U.S. patent application number 11/096834 was filed with the patent office on 2006-10-05 for optional telemetry antenna for implantable medical devices.
Invention is credited to Garry L. Dublin, William D. Verhoef, Eduardo H. Villaseca, Rodney S. Wallace.
Application Number | 20060224206 11/096834 |
Document ID | / |
Family ID | 37071567 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060224206 |
Kind Code |
A1 |
Dublin; Garry L. ; et
al. |
October 5, 2006 |
Optional telemetry antenna for implantable medical devices
Abstract
An implantable medical device ("IMD") configured in accordance
with an example embodiment of the invention generally includes a
housing, a connector header block coupled to the housing, and an
optional telemetry antenna coupled to the header block. The
optional antenna assembly is suitably configured to support the
intended IMD application (e.g., the desired telemetry range, the
intended IMD implant location, or other practical considerations).
The optional antenna assembly may be utilized by itself or in
cooperation with a permanent telemetry antenna of the IMD. In one
practical embodiment, the optional antenna assembly has a
connection end that is compliant with known pacemaker electrode
lead standards, which allows the IMD to leverage existing
connection methodologies.
Inventors: |
Dublin; Garry L.; (Maple
Grove, MN) ; Villaseca; Eduardo H.; (Minneapolis,
MN) ; Verhoef; William D.; (Andover, MN) ;
Wallace; Rodney S.; (Maple Grove, MN) |
Correspondence
Address: |
MEDTRONIC, INC.
710 MEDTRONIC PARK
MINNEAPOLIS
MN
55432-9924
US
|
Family ID: |
37071567 |
Appl. No.: |
11/096834 |
Filed: |
March 31, 2005 |
Current U.S.
Class: |
607/37 ;
607/32 |
Current CPC
Class: |
A61N 1/37229 20130101;
A61N 1/3752 20130101 |
Class at
Publication: |
607/037 ;
607/032 |
International
Class: |
A61N 1/36 20060101
A61N001/36 |
Claims
1. An implantable medical device ("IMD") comprising: a housing; a
header block coupled to said housing; a radio frequency ("RF")
module contained in said housing, said RF module being configured
to support RF telemetry for the IMD; and an optional antenna
assembly having a connector element located within said header
block and coupled to said RF module, forming a free end external to
said housing.
2. An IMD according to claim 1, said optional antenna assembly
being configured to provide far field radiation of RF transmit
energy provided by said RF module.
3. An IMD according to claim 1, said optional antenna assembly
being configured in accordance with a predetermined implant
location.
4. An IMD according to claim 1, said optional antenna assembly
being removably coupled to said header block.
5. An IMD according to claim 1, said connector element being IS-TAB
compliant.
6. An IMD according to claim 1, said optional antenna assembly
comprising: a radiating element coupled to said connector element;
and a biocompatible insulator covering at least a portion of said
radiating element.
7. An IMD according to claim 6, said radiating element being formed
from a round wire.
8. An IMD according to claim 6, said radiating element comprising
at least one helical section.
9. An IMD according to claim 6, said biocompatible insulator being
formed from a flexible material.
10. An IMD according to claim 6, said biocompatible insulator being
formed from a rigid material.
11. An IMD according to claim 1, further comprising a permanent
antenna assembly connected between said RF module and said optional
antenna assembly, said optional antenna assembly being configured
to cooperate with said permanent antenna assembly to provide
increased antenna gain.
12. An IMD according to claim 11, at least a portion of said
permanent antenna assembly being located within said header
block.
13. An IMD according to claim 12, said permanent antenna assembly
comprising a back wrap antenna element.
14. An IMD according to claim 1, further comprising an RF impedance
matching circuit coupled to said optional antenna assembly, said RF
impedance matching circuit being configured to match said optional
antenna assembly to said RF module.
15. An optional antenna assembly for an implantable medical device
("IMD") having a header block and a radio frequency ("RF") module
configured to support RF telemetry for the IMD, said optional
antenna assembly comprising: a connection end configured for
insertion into the header block; a free end configured for
deployment external to the header block; a connector element
located at said connection end, said connector element being
configured to establish electrical coupling with the RF module; a
radiating element coupled to said connector element; and a
biocompatible insulator covering at least a portion of said
radiating element.
16. An optional antenna assembly according to claim 15, said
connection end being IS-TAB compliant.
17. An optional antenna assembly according to claim 15, said
radiating element comprising at least one helical section.
18. An implantable medical device ("IMD") comprising: a housing; a
header block coupled to said housing; a radio frequency ("RF")
module contained in said housing, said RF module being configured
to support RF telemetry for the IMD; an antenna lead bore formed
within said header block, said antenna lead bore being configured
to receive optional antenna assemblies for the IMD; and an antenna
terminal located within said header block and coupled to said RF
module, said antenna terminal being accessible via said antenna
lead bore, said antenna terminal being configured to establish
electrical coupling with optional antenna assemblies for the
IMD.
19. An IMD according to claim 18, said antenna lead bore being
configured to receive IS-TAB compliant optional antenna assemblies,
and said antenna terminal being configured to establish electrical
coupling with IS-TAB compliant optional antenna assemblies.
20. An IMD according to claim 18, further comprising a permanent
antenna assembly connected between said RF module and said antenna
terminal, said permanent antenna assembly being configured to
support RF telemetry for the IMD.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to implantable
medical devices ("IMDs"). More particularly, the present invention
relates to telemetry antennas suitable for deployment in IMDs.
BACKGROUND
[0002] The prior art is replete with a variety of IMDs that provide
diagnostic and/or therapeutic capabilities. Such IMDs include,
without limitation: cardiac pacemakers; implantable
cardioverters/defibrillators ("ICDs"); and various tissue, organ,
and nerve stimulators or sensors. IMDs typically include functional
components contained within a hermetically sealed enclosure or
housing, which is sometimes referred to as a "can." In some IMDs, a
connector header or connector block is attached to the housing, and
the connector block facilitates interconnection with one or more
elongated electrical medical leads. The header block is typically
molded from a relatively hard, dielectric, non-conductive polymer
having a thickness approximating the thickness of the housing. The
header block includes a mounting surface that conforms to, and is
mechanically affixed against, a mating sidewall surface of the
housing.
[0003] It has become common to provide a communication link between
the hermetically sealed electronic circuitry of the IMD and an
external programmer, monitor, or other external medical device
("EMD") in order to provide for downlink telemetry transmission of
commands from the EMD to the IMD and to allow for uplink telemetry
transmission of stored information and/or sensed physiological
parameters from the IMD to the EMD. As the technology has advanced,
IMDs have become more complex in possible programmable operating
modes, menus of available operating parameters, and capabilities of
monitoring, which in turn increase the variety of possible
physiologic conditions and electrical signals handled by the IMD.
Consequently, such increasing complexity places increasing demands
on the programming system.
[0004] Conventionally, the communication link between the IMD and
the EMD is realized by encoded radio frequency ("RF") transmissions
between an IMD telemetry antenna and transceiver and an EMD
telemetry antenna and transceiver. The telemetry transmission
system that evolved into current common use relies upon the
generation of low amplitude magnetic fields by current oscillating
in an LC circuit of an RF telemetry antenna in a transmitting mode
and the sensing of currents induced by a closely spaced RF
telemetry antenna in a receiving mode. Short duration bursts of the
carrier frequency are transmitted in a variety of telemetry
transmission formats. In some products, the RF carrier frequency is
set at 175 kHz, and the prior art contains various RF telemetry
antenna designs suitable for use in such applications. To support
such products, the EMD is typically a programmer having a manually
positioned programming head having an external RF telemetry
antenna. Generally, the IMD antenna is disposed within the
hermetically sealed housing; however, the typically conductive
housing adversely attenuates the radiated RF field and limits the
data transfer distance between the programmer head and the IMD RF
telemetry antennas to a few inches. This type of system may be
referred to as a "near field" telemetry system.
[0005] It has been recognized that "far field" telemetry, or
telemetry over distances of a few to many meters from an IMD, would
be desirable. Various attempts have been made to provide antennas
with an IMD to facilitate far field telemetry. Many proposals have
been advanced for eliminating conventional RF telemetry antenna
designs and substituting alternative telemetry transmission systems
and schemes employing far higher carrier frequencies and more
complex signal coding to enhance the reliability and safety of the
telemetry transmissions while increasing the data rate and allowing
telemetry transmission to take place over a matter of meters rather
than inches.
[0006] Telemetry antennas, whether designed for near field or far
field operation, are susceptible to variations in the implanted
environment (the IMD and antenna are surrounded by varying amounts
of conductive body tissue when deployed). For example, a practical
telemetry antenna will be designed to provide adequate gain, gain
pattern, and bandwidth for the intended application. In this
regard, a given antenna designed and tuned for operation with a
subcutaneously implanted IMD may not perform effectively with a
sub-muscularly implanted IMD (due to the increased gain
requirements for a sub-muscle deployment). Furthermore, a given
antenna designed and tuned for operation with a near field
telemetry system may not perform effectively in a far field
telemetry system. Consequently, it may be necessary for an IMD
manufacturer to provide multiple versions of an IMD product, where
each version has a different antenna architecture that is
specifically designed to accommodate a particular implant location
and/or telemetry system.
[0007] It remains desirable to provide an IMD telemetry antenna
system that eliminates drawbacks associated with the IMD telemetry
antennas of the prior art. In particular, it is desirable to have
an interchangeable or optional telemetry antenna system for an IMD.
Furthermore, other desirable features and characteristics of the
present invention will become apparent from the subsequent detailed
description and the appended claims, taken in conjunction with the
accompanying drawings and the foregoing technical field and
background.
BRIEF SUMMARY
[0008] An IMD configured in accordance with an embodiment of the
invention includes an optional telemetry antenna having a
connection end that is secured within the header block of the IMD.
The optional telemetry antenna may be employed in addition to a
"fixed" antenna element, such as an antenna element that is
encapsulated within the header block, or it may serve as the only
antenna element for the IMD. The specific configuration, RF
characteristics, antenna gain, and other operational features of
the optional antenna are selected to suit the needs of the
particular IMD and/or the particular implant location. In this
regard, the IMD can be outfitted with an appropriate antenna that
is optimized to suit the needs of the particular IMD application,
e.g., in consideration of the operating environment, the age, sex,
size, or condition of the patient, or implant orientation within
the patient. The optional nature of the antenna facilitates the
adjustment of antenna gain to compensate for body losses based on
the implant depth.
[0009] The above and other aspects of the invention may be carried
out in one form by an IMD having a housing, a header block coupled
to the housing, an RF module contained in the housing, and an
optional antenna assembly having a connector element located within
the header block and coupled to the RF module, and a free end
external to the housing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] A more complete understanding of the present invention may
be derived by referring to the detailed description and claims when
considered in conjunction with the following figures, wherein like
reference numbers refer to similar elements throughout the
figures.
[0011] FIG. 1 is a perspective view of an IMD;
[0012] FIG. 2 is a schematic representation of an IMD and
functional elements associated with the IMD;
[0013] FIG. 3 is a front view of an IMD and an optional antenna
assembly before installation in the IMD;
[0014] FIG. 4 is a front view of the IMD shown in FIG. 3 after
installation of the optional antenna assembly;
[0015] FIG. 5 is a front view of another IMD and an optional
antenna assembly before installation in the IMD;
[0016] FIGS. 6 and 7 are front views of the IMD shown in FIG. 5
after installation of the optional antenna assembly;
[0017] FIG. 8 is a side view of an optional antenna assembly
configured in accordance with an example embodiment of the
invention;
[0018] FIG. 9 is a cross sectional view of a portion of an IMD
configured in accordance with an example embodiment of the
invention; and
[0019] FIGS. 10-15 are schematic representations of IMDs configured
in accordance with example embodiments of the invention.
DETAILED DESCRIPTION
[0020] The following detailed description is merely illustrative
and is not intended to limit the invention or the application and
uses of the invention. Furthermore, there is no intention to be
bound by any expressed or implied theory presented in the preceding
technical field, background, brief summary or the following
detailed description.
[0021] The following description refers to components or features
being "connected" or "coupled" together. As used herein, unless
expressly stated otherwise, "connected" means that one
component/feature is directly or indirectly connected to another
component/feature, and not necessarily mechanically. Likewise,
unless expressly stated otherwise, "coupled" means that one
component/feature is directly or indirectly coupled to another
component/feature, and not necessarily mechanically. Thus, although
the figures may depict example arrangements of elements, additional
intervening elements, devices, features, or components may be
present in an actual embodiment (assuming that the functionality of
the IMDs are not adversely affected).
[0022] The invention relates to an IMD having an optional RF
telemetry antenna. For the sake of brevity, conventional techniques
and aspects related to RF antenna design, IMD telemetry, RF data
transmission, signaling, IMD operation, connectors for IMD leads,
and other functional aspects of the systems (and the individual
operating components of the systems) may not be described in detail
herein. Furthermore, the connecting lines shown in the various
figures contained herein are intended to represent example
functional relationships and/or physical couplings between the
various elements. It should be noted that many alternative or
additional functional relationships or physical connections may be
present in a practical embodiment.
[0023] An IMD antenna generally has two functions: to convert the
electromagnetic power of a downlink telemetry transmission of an
EMD telemetry antenna propagated through the atmosphere (and then
through body tissues) into a UHF signal that can be processed by
the IMD transceiver into commands and data that are intelligible to
the IMD electronic operating system; and to convert the uplink
telemetry UHF signals of the IMD transceiver electronics into
electromagnetic power propagated through the body tissue and the
atmosphere so that the EMD telemetry antenna or antennas can
receive the signals.
[0024] FIG. 1 is a perspective view of an IMD 10 having a
hermetically sealed housing 12 and a connector header or block 14.
A set of IMD leads having electrodes (such as
cardioversion/defibrillation electrodes and pace/sense electrodes)
disposed in operative relation to a patient's heart are adapted to
be coupled to the header block 14 in a manner well known in the
art. For example, such leads may enter at an end 15 of header block
14 and be physically and electrically connected to conductive
receptacles, terminals, or other conductive features located within
header block 14. IMD 10 is adapted to be implanted subcutaneously
in the body of a patient such that it becomes encased within body
tissue and fluids, which may include epidermal layers, subcutaneous
fat layers, and/or muscle layers.
[0025] Hermetically sealed housing 12 is generally circular,
elliptical, prismatic, or rectilinear, with substantially planar
major sides (only one major side 16 is shown in FIG. 1) joined by
perimeter sidewalls. The perimeter sidewalls include a
substantially straight first sidewall 18, a substantially straight
second sidewall 20 opposing first sidewall 18, a substantially
straight upper sidewall 22, and a curvilinear lower sidewall 24
opposing upper sidewall 22. Housing 12 is typically formed from
pieces of a thin-walled biocompatible metal such as titanium. Two
half sections of housing 12 may be laser seam welded together using
conventional techniques to form a seam extending around the
perimeter sidewalls.
[0026] Housing 12 and header block 14 are often manufactured as two
separate assemblies that are subsequently physically and
electrically coupled together. Housing 12 may contain a number of
functional elements, components, and features, including (without
limitation): a battery; a high voltage output capacitor; integrated
circuit ("IC") devices; a processor; memory elements; a therapy
module or circuitry; an RF module or circuitry; and an antenna
matching circuit. These components may be assembled in spacers and
disposed within the interior cavity of housing 12 prior to seam
welding of the housing halves. During the manufacturing process,
electrical connections are established between components located
within housing 12 and elements located within header block 14. For
example, housing 12 and header block 14 may be suitably configured
with IC connector pads, terminals, feedthrough elements, and other
features for establishing electrical connections between the
internal therapy module and the therapy lead connectors within
header block 14 and for establishing connections between the
internal RF module and a portion of a telemetry antenna element
located within header block 14. Structures and techniques for
establishing such electrical (and physical) connections are known
to those skilled in the art and, therefore, will not be described
in detail herein.
[0027] Header block 14 is preferably formed from a suitable
dielectric material, such as a biocompatible synthetic polymer. In
some embodiments, the dielectric material of header block 14 may be
selected to enable the passage of RF energy that is either radiated
or received by a telemetry antenna (not shown in FIG. 1)
encapsulated within header block 14. The specific material for
header block 14 may be chosen in response to the intended
application of IMD 10, the electrical characteristics of the
environment surrounding the implant location, the desired operating
frequency range, the desired RF antenna range, and other practical
considerations.
[0028] In accordance with one example embodiment, header block 14
is approximately one inch wide (measured along upper sidewall 22),
approximately one-half inch high, and approximately one-half inch
thick. It should be appreciated that the shape, size, topology, and
placement of header block 14 relative to housing 12 may vary from
one application to another, and that the particular configuration
shown in FIG. 1 represents only one practical example. In this
regard, header block 14 may, but need not, have a "tail" or "back
wrap" portion 26 that extends partially down sidewall 20. Alternate
embodiments may include a longer or shorter back wrap 26, depending
upon the desired locations of electrical connections and interface
points, or depending upon the layout and routing of conductive
elements contained within header block 14 and back wrap 26. In
addition, header block 14 need not be located on upper sidewall 22
(or any sidewall) and may instead be located on one of the planar
major sides of housing 12. Furthermore, more than one header block
12 may be utilized in a practical implementation.
[0029] FIG. 2 is a simplified schematic representation of an IMD
100 and several functional elements associated therewith. IMD 100
generally includes a housing 102, a header block 104 coupled to
housing 102, a therapy module 106 contained within housing 102, an
RF module 108 contained within housing 102, and an RF impedance
matching circuit 110, which may also be contained within housing
102. Housing 102 and header block 104 may be configured as
described above in connection with FIG. 1. In practice, IMD 100
will also include a number of conventional components and features
necessary to support the functionality of IMD 100. Such
conventional elements will not be described herein.
[0030] Therapy module 106 may include any number of components,
including, without limitation: electrical devices, ICs,
microprocessors, controllers, memories, power supplies, and the
like. Briefly, therapy module 106 is configured to provide the
desired functionality associated with the IMD 100, e.g.,
defibrillation pulses, pacing stimulation, patient monitoring, or
the like. In this regard, therapy module 106 may be coupled to one
or more therapy leads 112. In practice, the connection ends of
therapy leads 112 are inserted into header block 104, where they
establish electrical contact with conductive elements coupled to
therapy module 106. Therapy leads 112 may be inserted into suitably
configured lead bores formed within header block 104. In FIG. 1,
lead bores are identified by reference number 28. In the example
embodiment, IMD 100 includes feedthrough elements 114 that bridge
the transition between housing 102 and header block 104. Therapy
leads 112 extend from header block 104 for routing and placement
within the patient.
[0031] RF module 108 may include any number of components,
including, without limitation: electrical devices, ICs, amplifiers,
signal generators, a receiver and a transmitter (or a transceiver),
modulators, microprocessors, controllers, memories, power supplies,
and the like. Although matching circuit 110 is illustrated as a
separate component coupled to RF module 108, it may instead be
incorporated into RF module 108 in a practical embodiment. Briefly,
RF module 108 supports RF telemetry communication for IMD 100,
including, without limitation: generating RF transmit energy;
providing RF transmit signals to antenna 116; processing RF
telemetry signals received by antenna 116, and the like. In
practice, RF module 108 may be designed to leverage the conductive
material used for housing 102 as an RF ground plane (for some
applications), and RF module 108 may be designed in accordance with
the intended application of IMD 100, the electrical characteristics
of the environment surrounding the implant location, the desired
operating frequency range, the desired RF antenna range, and other
practical considerations.
[0032] Matching circuit 110 may include any number of components,
including, without limitation: electrical components such as
capacitors, resistors, or inductors; filters; baluns; tuning
elements; attenuators; limiters; or the like. Matching circuit 110
is suitably configured to provide impedance matching between an
optional antenna assembly 116 and RF module 108, thus improving the
efficiency of antenna assembly 116. Matching circuit 110 may
leverage known techniques to alter the electrical characteristics
of antenna assembly 116 to suit the needs of the particular
application.
[0033] Antenna assembly 116 is coupled to matching circuit 110
and/or to RF module 108 to facilitate RF telemetry between IMD 100
and an EMD (not shown). Generally, antenna assembly 116 is suitably
configured for UHF or VHF operation. In the example embodiment
shown in FIG. 1, a first portion of antenna assembly 116 is located
within header block 104, and a second portion of antenna assembly
116 extends outside of header block 104 and outside of housing 102.
In the preferred embodiment of the invention, antenna assembly 116
is an optional feature of IMD 100. Antenna assembly 116 is coupled
to matching circuit 110 and/or to RF module 108 via an RF
feedthrough 118, which bridges housing 102. Although not shown in
FIG. 2, antenna assembly 116 may include a connection end that is
coupled to RF feedthrough via a conductive terminal or feature
located within header block 104. Briefly, a practical RF
feedthrough 118 includes a ferrule supporting a non-conductive
glass or ceramic annular insulator. The insulator supports and
electrically isolates a feedthrough pin from the ferrule. During
assembly of housing 102, the ferrule is welded to a suitably sized
hole or opening formed in housing 102. Matching circuit 110 and/or
RF module 108 is then electrically connected to the inner end of
the feedthrough pin. The connection to the inner end of the
feedthrough pin can be made by welding the inner end to a substrate
pad, or by clipping the inner end to a cable or flex wire connector
that extends to a substrate pad or connector. The outer end of the
feedthrough pin serves as a connection point for antenna assembly
116, or as a connection point for an internal connection socket,
terminal, or feature that receives the connection end of antenna
assembly 116.
[0034] In FIG. 2, RF feedthrough 118 is located on the upper
perimeter sidewall of housing 102 such that it defines a feed point
for antenna assembly 116, leading from housing 102 into header
block 104. Alternatively, RF feedthrough 118 may be located on the
lower perimeter sidewall of housing 102, on either of the major
perimeter sidewalls of housing 102, or on either of the major sides
of housing 102. In an alternate embodiment described in more detail
herein, RF feedthrough 118 is located on the back perimeter
sidewall of housing 102, leading into the back wrap 120 of header
block 104. Indeed, any of the antenna arrangements described herein
may be modified to accommodate different RF feedthrough locations.
For example, a given antenna assembly may utilize an input section
that leads from the RF feedthrough location to the main section of
the header block.
[0035] FIG. 3 is a front view of an IMD 200 and an optional antenna
assembly 202. Certain features and aspects of IMD 200 are similar
to those described above in connection with IMD 10 and IMD 100, and
shared features and aspects will not be redundantly described in
the context of IMD 200. IMD 200 generally includes a housing 204
and a header block 206 coupled to housing 202. FIG. 3 depicts IMD
before installation of optional antenna assembly 202. As used
herein, "optional antenna assembly" means that the antenna assembly
is not manufactured as a permanent feature of the given device, and
the antenna assembly is optional in that a clinician, manufacturer,
or technician has the option of installing one of a plurality of
available antenna assemblies (and, in some embodiments, no optional
antenna assembly) to suit the needs of the particular application.
In accordance with one example embodiment of the invention,
optional antenna assembly 202 can be removably coupled to header
block 206.
[0036] In practice, one antenna assembly may be suitably configured
for far field telemetry applications, while another antenna
assembly may be suitably configured for near field telemetry
applications. In addition, one antenna assembly may be suitably
configured for use when the IMD is implanted subcutaneously, while
another antenna assembly may be suitably configured for use when
the IMD is implanted sub-muscularly. Thus, for example, optional
antenna assembly 202 may be configured to provide far field
radiation of RF transmit energy provided by an RF module contained
within housing 204, and optional antenna assembly 202 may be
configured in accordance with a predetermined implant location
within the patient. It should be appreciated that the specific
configuration (size, shape, gain, gain pattern, and other RF
characteristics) of the optional antenna assembly may vary
according to any number of practical considerations other than the
above examples. Ultimately, depending upon the intended
application, the best antenna assembly can be selected for use with
IMD 200.
[0037] The arrow in FIG. 3 indicates that optional antenna assembly
202 can be inserted into an appropriate receptacle, such as an
antenna lead bore, formed within header block 206. In this example
embodiment, header block 206 includes a set screw feature 208 that
facilitates attachment of optional antenna assembly 202 to header
block 206. In this regard, set screw feature 208 may function to
provide physical and electrical coupling of optional antenna
assembly 202. FIG. 4 is a front view of IMD 200 after installation
of optional antenna assembly 202. A portion of optional antenna
assembly 202 (shown in dashed lines) resides within header block
206 after installation. Set screw feature 208 is tightened to
secure optional antenna assembly 202 within header block. The
coupling of optional antenna assemblies within an IMD header block
is described in more detail below. Those skilled in the art will
recognize that IMD 200 may employ well known set screw techniques
in connection with optional antenna assembly 202, including
techniques commonly used for pacemaker electrode leads.
Alternatively, IMD 200 may leverage other fastening methodologies
and techniques, including those that do not require set screws.
[0038] Notably, FIGS. 3 and 4 depict an embodiment where optional
antenna assembly 202 enters header block 206 from the side. In
practice, optional antenna assembly 202 may enter header block 206
at any suitable location. For example, FIGS. 5-7 depict another IMD
210 where optional antenna assembly 202 enters the header block 212
from the top. Certain features and aspects of IMD 210 are similar
to those described above in connection with IMD 10, IMD 100, and
IMD 200, and shared features and aspects will not be redundantly
described in the context of IMD 210. In contrast to header block
206 utilized by IMD 200, header block 212 is configured as a back
wrap header block. In further contrast to IMD 200, header block 212
may include one or more features that allow a flexible optional
antenna assembly 202 to be guided around and/or secured to header
block 212. For example, header block 212 may include a groove
formed on its upper surface for guiding optional antenna assembly
202, tabs to provide a pressure fit securing mechanism for optional
antenna assembly 202, or other elements designed to maintain
optional antenna assembly 202 in a specific position or
orientation, such as that shown in FIG. 7. A securing mechanism may
be convenient in some applications where it would be undesirable to
leave optional antenna assembly 202 "loose" within the implant
site.
[0039] FIG. 8 is a side view of an optional antenna assembly 300
configured in accordance with an example embodiment of the
invention, and FIG. 9 is a cross sectional view of a portion of an
IMD configured in accordance with an example embodiment of the
invention. FIG. 9 depicts antenna assembly 300 installed in a
header block 301 of the IMD. Antenna assembly 300 is suitable for
use with any of the IMD embodiments described herein. Antenna
assembly 300 generally includes a connection end 302, a free end
304, a body section 306 between connection end 302 and free end
304, an internal radiating element 308, and an external
biocompatible insulator 310. Connection end 302 is suitably
configured for insertion into header block 301 of a compatible IMD
for purposes of establishing electrical coupling between radiating
element 308 and the RF module of the IMD. In the example
embodiments described herein, free end 304 is configured for
deployment external to header block 301 and external to the housing
of the IMD. In other words, free end 304 (and possibly a portion of
body section 306) extend from header block 301, which may be
desirable to provide additional antenna gain for the IMD.
[0040] Optional antenna assembly 300 includes a connector element
312 located at connection end 312. At shown in FIG. 8, connector
element 312 is preferably located at the tip of antenna assembly
300. In practical embodiments, connector element 312 is formed from
a biocompatible and electrically conductive material, such as
niobium or titanium. As described in more detail below, connector
element 312 is coupled (directly or indirectly) to radiating
element 308 in a manner that facilitates the transmission of RF
energy to and from the RF module in the IMD. In this regard,
connector element 312 is suitably configured to establish
electrical coupling with the RF module when optional antenna
assembly 300 is installed in the IMD.
[0041] Biocompatible insulator 310 covers at least a portion of
radiating element 308. In practice, biocompatible insulator 310
serves as the outer layer of antenna assembly 300, and it may cover
all internal components of antenna assembly 300 except for
connector element 312. Biocompatible insulator 310 may be formed
from any suitable material, including, without limitation: silicone
rubber, polyurethane, or tecothane. Depending upon the intended
application, biocompatible insulator 310 may be formed from a
flexible material, a rigid material, or a combination thereof, and
it may be formed from a material having specific electrical
characteristics or properties (e.g., dielectric constant) that
enhance the RF performance of antenna assembly 300.
[0042] Antenna assembly 300 may include one or more sealing rings
314, which may be distinct elements or features incorporated into
biocompatible insulator 310. As shown in FIG. 9, sealing rings 314
seal connection end 302 within an antenna lead bore 316 formed
within header block 301. In practical embodiments, antenna lead
bore 316 is cylindrical in shape and sealing rings 314 have a
circular perimeter sized to form a contact seal with the interior
surface of antenna lead bore 316. Sealing rings 314 protect the
internal features of header block 310 against the ingress of body
fluids when the IMD is implanted in the patient.
[0043] In the example embodiment shown herein, optional antenna
assembly 300 leverages connection and sealing features that are
commonly used in connection with pacemaker electrode leads. In this
regard, at least a portion of antenna assembly 300 (e.g.,
connection end 302, and/or connector element 312) is compliant with
known standards, including, without limitation: IS-TAB; IS-1, and
IS-4. Likewise, header block 301 may include internal features that
are compliant with such standards to ensure compatibility with
connection end 302.
[0044] In practical embodiments, radiating element 308 is formed
from a biocompatible conductive material, such as, without
limitation: titanium alloy, niobium alloy, or the like. Radiating
element 308 may be formed from a solid wire having a round cross
section. In practical embodiments, radiating element 308 may be
formed from a round wire having a diameter of approximately 0.020
inches. Alternatively, radiating element 308 may be formed from a
hollow wire, a flat wire, a flat ribbon element, or a stamped
conductor having a generally rectangular cross section (or, for
that matter, any practical cross sectional shape). With brief
reference to FIG. 11, the radiating element may include at least
one helical section, or the entire radiating element may be
helical, depending upon the specific application. The use of
helical segments may be desirable to increase the effective
electrical length of radiating element 308 without increasing the
actual physical length of optional antenna assembly 300.
Furthermore, helical segments may be desirable to facilitate
impedance matching, tuning, or RF loading between antenna assembly
300 and the RF module contained in the IMD.
[0045] In accordance with one practical embodiment, an optional
antenna assembly 300 having a straight wire radiating element 308
is approximately eight centimeters long. It should be appreciated
that the physical length of optional antenna assembly 300, the
electrical length of radiating element 308, the shape of optional
antenna assembly 300, and/or other physical or electrical
characteristics of optional antenna assembly 300 can vary to suit
the needs of the given application. Variables to consider include,
without limitation: the wavelength of the RF telemetry signals;
whether the IMD supports near field or far field telemetry; the
implant location for the IMD; the implant depth for the IMD; the
type of IMD; the age of the patient; the size of the patient. For
example, a relatively long antenna assembly 300 (having relatively
more antenna gain) may be utilized for sub-muscle implantations,
while a relatively short antenna assembly 300 (having relatively
less antenna gain) may be utilized for subcutaneous implantations.
In addition, a relatively long antenna assembly 300 may be
necessary to support far field telemetry applications, while a
relatively short antenna assembly 300 may be suitable to support
near field telemetry applications. The optional nature of antenna
assembly 300 allows a single IMD design to be deployed in multiple
applications by selecting an appropriate configuration for antenna
assembly 300. Indeed, in certain IMDs having permanent antenna
elements, optional antenna assembly 300 need not be employed. With
such applications, antenna lead bore 316 can be filled with a
suitable biocompatible plug prior to implantation of the IMD.
[0046] Referring again to FIG. 9, header block 301 is configured to
secure optional antenna assembly 300 within antenna lead bore 316
using a set screw feature. Although FIGS. 3-7 depict set screw
features 208 that are accessible from the front of the header
blocks, the set screw 318 in FIG. 9 is accessible from the top of
header block 301. It should be appreciated that the specific
location and access orientation of set screw 318 may vary from that
shown and described herein. As mentioned above, antenna lead bore
316 is suitably sized and configured to receive optional antenna
assemblies for the IMD, such as optional antenna assembly 300. An
antenna terminal 320 (or equivalent structure), which is located
within header block 301, is accessible via antenna lead bore 316.
In FIG. 9, antenna terminal 320 is schematically represented by the
dashed lines. Antenna terminal 320 is generally configured to
establish electrical coupling between antenna assembly 300 and the
RF module 322 in the IMD. In the example embodiment, antenna
terminal 320 also establishes physical coupling between antenna
assembly 300 and header block 301. As mentioned above, antenna
terminal 320 may be configured to receive IS-TAB compliant optional
antenna assemblies.
[0047] In the example embodiment, antenna terminal 320 includes a
threaded structure supporting set screw 318, and an RF coupling
element 324 that establishes RF coupling with the connector element
of optional antenna assembly 300. RF coupling element 324 may be an
RF feedthrough, a conductive contact pad, or the like. Set screw
318 is tightened to force the connector element of optional antenna
assembly 300 against RF coupling element 324 to establish the
electrical connection. In addition, the tightening of set screw 318
may serve to secure optional antenna assembly 300 within header
block 301. A biocompatible seal or plug 326 covers set screw 318 to
protect the internal features of header block against the ingress
of body fluids after implantation of the IMD.
[0048] FIGS. 10-15 are schematic representations of IMDs configured
in accordance with example embodiments of the invention. Certain
features and aspects of these example IMD embodiments may be
similar to those described above in connection with FIGS. 1-9, and
shared features and aspects will not be redundantly described in
the context of these alternate embodiments. Furthermore, for the
sake of clarity, most of the internal structures of the IMDs are
not shown in FIGS. 10-15.
[0049] FIG. 10 depicts an IMD 400 having a relatively short
optional antenna assembly 402 installed in a header block 404.
Notably, antenna assembly 402 is relatively short in comparison to
antenna assembly 202 (see FIG. 4). Accordingly, IMD 400 may be
suitable for use with relatively shallow implant depths, or
suitable for use with near field telemetry applications. IMD 400
includes an RF feedthrough 406, which couples antenna assembly 402
to the RF module of IMD 400. In this example embodiment, optional
antenna assembly 402 represents the only RF telemetry antenna for
IMD 400. Although not required, antenna assembly 402 includes a
straight radiating element 408.
[0050] FIG. 11 depicts an IMD 500 having an optional antenna
assembly 502 installed in a header block 504. In contrast to IMD
400, antenna assembly 502 incorporates a radiating element 506
having helical sections 508. As mentioned above, helical sections
508 may be utilized to increase the electrical length of antenna
assembly 502 and/or to facilitate impedance matching. In this
example embodiment, optional antenna assembly 502 represents the
only RF telemetry antenna for IMD 500.
[0051] FIG. 12 depicts an IMD 600 having an optional antenna
assembly 602 installed in a header block 604. Notably, IMD 600
includes a permanent antenna assembly 606 connected between the RF
module (not shown) and optional antenna assembly 602. In practical
embodiments, permanent antenna assembly 606 may be connected
between an RF feedthrough 608, which in turn is coupled to the RF
module, and an antenna terminal 610 located within header block
604. In this particular embodiment, permanent antenna assembly 606
is completely contained within header block 604. In practice, the
radiating element of permanent antenna assembly 606 is encapsulated
within the dielectric material that forms header block 604.
Consequently, permanent antenna assembly 606 is preferably
dimensioned and otherwise configured to fit within the space
limitations of header block 604.
[0052] Permanent antenna assembly 606 may be dimensioned to provide
far field radiation of RF transmit energy provided by the RF module
contained within the IMD housing. In accordance with one practical
application, permanent antenna assembly 606 is suitably dimensioned
and tuned for reception and transmission of RF signals having a
carrier frequency within the range of 401 MHz to 406 MHz. Permanent
antenna assembly 606 may be dimensioned and tuned to account for
the intended operating environment and to account for the desired
operating range. Permanent antenna assembly 606 may be designed for
operation by itself or configured to cooperate with optional
antenna assembly 602 to provide increased antenna gain.
[0053] Permanent antenna assembly 606 may include a radiating
element formed from a conductive wire, such as a titanium wire, a
niobium wire, or the like. As described above in connection with
FIG. 8, the radiating element for permanent antenna assembly 606
may be formed from a solid wire having a round cross section, a
flat wire, a hollow wire, a flat ribbon element, or a stamped
conductor having any practical cross sectional shape.
[0054] FIG. 13 depicts an IMD 700 having an optional antenna
assembly 702 installed in a header block 704. IMD 700 includes a
permanent antenna assembly 706 connected between the RF module (not
shown) and optional antenna assembly 702. In practical embodiments,
permanent antenna assembly 706 may be connected between an RF
feedthrough 708, which in turn is coupled to the RF module, and an
antenna terminal 710 located within header block 604. In this
particular embodiment, a portion of permanent antenna assembly 706
is routed in a back wrap 712 of header block 704. Accordingly, RF
feedthrough 708 is located on a major sidewall 714 of the IMD
housing and permanent antenna assembly 706 may be routed along the
edge of major sidewall 714 and into the upper portion of header
block 704. In practice, the radiating element of permanent antenna
assembly 706 is encapsulated within the dielectric material that
forms header block 704 and back wrap 712. Other aspects of IMD 700
may be identical or similar to those described above in connection
with IMD 600.
[0055] FIG. 14 depicts an IMD 800 having an optional antenna
assembly 802 installed in a header block 804. In this example
embodiment, header block 804 includes a back wrap 806, and antenna
assembly 802 is inserted into the top of header block 804 for
coupling in back wrap 806. This embodiment may be desirable to
avoid extensive modifications to an existing header block design,
which may include other conductive elements, set screws, lead
terminals, or the like. IMD 800 includes an RF feedthrough 808,
which couples optional antenna assembly 802 to the RF module of IMD
800. In this example embodiment, optional antenna assembly 802
represents the only RF telemetry antenna for IMD 800.
[0056] FIG. 15 depicts an IMD 900 having an optional antenna
assembly 902 installed in a header block 904. In contrast to IMD
800, IMD 900 includes a permanent antenna assembly 906 connected
between the RF module (not shown) and optional antenna assembly
902. In practical embodiments, permanent antenna assembly 906 may
be connected between an RF feedthrough 908, which in turn is
coupled to the RF module, and an antenna terminal 910 located
within header block 904. In this particular embodiment, at least a
portion of permanent antenna assembly 906 is routed in a back wrap
912 of header block 904. Accordingly, RF feedthrough 908 is located
on a major sidewall 914 of the IMD housing and permanent antenna
assembly 906 may be routed along the edge of major sidewall 914 to
antenna terminal 910. In practice, the radiating element of
permanent antenna assembly 906 is encapsulated within the
dielectric material that forms header block 904 and back wrap
912.
[0057] While at least one example embodiment has been presented in
the foregoing detailed description, it should be appreciated that a
vast number of variations exist. It should also be appreciated that
the example embodiment or embodiments described herein are not
intended to limit the scope, applicability, or configuration of the
invention in any way. Rather, the foregoing detailed description
will provide those skilled in the art with a convenient road map
for implementing the described embodiment or embodiments. It should
be understood that various changes can be made in the function and
arrangement of elements without departing from the scope of the
invention as set forth in the appended claims and the legal
equivalents thereof.
* * * * *