U.S. patent application number 12/465853 was filed with the patent office on 2009-11-19 for ivus system with rotary capacitive coupling.
This patent application is currently assigned to Silicon Valley Medical Instruments, Inc.. Invention is credited to Thomas C. Moore, Robert Zelenka.
Application Number | 20090284332 12/465853 |
Document ID | / |
Family ID | 41315619 |
Filed Date | 2009-11-19 |
United States Patent
Application |
20090284332 |
Kind Code |
A1 |
Moore; Thomas C. ; et
al. |
November 19, 2009 |
IVUS SYSTEM WITH ROTARY CAPACITIVE COUPLING
Abstract
An imaging system comprises a catheter having a lumen, a
rotatable imaging probe within the catheter lumen including a
distal transducer and first and second conductors coupled to the
transducer, and a coupler that couples the rotatable first and
second conductors to non-rotatable third and fourth conductors,
respectively. The coupler includes a rotary capacitive coupler.
Inventors: |
Moore; Thomas C.;
(Livermore, CA) ; Zelenka; Robert; (Milpitas,
CA) |
Correspondence
Address: |
GRAYBEAL JACKSON LLP
155 - 108TH AVENUE NE, SUITE 350
BELLEVUE
WA
98004-5973
US
|
Assignee: |
Silicon Valley Medical Instruments,
Inc.
Fremont
CA
|
Family ID: |
41315619 |
Appl. No.: |
12/465853 |
Filed: |
May 14, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61127943 |
May 15, 2008 |
|
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Current U.S.
Class: |
333/24C |
Current CPC
Class: |
H01P 1/067 20130101;
A61B 8/4461 20130101; A61B 8/12 20130101; H01P 1/068 20130101 |
Class at
Publication: |
333/24.C |
International
Class: |
H01P 1/06 20060101
H01P001/06 |
Claims
1. An imaging system comprising: a catheter having a lumen; a
rotatable imaging probe within the catheter lumen including a
distal transducer and first and second conductors coupled to the
transducer; and a coupler that couples the rotatable first and
second conductors to non-rotatable third and fourth conductors,
respectively, the coupler including a rotary capacitive
coupler.
2. The system of claim 1, wherein the coupler comprises a parallel
plate capacitor.
3. The system of claim 1, wherein the coupler comprises a first
parallel plate capacitor that couples the first conductor to the
third conductor and a second parallel plate capacitor that couples
the second conductor to the fourth conductor.
4. The system of claim 1, wherein the coupler comprises a parallel
plate capacitor that couples the first conductor to the third
conductor and a cylindrical surface concentric capacitor that
couples the second conductor to the fourth conductor.
5. The system of claim 1, wherein the coupler comprises a
cylindrical surface concentric capacitor.
6. The system of claim 1, wherein the coupler comprises a first
cylindrical surface concentric capacitor that couples the first
conductor to the third conductor and a second cylindrical surface
concentric capacitor that couples the second conductor to the
fourth conductor.
7. The system of claim 1, wherein the coupler comprises a conical
surface concentric capacitor.
8. The system of claim 1, wherein the coupler comprises a conical
surface concentric capacitor that couples the first conductor to
the third conductor and a parallel plate capacitor that couples the
second conductor to the fourth conductor.
9. The system of claim 1, wherein the coupler comprises a conical
surface concentric capacitor that couples the first conductor to
the third conductor and a cylindrical surface concentric capacitor
that couples the second conductor to the fourth conductor.
10. The system of claim 1, wherein the coupler comprises a first
conical surface concentric capacitor that couples the first
conductor to the third conductor and a second conical surface
concentric capacitor that couples the second conductor to the
fourth conductor.
11. The system of claim 1, wherein the coupler is within the
catheter.
12. The system of claim 1, wherein the coupler is outside of the
catheter.
13. An imaging system comprising: a catheter having a lumen; a
distal rotatable imaging probe within the catheter lumen including
a first transducer, first and second conductors coupled to the
first transducer, a second transducer, and third and fourth
conductors coupled to the second transducer; a rotary capacitive
coupler that couples the rotatable first and second conductors to
non-rotatable fifth and sixth conductors, respectively; and a
rotary inductive coupler that couples the rotatable third and
fourth conductors to non-rotatable seventh and eighth conductors,
respectively.
14. The system of claim 13, wherein the rotary capacitive coupler
comprises a parallel plate capacitor.
15. The system of claim 13, wherein the rotary capacitive coupler
comprises a first parallel plate capacitor that couples the first
conductor to the third conductor and a second parallel plate
capacitor that couples the second conductor to the fourth
conductor.
16. The system of claim 13, wherein the rotary capacitive coupler
comprises a parallel plate capacitor that couples the first
conductor to the third conductor and a cylindrical surface
concentric capacitor that couples the second conductor to the
fourth conductor.
17. The system of claim 13, wherein the rotary capacitive coupler
comprises a cylindrical surface concentric capacitor.
18. The system of claim 13, wherein the rotary capacitive coupler
comprises a first cylindrical surface concentric capacitor that
couples the first conductor to the third conductor and a second
cylindrical surface concentric capacitor that couples the second
conductor to the fourth conductor.
19. The system of claim 13, wherein the rotary capacitive coupler
comprises a conical surface concentric capacitor.
20. The system of claim 13, wherein the rotary capacitive coupler
comprises a conical surface concentric capacitor that couples the
first conductor to the third conductor and a parallel plate
capacitor that couples the second conductor to the fourth
conductor.
21. The system of claim 13, wherein the rotary capacitive coupler
comprises a conical surface concentric capacitor that couples the
first conductor to the third conductor and a cylindrical surface
concentric capacitor that couples the second conductor to the
fourth conductor.
22. The system of claim 13, wherein the rotary capacitive coupler
comprises a first conical surface concentric capacitor that couples
the first conductor to the third conductor and a second conical
surface concentric capacitor that couples the second conductor to
the fourth conductor.
23. An imaging system comprising: a catheter having a lumen; a
rotatable imaging probe within the catheter lumen including a
distal transducer; and a coupler including a rotary capacitive
coupler that couples the rotatable transducer to non-rotatable
first and second conductors and a rotary inductive coupler that
couples the rotatable transducer to third and fourth non-rotatable
conductors.
Description
PRIORITY CLAIM
[0001] The present application claims the benefit of copending U.S.
Provisional Patent Application Ser. No. 61/127,943, filed May 15,
2008, which application is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention generally relates to rotary couplers.
The present invention more specifically relates to a capacitively
coupled rotary coupler for use in a minimally invasive imaging
catheter and system.
[0003] Intravascular catheters such as intravascular ultrasonic
(IVUS) catheters enable imaging of internal structures in the body.
In particular, coronary IVUS catheters are used in small arteries
of the heart to visualize coronary artery disease. An IVUS catheter
will, in general, employ at least one high frequency (20 MHz-45
MHz) ultrasonic transducer that creates pressure waves for
visualization. At least one transducer is typically housed within a
surrounding sheath or catheter member and mechanically rotated for
360.degree. visualization.
[0004] The highest frequencies at which commercially available
coronary imaging catheters operate are 40 MHz and 45 MHz. These
high frequency probes have an axial resolution of approximately 200
microns. An axial resolution of 200 microns is insufficient to
resolve structures with size features smaller than 200 microns. For
example, thin-cap fibroatheromas having a thin fibrous cap of 65
microns or less in thickness cannot currently be resolved. The
concern regarding thin-cap fibroatheromas is that they are prone to
rupture. Plaque rupture can lead to thrombus formation and critical
blockages in the coronary artery. The ability to reliably identify
thin-cap fibroatheromas can aid interventional cardiologists to
develop and evaluate clinical treatment strategies in order to
reduce post percutaneous coronary intervention morbidity rates.
Therefore, IVUS catheters and systems having improved axial
resolution capable of more clearly visualizing micron sized
features such as vulnerable plaques are needed in the art. The
ability for such systems to operate at high transducer frequencies
will be important in that effort.
[0005] One of the challenges of these minimally invasive imaging
systems is coupling the stationary ultrasound transceiver
(transmitter/receiver) to the mechanically rotating transducer.
Rotary inductive couplers are used in commercially available IVUS
systems. However, rotary inductive couplers are non-ideal for very
high frequency (30 MHz-300 MHz) operation because of their
relatively high series inductance. At such high frequencies, series
inductance will result in an insertion loss into a transmission
line of the IVUS catheter. Furthermore, the insertion loss
increases with increasing ultrasound imaging frequency which
degrades system performance. Rotating inductive couplers also
exhibit electrical impedance that can vary with rotational
position. The variation of impedance with rotational position
causes output signal amplitudes to vary with angular positions and
further degrades system performance. The present invention
addresses these and other issues towards providing imaging
catheters having improved resolution and more constant level
output.
SUMMARY
[0006] In one embodiment, an imaging system comprises a catheter
having a lumen, a rotatable imaging probe within the catheter lumen
including a distal transducer and first and second conductors
coupled to the transducer. The system further includes a coupler
that couples the rotatable first and second conductors to
non-rotatable third and fourth conductors. The coupler includes a
rotary capacitive coupler.
[0007] The coupler may comprise a parallel plate capacitor. The
coupler may comprise a first parallel plate capacitor that couples
the first conductor to the third conductor and a second parallel
plate capacitor that couples the second conductor to the fourth
conductor or a parallel plate capacitor that couples the first
conductor to the third conductor and a cylindrical surface
concentric capacitor that couples the second conductor to the
fourth conductor.
[0008] The coupler may comprise a cylindrical surface concentric
capacitor. The coupler may comprise a first cylindrical surface
concentric capacitor that couples the first conductor to the third
conductor and a second cylindrical surface concentric capacitor
that couples the second conductor to the fourth conductor.
[0009] The coupler may comprise a conical surface concentric
capacitor. The coupler comprises a conical surface concentric
capacitor that couples the first conductor to the third conductor
and a parallel plate capacitor that couples the second conductor to
the fourth conductor, a conical surface concentric capacitor that
couples the first conductor to the third conductor and a
cylindrical surface concentric capacitor that couples the second
conductor to the fourth conductor, or a first conical surface
concentric capacitor that couples the first conductor to the third
conductor and a second conical surface concentric capacitor that
couples the second conductor to the fourth conductor.
[0010] The coupler may be within the catheter or outside of the
catheter.
[0011] In another embodiment, an imaging system comprises a
catheter having a lumen and a distal rotatable imaging probe within
the catheter lumen including a first transducer, first and second
conductors coupled to the first transducer, a second transducer,
and third and fourth conductors coupled to the second transducer.
The system further includes a rotary capacitive coupler that
couples the rotatable first and second conductors to non-rotatable
fifth and sixth conductors, respectively, and a rotary inductive
coupler that couples the rotatable third and fourth conductors to
non-rotatable seventh and eighth conductors, respectively.
[0012] The coupler may comprise a parallel plate capacitor. The
coupler may comprise a first parallel plate capacitor that couples
the first conductor to the third conductor and a second parallel
plate capacitor that couples the second conductor to the fourth
conductor or a parallel plate capacitor that couples the first
conductor to the third conductor and a cylindrical surface
concentric capacitor that couples the second conductor to the
fourth conductor.
[0013] The coupler may comprise a cylindrical surface concentric
capacitor. The coupler may comprise a first cylindrical surface
concentric capacitor that couples the first conductor to the third
conductor and a second cylindrical surface concentric capacitor
that couples the second conductor to the fourth conductor.
[0014] The coupler may comprise a conical surface concentric
capacitor. The coupler comprises a conical surface concentric
capacitor that couples the first conductor to the third conductor
and a parallel plate capacitor that couples the second conductor to
the fourth conductor, a conical surface concentric capacitor that
couples the first conductor to the third conductor and a
cylindrical surface concentric capacitor that couples the second
conductor to the fourth conductor, or a first conical surface
concentric capacitor that couples the first conductor to the third
conductor and a second conical surface concentric capacitor that
couples the second conductor to the fourth conductor.
[0015] In a further embodiment, an imaging system comprises a
catheter having a lumen, a rotatable imaging probe within the
catheter lumen including a distal transducer, and a coupler
including a rotary capacitive coupler that couples the rotatable
transducer to non-rotatable first and second conductors and a
rotary inductive coupler that couples the rotatable transducer to
third and fourth non-rotatable conductors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The features of the present invention which are believed to
be novel are set forth with particularity in the appended claims.
The invention, together with further features and advantages
thereof, may best be understood by making reference to the
following descriptions taken in conjunction with the accompanying
drawings, in the several figures of which like reference numerals
identify identical elements, and wherein:
[0017] FIG. 1 is a high-level diagram of a catheter-based imaging
system comprising a rotary coupler as part of a catheter interface
module;
[0018] FIG. 2 is a schematic representation of electrical signal
paths of a catheter-based imaging system comprising a rotary
coupler as part of a catheter interface module;
[0019] FIG. 3 is a high-level diagram of a catheter-based imaging
system comprising a rotary coupler as part of a catheter;
[0020] FIG. 4 is a schematic representation of electrical signal
paths of a catheter-based imaging system comprising a rotary
coupler as part of a catheter;
[0021] FIG. 5 is a side perspective view of a parallel plate
capacitor;
[0022] FIG. 6 is a side perspective view of a cylindrical surface
concentric capacitor;
[0023] FIG. 7 is a side perspective view of a conical surface
concentric capacitor;
[0024] FIG. 8 is a diagram of a rotary capacitive coupler located
in a catheter interface module and comprised of a cylindrical
surface concentric capacitor and a parallel plate capacitor;
[0025] FIG. 9 is a diagram of a rotary capacitive coupler located
in a catheter and comprised of a cylindrical surface concentric
capacitor and a parallel plate capacitor;
[0026] FIG. 10 is a diagram of a rotary capacitive coupler
comprised of a conical surface concentric capacitor and a parallel
plate capacitor;
[0027] FIG. 11 is a diagram of a rotary capacitive coupler
comprised of cylindrical surface concentric capacitors;
[0028] FIG. 12 is a diagram of a rotary capacitive coupler
comprised of conical surface concentric capacitors;
[0029] FIG. 13 is a diagram of a rotary capacitive coupler
comprised of parallel plate capacitors; and
[0030] FIG. 14 is a schematic representation of electrical signal
paths for a two channel system comprised of a rotary inductive
coupler and a rotary capacitive coupler.
DETAILED DESCRIPTION OF THE INVENTION
[0031] A high-level diagram of the components of a catheter-based
imaging system is shown in FIG. 1. A catheter 1000A is coupled
mechanically and electrically to a catheter interface module 2000A
comprised of a rotary coupler 100. An imaging engine 3000 is in
electrical communication with the catheter interface module.
Following the imaging engine 3000 is a display engine 4000 and a
display 5000.
[0032] FIG. 2 shows an electrical schematic representation of the
transmit and receive signal paths of a catheter interface module
2000A and catheter 1000A having a primary purpose of coupling a
signal from a stationary electrical conduit to a rotating
electrical conduit. Diagrams for a rotary capacitive coupler 100
and ultrasonic transducer 220 are shown. In accordance with this
embodiment, the rotary capacitive coupler 100 is located outside of
the catheter 1000A and within the catheter interface module
2000A.
[0033] FIG. 3 shows a high-level diagram of the components of
another catheter-based imaging system. The components 1000B, 2000B,
3000, 4000, 5000 of the catheter-based imaging system in FIG. 3 are
substantially the same as the components 1000A, 2000A, 3000, 4000,
5000 of the catheter-based imaging system in FIG. 1 and hence,
reference characters for like elements are repeated in FIG. 3.
However, in this embodiment, a rotary coupler 100 is located in the
catheter 1000B.
[0034] FIG. 4 is an electrical schematic representation of the
system signal paths of the system of FIG. 3 and to the extent that
it is the same as the electrical schematic representation in FIG.
2, reference characters for like elements are repeated. However, as
may be noted in FIG. 4, the rotary capacitive coupler 100 is
located in the catheter 1000B.
[0035] FIGS. 5-7 show illustrations of parallel plate and
concentric capacitors which may be employed in the various
embodiments described hereinafter. FIG. 5 shows a side perspective
view of a parallel plate capacitor. The capacitance of the parallel
plate capacitor depends on the cross-sectional area A.sub.plate and
separation distance d.sub.plate of two parallel plates Plate1,
Plate2 and is closely approximated by
C = o r A plate d plate ##EQU00001##
where C is the capacitance in Farads (F), A.sub.plate is the area
of each plate in square meters (m.sup.2), .epsilon..sub.r is the
relative static permittivity or dielectric constant,
.epsilon..sub.0 is the permittivity of free space (i.e.,
8.854.times.10.sup.-12 F/m), and d.sub.plate is the separation
distance between the plates in meters (m).
[0036] FIG. 6 shows a side perspective view of a concentric
capacitor comprised of cylindrical surfaces. The capacitance per
unit length of the cylindrical surface concentric capacitor depends
on the radii r.sub.1, r.sub.2 of the drums (or cylinders) Drum1,
Drum2 and is approximately
2 .pi. 0 r ln ( r 1 r 2 ) . ##EQU00002##
The reactive impedance experienced by a signal of frequency f
across the capacitor is |Xc|=(2.pi.fC).sup.-1.
[0037] FIG. 7 shows a side perspective view of a concentric
capacitor comprised of conical surfaces. The capacitance of the
conical surface concentric capacitor is similar to the capacitance
of the cylindrical surface concentric capacitor. The cone
separation distance d.sub.cone can be varied by adjusting the
relative axial position of the cones Cone1, Cone2. The ability to
adjust the separation distance enables variation of the
capacitance.
[0038] For a given capacitance C of the capacitors of FIGS. 5-7,
the reactive impedance |Xc| decreases as frequency f increases.
Insertion loss for a rotary capacitive coupler decreases with
increasing frequency and increasing capacitance. Capacitance can be
increased by increasing the relative static permittivity of the
capacitor gap filler material, increasing the surface area of the
capacitor surfaces, or decreasing the gap between capacitor
surfaces. The gap filler material can be a variety of materials
including air, polyethylene, quartz, or glass. The benefit of
decreased insertion loss to imaging performance is improved axial
resolution of the imaging system due to use of higher transducer
frequencies
[0039] FIGS. 8 and 9 illustrate separate embodiments of an IVUS
system and catheter wherein a rotary capacitive coupler can either
be located in a catheter interface module (FIG. 8) or a catheter
(FIG. 9). FIG. 8 shows a diagram of a catheter interface module
2000A and catheter 1000A wherein a rotary capacitive coupler 100A
is located in the catheter interface module. The rotary capacitive
coupler comprises a cylindrical surface concentric capacitor 110
including concentric drums 110A, 112A and a parallel plate
capacitor 120 including plates 120A, 122A, respectively. The
advantage of this design is that the fixed non-rotatable drum 120A
acts as a shield to electrical noise for the parallel plate
capacitor.
[0040] A high frequency (>40 MHz) signal travels from a send
path 2 to the center conductor 212 of a catheter transmission line
210 in the catheter imaging core, through an ultrasound transducer
220, back through a transmission line shield 214, and finally back
to the return path conductor 4. The imaging core 200 components
212, 214, 220 rotate inside a catheter sheath by means of a drive
motor 30. The imaging core conductors 212, 214 are electrically
loaded by a transducer 220. The rotary coupler 100A comprising the
cylindrical surface concentric capacitor 110 and the parallel plate
capacitor 120 is used to electrically couple the fixed and rotating
components. A drive shaft 32 is mechanically coupled to the
rotating drum 112A and rotating plate 122A.
[0041] When operating in a send mode the send signal along
conductor 2 passes through a transmit/receive (T/R) switch 10 to
the conductor 12 leading to an input transmission line 20. The
outputs of the input transmission line 20 are a send signal
conductor 22 and a return signal conductor 24. The conductors 22,
24 are the inputs to the rotational coupler. The rotary coupler
transfers (or couples) electrical signals between the send signal
conductor 22 and the proximal end of the catheter transmission line
210 center conductor 202. The rotary coupler also transfers
electrical signals between the return signal conductor 24 and the
proximal end of the catheter transmission line shield 204. This is
achieved with two capacitors.
[0042] The send coupling capacitor 110 comprises concentric drums
110A, 112A. The return coupling capacitor 120 comprises parallel
plates 120A, 122A. Regarding the two capacitors, fixed components
110A, 120A remain stationary while rotating components 112A, 122A
rotate with the motor 30, drive shaft 32, and catheter imaging core
200. Input transmission line center conductor 22 electrically
connects to drum 110A, and the send signal on conductor 22 is
coupled to drum 112A which is electrically connected to catheter
transmission line center conductor 212. The input transmission line
shield 24 electrically connects to the fixed plate 120A, and the
signal on conductor 24 gets coupled to rotating plate 122A which is
electrically connected to catheter transmission line shield
conductor 214. A radiofrequency (RF) connector (not shown) is used
to connect conductors 102, 104 of the catheter interface module and
conductors 202, 204 of the catheter. Any RF connector can generally
be used, but a subminiature RF connector such as an SMB connector
is typically used. Consequently, signals on stationary input
transmission line conductors 22, 24 get coupled to the rotating
catheter transmission line conductors 202, 204.
[0043] The same rotational coupler serves to couple high frequency
(>40 MHz) signals generated by the transducer 220 (from
ultrasound reflections) back in the reverse (or return) direction.
In the return case, signals generated from the transducer 220 are
sent to the receiver 8 through the imaging core conductors 202, 204
and input transmission line input-side conductors 12, 14. The
rotary coupler capacitively couples the signals on the imaging core
proximal conductors 202, 204 to input transmission line
output.-side conductors 22, 24. The input transmission line 20
outputs the receive signals on input-side conductors 12, 14. The
signal on conductor 12 is sent to conductor 4 via the T/R switch 10
which would be set for the receive path. Note that the send and
receive cases are never allowed to occur simultaneously. A transmit
signal is sent to the transducer 220 (with the T/R switch 10 set to
send) before the T/R switch 10 is set to receive.
[0044] The diagram of a catheter interface module 2000B and
catheter 1000B in FIG. 9 is substantially the same as the diagram
of the catheter interface module 2000A and catheter 1000A in FIG. 8
and hence, reference characters for like elements are repeated in
FIG. 9. A rotary capacitive coupler 100A comprises a cylindrical
surface concentric capacitor 110 having concentric drums 110A, 112A
and a parallel plate capacitor 120 having parallel plates 120A,
122A and is located in the catheter. An RF connector (not shown) is
used to connect conductors 22, 24 of the catheter interface module
and conductors 106, 108 of the catheter. A subminiature RF
connector such as an SMB connector is typically used. Signals on
stationary input transmission line conductors 22, 24 are coupled to
the rotating catheter transmission line conductors 202, 204.
[0045] FIGS. 10-13 show various embodiments of rotary capacitive
couplers that may be employed in practicing the present invention.
The diagrams of the rotary capacitive couplers, drive motor, and
drive shaft in FIGS. 10-13 are substantially the same as the
diagram of the the rotary capacitive couplers, drive motor, and
drive shaft in FIG. 8 and hence, reference characters for like
elements are repeated in FIGS. 10-13.
[0046] The rotary capacitive coupler 100B illustrated in FIG. 10
comprises a conical surface concentric capacitor 111 having
concentric conical surfaces 110B, 112B and a parallel plate
capacitor 120 having plates 120B, 122B. The output-side input
transmission line conductors 22, 24 are electrically connected to
the rigidly fixed conical surface 110B and parallel plate 120B. The
rotatable conical surface 112B is electrically connected to
conductor 102 and mechanically connected to the drive shaft 32. The
rotatable parallel plate 122B is electrically connected to
conductor 104 and mechanically connected to the drive shaft 32.
[0047] FIG. 11 shows a rotary capacitive coupler 100C comprised of
two cylindrical surface concentric capacitors 113 and 115 having
concentric drums 110C, 112C and 120C, 122C, respectively. The
output-side input transmission line conductors 22, 24 are
electrically connected to the rigidly fixed cylindrical surfaces
110C, 120C. The rotatable cylindrical surface 112C is electrically
connected to conductor 102 and mechanically connected to the drive
shaft 32. The rotatable cylindrical surface 122C is electrically
connected to conductor 104 and mechanically connected to the drive
shaft 32.
[0048] FIG. 12 shows a rotary capacitive coupler 100D comprised of
two conical surface concentric capacitors 117 and 119 having
concentric surfaces 110D, 112D and 120D, 122D, respectively. The
output-side input transmission line conductors 22, 24 are
electrically connected to the rigidly fixed conical surfaces 110D,
120D. The rotatable conical surface 112D is electrically connected
to conductor 102 and mechanically connected to the drive shaft 32.
The rotatable conical surface 122D is electrically connected to
conductor 104 and mechanically connected to the drive shaft 32.
[0049] FIG. 13 shows a rotary capacitive coupler 100E comprised of
two parallel plate capacitors 121 and 123 having plate pairs 110E,
112E and 120E, 122E, respectively. The output-side input
transmission line conductors 22, 24 are electrically connected to
the rigidly fixed parallel plates 110E, 120E. The rotatable
parallel plate 112E is electrically connected to conductor 102 and
mechanically connected to the drive shaft 32. The rotatable
parallel plate 122E is electrically connected to conductor 104 and
mechanically connected to the drive shaft 32.
[0050] FIG. 14 illustrates still another embodiment wherein an IVUS
system comprises a rotary capacitive coupler 100 and a rotary
inductive coupler 100-HF. A catheter interface module 2000C
comprises the rotary inductive coupler 100-HF and the rotary
capacitive coupler 100 on a single rotating shaft with two sets of
independent electrical connections. The catheter 1000C comprises a
high frequency (less than approximately 30 MHz) transducer 220-HF
and very high frequency (greater than approximately 30 MHz)
transducer 220.
[0051] This invention overcomes drawbacks associated with rotary
inductive couplers used in minimally invasive, high-frequency IVUS
imaging systems and catheters. In particular, rotary capacitive
couplers improve system performance by reducing insertion loss and
impedance variation with angular position. The rotary capacitive
couplers disclosed heretofore comprise parallel plate capacitors,
cylindrical surface concentric capacitors, and conical surface
concentric capacitors. A parallel plate capacitor comprises a first
rigidly fixed plate and a second rotatable plate. A cylindrical
surface concentric capacitor comprises a first rigidly fixed
cylindrical surface and a second rotatable cylindrical surface. A
conical surface concentric capacitor comprises a first rigidly
fixed conical surface and a second rotatable conical surface. The
exemplary rotary capacitive couplers can be combined for system
performance advantages. Furthermore, a rotary inductive coupler and
a rotary capacitive coupler can be used in a two channel IVUS
system and catheter for high frequency and very high frequency
operation.
[0052] While particular embodiments of the present invention have
been shown and described, modifications may be made, and it is
therefore intended to cover in the appended claims, all such
changes and modifications which fall within the true spirit and
scope of the invention as defined by those claims.
* * * * *