Method and apparatus for low complexity ultrasound based heart rate detection

• US 10,376,243 B2
• Filed: 09/25/2014
• Issued: 08/13/2019
• Est. Priority Date: 09/27/2013
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Ravindran, Sourabh, Spaulding, Jonathon David
• Primary Examiner(s): Chen, Tse W
• Assistant Examiner(s): Ip, Jason M
• Application Number:
  US14/497,295
• Publication Number:
  US 20150094592A1
• Time in Patent Office: 1,783 Days
• CPC Class Codes: A61B 8/02 Measuring pulse or heart rate
• CPC Class Codes: A61B 8/462 characterised by constructional features of the display
• CPC Class Codes: A61B 8/488 involving Doppler signals
• CPC Class Codes: A61B 8/5207 involving processing of raw data to produce diagnostic data, e.g. for generating an image reconstruction G06T11/00
• CPC Class Codes: A61B 8/5223 for extracting a diagnostic or physiological parameter from medical diagnostic data for algorithms to analyse biomedical images G06T7/0012
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment

Abstract

A method for ultrasound based heart rate detection in a heart rate monitoring system is provided that includes receiving a demodulated Doppler ultrasound signal, applying a bandpass filter to the demodulated Doppler ultrasound signal to remove a direct current (DC) component and out-of-band noise, wherein a filtered demodulated Doppler ultrasound signal is generated, rectifying the filtered demodulated Doppler ultrasound signal to generate a rectified filtered demodulated Doppler ultrasound signal, applying a low-pass filter to the rectified filtered demodulated Doppler ultrasound signal to filter out undesired components to leave a resulting signal corresponding to power shift due to heart rate, detecting peaks in the resulting signal, and computing a heart rate based on the detected peaks.

Claims

1. A method comprising:

receiving a demodulated Doppler ultrasound signal;

applying a bandpass filter to the demodulated Doppler ultrasound signal to generate a filtered demodulated Doppler ultrasound signal;

determining a peak in the filtered demodulated Doppler ultrasound signal;

determining, using a first low-pass filter, an average of the filtered demodulated Doppler ultrasound signal;

estimating a signal-to-noise ratio (SNR) based on the peak and average of the filtered demodulated Doppler ultrasound signal;

modifying a lower cutoff frequency of the bandpass filter based on the estimated SNR when the estimated SNR is below a pre-determined SNR threshold;

applying the modified bandpass filter to the filtered demodulated Doppler ultrasound signal to generate a double-filtered demodulated Doppler ultrasound signal;

rectifying the double-filtered demodulated Doppler ultrasound signal to generate a rectified filtered demodulated Doppler ultrasound signal;

applying a second low-pass filter to the rectified filtered demodulated Doppler ultrasound signal to generate a resulting signal;

detecting peaks in the resulting signal; and

computing a heart rate based on the detected peaks.

2. The method of claim 1, wherein rectifying the filtered demodulated Doppler ultrasound signal comprises applying one selected from a group consisting of an active full wave rectifier or an active half wave rectifier to the filtered demodulated Doppler ultrasound signal.

3. The method of claim 1, wherein the demodulated Doppler ultrasound signal is an in phase (I) component of the Doppler ultrasound signal.

4. The method of claim 1, wherein a passband of the second low-pass filter is set to a highest expected frequency for a heart rate.

5. The method of claim 4, wherein the highest expected frequency is 4 Hertz.

6. A heart rate monitoring system comprising:

a bandpass filter adapted to;

receive a demodulated Doppler ultrasound signal;

filter the demodulated Doppler ultrasound signal to generate a filtered demodulated Doppler ultrasound signal;

a signal-to-noise-ratio (SNR) estimator coupled to the bandpass filter, the SNR estimator comprising a first low-pass filter and adapted to;

determine a peak in the filtered demodulated Doppler ultrasound signal;

determine, using the first low-pass filter, an average of the filtered demodulated Doppler ultrasound signal; and

estimate a SNR based on the peak and average of the filtered demodulated Doppler ultrasound signal;

a frequency adapter coupled to the SNR estimator and adapted to modify a lower cutoff frequency of the bandpass filter based on the estimated SNR when the estimated SNR is below a pre-determined SNR threshold;

the modified bandpass filter further adapted to filter the filtered demodulated Doppler ultrasound signal to generate a double-filtered demodulated Doppler ultrasound signal;

a rectifier coupled to the frequency adapter and adapted to rectify the double-filtered demodulated Doppler ultrasound signal to generate a rectified filtered demodulated Doppler ultrasound signal;

a second low-pass filter coupled to the rectifier and adapted to filter the rectified filtered demodulated Doppler ultrasound signal to generate a resulting signal;

a microcontroller coupled to the second low-pass filter and adapted to;

detect peaks in the resulting signal; and

compute a heart rate based on the detected peaks.

7. The heart rate monitoring system of claim 6, wherein the rectifier is either an active full wave rectifier or an active half wave rectifier.

8. The heart rate monitoring system of claim 6, wherein the demodulated Doppler ultrasound signal is an in phase (I) component of the Doppler ultrasound signal.

9. The heart rate monitoring system of claim 6, wherein a passband of the second low-pass filter is set to a highest expected frequency for a heart rate.

10. The heart rate monitoring system of claim 9, wherein the highest expected frequency is 4 Hertz.