SYSTEM AND METHOD FOR RECEIVING TELEMETRY DATA FROM AN IMPLANTABLE MEDICAL DEVICE

• US 20070135865A1
• Filed: 02/26/2007
• Published: 06/14/2007
• Est. Priority Date: 01/04/2001
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Schleifer, Fred, Schmitt, Steven, Bange, Joseph
• Granted Patent: US 8,489,197 B2
• Time in Patent Office: Days
• US Class Current: 607/59
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/37211 Means for communicating with stimulators
• CPC Class Codes: A61N 1/37252 Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

A system and method for receiving telemetry data from implantable medical devices such as cardiac pacemakers with improved noise immunity is disclosed. Ambient noise levels and signal strength are monitored and used to adaptively adjust the detection sensitivity of the receiver. Filtering of the received signal is performed to remove both broadband and narrowband noise. Removal of narrowband noise is accomplished with notch filters that are dynamically adjusted in accordance with a detected noise spectrum.

Claims

1. A system for receiving data from an implantable medical device, the system comprising:

means for receiving a signal transmitted from an implantable medical device, the signal being a carrier waveform modulated with transmit pulses;

means for producing an correlation signal corresponding to a cross-correlation between the received signal and an expected transmit pulse; and

means for detecting the transmit pulses by comparing the correlation signal with a threshold value.

2. The system of claim 1 further comprising means for adjusting the threshold value.

3. The system of claim 2 wherein the means for adjusting the threshold value comprises:

means for detecting peak noise values from the received signal;

means for detecting peak signal values from the received signal; and

means for adjusting the threshold value based on the peak noise values and peak signal values.

4. The system of claim 1 further comprising means for removing narrowband noises from the received signal.

5. The system of claim 4 wherein the means for filtering narrowband noises comprises:

means for producing a power spectrum of the received signal; and

means for detecting narrowband noise peaks based on the power spectrum of the received signal and a template spectrum corresponding to an expected received signal without noise.

6. The system of claim 5 wherein the means for filtering narrowband noises further comprises means for synthesizing one or more infinite impulse response (IIR) notch filters based on the narrowband noise peaks.

7. A method for receiving telemetry data from an implantable medical device, comprising:

receiving a transmitted signal modulated with data from an implantable device;

digitizing the received signal into input signal samples;

filtering the input samples with a matched filter having filter coefficients corresponding to a transmit pulse;

detecting transmit pulses within the input signal samples by comparing output values of the matched filter with a pulse threshold value; and

,

adjusting the pulse threshold value in accordance with measured peak values of noise and the transmitted signal.

8. The method of claim 7 further comprising measuring noise peak values at a time when the implantable device is known not to be transmitting in accordance with a communications protocol.

9. The method of claim 7 further comprising computing the pulse threshold value as a fraction of a weighted moving average of measured signal peak values that exceed a specified minimum pulse threshold value.

10. The method of claim 9 further comprising adjusting the minimum pulse threshold value in accordance with measured noise peak values.

11. The method of claim 10 further comprising adjusting the minimum pulse threshold by comparing a current minimum pulse threshold value with a measured noise peak value, setting the minimum pulse threshold value equal to the measured noise peak value if the measured noise peak value is greater than the current minimum pulse threshold value, and setting the minimum pulse threshold value equal to a weighted moving average of measured noise peak values if the measured noise peak value is less than the current minimum pulse threshold value.

12. The method of claim 11 further comprising leaving the pulse threshold value unchanged if the current measured signal peak value is below the current minimum threshold value and setting the pulse threshold value equal to an updated weighted moving average of measured signal peak values otherwise.

13. The method of claim 11 further comprising:

filtering the input signal samples prior to being input to the matched filter with a plurality of notch filters for removing narrowband noise therefrom, the filters having notch frequencies corresponding to frequency components of the narrowband noise;

detecting a noise spectrum of the input signal samples; and

,

updating filter coefficients of the notch filters so that the notch frequencies correspond to the detected noise spectrum.

14. The method of claim 13 further comprising detecting a noise spectrum by discrete Fourier transforming a set of input samples to produce a power spectrum of the input signal and subtracting a template spectrum therefrom, the template spectrum corresponding to a representative input signal without noise.

15. The method of claim 13 further comprising setting the notch frequencies of the notch filters to match those spectral components of the noise spectrum that exceed a specified spectral threshold value.