SENSOR SYSTEM, IMPLANTABLE SENSOR AND METHOD FOR REMOTE SENSING OF A STIMULUS IN VIVO

• US 20140378783A1
• Filed: 02/05/2013
• Published: 12/25/2014
• Est. Priority Date: 02/07/2012
• Status: Active Grant

• Current Assignee: IO Surgical, LLC
• Original Assignee: IO Surgical, LLC
• Inventors: Fiorella, David, Ledet, Eric Howard, Wachs, Rebecca Ann, Cole, Keegan Paul
• Granted Patent: US 9,662,066 B2
• Time in Patent Office: Days
• US Class Current: 600/301
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/03 Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs A61B5/205 takes precedence
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/1036 Measuring load distribution, e.g. podologic studies
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/4504 Bones A61B5/4547 takes precedence
• CPC Class Codes: A61B 5/4851 Prosthesis assessment or monitoring
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: H01F 5/003 Printed circuit coils
• CPC Class Codes: H01F 5/06 Insulation of windings

Abstract

A sensor system for sensing a stimulus in vivo includes an implantable sensor. The sensor comprises a passive resonator circuit having a resonant frequency and including at least a pair of generally parallel spirally wound unconnected conductive coils sandwiching a layer of solid dielectric material that manifest a change in property affecting the resonant frequency in response to application of the stimulus to the layer. A resonant frequency of the sensor is modulated by altering the spacing or gap between the coils or altering the overlapping area of the coils. The sensor is energized through application of radiofrequency energy and the responding resonant frequency is detected. The sensor can be advantageously attached to a medical implant to form a practical smart implant for clinical purposes.

Claims

1. A sensor system for sensing a stimulus in vivo, comprising:

a sensor implantable in a patient, the sensor including at least a first single component L-C element, a second single component L-C element spaced from and electrically unconnected to the first element, and a solid dielectric layer sandwiched between the first element and the second element, the solid dielectric layer having a property that varies in response to application of the stimulus to said solid dielectric layer;

an energizer, external to said patient, energizing the first element and the second element with radiofrequency energy such that the energized first element and second element form a passive resonator circuit having a resonant frequency that varies with said property; and

a detector, external to the patient, determining the resonant frequency of the passive resonator circuit as a measure of the stimulus applied to the dielectric layer in vivo.

2. The sensor system of claim 1, wherein the stimulus comprises at least one of force, load, strain, shear, temperature, absolute pressure, displacement, pH, deformation, chemical marker and biomarker.

3. The sensor system of claim 1, wherein the variable property comprises at least one of surface deformation, surface displacement, layer dimension, layer size, layer shape, layer volume, capacitance and inductance.

4. The sensor system of claim 1, wherein the sensor devoid of an enclosure.

5. The sensor system of claim 1, wherein the first element comprises a first flat spiral shaped conductive coil wound clockwise, and the second element comprises a second flat spiral shaped conductive coil wound counterclockwise.

6. The sensor system of claim 1, wherein the sensor is attached to a medical implant.

7. The sensor system of claim 6, wherein the sensor is attached to said medical implant without modifying geometry of the implant.

8. The sensor system of claim 1, wherein said stimulus comprises force and the variable property comprises a dimension of the solid dielectric layer, or the stimulus comprises strain and the variable property comprises surface displacement.

9. The sensor system of claim 1, further comprising at least one additional said sensor providing multi-axial sensing of said stimulus and/or concurrent sensing of multiple stimuli.

10. The sensor system of claim 1, wherein the energizer and the detector comprise a grid dip oscillator and an antenna.

11. A method of sensing a stimulus in vivo, comprising:

selecting a solid dielectric material that manifests a change in property in response to application of the stimulus to the solid dielectric material;

implanting in a position in a patient subject to the stimulus, a passive resonator circuit having a resonant frequency and comprising at least a pair of generally parallel spirally wound unconnected conductive coils sandwiching a layer of the solid dielectric material, stimulus produced variations in said property affecting said resonant frequency;

energizing the passive resonator circuit with radiofrequency energy from a source external to the patient;

remotely detecting the resonant frequency of the energized passive resonator circuit; and

determining a value of the stimulus applied to the layer of dielectric material in vivo from the detected resonant frequency.

12. The method of claim 11, wherein the implanting comprises attaching the passive resonator circuit to a medical implant, and further comprising using the determined value of the stimulus for at least one of:

determining progression of healing, outcome prognosis, detecting implant failure, intra-operative monitoring, and personalized post-operative care.

13. A sensor for sensing a stimulus, comprising a passive resonator circuit having a resonant frequency and including at least a pair of generally parallel spirally wound unconnected conductive coils sandwiching a layer of solid dielectric material that manifests a change in property affecting the resonant frequency in response to application of the stimulus to the layer.

14. The sensor of claim 13, wherein the stimulus comprises at least one of force, load, strain, shear, temperature, absolute pressure, displacement, pH, deformation, chemical marker and biomarker.

15. The sensor of claim 13, wherein the variable property comprises at least one of surface deformation, surface displacement, layer dimension, layer size, layer shape, layer volume, capacitance and inductance.

16. The sensor of claim 13, wherein the passive resonator circuit is un-encapsulated.

17. The sensor of claim 16, wherein the passive resonator circuit is adapted to operate in an aqueous environment.

18. The sensor of claim 16, wherein the passive resonator circuit is remotely energized, batteryless and telemetryless.

19. The sensor of claim 13, wherein a first coil of said pair is wound clockwise, and a second coil of said pair is wound counterclockwise.

20. The sensor of claim 19, wherein the first coil and the second coil are flat, substantially parallel to each other, and disposed on opposite surfaces of the solid dielectric layer.

21. The sensor of claim 20, wherein the first coil and the second coil are adhered to respective opposite surfaces of the solid dielectric layer.

22. The sensor of claim 19, wherein the first coil and the second coil comprise insulated wires wound concentrically that maintain their respective shape after being wound.

23. The sensor of claim 22, wherein windings of each coil are bonded together to maintain their respective shape.

24. The sensor of claim 22, further including a substrate to maintain the shape of the wound coil.

25. The sensor of claim 24, wherein the substrate comprises at least one of an epoxy, a polymer, an elastomer, a ceramic, a composite material, and a rigid support material.

26. The sensor of claim 13, wherein each coil comprises a conductor wound concentrically and continuously around itself from a central point outward with an insulator between windings.

27. The sensor of claim 13, wherein at least one coil of the pair comprises a micro machined or micro fabricated part.

28. The sensor of claim 13, further in combination with an energizer energizing the passive resonator circuit with radiofrequency energy, and a detector determining a resonant frequency of the passive resonator circuit as a measure of the stimulus applied to the layer of solid dielectric material.

29. The sensor of claim 13, wherein the passive resonator circuit is composed of biocompatible material and adapted for implantation in a patient for sensing the stimulus in vivo.

30. A smart implant comprising the sensor of claim 29, in combination with a medical implant.

31. A sensor system comprising the smart implant of claim 30, further in combination with an energizer, external to the patient, energizing the passive resonator circuit with radiofrequency energy, and a detector, external to the patient, determining a resonant frequency of the passive resonator circuit as a measure of the stimulus applied to the layer of solid dielectric material in vivo.