2 to the shape memory alloy wire in the medical device 1.
The control unit 3 and the energy supply 2 may be integrated in one
unit. The system 10 may further comprise a pump 4 for circulating
fluid through the lumens specifically designated therefore within
the medical device 1. The pump 4 may also be controlled by the
control unit 3 with respect to supplying fluid flow for the medical
device at required temperature and volumetric flow rate. The pump
may function in two regimes. The first regime is for cooling the
shape memory alloy wires, therewith shortening the reaction time of
the shape memory alloy wires to an alteration of the quantity of
energy received from the electrical energy source 2. Alternatively,
the pump 4 may also function as energy supply by providing fluid
flow in the lumens at a higher temperature than that of the shape
memory alloy wire, thereby transferring heat from the fluid in the
lumens to the shape memory alloy wire positioned adjacent to the
lumens in the medical device. The control unit 3 may further
control the compression of the rod 18 between the fixture 16 and
the distal end 13 of the medical device 1. The fixture 16 may be an
electrically controllable spindle mechanism.
[0055] Controlling the deflection of the medical device comprising
one or multiple shape memory alloy wires extending at least
partially along the elongated body can be realized in steps. In a
first step the control unit 3 provides a finite compression to the
rod 18 fixed between the distal end 13 and the fixture 16 of the
deflectable medical device 1. In the second step the control unit 3
regulates the quantity of energy necessary for the one or multiple
shape memory alloy wires 15 to deflect the medical device 1
according to the required performance, and the energy supply 2
provides the respective quantity of energy to the one or multiple
shape memory alloy wires 15. In step three the control unit 3
regulates the parameters of the pump 4 with respect to temperature
of the fluid and volumetric fluid flow rate, according to the
required deflection performance of the medical device 1. The steps
may be carried out consecutively or simultaneously.
[0056] The control unit comprises a computer, a computer-readable
medium having stored a computer-executable program and a user
interface. The computer program comprises program code means for
causing a deflectable medical device to carry out the steps for
deflection of the medical device when the computer program is run
on the computer of the control unit controlling the deflectable
medical device.
[0057] Although medical device was used in the exemplary
description of the invention, that should not be construed as
limiting the scope.
[0058] Other variations to the disclosed embodiments can be
understood and effected by those skilled in the art in practicing
the claimed invention, from a study of the drawings, the
disclosure, and the appended claims.
[0059] A single unit or device may fulfill the functions of several
items recited in the claims. The mere fact that certain measures
are recited in mutually different dependent claims does not
indicate that a combination of these measures cannot be used to
advantage.
[0060] In the claims, the word "comprising" does not exclude other
elements or steps, and the indefinite article "a" or "an" does not
exclude a plurality.
[0061] Any reference signs in the claims should not be construed as
limiting the scope.
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