U.S. patent application number 13/811210 was filed with the patent office on 2013-09-05 for implantable radio-frequency sensor.
This patent application is currently assigned to KYMA MEDICAL TECHNOLOGIES LTD.. The applicant listed for this patent is Assaf Bernstein, Eyal Cohen, Moshe Mosesko, Dov Oppenheim, Uriel Weinstein. Invention is credited to Assaf Bernstein, Eyal Cohen, Moshe Mosesko, Dov Oppenheim, Uriel Weinstein.
Application Number | 20130231550 13/811210 |
Document ID | / |
Family ID | 45496578 |
Filed Date | 2013-09-05 |
United States Patent
Application |
20130231550 |
Kind Code |
A1 |
Weinstein; Uriel ; et
al. |
September 5, 2013 |
Implantable Radio-Frequency Sensor
Abstract
Diagnostic apparatus (24) includes a sealed case (40), including
a biocompatible material and configured for implantation within a
body of a human subject (22). At least one antenna (42) is
configured to be implanted in the body in proximity to a target
tissue (28) and to receive radio frequency (RF) electromagnetic
waves propagated through the target tissue and to output a signal
in response to the received waves. Processing circuitry (44, 46),
which is contained within the case, is coupled to receive and
process the signal from the antenna so as to derive and output an
indication of a characteristic of the target tissue
Inventors: |
Weinstein; Uriel; (Mazkeret
Batia, IL) ; Bernstein; Assaf; (Givat Nilly, IL)
; Cohen; Eyal; (Ariel, IL) ; Oppenheim; Dov;
(Jerusalem, IL) ; Mosesko; Moshe; (Kadima,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Weinstein; Uriel
Bernstein; Assaf
Cohen; Eyal
Oppenheim; Dov
Mosesko; Moshe |
Mazkeret Batia
Givat Nilly
Ariel
Jerusalem
Kadima |
|
IL
IL
IL
IL
IL |
|
|
Assignee: |
KYMA MEDICAL TECHNOLOGIES
LTD.
Kfar Saba
IL
|
Family ID: |
45496578 |
Appl. No.: |
13/811210 |
Filed: |
July 21, 2011 |
PCT Filed: |
July 21, 2011 |
PCT NO: |
PCT/IB11/53244 |
371 Date: |
March 8, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61366173 |
Jul 21, 2010 |
|
|
|
Current U.S.
Class: |
600/407 |
Current CPC
Class: |
A61B 5/0809 20130101;
A61B 5/0031 20130101; A61B 5/4244 20130101; A61B 5/05 20130101;
A61B 5/14542 20130101; A61B 5/0059 20130101; A61B 2562/164
20130101; A61B 5/686 20130101; A61B 5/416 20130101; A61B 5/6833
20130101; A61N 1/37229 20130101; A61B 5/01 20130101; A61B 5/4552
20130101; A61B 5/0205 20130101; A61N 1/36521 20130101; A61B 5/0422
20130101; A61B 5/0537 20130101; A61B 1/313 20130101; A61B 5/0215
20130101; A61B 5/076 20130101; A61B 2562/0214 20130101; A61B 5/4875
20130101; A61B 17/3468 20130101; A61N 1/3702 20130101; A61B 5/0028
20130101; A61B 5/0538 20130101; A61B 5/72 20130101; A61B 2560/0219
20130101; A61N 1/3756 20130101 |
Class at
Publication: |
600/407 |
International
Class: |
A61B 5/0205 20060101
A61B005/0205; A61B 5/00 20060101 A61B005/00 |
Claims
1. Diagnostic apparatus, comprising: a sealed case, comprising a
biocompatible material and configured for implantation within a
body of a human subject; at least one antenna, which is configured
to be implanted in the body in proximity to a target tissue and to
receive radio frequency (RF) electromagnetic waves propagated
through the target tissue and to output a signal in response to the
received waves; and processing circuitry, which is contained within
the case and is coupled to receive and process the signal from the
antenna so as to derive and output an indication of a
characteristic of the target tissue.
2. The apparatus according to claim 1, wherein the at least one
antenna is configured to transmit the waves into the body and to
receive the transmitted waves following propagation of the waves
through the target tissue.
3. The apparatus according to claim 2, wherein the at least one
antenna is configured to receive the waves after reflection of the
waves from a tissue in the body, and wherein the processing
circuitry is configured to detect a modulation of the reflection
due to at least one of a heartbeat and a respiratory motion of the
subject.
4. The apparatus according to claim 3, wherein the modulation
comprises a cyclical variation due to the heartbeat.
5. The apparatus according to claim 2, and comprising a reflector
configured for implantation in the body in a location across the
target tissue from the case containing the at least one antenna,
wherein the reflector serves as the structure for reflecting the
waves toward the at least one antenna.
6. The apparatus according to claim 5, wherein the reflector is a
part of an implanted cardiac device (ICD) that is implanted in the
body.
7. The apparatus according to claim 1, and comprising a
transmitter, which is configured to be implanted in the body in a
location across the target tissue from the case containing the at
least one antenna and to transmit the waves through the target
tissue.
8. The apparatus according to claim 1, wherein the processing
circuitry is configured to process the signal so as to derive a
measure of a fluid content of the target tissue.
9. The apparatus according to claim 8, wherein the case is
configured for implantation in a thorax, and wherein the target
tissue is lung tissue.
10. The apparatus according to claim 8, wherein the target tissue
is spleen, liver, tongue or palate tissue.
11. The apparatus according to claim 1, wherein the indication
comprises a time trend of the characteristic of the target
tissue.
12. The apparatus according to claim 1, wherein the at least one
antenna comprises a plurality of antennas.
13. The apparatus according to claim 12, wherein the processing
circuitry is configured to drive the antennas in a multi-static
mode so as to spatially resolve the characteristic of the target
tissue.
14. The apparatus according to claim 1, wherein the at least one
antenna is contained inside the case.
15. The apparatus according to claim 14, wherein the at least one
antenna comprises a trace printed on a substrate, and wherein the
case comprises a window, and the antenna is configured to receive
the waves through the window.
16. The apparatus according to claim 15, wherein the substrate is
sealed to the case by brazing.
17. The apparatus according to claim 1, wherein the at least one
antenna is located partially outside the case and is connected to
the processing circuitry via a sealed brazing to the case.
18. The apparatus according to claim 1, wherein the at least one
antenna comprises a trace printed on a substrate and a backlobe
suppression structure behind the trace.
19. The apparatus according to claim 18, wherein the backlobe
suppression structure is selected from a group of structures
consisting of an air cavity and an electromagnetic bandgap (EBG)
backing.
20. The apparatus according to claim 1, wherein the at least one
antenna is selected from a group of antenna types consisting of a
spiral antenna, a bowtie antenna, an elliptic bowtie antenna, and a
slotted antenna.
21.-48. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application 61/366,173, filed Jul. 21, 2010, which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to methods and
systems for medical diagnostic measurement and monitoring, and
specifically to radio frequency (RF)-based measurement and
monitoring of physiological conditions.
BACKGROUND OF THE INVENTION
[0003] Radio-frequency (RF) electromagnetic radiation has been used
for diagnosis and imaging of body tissues. For example, PCT
International Publication WO 2011/067623, which is assigned to the
assignee of the present patent application and whose disclosure is
incorporated herein by reference, describes diagnostic apparatus
that includes an antenna, which directs RF electromagnetic waves
into a living body and generates signals responsively to the waves
that are scattered from within the body. The signals are processed
so as to locate a feature in a blood vessel in the body.
[0004] As another example, U.S. Patent Application Publication
2011/0130800, which is assigned to the assignee of the present
patent application and whose disclosure is incorporated herein by
reference, describes diagnostic apparatus, which includes a
plurality of antennas, which are configured to be disposed at
different, respective locations on the thorax of a living body. The
antennas direct radio frequency (RF) electromagnetic waves from
different, respective directions toward the heart in the body and
output RF signals responsively to the waves that are scattered from
the heart. The RF signals are processed over time so as to provide
a multi-dimensional measurement of a movement of the heart.
[0005] U.S. Patent Application Publication 2010/0256462 describes a
method for monitoring thoracic tissue fluid content by intercepting
reflections of electromagnetic (EM) radiation reflected from
thoracic tissue of a patient in radiation sessions during a period
of at least 24 hours. A change of a dielectric coefficient of the
thoracic tissue is detected by analyzing the reflections. PCT
International Publication WO 2009/031149 describes a wearable
monitoring apparatus comprising at least one transducer configured
for delivering EM radiation to internal tissue and intercepting at
least one reflection of the EM radiation therefrom. A housing for
containing the transducer, along with a reporting unit and a
processing unit, is configured to be disposed on the body of an
ambulatory user.
[0006] The citation of certain references above is intended to
provide a general overview of the state of the art and does not
constitute an admission that any of the references should be
considered prior art against the present patent application.
SUMMARY
[0007] Embodiments of the present invention that are described
hereinbelow provide implantable devices for measuring tissue
characteristics using RF electromagnetic radiation and methods of
measurement and monitoring using such devices.
[0008] There is therefore provided, in accordance with an
embodiment of the present invention, diagnostic apparatus,
including a sealed case, which includes a biocompatible material
and configured for implantation within a body of a human subject.
At least one antenna is configured to be implanted in the body in
proximity to a target tissue and to receive radio frequency (RF)
electromagnetic waves propagated through the target tissue and to
output a signal in response to the received waves. Processing
circuitry, which is contained within the case, is coupled to
receive and process the signal from the antenna so as to derive and
output an indication of a characteristic of the target tissue.
[0009] In some embodiments, the at least one antenna is configured
to transmit the waves into the body and to receive the transmitted
waves following propagation of the waves through the target tissue.
In a disclosed embodiment, the at least one antenna is configured
to receive the waves after reflection of the waves from a tissue in
the body, and the processing circuitry is configured to detect a
modulation of the reflection due to at least one of a heartbeat and
a respiratory motion of the subject. The modulation may include a
cyclical variation due to the heartbeat.
[0010] Additionally or alternatively, the apparatus may include a
reflector configured for implantation in the body in a location
across the target tissue from the case containing the at least one
antenna, wherein the reflector serves as the structure for
reflecting the waves toward the at least one antenna. The reflector
may be a part of an implanted cardiac device (ICD) that is
implanted in the body.
[0011] In another embodiment, the apparatus includes a transmitter,
which is configured to be implanted in the body in a location
across the target tissue from the case containing the at least one
antenna and to transmit the waves through the target tissue.
[0012] In some embodiments, the processing circuitry is configured
to process the signal so as to derive a measure of a fluid content
of the target tissue. In a disclosed embodiment, the case is
configured for implantation in a thorax, and the target tissue is
lung tissue. In alternative embodiments, the target tissue is
spleen, liver, tongue or palate tissue.
[0013] In one embodiment, the indication includes a time trend of
the characteristic of the target tissue.
[0014] The at least one antenna may include a plurality of
antennas. In one embodiment, the processing circuitry is configured
to drive the antennas in a multi-static mode so as to spatially
resolve the characteristic of the target tissue.
[0015] In some embodiments, the at least one antenna is contained
inside the case. Typically, the at least one antenna includes a
trace printed on a substrate, and wherein the case includes a
window, and the antenna is configured to receive the waves through
the window. The substrate may be sealed to the case by brazing.
[0016] In another embodiment, the at least one antenna is located
partially outside the case and is connected to the processing
circuitry via a sealed brazing to the case.
[0017] In some embodiments, the at least one antenna includes a
trace printed on a substrate and a backlobe suppression structure
behind the trace. The backlobe suppression structure may be
selected from a group of structures consisting of an air cavity and
an electromagnetic bandgap (EBG) backing.
[0018] The at least one antenna may be selected from a group of
antenna types consisting of a spiral antenna, a bowtie antenna, an
elliptic bowtie antenna, and a slotted antenna.
[0019] In a disclosed embodiment, the processing circuitry is
configured to convey the indication of the characteristic via a
wireless link to a monitoring station outside the body.
Additionally or alternatively, the processing circuitry may be
configured to communicate with at least one other implanted
device.
[0020] The at least one antenna may also be configured to receive
electrical energy to power the processing circuitry via an
inductive link to a transmitter outside the body. Alternatively,
the apparatus includes a power antenna, which is configured to
receive electrical energy to power the processing circuitry via an
inductive link to a transmitter outside the body.
[0021] In a disclosed embodiment, the apparatus includes one or
more electrodes on the case for receiving electrical signals within
the body. Additionally or alternatively, the apparatus may include
a bio-impedance sensor. Further additionally or alternatively, the
apparatus includes an implanted cardiac device, which is configured
to pace a heart of the subject responsively to the indication
provided by the processing circuitry.
[0022] There is also provided, in accordance with an embodiment of
the present invention, diagnostic apparatus including a radio
frequency (RF) reflector, which is configured to be implanted in a
body of a human subject in proximity to a target tissue. A
diagnostic device is configured to transmit RF electromagnetic
waves toward the RF reflector and to receive the waves reflected by
the RF reflector through the target tissue, and to process the
received waves so as to derive and output an indication of a
characteristic of the target tissue.
[0023] There is additionally provided, in accordance with an
embodiment of the present invention, a diagnostic method, which
includes implanting a diagnostic device in proximity to a target
tissue in a body of a human subject. The device receives radio
frequency (RF) electromagnetic waves propagated through the target
tissue and processes the received waves so as to derive an
indication of a characteristic of the target tissue.
[0024] In a disclosed embodiment, implanting the device includes
using an external antenna outside the body to identify an optimal
location for implantation of the device.
[0025] The present invention will be more fully understood from the
following detailed description of the embodiments thereof, taken
together with the drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a schematic pictorial illustration showing a
monitoring system including an implanted RF monitoring device, in
accordance with an embodiment of the invention;
[0027] FIG. 2 is a schematic sectional view of a RF monitoring
device implanted in a human body, in accordance with an embodiment
of the invention;
[0028] FIG. 3 is a block diagram that schematically shows
functional components of an implantable RF monitoring device, in
accordance with an embodiment of the invention;
[0029] FIG. 4A is a schematic pictorial illustration of an
implantable RF monitoring device, in accordance with an embodiment
of the invention;
[0030] FIG. 4B is a schematic exploded view of the device of FIG.
4A;
[0031] FIG. 5 is a schematic pictorial illustration showing a RF
monitoring device implanted in a human body, in accordance with
another embodiment of the invention;
[0032] FIGS. 6A and 6B are schematic pictorial illustrations, in
side and front views respectively, showing a RF monitoring device
implanted in a human body, in accordance with a further embodiment
of the invention;
[0033] FIG. 7 is a schematic pictorial illustration of a part of a
RF monitoring device, in accordance with another embodiment of the
present invention;
[0034] FIG. 8 is a schematic, partly-exploded view of a RF
monitoring device, in accordance with yet another embodiment of the
present invention;
[0035] FIG. 9 is a schematic exploded view of an antenna used in
the embodiment of FIG. 8; and
[0036] FIG. 10 is a schematic pictorial illustration of a RF
monitoring device, in accordance with an additional embodiment of
the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
Overview
[0037] A number of chronic medical conditions lead to accumulation
of fluid in and around body organs. For example, pulmonary edema is
associated with chronic heart failure and other pathologies. As
another example, conditions such as kidney failure and certain
inflammatory disorders may lead to pericardial effusion. Monitoring
such fluid levels in the patient's body over extended periods can
be helpful in ongoing risk assessment and adjustment of treatment.
Similarly, monitoring accumulation of blood in the splanchnic
system can be of medical benefit in assessing fluid status.
[0038] Embodiments of the present invention that are described
hereinbelow provide implantable devices and methods that can be
used for long-term measurement and monitoring of tissue
characteristics, such as fluid accumulation in and around body
organs. In these embodiments, a diagnostic device comprises at
least one antenna and associated processing circuitry, which are
contained inside or connected to a sealed case made from a
biocompatible material. The device is implanted within the body of
a human subject in proximity to a target tissue, such as the lung.
The antenna receives radio frequency (RF) electromagnetic waves
transmitted through the target tissue. These waves may be
transmitted by the antenna itself and then reflected back through
the target tissue to the device, or they may be transmitted from
another source. The processing circuitry processes the signals that
are output by the antenna in order to derive and output an
indication of a characteristic of the target tissue, such as the
tissue fluid content.
[0039] In a disclosed embodiment, the device is implanted in the
thorax, adjacent to the lung. The processing circuitry drives the
antenna (or antennas) to transmit RF waves through the lung toward
the heart, and to receive waves reflected from the heart and
transmitted back through the lung. Alternatively, the waves may be
reflected back from a dedicated reflector or another reflective
object. Further alternatively, the waves may be transmitted through
the lung by a separate transmitter, which is implanted in the body
in a location across the target tissue from the receiver. The
processing circuitry processes the output signals from the antenna
in order to derive a measure of the fluid content of the lung. The
processing circuitry periodically reports the fluid level by
telemetric link to a monitor outside the patient's body, for use by
a physician in tracking the patient's condition and making
treatment changes as appropriate.
[0040] Although the embodiments described herein are directed
specifically to monitoring of fluid levels in the lungs, the
principles of the present invention may similarly be applied in
other monitoring applications. For example, implanted devices of
the types described herein may be used, mutatis mutandis, in
monitoring pericardial fluid levels. As another example, such a
device may be used to monitor bladder fill level and/or muscle
properties in patients suffering from urinary disorders, in order
to provide an alert when the bladder should be emptied. In other
embodiments, such devices may be used in long-term monitoring of
fluid levels in the brain, tongue, palate or spleen, as well as in
body extremities, such as the thighs. More generally, the devices
and methods described herein may be adapted for use in
substantially any long-term diagnostic application in which tissue
characteristics are evaluated using RF electromagnetic waves,
including not only fluid monitoring but also imaging applications,
as well.
System Description
[0041] Reference is now made to FIGS. 1 and 2, which schematically
illustrate a RF-based monitoring system 20, in accordance with an
embodiment of the invention. FIG. 1 is a pictorial illustration,
showing a RF monitoring device 24 implanted in a thorax 26 of a
patient 22, while FIG. 2 is a sectional view taken through the
body, showing the relation of device 24 to organs in the thorax.
Device 24, which is typically similar in shape and size to a
conventional implanted cardiac device (ICD), such as a pacemaker,
is implanted below the patient's skin adjacent to ribs 34 and
transmits and receives RF electromagnetic waves through target
tissue, such as a lung 28, as indicated by arrows in the
figure.
[0042] In the pictured example, device 24 is implanted in the
axillary region using a minimally-invasive procedure. The waves
transmitted by device 24 pass through lung 28 and mediastinum 30,
reflect back from heart 32 through lung 28, and are then received
and detected by device 24. Alternatively, the device may be
implanted in other suitable locations, such as the infra-mammary or
dorsal regions of thorax 26. An external antenna may be used during
implantation to choose an optimal antenna location, based upon
which the surgeon implants device 24 and its implanted antenna at
the location giving the best signal. In some alternative
embodiments, as shown in FIGS. 5, 6A and 6B, for example, the
monitoring device may be used in conjunction with an implanted
reflector, instead of or in addition to sensing reflections from
the heart.
[0043] RF monitoring device 24 processes the received RF waves to
derive an indication of tissue characteristics, such as tissue
fluid content. Device 24 collects these indications over time and
periodically transmits the data to a telemetry station 34,
typically via a suitable short-range wireless link. Station 34
typically comprises a general-purpose computer with suitable
communication circuits and software, and may be located in a clinic
or hospital or in the home or workplace of patient 22. Station 34
may also be configured to program device 24 over the wireless link,
as well as to provide RF energy to recharge the battery in device
24, as described below.
[0044] FIG. 3 is a block diagram that schematically shows
functional elements of RF monitoring device 24, in accordance with
an embodiment of the invention. The elements of device 24 are
contained in a sealed case 40, comprising a suitable biocompatible
material, such as titanium or stainless steel. The case may be
coated with a tissue-growth inducing material, as is known in the
art. Case 40 contains, inter alia, processing circuitry including a
RF front end 44 and a digital processing circuit 46. Front end 44
drives one or more antennas 42 to emit RF waves through lung 28.
The front end receives and processes the signals that are output by
antennas 42 in response to the reflected waves and outputs a
digitized indication of the amplitude and phase of the signals to
digital processing circuit 46. Typically, for high resolution in
the presence of background noise, front end 44 and circuit 46 apply
coherent methods of signal processing to correlate the reflected
signals with the transmitted signals, but alternatively
non-coherent processing methods may be used.
[0045] In one embodiment, front end 44 generates signals at
multiple different frequencies for exciting the transmitting
antennas. Device 24 may operate in an ultra-wide-band (UWB) mode,
in which the signals are spread over a wide range of frequencies,
such as from about 500 MHz to about 2.5 GHz (although higher and
lower frequencies outside this range may also be used). UWB
transmission and detection techniques of this sort are described,
for example, in the above-mentioned PCT International Publication
WO 2011/067623 and U.S. Patent Application Publication
2011/0130800. The UWB signal provides the frequency-domain
equivalent of a very short pulse in the time domain and can thus be
used for measuring the range of a reflecting spot in the body with
high accuracy. The UWB signal can be transmitted as a short pulse
or as a train of narrowband signals that together constitute a
wideband signal, or other waveforms used in radar pulse compression
(such as chirped, stepped-frequency, or phase-coded pulses). Use of
these sorts of waveforms in making measurements inside the body is
described in the above-mentioned publications and may similarly be
applied, mutatis mutandis, in system 20.
[0046] Digital processing circuit 46 measures the time delay for RF
waves to travel from antenna 42 to heart 32 via lung 28 and back to
the antenna. The waves reflected from the heart can be identified
based on the modulation, typically comprising a cyclical change, of
the resulting signal during a heartbeat. The short-term time
cyclical variation of the delay from antenna to heart and back can
also be used to measure heart movement, while long-term variation
is indicative of changes in the pulmonary fluid level. Additionally
or alternatively, electrodes 56, which may be built into case 40 or
mounted externally, may measure an electrocardiogram (ECG) signal
for correlation with the actual heart movement. Further
additionally or alternatively, circuit 46 may detect modulation of
the waves due to respiratory motion.
[0047] Further additionally or alternatively, device may comprise
other sensors 58, either in case 40 or connected to it externally.
Sensors 58 may measure, for example, bio-impedance, fluid content,
temperature, salinity, or motion (of the heart, lungs, or entire
body) and may be useful in filling out the picture of fluid status
that is provided by RF measurement.
[0048] As the RF waves pass through body tissue, such as lung 28,
the group velocity of the waves will vary as a function of the
fluid content of the tissue. Generally speaking, the higher the
fluid content, the greater will be the dielectric constant of the
tissue, and hence the lower the velocity. Equivalently, fluid in
the lungs can be considered to increase the RF path length of the
waves, defined by the length of time required for the waves to pass
through the tissue and back to device 24. The result of this
decrease in velocity or increase in RF path length is that the
delay of the reflected waves will increase as the fluid content of
lungs 28 increases. Digital processing circuit 46 measures this
delay periodically and/or on command in order to compute an
indication of the lung's fluid content. Typically, circuit 46
comprises a memory (not shown), which stores the computed
values.
[0049] In addition to or alternatively to measuring the RF path
length or delay, digital processing circuit may measure other
signal characteristics, such as the amplitude of the reflected
signals from the transition layer between ribs 34 and lung 28. The
amplitude of this reflection is typically stronger and differently
shaped in patients suffering from pulmonary edema in comparison to
healthier subjects. The signal amplitude and shape may also be
fitted parametrically to a stratified model of the various tissues
traversed by the RF waves, wherein the fit parameters include the
fluid content.
[0050] Additionally or alternatively, circuit 46 may compute other
parameters relating to tissue characteristics, such as the volume,
shape, physical properties, locations and/or movement of structures
in the path of the RF waves within the body. For example, the RF
waves and signal processing carried out in front end 44 and circuit
46 may be adjusted to measure pericardial fluid content within
mediastinum 30. As another example, antennas 42 can be driven in a
multi-static configuration to measure the electromagnetic
properties of different sub-volumes within thorax 26, and thus
provide data that are spatially resolved in two or three
dimensions. Such multi-static techniques (using extracorporeal
antennas) are described, for example, in the above-mentioned WO
2011/067623 and US 2011/0130800, which also describe digital signal
processing methods that can be used to compute the complex
dielectric constants for the individual sub-volumes.
[0051] A communication interface 48 transmits and receives data to
and from telemetry station 34 (FIG. 1) via a communication antenna
50. The transmitted data typically comprise the indications of
tissue characteristics that have been computed over time and stored
by digital processing circuit 46. These indications may include
statistical parameters computed by circuit 46 over the tissue
measurement results, such as time trend parameters of the measured
fluid level. Alternatively or additionally, the indications of
tissue characteristics may include raw data collected from front
end 44, and communication interface 48 may transmit data either
intermittently or continuously as they are measured. Further
alternatively or additionally, interface 48 may communicate with
other implanted diagnostic and/or therapeutic devices, such as an
intravascular pressure sensor or an ICD, or with non-invasive
monitoring devices, such as a bio-impedance measurement device.
[0052] A power source 52 supplies operating power to the circuits
of device 24. Power source 52 typically comprises an energy storage
component, such as a single-use or rechargeable battery. In the
case of a rechargeable storage component, power source 52 may be
coupled to a power antenna 54, which receives RF power from a
suitable power transmission antenna (not shown) outside the body.
Alternatively, one or more of antennas 42 may additionally receive
this RF power, instead of or in addition to power antenna 54. The
power transmission antenna may comprise, for example, a coil, which
is positioned outside thorax 26 in proximity to device 24 and
provides power to antenna 54 by magnetic induction. The power
transmission coil may be placed under a mattress on which the
patient lies, or it may be worn as a vest, a bra or a necklace, for
example. Power source 52 rectifies the received power in order to
charge its energy storage component.
[0053] FIG. 4A is a schematic pictorial illustration of RF
monitoring device 24, in accordance with an embodiment of the
invention, while FIG. 4B shows a schematic exploded view of the
device of FIG. 4A. Case 40 comprises front and rear covers 62, 64,
typically comprising titanium. Antennas 42 are printed, using hard
gold or another suitable biocompatible conductor, on a main circuit
board 66, which typically comprises a biocompatible ceramic
substrate with brazing to enable it to be hermetically sealed
against covers 62 and 64. Board 66 also has pads and conductors for
mounting and connecting the components (not shown) of front end 44,
processing circuit 46, and communication interface 48. These
components are typically embodied in one or more integrated
circuits, as are known in the art. Front cover 62 comprises windows
60 containing antennas 42, which are sealed by bonding the
perimeters of the windows to brazing surrounding the antennas on
board 66.
[0054] Antennas 42 in this example each comprise a pair of printed
conductive loops with a center feed, in an elliptic bowtie
configuration. For enhanced efficiency and directionality, antennas
42 are backed by conductive air-filled cavities 68 on the side of
board 66 opposite windows 60. Cavity antennas of this sort (in an
extracorporeal configuration) are described, for example, in the
above-mentioned PCT International Publication WO 2011/067623.
Alternatively, device 24 may comprise any other suitable type of
antenna, such as a spiral, bowtie, or slotted antenna, with a
cavity, electromagnetic bandgap (EBG) backing, or no backing.
[0055] Power antenna 54 comprises a coil 72 with a magnetic or
ferritic core 74, covered by a non-conductive biocompatible cover
78. Coil 72 is connected via feed-throughs between covers 62 and 64
to power source 52. Cover 78 typically comprises a suitable
biocompatible plastic or other dielectric material, such as
silicone molded over coil 72 and core 74. Coil 72 may also serve as
communication antenna 50. Alternatively, a separate communication
antenna 70 may be connected to board 66 and positioned to transmit
and receive communication signals through a window 72 in cover 64.
As still another alternative, one or both of antennas 42 may serve
as the communication antenna (although in this case it may be
preferable that the antenna not have a cavity or other backing in
order to strengthen the backlobe radiation transmitted by the
antenna out of the body).
[0056] As noted earlier, device 24 comprises electrodes 56, which
are shown in FIGS. 4A and 4B as external elements on cover 62. The
ECG signals sensed by these electrodes may be used not only in
synchronizing the measurements of RF reflections to the patient's
heartbeat, but also as a diagnostic indicator in and of themselves,
which is processed and stored by circuit 46. This diagnostic
indicator can then be used, for example, to detect cardiac
arrhythmias, in a manner similar to a Holier monitor. Alternatively
or additionally, device 24 can comprise sensors for other sorts of
intra-body clinical measurements, such as temperature, blood
pressure, and/or blood oxidation, thereby broadening the usefulness
and improving the diagnostic accuracy of system 20.
Alternative Embodiments
[0057] FIG. 5 is a schematic pictorial illustration of a monitoring
system 80 comprising a RF monitoring device 82 implanted in a human
body, in accordance with another embodiment of the invention.
Device 82 is similar in structure and function to device 24, as
described above, but in this embodiment, device 82 operates in
conjunction with an internally-placed reflector 84 on the opposite
side of the patient's lung, as shown in the figure, rather than
relying on reflections from the heart. The use of a dedicated
reflector strengthens the reflected waves that are received by
device 82 and provides a constant physical path length to which the
measured RF path length can be compared. Alternative placements of
the monitoring device and reflector are shown in FIGS. 6A and 6B.
As yet another alternative, the RF reflector may be positioned
outside the patient's body.
[0058] Reflector 84 may be a passive structure made of
biocompatible conducting material, or it may comprise one or more
active components, which can be modulated to enhance signal
extraction by device 82. The modulation of this reflector can be
triggered and powered externally by means of a magnetic pulse
source or a low-frequency electromagnetic wave. As another
alternative, an internal active or passive reflector of this sort
can be used in conjunction with an external RF
transmitter/receiver, in place of device 82.
[0059] In an alternative embodiment, reflector 84 may be replaced
by a RF transmitter, which transmits RF waves through the lung to
device 82. In this case, device 82 may comprise only a RF receiver
(together with the processing circuitry and other components shown
in FIG. 3). As still another alternative, transmit/receive devices
on opposite sides of the heart may each transmit RF waves and
receive the RF waves transmitted by the counterpart device.
[0060] FIGS. 6A and 6B are schematic pictorial illustrations, in
side and front views respectively, showing a system 90 in which a
RF monitoring device 92 is implanted in a human body, in accordance
with a further embodiment of the invention. In this embodiment,
device 92 is similar in structure and function to device 24, but is
implanted in an infra-mammary location and operates in conjunction
with a reflector 94 in a dorsal location, between the fourth and
sixth ribs, for example. Alternatively, the locations of device 92
and reflector 94 may be reversed.
[0061] FIG. 6B also shows an ICD 96, which may be used in
conjunction with device 92 or integrated with device 92. For
example, device 92 and pacemaker 96 may share a power source and/or
communication circuits for communicating with station 34 outside
the body. Device 92 and ICD 96 may even be contained in the same
case, which may be implanted, for example, in the infra-mammary
region. The measurements provided by device 92, particularly with
regard to the level of pulmonary fluid accumulation, may be used as
an input in controlling the pacing of the heart by ICD 96.
[0062] ICD 96 may alternatively serve as the reflector for device
92, in place of reflector 94. In this case, the ICD may simply be
configured as a passive reflector, or it may comprise a modulated
reflector, as described above.
[0063] FIG. 7 is a schematic pictorial illustration of a part of a
RF monitoring device 100, in accordance with another embodiment of
the present invention. This figure shows the internal side of case
102 of device 100, to which a cylindrical antenna support 104 is
attached, by laser welding along a seam 106, for example. A
substrate 108 of the antenna is mounted on support 104. Substrate
108 typically comprises a ceramic material, such as a
low-temperature co-fired ceramic (LTCC), for example, Dupont
951LTCC. Substrate 108 comprises a metal coating around its
perimeter, and is brazed to support 104 (as well as to the
overlying front side of case 102, which is not shown in this
figure) using a titanium ring 110 and a suitable filler material.
The brazing serves the dual purposes of electromagnetically sealing
the antenna to its backing and mechanically sealing the substrate
to the case.
[0064] FIG. 8 is a schematic, partly-exploded view of a RF
monitoring device 120, in accordance with yet another embodiment of
the present invention. In this embodiment, an antenna 124 is
attached externally to a sealed case 122 of device 120. Antenna 124
in this example comprises a conductive spiral 126, but this sort of
external configuration in equally applicable to other antenna
types. Antenna 124 is inserted into a slot 128 in case 122, and an
edge 130 of the antenna is then sealed to case 122 by brazing, for
example. The antenna is thus partially inside and partially outside
the case, with sealed RF connections from the circuits inside the
case to the outer antenna using printed electrical traces.
[0065] FIG. 9 is a schematic exploded view of antenna 124, in
accordance with an embodiment of the present invention. Antenna 124
comprises a stack of three layers, each on a respective ceramic
substrate 132, 134, 138. Spiral 126 is printed on the upper layer.
An EBG structure 136 is printed on the middle layer, serving as a
backing for spiral 126, with EBG elements of different sizes
corresponding to the different frequencies radiated by different
areas of the spiral. The lower layer serves as a ground plane, with
vias 140 passing through all the layers of antenna 124. The vias
are connected via leads (not shown) on substrate 138 to the
circuits inside case 122. The two central vias provide the signals
for exciting spiral 126.
[0066] FIG. 10 is a schematic pictorial illustration of a RF
monitoring device 150, in accordance with an additional embodiment
of the present invention. Here a bowtie antenna 154 is connected by
a coaxial cable 156 to circuits inside a case 152. The cable and
case are sealed by a feedthrough in a header 158, which may
comprise a suitable epoxy and/or polyurethane. Device 150 in this
embodiment also has a communication antenna 160, as described
above.
[0067] As noted earlier, although the embodiments shown in the
figures relate specifically to measurement of the fluid content of
the lungs, the principles of the present invention may similarly be
applied in monitoring of other organs, such as the heart, bladder,
tongue, palate, spleen, brain, or body extremities. It will thus be
appreciated that the embodiments described above are cited by way
of example, and that the present invention is not limited to what
has been particularly shown and described hereinabove. Rather, the
scope of the present invention includes both combinations and
subcombinations of the various features described hereinabove, as
well as variations and modifications thereof which would occur to
persons skilled in the art upon reading the foregoing description
and which are not disclosed in the prior art.
* * * * *