Non-invasive monitoring of intracranial dynamic effects and brain density fluctuations

• US 20050033171A1
• Filed: 07/26/2004
• Published: 02/10/2005
• Est. Priority Date: 07/24/2003
• Status: Active Grant

• Current Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Original Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Inventors: Wrobel, Miroslaw, Stergiopoulos, Stergios
• Granted Patent: US 7,854,701 B2
• Time in Patent Office: Days
• US Class Current: 600/437
• CPC Class Codes: A61B 5/031 Intracranial pressure
• CPC Class Codes: A61B 5/4064 Evaluating the brain A61B5/031, A61B5/369, A61B5/14553 take precedence
• CPC Class Codes: A61B 8/0808 for diagnosis of the brain
• CPC Class Codes: G01N 2291/02483 Other human or animal parts, e.g. bones
• CPC Class Codes: G01N 29/0672 by acoustic tomography medical tomography A61B8/13
• CPC Class Codes: G01N 29/075 by measuring or comparing phase angle measuring frequencies or phase angles per se G01R23/00, G01R25/00
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01S 15/8909 using a static transducer configuration
• CPC Class Codes: G01S 7/52036 using analysis of echo signal for target characterisation

Abstract

The present invention relates to a method and apparatus for non-invasive monitoring of brain density variations. At least two ultrasonic pulses having different frequencies are provided into the brain for transmission therethrough. The reflected ultrasonic pulses are then sensed and the sensed signal data are then processed for determining at least two phase differences between the phases of the at least two reflected ultrasonic pulses and the phases of the at least two provided ultrasonic pulses. A phase of at least a beat frequency is determined in dependence upon the at least two phase differences. Finally, data indicative of a brain density variation are determined based on the at least two phase differences and the at least a beat frequency. Repeating the process enables continuous monitoring of brain density variations. The method and apparatus for non-invasive monitoring of brain density variations is highly beneficial in clinical settings as well as during emergency and rescue operations by enabling early detection of brain density variations, which are directly related to intracranial pressure (ICP) changes; and provide diagnosis and assessment of head injuries, haemorrhage, stroke and variations of blood flow in the skull due to drug effects, changes in brain temperature and stress.

Claims

1. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary comprising:

a) providing at least two ultrasonic pulses having different frequencies into the medium for transmission therethrough;

b) sensing the at least two ultrasonic pulses after traveling through the medium and providing a receive signal in dependence thereupon;

c) processing the receive signal for determining at least two phase differences between the phases of the at least two sensed ultrasonic pulses and the phases of the at least two provided ultrasonic pulses;

d) determining data indicative of a density variation of the medium based on the at least two phase differences.

2. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 1 comprising converting the receive signal into digital receive signal data.

3. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 1 comprising determining phase of at least a beat frequency in dependence upon the at least two phase differences, and determining the data indicative of a density variation of the medium based on the at least two phase differences and the at least a beat frequency.

4. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 3 comprising:

repeating the steps a) to d).

5. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 3 comprising:

varying the frequencies of the at least two ultrasonic pulses; and

,

repeating the steps a) to d).

6. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 5 comprising:

adjusting the frequencies of the at least two ultrasonic pulses such that an initial phase of the at least a beat frequency is approximately π

.

7. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 5 comprising:

using a processor determining the different frequencies of the at least two ultrasonic pulses; and

,

using an ultrasonic pulse generator in communication with the processor generating the at least two ultrasonic pulses in dependence upon the determined different frequencies.

8. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 7 wherein the frequencies of the at least two ultrasonic pulses are related to each other by ratios of integer numbers.

9. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 7 comprising:

generating a sequence of the at least two ultrasonic pulses according to predetermined parameters indicative of;

number of pulses, width of each of the pulses, delay of each of the pulses, and repetition rate.

10. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 4 wherein the receive signal is converted using a variable sampling frequency.

11. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 3 wherein step c) comprises:

detecting a position of each of the at least two sensed ultrasonic pulses in the receive signal.

12. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 11 comprising:

determining an envelope of the receive signal; and

,

detecting edges of the sensed ultrasonic pulses.

13. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 11 wherein step c) comprises:

sampling data points from a center of each pulse;

transforming the sampled data points into Fourier domain;

determining the phase of each pulse using a frequency bin closest to the frequencies of the at least two provided ultrasonic pulses.

14. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 13 comprising:

testing linearity of the phase of the transformed data points with respect to frequency; and

,

removing erroneous data points.

15. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 14 comprising:

averaging each of the at least two phase differences.

16. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 3 wherein the at least two ultrasonic pulses are reflected from the at least a solid boundary.

17. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 16 comprising:

performing beam steering for detecting the reflected ultrasonic pulses.

18. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 3 wherein the medium is a human brain.

19. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 18 wherein the frequencies are within a range from 0.5 MHz to 2.5 MHz.

20. A method for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 8 wherein the medium is a human brain comprising:

determining most responsive frequencies of the at least two ultrasonic pulses;

correlating the most responsive frequencies to at least a pathological condition of a human brain; and

,

providing data indicative of a pathological condition of a human brain.

21. An apparatus for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary comprising:

an ultrasonic pulse generator for generating at least two ultrasonic pulses having different frequencies;

a transmitter in signal communication with the ultrasonic pulse generator for coupling the at least two ultrasonic pulses into the medium for transmission therethrough;

at least a sensor for sensing the at least two ultrasonic pulses after traveling through the medium and for providing a receive signal in dependence thereupon;

an analog-to-digital converter in signal communication with the at least a sensor for converting the receive signal into digital receive signal data;

a processor in communication with the ultrasonic pulse generator and the analog-to-digital converter, the processor for;

a) providing at least a control signal to the ultrasonic pulse generator indicative of at least a parameter of the at least two ultrasonic pulses;

b) processing the digital receive signal data for determining at least two phase differences between the phases of the at least two sensed ultrasonic pulses and the phases of the at least two provided ultrasonic pulses; and

,

c) determining data indicative of a density variation based on the at least two phase differences and the at least a beat frequency.

22. An apparatus for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 21 wherein the ultrasonic pulse generator is a direct digital synthesizer.

23. An apparatus for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 22 wherein the at least a sensor comprises a sensor array.

24. An apparatus for non-invasive monitoring density variations of a medium substantially confined within at least a solid boundary as defined in claim 22 comprising a user interface in communication with the processor for receiving instructions from a user and for providing at least a control signal in dependence thereupon to the processor and for displaying the data indicative of a density variation.

25. An apparatus for non-invasive monitoring of brain density variations comprising:

an ultrasonic pulse generator for generating at least two ultrasonic pulses having different frequencies;

a transmitter in signal communication with the ultrasonic pulse generator for coupling the at least two ultrasonic pulses into the brain for transmission therethrough;

a sensor array probe for sensing the at least two ultrasonic pulses after traveling through the medium and for providing a receive signal in dependence thereupon;

an analog-to-digital converter in signal communication with the sensor array for converting the receive signal into digital receive signal data;

a processor in communication with the ultrasonic pulse generator, the analog-to-digital converter, and the sensor array, the processor for;

a) providing at least a control signal to the ultrasonic pulse generator indicative of at least a parameter of the at least two ultrasonic pulses;

b) performing beam steering for detecting the at least two ultrasonic pulses;

c) processing the digital receive signal data for determining at least two phase differences between the phases of the at least two sensed ultrasonic pulses and the phases of the at least two provided ultrasonic pulses;

d) determining at least a beat frequency phase in dependence upon the at least two phase differences;

e) determining at least a density variation based on the at least two phase differences and the at least a beat frequency; and

,

f) repeating the steps a) to e) while varying the frequencies of the at least two ultrasonic pulses.

26. An apparatus for non-invasive monitoring of brain density variations as defined in claim 25 wherein the medium is a human brain, the apparatus comprising non-volatile memory having stored thereupon data indicative of a plurality of pathological conditions of a human brain, the processor for:

determining most responsive frequencies of the at least two ultrasonic pulses in dependence upon the at least a density variation

correlating the most responsive frequencies to the data indicative of a plurality of pathological conditions of a human brain; and

,

providing data indicative of a pathological condition of the human brain.

27. An apparatus for non-invasive monitoring of brain density variations as defined in claim 26 comprising a user interface in communication with the processor for receiving instructions from a user and for providing at least a control signal in dependence thereupon to the processor, and for displaying the data indicative of a density variation and the data indicative of the pathological condition.