System and method for grading microemboli monitored by a multi-gate doppler ultrasound system

• US 20060264759A1
• Filed: 05/20/2005
• Published: 11/23/2006
• Est. Priority Date: 05/20/2005
• Status: Active Grant

• Current Assignee: Spentech Incorporated
• Original Assignee: Spentech Incorporated
• Inventors: Spencer, Merrill P., Dewaraja, Asanka S., Mera, Thomas O., Moehring, Mark A.
• Granted Patent: US 7,771,358 B2
• Time in Patent Office: Days
• US Class Current: 600/469
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/0808 for diagnosis of the brain

Abstract

Systems and methods for grading signals from microemboli in blood flow monitored using a Doppler ultrasound system. Signals from microemboli in blood flow are graded by calculating a value related to a power for the signals from microemboli in blood flow and categorizing the signals into one of at least two grades based on the calculated value. Alternatively, signals can be categorized by assessing a power value for the microemboli in blood flow during a period of monitoring. In response to the power value being greater than or equal to a threshold value, the microemboli in blood flow are categorized based on the power value, and in response to the power value being less than the threshold value, a number of microemboli are counted during at least a portion of the period of monitoring and the microemboli are categorized based on the number.

Claims

1. A method for grading signals from microemboli in blood flow, the blood flow monitored using a Doppler ultrasound system, the method comprising:

calculating a value related to a power for the signals from microemboli in blood flow; and

categorizing the signals from microemboli in blood flow into one of at least two grades based on the calculated value.

2. The method of claim 1, further comprises acquiring signals from microemboli in blood flow by:

for a period of monitoring and a background period, extracting Doppler shift signals from echo signals resulting from ultrasound delivered to a region in which blood flow is detected;

calculating signal-to-background data from the Doppler shift signals from the period of monitoring and the background period; and

determining from the signal-to-background data the presence of microemboli in the blood flow during the period of monitoring.

3. The method of claim 2 wherein calculating signal-to-background data from the Doppler shift signals comprises:

calculating mean background power for a depth range from the Doppler shift signals from the background period;

calculating Doppler signal power values for the depth range over the period of monitoring from the Doppler shift signals from the period of monitoring; and

dividing the Doppler signal power values by the mean background power for corresponding depths of the depth range.

4. The method of claim 3 wherein determining from the signal-to-background data the presence of microemboli in the blood flow during the period of monitoring comprises:

identifying the signal-to-background data representing a signal-to-background ratio greater than a threshold value.

5. The method of claim 2 wherein calculating a value related to a power for the signals from microemboli in the blood flow comprises:

dividing the signal-to-background data over the period of monitoring into sub-periods having corresponding portions of the signal-to-background data;

cross-correlating the signal-to-background data for a first half-sub-period to the signal-to-background data for a second half-sub-period;

calculating correlative data in response to cross-correlating the signal-to-background data for the first and second half-sub-periods of the sub-periods;

summing the correlative data;

converting the sum to a decibel value to be used as the value related to the power for the signals from microemboli in the blood flow.

6. The method of claim 5 wherein delivering ultrasound to a region in which blood flow is present comprises:

delivering ultrasound from first and second ultrasound probes for bilateral monitoring of the region;

wherein extracting, calculating, and determining are performed for echo signals resulting from the ultrasound delivered by the respective ultrasound probes to provide decibel values for each of the probes;

calculating beam power for the ultrasound delivered by each probe; and

the value related to the power for the microemboli is provided by weighting the decibel values for each of the probes in accordance with the beam power calculated for each probe.

7. The method of claim 1 wherein categorizing the signals from microemboli in blood flow comprises:

categorizing the signals from microemboli in blood flow into at least one high grade in response to the value being greater than or equal to a threshold value; and

in response to the value being less than the threshold value, the method further comprising;

calculating a count value corresponding to a number of signals from microemboli in the blood flow; and

categorizing the signals from microemboli in blood flow into one of a plurality of grades based on the count value.

8. The method of claim 1 wherein categorizing the signals from microemboli in blood flow into one of at least two grades comprises categorizing the signals from microemboli in blood flow into a grade of a six-level logarithmic scale.

9. The method of claim 1, further comprising:

in the event the value is greater than the threshold value, determining whether the signals from microemboli in the blood flow over a period of monitoring is graded as a first high grade or a second high grade for sub-periods of the period of monitoring.

10. A method for categorizing microemboli in blood flow monitored using a Doppler ultrasound system, the method comprising:

assessing a power value for the microemboli in the blood flow during a period of monitoring;

in response to the power value being greater than or equal to a threshold value, categorizing the microemboli in the blood flow based on the power value; and

in response to the power value being less than the threshold value, counting a number of microemboli during at least a portion of the period of monitoring and categorizing the microemboli based on the number.

11. The method of claim 10 wherein assessing a power value for the microemboli in the blood flow during a period of monitoring comprises assessing a power value for bubble emboli in cerebral blood flow during the period of monitoring.

12. The method of claim 11 wherein categorizing the microemboli in the blood flow based on the power value comprises categorizing the bubble emboli in a grade for a grading scale related to functional conductance of patent foramen ovale.

13. A Doppler ultrasound system, comprising:

a probe having an ultrasound transducer;

a transmitter circuit operably coupled to the ultrasound transducer and configured to generate drive signals for driving the ultrasound transducer to deliver ultrasound;

a receiver circuit operably coupled to the ultrasound transducer and configured to receive echo signals detected by the ultrasound transducer and generate in response thereto echo data representative of the echo signals; and

a processing system operably coupled to the transmitter and receiver circuits and configured to control the transmit circuit in generating drive signals for the ultrasound transducer and configured to process the echo data from the receiver circuit and extract therefrom Doppler shift signals represented by Doppler shift data, the processing system further configured to process the Doppler shift data to calculate a value related to a power for the signals from microemboli in blood flow and categorize the signals from microemboli in blood flow into one of at least two grades based on the calculated value.

14. The system of claim 13 wherein the processing system comprises a processor configured to extract Doppler shift signals from echo signals resulting from ultrasound delivered to a region in which blood flow is detected for a period of monitoring and a background period and configured to calculate signal-to-background data from the Doppler shift signals from the period of monitoring and the background period, the processor further configured to determine from the signal-to-background data the presence of signals from microemboli in the blood flow during the period of monitoring.

15. The system of claim 14 wherein the processor configured to calculate signal-to-background data from the Doppler shift signals comprises a processor configured to calculate mean background power for a depth range from the Doppler shift signals from the background period, calculate Doppler signal power values for the depth range over the period of monitoring from the Doppler shift signals from the period of monitoring, and divide the Doppler signal power values by the mean background power for corresponding depths of the depth range.

16. The system of claim 14 wherein the processing system configured to process the Doppler shift data to calculate a value related to a power for the signals from microemboli in blood flow comprises a processor configured to divide the signal-to-background data over the period of monitoring into sub-periods having corresponding portions of the signal-to-background data and cross-correlate the signal-to-background data for a first half-sub-period to the signal-to-background data for a second half-sub-period, the processor further configured to calculate correlative data in response to cross-correlating the signal-to-background data for the first and second half-sub-periods of the sub-periods, sum the correlative data, and convert the sum to a decibel value to be used as the value related to the power for the signals from microemboli in the blood flow.

17. The system of claim 16 wherein the probe comprises a first probe, the transmitter circuit comprises a first transmitter circuit, and the receiver circuit comprises a first receiver circuit, and the system further comprises a second probe having an ultrasound transducer, a second transmitter circuit operably coupled to the ultrasound transducer of the second probe, and a second receiver circuit operably coupled to the ultrasound transducer of the second probe,

the processing system comprises a processor configured to control the first and second transmit and receive circuits to deliver ultrasound from first and second probes for bilateral monitoring of a region, and the extracting, calculating, and determining are performed for echo signals resulting from the ultrasound delivered by the respective ultrasound probes to provide decibel values for each of the probes, the processor further configured to calculate beam power for the ultrasound delivered by each probe and calculate the value related to the power for the microemboli by weighting the decibel values for each of the probes in accordance with the beam power calculated for each probe.

18. The system of claim 13 wherein the processing system configured to categorize the signals from microemboli in blood flow comprises a processor configured to categorize the signals from microemboli in blood flow into at least one high grade in response to the value being greater than or equal to a threshold value and in response to the value being less than the threshold value, the processor is further configured to calculate a count value corresponding to a number of signals from microemboli in the blood flow and categorize the signals from microemboli in blood flow into one of a plurality of grades based on the count value.

19. The system of claim 13 wherein the processing system comprises a processor configured to determine whether the signals from microemboli in the blood flow over a period of monitoring is graded as a first high grade or a second high grade for sub-periods of the period of monitoring in the event the value is greater than a threshold value.

20. A processing system for a Doppler ultrasound system having a probe having an ultrasound transducer, transmit beam forming circuits, and receive beam forming circuits, the processing system comprising:

a processor configured to extract Doppler shift signals from echo signals detected by the beam forming circuits and further configured to process the Doppler shift signals to assess a power value for microemboli in blood flow monitored by the Doppler ultrasound system during a period of monitoring and categorize microemboli in blood flow based on the power value in response to the power value being greater than or equal to a threshold value, the processor further configured to count a number of microemboli in blood flow during at least a portion of the period of monitoring and categorize the microemboli in blood flow based on the number in response to the power value being less than the threshold value.

21. The system of claim 20 wherein the processor configured to assess a power value for microemboli in the blood flow during a period of monitoring comprises a processor configured to assess a power value for bubble emboli in cerebral blood flow during the period of monitoring.

22. The system of claim 21 wherein the processor is configured categorize the bubble emboli in a grade for a grading scale related to functional conductance of patent foramen ovale.