U.S. patent application number 09/755873 was filed with the patent office on 2002-07-04 for method of mounting a transducer to a driveshaft.
Invention is credited to Koger, James D., Serrano, Manuel.
Application Number | 20020087081 09/755873 |
Document ID | / |
Family ID | 25041024 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020087081 |
Kind Code |
A1 |
Serrano, Manuel ; et
al. |
July 4, 2002 |
Method of mounting a transducer to a driveshaft
Abstract
A method of mounting a transducer to a driveshaft which
eliminates the need for a transducer housing, the improved method
directly attaches the transducer to a rigid distal tip of a
drive-shaft which is part of a rotatable imaging core of a catheter
assembly. The method contemplates heat treating the distal tip of
the drive-shaft to make it rigid, machining the distal tip to be
dimensioned to hold the transducer, and attaching the transducer to
the distal tip by clamping, crimping, or an adhesive.
Inventors: |
Serrano, Manuel; (Menlo
Park, CA) ; Koger, James D.; (Santa Cruz,
CA) |
Correspondence
Address: |
LYON & LYON LLP
633 WEST FIFTH STREET
SUITE 4700
LOS ANGELES
CA
90071
US
|
Family ID: |
25041024 |
Appl. No.: |
09/755873 |
Filed: |
January 4, 2001 |
Current U.S.
Class: |
600/459 ;
600/466 |
Current CPC
Class: |
A61B 8/12 20130101; A61B
8/4461 20130101; A61B 8/445 20130101 |
Class at
Publication: |
600/459 ;
600/466 |
International
Class: |
A61B 008/14 |
Claims
I claim:
1. A method of mounting a transducer to a driveshaft comprising the
steps of: providing an elongate tubular element including a lumen;
providing a rotatable imaging core adapted to pass through the
lumen, the imaging core including a flexible drive-shaft and a
transducer; processing the distal tip of the drive-shaft; and
attaching the transducer to the distal tip of the drive-shaft.
2. The method of claim 1 wherein the step of processing the distal
tip of the drive-shaft comprises the step of hardening the distal
tip by welding.
3. The method of claim 2 wherein the drive-shaft is made of
flexible wound wires and wherein the step of hardening the distal
tip by welding joins the wound wires of the distal tip together
such that a rigid distal tip is formed.
4. The method of claim 2 wherein the step of hardening the distal
tip by welding includes the step of applying electrodes at two
locations on the drive shaft for electrical conductivity
therebetween.
5. The method of claim 1 wherein the step of processing the distal
tip of the drive-shaft comprises the step of hardening the distal
tip by soldering.
6. The method of claim 1 wherein the step of processing the distal
tip of the drive-shaft comprises the step of hardening the distal
tip with an adhesive.
7. The method of claim 5 wherein the drive-shaft is made of
flexible wound wires having interstices therebetween and wherein
the step of hardening the distal tip by soldering fills a
substantial amount of the interstitial spaces such that a rigid
distal tip is formed.
8. The method of claim 5 further comprising the step of using a
cold clamp having a high specific heat to dissipate excess heat
during soldering.
9. The method of claim 5 further including inserting a plug into
the lumen in order to keep the lumen open during soldering.
10. The method of claim 9 wherein the plug is ceramic.
11. The method of claim 9 wherein the plug is a piece of
fiber-optic.
12. The method of claim 1 wherein the step of processing the distal
tip of the drive-shaft comprises the step of grinding the distal
tip to form an arcuate recession with opposing tapered side
walls.
13. The method of claim 1 wherein the step of processing the distal
tip of the drive-shaft comprises the step of milling the distal tip
to form an arcuate recession with opposing tapered side walls.
14. The method of claim 1 wherein the step of attaching the
transducer to the distal tip of the drive-shaft comprises the step
of crimping the tapered side walls about the perimeter of the
transducer so that the transducer is held in place
therebetween.
15. The method of claim 1 wherein the step of attaching the
transducer to the distal tip of the drive-shaft comprises the step
of providing a clamping member to attach the transducer to the
distal tip of the drive shaft.
16. The method of claim 15 wherein the clamping member is fixedly
attached to the drive-shaft and removably attached to the
transducer.
17. The method of claim 1 wherein the step of attaching the
transducer to the distal tip of the drive-shaft comprises the step
of using an adhesive to attach the transducer to the distal tip of
the drive-shaft.
18. The method of claim 17 wherein the adhesive is a UV cure
epoxy.
19. The method of claim 1 wherein the lumen is configured to allow
the passage of the rotatable imaging core.
20. The method of claim 1 further comprising a generally
cylindrical imaging window.
21. The method of claim 1 wherein the transducer has a generally
circular surface.
22. The method of claim 1 wherein the elongate tubular element
further includes a second lumen
23. The method of claim 22 wherein the second lumen is adapted to
house a steering pullwire.
24. An ultrasonic imaging catheter assembly comprising: an elongate
tubular element including a lumen; a rotatable imaging core adapted
to pass through the lumen, the rotatable imaging core including a
flexible drive-shaft attached to a transducer; wherein the
driveshaft has a distal tip adapted for mounting to the
transducer.
25. The ultrasonic imaging catheter assembly of claim 24 wherein
the transducer is mounted to the distal tip by soldering.
26. The ultrasonic imaging catheter assembly of claim of claim 25
wherein a cold clamp having a high specific heat is used to
dissipate excess heat during soldering.
27. The ultrasonic imaging catheter assembly of claim of claim 26
wherein the cold clamp is made of aluminum.
28. The ultrasonic imaging catheter assembly of claim of claim 26
wherein the cold clamp is made of copper.
29. The ultrasonic imaging catheter assembly of claim 25 further
including a plug for keeping the lumen open during soldering.
30. The ultrasonic imaging catheter assembly of claim 29 wherein
the plug is ceramic.
31. The ultrasonic imaging catheter assembly of claim 29 wherein
the plug includes a piece of fiber-optic.
32. The ultrasonic imaging catheter assembly of claim 24 wherein
the distal tip of the drive-shaft is welded to be rigid.
33. The ultrasonic imaging catheter assembly of claim 32 wherein
the rigid distal tip of the drive shaft has an arcuate recession
with opposing tapered side walls.
34. The ultrasonic imaging catheter assembly of claim 33 wherein
the tapered side walls are crimped about the perimeter of the
transducer so that the transducer is held therebetween.
35. The ultrasonic imaging catheter assembly of claim 24 wherein a
clamping member is used to removably attach the transducer to the
distal tip of the drive-shaft.
36. The ultrasonic imaging catheter assembly of claim 24 wherein an
adhesive is used to attach the transducer to the distal tip of the
drive-shaft.
37. The ultrasonic imaging catheter assembly of claim 36 wherein
the adhesive is a UV cure epoxy.
38. The ultrasonic imaging catheter assembly of claim 24 wherein
the lumen is configured to allow the passage of the rotatable
imaging core.
39. The ultrasonic imaging catheter assembly of claim 24 further
comprising a generally cylindrical imaging window.
40. The ultrasonic imaging catheter assembly of claim 24 wherein
the transducer has a generally circular surface.
41. The ultrasonic imaging catheter assembly of claim 24 wherein
the elongate tubular element further includes a second lumen.
42. The ultrasonic imaging catheter assembly of claim 41 wherein
the second lumen is adapted to house a steering pullwire.
Description
FIELD OF THE INVENTION
[0001] The present invention relates, in general, to transducer
mountings for ultrasound catheter assemblies used in diagnostic or
therapeutic applications.
DISCUSSION OF RELATED ART
[0002] Mechanically scanned ultrasound catheter assemblies employ a
single transducer mounted inside a rotating housing. In particular,
the transducer transmits and receives ultrasonic waves while the
transducer housing rotates about a fixed axis in an acoustic window
located at a distal tip of the catheter. The rotational motion of
the transducer housing is accomplished by a flexible drive-shaft
that extends through an axially disposed lumen of the catheter,
wherein the drive-shaft has one end connected to the transducer
housing. Once the distal end of the catheter is positioned, for
example, in a patient's vascular system, a cross-sectional image of
the tissue surrounding the distal catheter tip is produced by using
imaging and control circuitry that are electrically coupled to the
transducer via an electrical conductor extending through the drive
shaft.
[0003] With respect to FIG. 1, a conventional prior art ultrasound
catheter assembly 100, which appears in U.S. Pat. No. 5,842,994, is
depicted. U.S. Pat. No. 5,842,994 is hereby incorporated by
reference. The catheter assembly 100 comprises a first elongate
tubular element 120, which forms an axially disposed lumen 130. An
acoustic imaging window 140 is attached to a distal end of the
first tubular element 120, thereby forming an enclosed tip of the
catheter assembly 110. A flexible drive-shaft 150 extends through
the lumen 130 and is connected at a distal end to a transducer
housing 60 disposed in the acoustic imaging window 140. The
transducer housing 60 has a generally cylindrical transducer 170
mounted therein, exposing a circular active surface area, or
aperture. A second elongate tubular element 180 forms an additional
lumen 190 used for other catheter functions such as housing
pullwires or delivering liquid to a distally disposed balloon
during angioplasty.
[0004] With further reference to FIG. 1, the transducer housing 60
is an expensive, high-precision part that requires a particular
joining operation to attach it to the drive-shaft 150. In addition,
the joint created between the drive-shaft 150 and the transducer
housing 60 may potentially fail. Therefore, it would be
advantageous to eliminate the transducer housing 60 from catheter
assembly 110. FIG. 1A depicts an alternative conventional prior art
ultrasound catheter, which includes opening 65 adapted to permit
flushing from the proximal end of catheter assembly 100 and
dimensioned for the passage of guide wires. This alternative
catheter does not include first elongate tubular element 120 or
second elongate tubular element 180.
SUMMARY OF THE INVENTION
[0005] An aspect of the invention involves a method of making a
transducer mounting to a driveshaft by providing an elongate
tubular element including a lumen, providing a rotatable imaging
core adapted to pass through the lumen, the imaging core including
a flexible driveshaft and a transducer. The method optionally
contemplates treating and machining the distal tip of the
drive-shaft, and then attaching the transducer to the distal
tip.
[0006] Another separate aspect of the invention involves a method
of making a transducer mounting to a driveshaft comprising a step
of treating the distal tip of the drive-shaft by hardening the
distal tip with a welding process, wherein the drive-shaft is
initially made of flexible wound wires and the welding process
joins the wound wires of the distal tip together such that a rigid
distal tip is formed. This method optionally contemplates the use
of electrical welding by applying electrodes at two locations on
the drive shaft for electrical conductivity therebetween.
[0007] A further separate aspect of the invention involves a method
of making a transducer mounting to a driveshaft comprising a step
of treating the distal tip of the drive-shaft by hardening the
distal tip with a soldering process, wherein the drive-shaft is
made of flexible wound wires having interstices therebetween and
the soldering process fills the interstitial spaces such that a
rigid distal tip is formed. This method optionally contemplates the
use of a cold clamp having a high specific heat to dissipate excess
heat during soldering. In addition, this method may incorporate the
use of a ceramic or fiber-optic plug for keeping the central lumen
open during soldering.
[0008] An additional separate aspect of the invention involves a
method of making a transducer mounting to a driveshaft comprising a
step of machining the distal tip of the drive-shaft by grinding or
drilling the distal tip to form an arcuate recession with opposing
tapered side walls. This method optionally contemplates attaching
the transducer to the distal tip of the drive-shaft by crimping the
tapered side walls about the perimeter of the transducer so that
the transducer is held in place therebetween. In addition, a
clamping member or an adhesive may be used to secure the transducer
to the distal tip of the drive shaft.
[0009] Yet another separate aspect of the invention involves an
ultrasonic imaging catheter assembly comprising an elongate tubular
element including a lumen, a rotatable imaging core adapted to pass
through the lumen, the rotatable imaging core including a flexible
drive-shaft attached to a transducer, wherein the driveshaft has a
rigid distal tip adapted to be mounted to the transducer.
[0010] An additional separate aspect of the invention involves an
ultrasonic imaging catheter assembly having a drive-shaft with a
rigid distal tip which includes an arcuate recession with opposing
tapered side walls, wherein the transducer is attached to the
distal tip of the drive-shaft by crimping the tapered side walls
about the perimeter of the transducer so that the transducer is
held in place therebetween. Alternatively, a clamping member or an
adhesive may be used to secure the transducer to the distal tip of
the drive shaft.
[0011] The invention may include any one of these separate aspects
individually, or any combination of these separate aspects.
[0012] Other features and advantages of the invention will be
evident from reading the following detailed description, which is
intended to illustrate, but not limit, the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The drawings illustrate the design and utility of preferred
embodiments of the present invention, in which similar elements are
referred to by common reference numerals.
[0014] FIG. 1 is a cut-away partial side view of a prior art
ultrasound catheter assembly.
[0015] FIG. 1 A is a cut-away partial side view of a prior art
ultrasound catheter assembly.
[0016] FIG. 2 is a cut-away partial side view of an ultrasound
catheter assembly according to an example embodiment of the present
invention.
[0017] FIG. 2A is a cross-sectional view taken along line 2A-2A of
FIG. 2.
[0018] FIG. 3 is a cut-away partial side view of the ultrasound
catheter assembly of FIG. 2.
[0019] FIG. 3A is a cross-sectional view taken along line 3A-3A of
FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] With respect to FIGS. 2 and 3 , a preferred ultrasound
catheter assembly 100 includes an elongate tubular element 115
having tubular section 120, which forms an axially disposed lumen
130. A dome-shaped acoustic imaging window 140 is attached to a
distal end of the elongate tubular element 115, thereby forming an
enclosed tip of the catheter assembly 100. Alternatively, the shape
of the acoustic imaging window 140 may be virtually any shape or
combination of shapes. An imaging core 145 comprising a flexible
drive-shaft 150 having a rigid distal tip 160 and a generally
cylindrical transducer 170 is disposed within lumen 130. The
imaging core 145 is capable of translation along its center axis
185.
[0021] As best seen in FIG. 2A, axially disposed lumen 130 has a
substantially "D-shaped" cross-section wherein the inner dimensions
of lumen 130 are sufficient for transducer 170 to be translated
therein. With further reference to FIG. 2A, a solid section 180 of
elongate tubular element 115 forms an additional lumen 190 used for
other catheter functions such as, by way of non-limiting examples,
housing pullwires, drug delivery, balloon angioplasty, laser
ablation, or for housing a stiffening member to help prevent the
collapsing of the catheter assembly.
[0022] A cover tube 200 formed of a suitable material, such as a
heat shrinkable nylon, urethane, polyethylene or other plastic, is
disposed around tubular element 115, wherein cover tube 200
provides both structural integrity to the catheter assembly 100, as
well as a smooth outer surface for ease in axial movement in a
patient's body passage with minimal friction. Preferably, the
acoustic imaging window 140 has its proximal end open and its
distal end rounded and is attached to a distal outer
circumferential portion of the tubular element 115 to form an
enclosed catheter tip 210, with respective ends of the cover tube
200 and acoustic imaging window 140 bonded together at a common
joint 220. The outer diameter of the proximal end of window 140 is
preferably substantially equal to that of the installed cover tube
200, so that a smooth outer surface is provided at joint 220.
[0023] Referring to FIGS. 2 and 3, the transducer 170 is attached
to the flexible drive-shaft 150 at a cut-away portion 165 of rigid
distal tip 160 such that its active surface 175 slopes at a slight
angle with respect to the center axis 185 of drive-shaft 150. This
tilting of transducer 170 helps to minimize internal reflections
inside of catheter tip 210. The transducer 170 can be fixedly
attached in a number of ways including by an adhesive such as a UV
(ultraviolet light) cure epoxy, by crimping of opposing tapered
side walls 195 surrounding cut-away portion 165, by a clamp 205,
any other known method of affixing, or any combination of these
methods.
[0024] As best seen in FIGS. 3 and 3A, drive-shaft 150 has a
central lumen 225 adapted for the passage of transducer wires or
coaxial cable, which extend through relieved area 163. The
driveshaft 150 is made of wound wire such as a superalloy or
stainless steel in order to be flexible inside of a patient's blood
vessel, for example. However, distal tip 160 of drive-shaft 150
preferably should be hardened and machined in order to mount
transducer 170. Hardening of distal tip 160 can be accomplished by
a number of means including welding and soldering.
[0025] Welding of the distal tip 160 is preferably accomplished
electrically, by applying electrodes at two locations along distal
tip 160 for conductivity therebetween. The two locations can be the
end of distal tip 160 and, for example, location 230 along the
drive-shaft 150. By running sufficient electricity between these
two locations, the wound wires of drive-shaft 150 will heat up,
begin to liquefy, and bond together, eliminating some of the
interstitial spaces between the wound wires. Although electrical
welding of the distal tip 160 should be continued until the wires
have fused together, it should be terminated before unwanted
deformation of the distal tip 160 has occurred. After welding and a
brief cool-down period, the distal tip 160 will be more rigid than
the rest of the drive-shaft 150 due to the fusing between the wound
wires.
[0026] Alternatively, the hardening of the distal tip 160 can be
accomplished by a soldering process wherein the interstitial spaces
between the wound wires are filled with softened metal. Although
many different solders can be used, the solder is preferably a 5%
silver solder mixed with 95% tin. During the soldering process, the
silver solder should be heated to approximately 850-900 degrees
Fahrenheit and melted into the interstitial spaces in the distal
tip 160 of driveshaft 150. Alternatively, a brazing process can be
used, which requires greater temperatures to melt solder having a
higher percentage of silver.
[0027] During soldering, a cold clamp can be utilized to dissipate
excess heat and to limit unnecessary fusion of the wound wires of
the rest of the flexible drive-shaft 150. Ideally, the cold clamp
is made of metal such as aluminum or copper having a high specific
heat. Also, the cold clamp is circular so that it can encircle the
perimeter of drive shaft 150 at location 230. Before soldering, a
plug should be inserted within central lumen 225 so that it is not
stopped up by melted metal. Preferably, the plug is made of a
material having a high melting point such as a ceramic rod or a
piece of fiber optic. In addition, the plug can have an outer
coating to prevent adherence to the solder.
[0028] The hardening of the distal tip may also be accomplished
using an adhesive such as an epoxy wherein an adhesive is used to
fill the interstitial spaces of the wound wire of distal tip 160.
After the distal tip 160 has been hardened so that it is rigid, it
can be machined to create an effective mount for transducer
170.
[0029] During machining, a cut-away portion 165 in the form of an
arcuate recession with opposing tapered side walls 195 is formed on
the rigid distal tip 160 using a milling or grinding process. In
addition, relieved area 163 is formed within cut-away portion 165
using a similar milling or grinding process. Cut-away portion 165
is adapted to receive the cylindrical transducer 170. The opposing
tapered walls 195 of machined distal tip 160 can be crimped
inwardly about the perimeter of the transducer 170 to hold it
fixedly in place. Additionally, an epoxy or other adhesive such as
a UV cure epoxy can be used to further secure transducer 170 to
distal tip 160. Alternatively, clamping member 205 can be used to
secure the transducer 170 to the distal tip 160 of the drive-shaft
150. The clamping member is fixedly attached to the driveshaft 150
and removably attached to the transducer 170.
[0030] Any one or more of the features depicted in FIGS. 1-3, or
described in the accompanying text, may be interchanged with that
of another figure to form still other embodiments.
[0031] While preferred embodiments and methods have been shown and
described, it will be apparent to one of ordinary skill in the art
that numerous alterations may be made without departing from the
spirit or scope of the invention. Therefore, the invention is not
limited except in accordance with the following claims.
* * * * *