Noninvasive monitoring hydrocephalus, cerebral edema, and intracranial bleeding using electromagnetic wave propagation properties

• US 9,456,757 B1
• Filed: 10/04/2012
• Issued: 10/04/2016
• Est. Priority Date: 10/03/2011
• Status: Active Grant

• Current Assignee: Eugene Zheng, Weining Hu, Zheng Yi
• Original Assignee: Eugene Zheng, Weining Hu, Zheng Yi
• Inventors: Zheng, Eugene, Hu, Weining, Zheng, Yi
• Primary Examiner(s): EISEMAN, ADAM JARED
• Application Number:
  US13/573,724
• Time in Patent Office: 1,461 Days
• Field of Search: 600/547
• US Class Current: 1/1
• CPC Class Codes: A61B 5/02042 Determining blood loss or bleeding, e.g. during a surgical procedure
• CPC Class Codes: A61B 5/031 Intracranial pressure
• 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 5/4064 Evaluating the brain A61B5/031, A61B5/369, A61B5/14553 take precedence
• CPC Class Codes: A61B 5/4878 Evaluating oedema
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7228 Signal modulation applied to the input signal sent to patient or subject; demodulation to recover the physiological signal modulation H03C
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence

Abstract

The present invention describes a system and methods to monitor hydrocephalus and cerebral edema in noninvasive or minimum invasive ways. The system monitors the changes of electromagnetic wave propagations in brain tissues changed by the tissue pathological statues. One of the tissue properties monitored is the tissue permittivity that determines the wave propagation velocity. By avoiding the tissue conductivity that has variations due to many different reasons including non-pathological factors, this approach has advantages of acquiring reliable pathological information of brain tissue and being independent to electrode properties and skin conditions. Several parameters are defined to quantitatively measure and assess hydrocephalus and cerebral edema: relative phase shift (RPS), travel-time difference (TTD), and change of relative wave velocity. The parameters are defined and normalized in distance and time for measuring relative changes for the monitoring applications. The method includes non-invasive and minimum invasive approaches. Amplitude modulated wave and coded waves are used to reduce interference and effectively detect small changes of tissue properties in preferred frequency ranges.

Claims

1. A system for monitoring hydrocephalus, cerebral edema, and intracranial bleeding in noninvasive way, the system comprising:

at least one signal generator configured to generate an electromagnetic wave;

at least one source electrode or coil configured to emit the electromagnetic wave to a brain tissue;

at least one detecting electrode configured to detect said wave that propagates through said brain tissue;

a digitizer operatively connected to said electrode and configured to digitize a signal detected at said electrode;

a quadrature detector operatively connected to the digitizer and configured to demodulate the digitized signal and obtain in-phase and quadrature components of the signal;

an envelope and phase detector operatively connected to the quadrature detector and configured to estimate a magnitude and phase of the signal;

a special-purpose processor operatively connected to the envelope and phase detector and specially configured to estimate tissue characteristics that are related to status of hydrocephalus, cerebral edema, and intracranial bleeding from the magnitude and phase.

2. The monitoring system as described in claim 1 wherein said source electrode or coil and detecting electrode are configured to be noninvasively applied to skin a surface of head for transmitting and receiving said wave.

3. The monitoring system as described in claim 1 wherein said source electrode or coil comprises an electrode comprising a metal plate, and wherein the detecting electrode comprises a metal plate.

4. The monitoring system as described in claim 1, further comprising an earplug, wherein said source electrode or coil comprises an electrode disposed inside the earplug.

5. The monitoring system as described in claim 1 wherein said source electrode or coil comprises an electrode, and the at least one detecting electrode comprises two electrodes, wherein said envelope and phase detector is configured to obtain a phase difference between signals from said two detecting electrodes, and wherein the processor is specially configured to calculate said tissue characteristics from said phase difference.

6. The monitoring system as described in claim 1 wherein said tissue characteristics related to status of hydrocephalus, cerebral edema, and intracranial bleeding include at least one of:

relative attenuation coefficient (RAC), relative phase shift (RPS), Wave Speed Change (WSC), travel time difference (TTD), and complex wave number.

7. The monitoring system as described in claim 6 wherein the special-purpose processor is specially configured to estimate the relative attenuation coefficient (RAC) by comparing the attenuation of said wave propagation through brain tissue to a baseline for assessing status of hydrocephalus, cerebral edema, and intracranial bleeding, wherein the baseline is either an attenuation previously measured or a defined number.

8. The monitoring system as described in claim 6 wherein the special-purpose processor is specially configured to estimate the relative phase shift (RPS) by comparing the phase shift of said wave propagating through said brain tissue to a baseline for assessing status of hydrocephalus, cerebral edema, and intracranial bleeding wherein the baseline is either a phase shift previously measured or a defined number.

9. The monitoring system as described in claim 6 wherein the special-purpose processor is specially configured to estimate the wave speed difference (WSD) by comparing the wave speed difference of said wave propagating through said brain tissue to a baseline for assessing status of hydrocephalus, cerebral edema, and intracranial bleeding, wherein the baseline is either a phase shift previously measured or a defined number.

10. The monitoring system as described in claim 6 wherein the special-purpose processor is specially configured to estimate the travel time difference (TTD) by comparing the travel time of said wave propagation through said brain tissue with a baseline for assessing status of hydrocephalus, cerebral edema, and intracranial bleeding, wherein the baseline is either a travel time previously measured a defined number.

11. The monitoring system as described in claim 1, wherein said signal generator is configured to generate electromagnetic waves from 0 Hz to 100 kHz.

12. The monitoring system as described in claim 6 wherein the processor is specially configured to calculate the complex wave number of brain tissue to assess status of hydrocephalus, cerebral edema, and intracranial bleeding.

13. The monitoring system as described in claim 1 wherein said electromagnetic wave includes continuous wave having a single frequency, broadband pulses having multiple frequencies, and coded wave with prescribed frequencies and wave patterns.

14. The monitoring system of claim 5, the system further comprising a ground reference electrode.

15. The monitoring system of claim 2, where said source electrode or coil comprises an electrode adapted to be in direct contact with the skin surface without insulators between the conductor of the electrodes and tissue surface.

16. The monitoring system of claim 1, further comprising a ground reference electrode, wherein said source electrode or coil comprises an electrode, where said envelope and phase detector is configured to obtain a phase difference between signals at the source (electrode and detecting electrode, and the processor is specially configured to calculate said tissue characteristics from the phase difference.

17. The monitoring system of claim 7, wherein estimating the RAC comprising estimating RAC according to

18. The monitoring system of claim 8, wherein estimating the RPS comprising estimating RPS according to

19. The monitoring system of claim 9, wherein estimating the WSD comprising estimating WSD according to

20. The monitoring system of claim 10, wherein estimating the TTD comprising estimating TTD according to