Signal processing method and device for signal-to-noise improvement

• US 7,060,035 B2
• Filed: 06/19/2003
• Issued: 06/13/2006
• Est. Priority Date: 09/13/2001
• Status: Expired due to Term

• Current Assignee: Conmed Corporation (Jefferies Financial Group, Inc.)
• Original Assignee: Conmed Corporation (Jefferies Financial Group, Inc.)
• Inventors: Wasserman, Yoram
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US10/465,128
• Publication Number:
  US 20040010188A1
• Time in Patent Office: 1,090 Days
• Field of Search: 600/509, 600/513, 600/521, 600/300, 600/508
• US Class Current: 600/508
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

A method and apparatus extract a signal component of a measured signal using one of two methods. If the signal component in the measured signal is a periodic signal with a certain well-defined peak-to-peak intensity value, upper and lower envelopes of the measured signal are determined and analyzed to extract said signal component of the measured signal. This signal component can further be used to calculate a desired parameter of the sample. The DC component of the signal is determined as the median value of the upper envelope, and the AC component is determined as the median value of the difference between the upper and lower envelopes. If the signal component of the measured signal is a periodic signal characterized by a specific asymmetric shape, a specific adaptive filtering is applied to the measured signal, resulting in the enhancement of the signal component relative to a noise component. This adaptive filtering is based on a derivative of the Gaussian Kernel having specific parameters matching the characteristics of the signal component.

Claims

1. A method for processing measured data representative of a first measured signal including a first signal component in the form of a substantially periodic signal with substantially well-defined peak-to-peak intensity value, and a second measured signal including a second signal component characterized by a specific asymmetric shape, to extract the signal components from noise components, the method comprising the steps of:

processing the first measured signal by determining upper and lower envelopes thereof, and analyzing the upper and lower envelope values to extract the first signal component;

defining a kernel function being a derivative of a Gaussian with parameters matching characteristics of the second signal component, and processing the second measured signal by filtering it with the kernel function parameters, thereby enhancing the second signal component relative to the noise component in the filtered second measured signal.

2. The method, as set forth in claim 1, wherein the first signal component is a pulsatile blood-related signal.

3. The method, as set forth in claim 1, wherein said second measured signal is ECG, the second signal component being representative of a QRS segment in the ECG signal.

4. A measurement system to be applied to a sample to determine a desired parameter thereof, the system comprising:

a measurement device operable to apply an external field to a measurement location on the sample or medium, detect a response of the measurement location to the application of the external field, and generate measured data indicative thereof, the measured data containing a first measured signal including a signal component in the form of a substantially periodic signal with a substantially well-defined peal-to-peak intensity value, and a second measured signal including a second signal component characterized by a specific asymmetric shape; and

a control unit connectable to the measurement device for receiving and processing the measured data, the control unit comprising data processing and analyzing preprogrammed to process the first measured signal by determining upper and lower envelopes thereof and analyze the upper and lower envelope values to extract the first signal component from a noise component in the first measured signal, and to process the second measured signal by filtering it with a predefined kernel function being a derivative of a Gaussian with parameters matching the characteristics of the second signal component, thereby enhancing the second signal component relative to a noise component in the filtered measured signal.

5. The system, as set forth in claim 4, wherein the first signal component is a pulsatile blood-related signal.

6. The system, as set forth in claim 4, wherein the second measured signal is ECG, the second signal component being representative of a QRS segment in the ECG signal.

7. A method for determining a parameter of a signal having a signal component, including the steps of:

(i) defining a kernel function as a derivative of a Gaussian with parameters selected for enhancing characteristics of the signal component; and

(ii) applying a spectral filter to the signal, the spectral filter using the kernel function and responsively enhancing the signal component; and

,

(iii) determining a parameter of the signal as a function of the enhanced signal component.

8. A method, as set forth in claim 7, wherein the characteristics of the signal component are a specific asymmetric shape.

9. An apparatus, comprising:

a detector for receiving a measured signal; and

,

a controller coupled to the detector and adapted to receive the measured signal, define a kernel function as a derivative of a Gaussian with parameters selected for enhancing characteristics of the signal component, apply a spectral filter to the signal, the spectral filter using the kernel function and responsively enhance the signal component, and to determine a parameter of the signal as a function of the enhanced signal component.

10. An apparatus, as set forth in claim 9, wherein the characteristics of the signal component are a specific asymmetric shape.