Detection of fluids in tissue

• US 20030036713A1
• Filed: 07/26/2002
• Published: 02/20/2003
• Est. Priority Date: 07/26/2001
• Status: Active Grant

• Current Assignee: Bayer Healthcare LLC (Bayer AG)
• Original Assignee: Medrad Incorporated (Bayer AG)
• Inventors: Hirschman, Alan D., Bouton, Chad
• Granted Patent: US 7,122,012 B2
• Time in Patent Office: Days
• US Class Current: 600/587
• CPC Class Codes: A61B 2562/02 Details of sensors specially adapted for in-vivo measurements
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 2562/143 for coupling microwaves
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/0507 using microwaves or terahertz waves
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/411 Detecting or monitoring allergy or intolerance reactions to an allergenic agent or substance
• CPC Class Codes: A61B 5/4878 Evaluating oedema
• CPC Class Codes: A61M 5/16836 by sensing tissue properties at the infusion site, e.g. for detecting infiltration detecting tissue temperature for diagnostic purposes A61M39/0247
• CPC Class Codes: G01N 22/00 Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more G01N3/00 - G01N17/00, G01N24/00 take precedence
• CPC Class Codes: H01Q 1/273 Adaptation for carrying or wearing by persons or animals
• CPC Class Codes: H01Q 1/40 Radiating elements coated with or embedded in protective material
• CPC Class Codes: H01Q 13/18 the slot being backed by, or formed in boundary wall of, a resonant cavity longitudinally slotted cylinder H01Q13/12 ; Open cavity antennas
• CPC Class Codes: H01Q 21/06 Arrays of individually energised antenna units similarly polarised and spaced apart
• CPC Class Codes: H01Q 21/065 Patch antenna array
• CPC Class Codes: H01Q 21/20 the units being spaced along or adjacent to a curvilinear path slotted waveguide arrays H01Q21/005; circularly or helically slotted waveguides H01Q21/0062
• CPC Class Codes: H01Q 9/0407 Substantially flat resonant element parallel to ground plane, e.g. patch antenna dipole H01Q9/285; monopole H01Q9/40
• CPC Class Codes: H01Q 9/0414 in a stacked or folded configuration

Abstract

A method of detecting a change (that is, an increase or a decrease) in the level of fluid in tissue in a first area of a body includes the steps of: applying electromagnetic energy, preferably in the frequency range of approximately 300 MHz to approximately 30 GHz, to a first volume of the body; measuring a resultant or returned signal; comparing the signal to a reference signal to determine if the fluid level in the tissue has changed. In one embodiment, the method detects changes in the level of fluid in tissue of a body by applying electromagnetic energy to a first volume of the body over a period of time (for example, using an antenna or antennae); measuring a resultant signal or a signal returned from the tissue; and comparing the signal to a reference signal to determine if a level of fluid in the tissue has changed during the period of time.

Claims

1. A method of detecting a change in the level of fluid in tissue of a body comprising the steps of:

applying electromagnetic energy in the frequency range of approximately 300 MHz to approximately 30 GHz a first volume of the body over a period of time;

measuring a resultant signal; and

comparing the signal to a reference signal to determine if fluid level in the tissue has changed during the period of time.

2. The method of claim 1 wherein the electromagnetic energy is in the frequency range of approximately 1 GHz to approximately 10 GHz.

3. The method of claim 1 wherein the electromagnetic energy is in the frequency range of approximately 3 GHz to approximately 5 GHz.

4. The method of claim 1 wherein the reference signal is a baseline signal measured in the first volume of the body.

5. The method of claim 1 wherein the reference signal is produced by applying electromagnetic energy in the frequency range of approximately 300 MHz to approximately 30 GHz to the tissue in a second volume of the body.

6. The method of claim 5 wherein tissue in the second volume of the body is similar in electromagnetic properties to tissue in the first volume of the body.

7. The method of claim 1 wherein the reference signal is developed by applying electromagnetic energy in the frequency range of approximately 300 MHz to approximately 30 GHz to tissue of a plurality of bodies.

8. The method of claim 1 wherein the measured signal is a function of the permittivity of tissue in the first volume of the body or the permeability of tissue in the first volume of the body.

9. The method of claim 4 wherein the step of applying electromagnetic energy includes the step of coupling a transmitter with skin.

10. The method of claim 9 wherein the transmitter includes a generally planar resonant structure.

11. The method of claim 10 wherein the transmitter includes a superstrate adjacent the resonant structure having an impedance suitable to couple with skin.

14. The method of claim 9 further comprising the step of coupling a receiver with the skin.

15. The method of claim 14 wherein the receiver includes a generally planar resonant structure.

16. The method of claim 15 wherein the receiver includes a superstrate adjacent the resonant structure having an impedance suitable to couple with skin.

17. The method of claim 16 wherein an outward side of the receiver superstrate is shaped to conform to skin.

18. The method of claim 17 wherein the periphery of the outward side of the receiver superstrate is tapered.

19. The method of claim 14 wherein the transmitter is an antenna including a first generally planar resonant structure and the receiver is an antenna including a second generally planar resonant structure, the transmitter being connected to a first base member and the receiver being connected to a second base member, the first base member and the second base member being connected by a flexible bridge.

20. The method of claim 4 wherein the step of comparing the measured signal to the baseline measurement includes the step of calculating a complex distance between the measured signal and the baseline measurement.

21. The method of claim 4 wherein an area under a complex distance curve across a frequency range of interest is calculated, and the calculated area is compared to the area under a baseline curve over the frequency range of interest.

22. The method of claim 1 wherein the change in fluid level in the tissue occur over a period of approximately one second to three days.

23. The method of claim 1 wherein the fluid is a body fluid.

24. The method of claim 23 wherein the change in the level of the fluid is caused by edema.

25. The method of claim 23 wherein the change in the level of the fluid is caused by a hematoma.

26. The method of claim 1 wherein the fluid is a fluid introduced to the body.

27. The method of claim 26 wherein the fluid is introduced by injection, infusion or intravenous drip.

12. The method of claim 12 wherein an outward side of the transmitter superstrate is shaped to conform to skin.

13. The method of claim 13 wherein the periphery of the outward side of the transmitter superstrate is tapered.

28. A method of detecting extravasation of a fluid injected into a vascular structure of a body in tissue outside of the vascular structure, comprising the steps of:

applying electromagnetic energy in the frequency range of approximately 300 MHz to approximately 30 GHz a first volume of the body during a period of time in which a fluid is injected into the vascular structure;

measuring a resultant signal; and

comparing the signal to a reference signal to determine if fluid level in the tissue has changed during the period of time.

29. A method of detecting extravasation of a fluid injected into a vascular structure of a body in tissue outside of the vascular structure, comprising the steps of:

placing at least one antenna in operative connection with the skin of the body;

applying electromagnetic energy to a first volume of the body using the antenna;

injecting the fluid into the vascular structure;

measuring a returned signal; and

comparing the signal to a reference signal to determine if extravasation has occurred.

30. The method of claim 29 wherein the electromagnetic energy is in the frequency range of approximately 300 MHz to approximately 30 GHz.

31. The method of claim 29 wherein the electromagnetic energy is in the frequency range of approximately 1 GHz to approximately 10 GHz.

32. The method of claim 29 wherein the electromagnetic energy is in the frequency range of approximately 3 GHz to approximately 5 GHz.

33. The method of claim 29 wherein the reference signal is a baseline signal measured in the first volume.

34. The method of claim 29 wherein the reference signal is produced by applying electromagnetic energy to tissue in a second area of the body.

35. The method of claim 34 wherein the tissue in the second area is similar in electromagnetic properties to the tissue in the first area.

36. The method of claim 29 wherein the reference signal is developed by applying electromagnetic energy to tissue of a plurality of bodies in which there is no extravasation.

37. The method of claim 29 wherein the measured signal is a function of the permittivity of the tissue or the permeability of the tissue.

38. The method of claim 33 wherein at least one transmitter antenna to transmit electromagnetic energy into the first volume of the body is placed in operative connection with the skin and at least on receiver antenna to measure a resultant signal is placed in operative connection with the skin.

39. The method of claim 38 wherein the transmitter antenna includes a generally planar resonant structure.

40. The method of claim 39 wherein the transmitter antenna includes a superstrate adjacent the resonant structure having an impedance suitable to couple with skin.

41. The method of claim 40 wherein an outward side of the transmitter antenna superstrate is shaped to conform to skin.

42. The method of claim 41 wherein the periphery of the outward side of the transmitter antenna superstrate is tapered.

43. The method of claim 38 wherein the receiver antenna includes a generally planar resonant structure.

44. The method of claim 43 wherein the receiver antenna includes a superstrate adjacent the resonant structure having an impedance suitable to couple with skin.

45. The method of claim 44 wherein an outward side of the receiver antenna superstrate is shaped to conform to skin.

46. The method of claim 45 wherein the periphery of the outward side of the receiver antenna superstrate is tapered.

47. The method of claim 38 wherein the transmitter antenna is connected to a first base member and the receiver antenna is connected to a second base member, the first base member and the second base member being connected by a flexible bridge.

48. The method of claim 33 wherein the step of comparing the measured signal to the baseline measurement includes the step of calculating a complex distance between the measured signal and the baseline measurement.

49. The method of claim 33 wherein an area under a complex distance curve across a frequency range of interest is calculated, and the calculated area is compared to the area under a baseline curve over the frequency range of interest.

50. The method of claim 29 wherein a site at which the injection occurs remain open for palpation or visualization during the injection.

51. The method of claim 47 wherein a site at which the injection occurs remain open for palpation or visualization during the injection.

52. A method of detecting a change in the level of fluid in tissue in a body comprising the steps of:

transmitting electromagnetic energy in the vicinity of a surface of the body such that changes in the surface geometry of the surface resulting from a change in fluid level of underlying tissue affect a resultant signal;

measuring the resultant signal; and

comparing the resultant signal to a reference signal.

53. An injection system comprising:

an injector to inject a fluid into a vascular structure in a body;

at least a first transmitter including an antenna to transmit electromagnetic energy to a first volume of the body;

at least a first receiver to measure a returned signal;

a memory storing a reference signal, the reference signal created by transmitting electromagnetic energy into the first volume of the body prior to an injection and measuring a resultant signal; and

a signal processor in communication with the first receiver and the memory, the processor comparing the returned signal to the reference signal to determine if the level of fluid in tissue outside the vascular structure has changed.

54. A system for injection of an injection fluid into a body, comprising:

a pressurizing chamber in which injection fluid is pressurized for injection into a vascular structure of a body; and

an extravasation detector, the extravasation detector comprising at least a first transmitter including an antenna to transmit electromagnetic energy to a first volume of the body, at least a first receiver to measure a returned signal, a memory storing a reference signal, the reference signal created by transmitting electromagnetic energy into the first volume of the body prior to an injection of fluid and measuring a resultant signal, and a signal processor in communication with the first receiver and the memory, the processor comparing the returned signal to the reference signal to determine if the level of fluid in tissue outside the vascular structure has changed.

55. A method of detecting a change in the level of fluid in tissue of a body comprising the steps of:

applying electromagnetic energy to a first volume of the body using at least one antenna;

measuring a resultant signal using at least one other antenna; and

comparing the signal to a reference signal.