Microwave hemorrhagic stroke detector

• US 7,226,415 B2
• Filed: 09/23/2002
• Issued: 06/05/2007
• Est. Priority Date: 04/23/1999
• Status: Expired due to Term

• Current Assignee: Regents of the University of California (University of California)
• 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:
  US10/252,176
• Publication Number:
  US 20030018244A1
• Time in Patent Office: 1,716 Days
• Field of Search: None
• 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 stoke in human or animal patients as well as for the detection of hemorrhage within a patient'"'"'s body.

Claims

1. An apparatus for detecting blood flow, 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 whether blood is flowing within said medium, wherein said means for detecting said transmitted signal comprise at least one microwave receiver antenna, wherein said at least one microwave receiver antenna comprises a parabolic reflector antenna, 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.

2. An apparatus for detecting blood flow, 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 whether blood is flowing within said medium, wherein said means for detecting said transmitted signal comprise at least one microwave receiver antenna, wherein said at least one microwave receiver antenna comprises a parabolic reflector antenna, wherein said housing comprises microwave absorber material, 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, wherein said housing further comprises an element insert, wherein said element insert comprises a bag designed to fit within said housing and over a patient'"'"'s head.

3. The apparatus for detecting blood flow of claim 2, wherein said bag is filled with dielectric material.

4. The apparatus for detecting blood flow of claim 3, wherein said bag comprises a material which can stretch and expand to fill said housing and conform to said patient'"'"'s head.

5. The apparatus for detecting blood flow of claim 4, wherein said element insert further comprises an inlet quick disconnect to enable said element insert to be connected to a dielectric liquid fill tube through which dielectric filling liquid may be input to said element insert.

6. The apparatus for detecting blood flow of claim 5, wherein said element insert comprises material having about the same refractive index, in the microwave band being used, as said dielectric liquid.

7. The apparatus for detecting blood flow of claim 6, wherein said element insert comprises silicone rubber impregnated with TiO₂.

8. The apparatus for detecting blood flow of claim 6, wherein said element 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 element 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 element insert can then be tuned by adjusting the density of the particles within the silicone rubber.

9. The apparatus for detecting blood flow of claim 6, wherein said element 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.

10. The apparatus for detecting blood flow of claim 6, wherein said element insert immobilizes and positions said patient'"'"'s head at the center of said apparatus for detecting blood flow while it is analyzing said microwave signal and said detected signal to determine whether a hemorrhage exists.

11. The apparatus for detecting blood flow of claim 3, 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.

12. The apparatus for detecting blood flow of claim 3, 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.

13. An apparatus for detecting blood flow, 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 whether blood is flowing within said medium, wherein said means for detecting said transmitted signal comprise at least one microwave receiver antenna, wherein said at least one microwave receiver antenna comprises a parabolic reflector antenna, wherein said housing comprises microwave absorber material, 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, wherein said housing further comprises an element insert, 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, wherein said at least one microwave transmitter and said at least one microwave receiver antenna rotates about an axis of rotation of said housing.

14. An apparatus for detecting blood flow, 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 whether blood is flowing within said medium, 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.

15. A method for detecting blood flow within a medium, comprising:

producing a 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 blood is flowing within said medium, 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, wherein said reconstruction algorithm comprises taking the integral of the refractive index at all points along the path traveled by the pulse between the transmitter and receiver and reconstructing an image from a set of path integrals.

16. A method for detecting blood flow within a medium, comprising:

producing a 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 blood is flowing within said medium, 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, wherein said reconstruction algorithm comprises;

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

calculating a normal signal;

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

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

17. The method of claim 16, further comprising applying a post-processing algorithm to said map to highlight blood flow in a head or body map.

18. A microwave hemorrhage detector, comprising:

means for producing a pulsed microwave signal, wherein said microwave signal is transmitted across a medium 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 fluid is flowing 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.

19. The apparatus of claim 18, further comprising a contrast agent inserted into said medium to increase the difference between the index of refraction between said fluid and said medium.

20. The apparatus of claim 19, wherein said contrast agent is selected from the group consisting of microbubbles and microballoons.

21. An apparatus for detecting blood flow, 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 with a reconstruction algorithm to determine whether blood is flowing within said medium, wherein said reconstruction algorithm comprises taking the integral of the refractive index at a plurality of points along the path traveled by said microwave signal between said means for producing a microwave signal and said means for detecting said transmitted signal and reconstructing an image from a set of path integrals.

22. An apparatus for detecting blood flow, comprising;

means for producing a pulsed microwave signal, wherein said pulsed 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 pulsed microwave signal and said detected signal with a reconstruction algorithm to determine whether blood is flowing within said medium, wherein said reconstruction algorithm comprises;

suppressing the effects of the 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 using a standard tomographic back projection method.