Microwave hemorrhagic stroke detector

• US 6,454,711 B1
• Filed: 04/23/1999
• Issued: 09/24/2002
• Est. Priority Date: 04/23/1999
• Status: Expired due to Term

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Haddad, Waleed S., Trebes, James E.
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US09/298,342
• Time in Patent Office: 1,250 Days
• Field of Search: 600/407, 600/430, 600/504, 600/481, 600/371
• US Class Current: 600/371
• CPC Class Codes: A61B 5/0507 using microwaves or terahertz waves
• CPC Class Codes: A61B 5/4076 Diagnosing or monitoring particular conditions of the nervous system A61B5/4821, A61B5/4824 take precedence

Abstract

The microwave hemorrhagic stroke detector includes a low power pulsed microwave transmitter with a broad-band antenna for producing a directional beam of microwaves, an index of refraction matching cap placed over the patients head, and an array of broad-band microwave receivers with collection antennae. The system of microwave transmitter and receivers are scanned around, and can also be positioned up and down the axis of the patients head. The microwave hemorrhagic stroke detector is a completely non-invasive device designed to detect and localize blood pooling and clots or to measure blood flow within the head or body. The device is based on low power pulsed microwave technology combined with specialized antennas and tomographic methods. The system can be used for rapid, non-invasive detection of blood pooling such as occurs with hemorrhagic stroke in human or animal patients as well as for the detection of hemorrhage within a patient'"'"'s body.

Claims

1. A microwave hemorrhage detector, comprising:

means for producing a pulsed microwave signal, wherein said microwave signal is transmitted across a medium selected from a group consisting of a portion of a human body and a portion of an animal body to produce a transmitted signal;

means for detecting said transmitted signal to produce a detected signal; and

means for analyzing said microwave signal and said detected signal to determine whether a hemorrhage exists within said medium, wherein said microwave signal and said detected signal are analyzed to produce a value selected from the group consisting of the real part of the refractive index and the loss due to absorption.

2. The microwave hemorrhage detector of claim 1, wherein said means for producing a microwave signal comprise at least one microwave transmitter.

3. The microwave hemorrhage detector of claim 2, wherein said at least one microwave transmitter is capable of producing microwave pulses having a pulse duration within a range of 60 ps to 120 ps and having a center frequency within a range of 2 Hz to 5 GHz.

4. The microwave hemorrhage detector of claim 3, wherein said at least one microwave transmitter includes a wide angle horn transmitter.

5. The microwave hemorrhage detector of claim 1, wherein said means for detecting said transmitted signal comprise at least one microwave receiver antenna.

6. The microwave hemorrhage detector of claim 5, wherein said at least one microwave receiver antenna is capable of receiving microwave pulses having a pulse duration within a range of 60 ps to 120 ps and having a center frequency within a range of 2 Hz to 5 GHz.

7. The microwave hemorrhage detector of claim 6, wherein said at least one microwave receiver antenna comprises an array of at least 4 receiver antennas mounted with a gap of 3 to 5 mm between them, wherein said gap comprises microwave absorbing material to help reduce any residual crosstalk between antennas.

8. The microwave hemorrhage detector of claim 5, wherein said at least one microwave receiver antenna comprises a wide angle horn antenna.

9. The microwave hemorrhage detector of claim 1, further comprising a housing, wherein said means for producing a microwave signal comprise at least one microwave transmitter, wherein said means for detecting said transmitted signal comprise at least one microwave receiver antenna, wherein said at least one microwave transmitter and said at least one microwave receiver antenna are fixedly and operatively mounted to said housing.

10. The microwave hemorrhage detector of claim 9, wherein said housing comprises microwave absorber material.

11. The microwave hemorrhage detector of claim 10, wherein said microwave absorber material provides shielding, prevents entry of signals from outside objects, reduces residual crosstalk within said means for producing a microwave signal and reduces residual crosstalk within said means for detecting said transmitted signal.

12. The microwave hemrorrhage detector of claim 11, wherein said housing further comprises a helmet insert.

13. The microwave hemorrhage detector of claim 12, wherein said helmet insert comprises a bag designed to fit within said housing and over a patient'"'"'s head.

14. The microwave hemorrhage detector of claim 13, wherein said bag is filled with dielectric material.

15. The microwave hemorrhage detector of claim 14, wherein said bag comprises a material which can stretch and expand to fill said housing and conform to said patient'"'"'s head.

16. The microwave hemorrhage detector of claim 15, wherein said helmet insert further comprises an inlet quick disconnect to enable said helmet insert to be connected to a dielectric liquid fill tube through which dielectric filling liquid may be input to said helmet insert.

17. The microwave hemorrhage detector of claim 16, wherein said helmet insert comprises material having about the same refractive index, in the microwave band being used, as said dielectric liquid.

18. The microwave hemorrhage detector of claim 17, wherein said helmet insert comprises silicone rubber impregnated with TiO₂.

19. The microwave hemorrhage detector of claim 17, wherein said helmet insert comprises silicone rubber impregnated with particles which have a refractive index that is high enough to adjust the refractive index of said silicon rubber such that said helmet insert comprises material having about the same refractive index, in the microwave band being used, as said dielectric liquid, wherein the refractive index of said helmet insert can then be tuned by adjusting the density of the particles within the silicone rubber.

20. The microwave hemorrhage detector of claim 17, wherein said helmet insert serves as a dielectric matching medium between said means for producing a microwave signal, said means for detecting said transmitted microwave signal and said patient'"'"'s head, thus providing a uniform medium into which the microwave radiation is launched which, in turn, minimizes reflections at interfaces.

21. The microwave hemorrhage detector of claim 17, wherein said helmet insert immobilizes and positions said patient'"'"'s head at the center of said microwave hemorrhage detector while it is analyzing said microwave signal and said detected signal to determine whether a hemorrhage exists.

22. The microwave hemorrhage detector of claim 14, wherein said dielectric material is selected from a group consisting of water doped with microballoons or oil emulsion, gelatin doped with salt or oils to raise or lower n_r, silicone doped with water globules or other high n_r, plastics doped with TiO₂ powder, silicone doped with TiO₂ or other high nr material, and open cell foam impregnated with gelatin.

23. The microwave hemorrhage detector of claim 14, wherein said dielectric material comprises a dopant, wherein the density, type and particle size of said dopant can be varied in order to tune dielectric properties of said dielectric material.

24. The microwave hemorrhage detector of claim 9, wherein said at least one microwave transmitter and said at least one microwave receiver antenna rotates about an axis of rotation of said housing.

25. The microwave hemorrhage detector of claim 1, further comprising a housing, wherein said means for producing a microwave signal comprise a plurality of microwave transmitter/receiver units fixedly and operatively mounted to said housing, wherein said detector further comprises means for electronically multiplexing said plurality of microwave transmitter/receiver units such that microwave signals are transmitted and received in a selected pattern about an axis of rotation of said housing.

26. The microwave hemorrhage detector of claim 1, wherein said means for analyzing said microwave signal and said detected signal comprises a reconstruction algorithm which analyses said microwave signal and said detected signal to determine whether a hemorrhage exists within said medium.

27. The microwave hemorrhage detector of claim 1, further comprising a contrast agent comprising microbubbles, wherein said contrast agent is inserted into said medium to increase the difference between the index of refraction between a hemorrhage and said medium.

28. A method for determining whether a hemorrhage exists within a medium, comprising:

producing a pulsed microwave signal;

transmitting said microwave signal through a medium selected from a group consisting of a portion of a human body and a portion of an animal body to produce a transmitted signal;

detecting said transmitted signal after it has passed through said medium to produce a detected signal; and

analyzing said microwave signal and said detected signal to determine whether a hemorrhage exists within said medium, wherein said microwave signal and said detected signal are analyzed to produce a value selected from the group consisting of the real part of the refractive index and the loss due to absorption.

29. The method of claim 28, wherein said microwave signal is transmitted through said medium at a plurality of angles, wherein the step of analyzing said microwave signal and said detected signal is carried out with a reconstruction algorithm.

30. The method of claim 29, wherein said reconstruction aIlgorithn comprises taking the integral of the refractive index at all points along the path traveled by said microwave signal and said transmitted signal between the transmitter and receiver and reconstructing an image from a set of path integrals.

31. The method of claim 29, wherein said transmitted signal comprises a pulse shape, wherein said reconstruction algorithm comprises:

suppressing the effects of said pulse shape of said transmitted signal in each said detected signal;

calculating a normal signal;

storing said normal signal in the memory of a controlling computer system; and

reconstructing a data set from said normal signal to form a map of said medium by means of a standard tomographic back projection method.

32. The method of claim 31, further comprising applying a post-processing algorithm to said map to highlight hemorrhage regions in a head map.

33. The method of claim 30, further comprising inserting a contrast agent comprising microbubbles into said medium to increase the difference between the index of refraction between a hemorrhage and said medium.

34. An apparatus, comprising:

means for producing a microwave signal, wherein said microwave signal is transmitted through a medium selected from a group consisting of a portion of a human body and a portion of an animal body to produce a transmitted signal;

means for detecting said transmitted signal to produce a detected signal; and

means for analyzing said microwave signal and said detected signal to determine the index of refraction, at the wavelength of said microwave signal, of selected points within said medium.

35. The apparatus of claim 34, wherein said means for producing a microwave signal comprise at least one microwave transmitter.

36. The apparatus of claim 35, wherein said at least one microwave transmitter is capable of producing microwave pulses having a pulse duration within a range of 60 ps to 120 ps and having a center frequency within a range of 2 Hz to 5 GHz.

37. The apparatus of claim 36, wherein said at least one microwave transmitter includes a wide angle horn transmitter.

38. The apparatus of claim 34, wherein said means for detecting said transmitted signal comprise at least one microwave receiver antenna.

39. The apparatus of claim 38, wherein said at least one microwave receiver antenna is capable of receiving microwave pulses having a pulse duration within a range of 60 ps to 120 ps and having a center frequency within a range of 2 Hz to 5 GHz.

40. The apparatus of claim 38, wherein said at least one microwave receiver antenna comprises an array of at least 4 receiver antennas mounted with a gap of 3 to 5 mm between them, wherein said gap comprises microwave absorbing material to help reduce any residual crosstalk between antennas.

41. The apparatus of claim 38, wherein said at least one microwave receiver antenna comprises a wide angle horn antenna.

42. The apparatus of claim 34, further comprising a housing, wherein said means for producing a microwave signal comprise at least one microwave transmitter, wherein said means for detecting said transmitted signal comprise at least one microwave receiver antenna, wherein said at least one microwave transmitter and said at least one microwave receiver antenna are fixedly and operatively mounted to said housing.

43. The apparatus of claim 42, wherein said housing comprises microwave absorber material.

44. The apparatus of claim 43, wherein said microwave absorber material provides shielding, prevents entry of signals from outside objects, reduces residual crosstalk within said means for producing a microwave signal and reduces residual crosstalk within said means for detecting said transmitted signal.

45. The apparatus of claim 44, wherein said housing further comprises a helmet insert.

46. The apparatus of claim 45, wherein said helmet insert comprises a bag designed to fit within said housing and over a patient'"'"'s head.

47. The apparatus of claim 46, wherein said bag is filled with dielectric material.

48. The apparatus of claim 47, wherein said bag comprises a material which can stretch and expand to fill said housing and conform to said patient'"'"'s head.

49. The apparatus of claim 48, wherein said helmet insert further comprises an inlet quick disconnect to enable said helmet insert to be connected to a dielectric liquid fill tube through which dielectric filling liquid may be input to said helmet insert.

50. The apparatus of claim 49, wherein said helmet insert comprises material having about the same refractive index, in the microwave band being used, as said dielectric liquid.

51. The apparatus of claim 50, wherein said helmet insert comprises silicone rubber impregnated with TiO₂.

52. The apparatus of claim 50, wherein said helmet insert comprises silicone rubber impregnated with particles which have a refractive index that is high enough to adjust the refractive index of said silicon rubber such that said helmet insert comprises material having about the same refractive index, in the microwave band being used, as said dielectric liquid, wherein the refractive index of said helmet insert can then be tuned by adjusting the density of the particles within the silicone rubber.

53. The apparatus of claim 50, wherein said helmet insert serves as a dielectric matching medium between said means for producing a microwave signal, said means for detecting said transmitted microwave signal and said patients head, thus providing a uniform medium into which the microwave radiation is launched which, in turn, minimizes reflections at interfaces.

54. The apparatus of claim 50, wherein said helmet insert immobilizes and positions said patient'"'"'s head at the center of said microwave hemorrhage detector while it is analyzing said microwave signal and said detected signal to determine whether a hemorrhage exists.

55. The apparatus of claim 47, wherein said dielectric material is selected from a group consisting of water doped with microballoons or oil emulsion, gelatin doped with salt or oils to raise or lower n_r, silicone doped with water globules or other high n_r, plastics doped with TiO₂ powder, silicone doped with TiO₂ or other high n_r material, and open cell foam impregnated with gelatin.

56. The apparatus of claim 47, wherein said dielectric material comprises a dopant, wherein the density, type and particle size of said dopant can be varied in order to tune dielectric properties of said dielectric material.

57. The apparatus of claim 42, wherein said at least one microwave transmitter and said at least one microwave receiver antenna rotates about an axis of rotation of said housing.

58. The apparatus of claim 34, further comprising a housing, wherein said means for producing a microwave signal comprise a plurality of microwave transmitter/receiver units fixedly and operatively mounted to said housing, wherein said detector further comprises means for electronically multiplexing said plurality of microwave transmitter/receiver units such that microwave signals are transmitted and received in a selected pattern about an axis of rotation of said housing.

59. The apparatus of claim 34, wherein said means for analyzing said microwave signal and said detected signal comprises a reconstruction algorithm which analyses said microwave signal and said detected signal to determine whether a hemorrhage exists within said medium.

60. The apparatus of claim 34, further comprising a contrast agent comprising microbubbles, wherein said contrast agent is inserted into said medium to increase the difference between the index of refraction between a hemorrhage and said medium.