Implantable dielectrometer
Diagnostic apparatus ( 24 ) includes a sealed case ( 80 ), comprising a biocompatible material and configured for implantation within a body of a human subject ( 22 ). A dielectrometric probe ( 26, 50, 63, 66, 70, 102, 160 ) is connected to the case and includes first and second conductors ( 40, 42, 54, 56, 64, 67, 68, 72, 74, 162, 164 ), which are configured to be placed in proximity to a target tissue ( 34 ) in the body. A driving circuit ( 82 ), which is contained in the case, is coupled to apply a radio-frequency (RF) signal to the probe and to sense the signal returned from the probe. Processing circuitry ( 84 ) is configured to evaluate, responsively to the returned signal, a dielectric property of the target tissue.
1. A diagnostic method, comprising:
implanting a dielectrometer probe, comprising first and second conductors, in proximity to a target tissue in a body of a human subject;
applying a radio-frequency (RF) signal to the probe; and
evaluating, responsively to a signal from the probe, a dielectric property of the target tissue including finding a complex permittivity of the target tissue,
wherein finding the complex permittivity of the target tissue includes one of:
measuring a reflection of the signal from the probe, which is indicative of an impedance mismatch at the target tissue;
measuring a delay of the signal transmitted through the probe; and
measuring a resonant frequency of the probe.
2. The method according to claim 1 , wherein applying the RF signal comprises applying RF signals and sensing returned signals at multiple different frequencies.
3. The method according to claim 1 , wherein finding the complex permittivity further includes measuring an impedance between the first and second conductors.
4. A diagnostic method, comprising:
implanting a dielectrometer probe, comprising first and second conductors, in proximity to a target tissue in a body of a human subject;
applying a radio-frequency (RF) signal to the probe; and
evaluating, responsively to a signal from the probe, a dielectric property of the target tissue;
wherein the first and second conductors are arranged to:
provide a coaxial contact to the target tissue at a distal end of the probe, or
define a resonant ring in proximity to the target tissue.
5. The method according to claim 4 , wherein the first and second conductors are arranged to provide a coaxial contact to the target tissue at a distal end of the probe, and the coaxial contact comprises a patch, which is placed against the target tissue.
6. The method according to claim 4 , wherein the first and second conductors are arranged to provide a coaxial contact to the target tissue at a distal end of the probe, and the coaxial contact comprises a coaxial tip, in which the first conductor is concentrically contained within the second conductor, wherein the tip is inserted into the target tissue.
7. A diagnostic method, comprising:
implanting a dielectrometer probe, comprising first and second conductors, in proximity to a target tissue in a body of a human subject; the first and second conductors arranged to define a transmission line in proximity to the target tissue;
applying a radio-frequency (RF) signal to the probe; and
evaluating, responsively to a signal from the probe, a dielectric property of the target tissue; wherein:
the transmission line is defined by arranging the first conductor as a ground plane and the second conductor as a microstrip parallel to the ground plane; or
the transmission line comprises a coplanar waveguide.
8. The method according to claim 4 , wherein the first and second conductors are arranged to define a transmission line in proximity to the target tissue and the transmission line is defined by arranging the first and second conductors as parallel lines.
9. The method according to claim 1 , further comprising deriving a measure of a fluid content of the target tissue from the dielectric property.
10. The method according to claim 9 , wherein deriving the measure comprises measuring the fluid content continuously.
11. The method according to claim 9 , wherein deriving the measure comprises measuring the fluid content intermittently.
12. The method according to claim 9 , wherein deriving the measure comprises measuring changes in the fluid content over time.
13. The method according to claim 1 , further comprising implanting a case, which is connected to the probe, in a thorax of the subject.
14. The method according to claim 4 , further comprising deriving a measure of a fluid content of the target tissue from the dielectric property.
15. The method according to claim 14 , wherein deriving the measure comprises measuring changes in the fluid content over time.
16. The method according to claim 4 , wherein applying the RF signal comprises applying RF signals and sensing returned signals at multiple different frequencies.
17. The method according to claim 7 , further comprising deriving a measure of a fluid content of the target tissue from the dielectric property.
18. The method according to claim 14 , wherein deriving the measure comprises measuring changes in the fluid content over time.
19. The method according to claim 7 , wherein applying the RF signal comprises applying RF signals and sensing returned signals at multiple different frequencies.