Implantable Radio-Frequency Sensor
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
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)