Method and apparatus for automatic evoked potentials assessment

• US 8,700,141 B2
• Filed: 03/10/2010
• Issued: 04/15/2014
• Est. Priority Date: 03/10/2010
• Status: Expired due to Fees

• Current Assignee: Brainscope SPV LLC
• Original Assignee: Brainscope Company Inc.
• Inventors: Causevic, Elvir
• Primary Examiner(s): Natnithithadha, Navin
• Assistant Examiner(s): BERHANU, ETSUB D
• Application Number:
  US12/720,907
• Publication Number:
  US 20110224570A1
• Time in Patent Office: 1,497 Days
• Field of Search: 600/544, 600/545
• US Class Current: 600/544
• CPC Class Codes: A61B 5/378 Visual stimuli
• CPC Class Codes: A61B 5/38 Acoustic or auditory stimuli
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: G06F 2218/14 by matching peak patterns

Abstract

Systems and methods for assessing a patient'"'"'s neurologic state based on auditory evoked responses are provided.

Claims

1. A system for monitoring brain electrical activity of a patient, comprising:

a set of electrodes;

at least one auditory stimulus generator;

a detection system operatively connected to the set of electrodes and configured to receive electrical signals detected by the electrodes after production of an auditory stimulus by the stimulus generator, the electrical signals representing the patient'"'"'s auditory evoked response, and to transmit the electrical signals to a signal processor; and

the signal processor configured to;

reject artifacts present in the electrical signals using a plurality of automated artifact detectors working in parallel to generate artifact-free signals;

perform non-linear denoising on the artifact-free signals to produce denoised signals;

transform the denoised signals to a non-linear wavelet transform domain;

automatically detect locations of one or more peaks of the patient'"'"'s auditory evoked response in the non-linear wavelet transform domain;

extract a set of quantitative non-linear features related to the patient'"'"'s auditory evoked response; and

compare the set of non-linear features to one or more feature sets stored in a storage system and determine if the non-linear features are indicative of an abnormal neurologic state.

2. The system of claim 1, wherein the processor is further configured to extract a set of linear features related to the patient'"'"'s auditory evoked response.

3. The system of claim 1, wherein the storage system includes a database of normal values for auditory evoked response data.

4. The system of claim 1, wherein the storage system includes a database of auditory evoked response data for a group of patients, and the processor is configured to compare the set of non-linear features to one or more feature sets of the group of patients and to classify the patient'"'"'s neurologic state based on the comparison.

5. The system of claim 4, wherein the patient'"'"'s neurologic state is classified based on a similarity between one or more non-linear features of the patient'"'"'s auditory evoked response and one or more non-linear features of at least one other patient having a known neurologic state.

6. The system of claim 1, wherein the storage system includes a database of prior auditory evoked response measurements from the same patient, and the signal processor is configured to compare the set of non-linear features to one or more feature sets stored from the prior measurements and determine if any changes have occurred.

7. The system of claim 1, wherein the signal processor is further configured to detect the amplitude or the timing of the one or more peaks in the patient'"'"'s auditory evoked response.

8. The system of claim 1, further including a communication device configured to automatically generate a signal representing the patients neurologic state.

9. The system of claim 8, wherein the communication system includes a visual display indicating a deviation from a baseline measurement.

10. The system of claim 8, wherein the communication system includes a visual display indicating a deviation from a baseline measurement indicative of intracranial pressure for a patient.

11. The system of claim 1, wherein the electrode set is positioned on a head band and includes at least two electrodes positioned on the head band to allow detection of auditory evoked response signals when the headband is positioned on a patient.

12. The system of claim 1, further including a communication system configured to transmit data related to auditory evoked response signals to a location distant from the system.

13. The system of claim 1, wherein at least one of said automated artifact detectors is configured to detect at least one of:

horizontal eye movements, vertical eye movements, impulse artifacts, muscle activity, or significantly low amplitude signal.

26. The system of claim 13 or method of claim 25, wherein said horizontal eye movement artifacts detection comprises:

band-pass filtering the electrical signals with an FIR filter, wherein the high-pass cut-off frequency of the band-pass filter is selected such that frequencies below the delta_—

1 band are removed;

identifying one or more time segments of the electrical signals which correspond to a difference in electrical signals from an F7 electrode and F8 electrode exceeding a threshold as candidate segments having horizontal eye movement artifacts; and

determining the mean-squared-error between the signals from the F7 electrode and F8 electrode to filter out false detection of horizontal eye movement artifacts if the mean-squared-error is above a threshold indicating presence of pathology rather than presence of horizontal eye movement artifacts.

27. The system of claim 13 or method of claim 25, wherein said vertical eye movement artifacts detection comprises:

low-pass filtering portions of the electrical signals corresponding to an Fp1 electrode and an Fp2 electrode;

identifying bumps in the low-pass filtered portions;

determining whether a difference between a value of the global extremum of each bump and average values of the low-pass filtered portions of the electrical signal to the side of the bump exceed a threshold; and

determining whether the bumps corresponding to Fp1 and Fp2 occur concurrently.

28. The system of claim 13 or method of claim 25, wherein said muscle activity artifacts detection comprises:

band-pass filtering the electrical signals within a first range to produce a first band-passed signal and band-pass filtering the electrical signals within a second range to produce a second band-passed signal;

determining a variance of the first band-passed signal over a first time-segment;

determining a variance of the second band-passed signal over each of a plurality of a second time-segment that is a subsection of the first time-segment; and

determining whether each of the variances for each second time-segment of the second band-passed signal relative to the variance of the first band-passed signal is above a threshold and whether the variance of each second time-segment of the second band-passed signal is above a minimum variance.

29. The system of claim 13 or method of claim 25, wherein said impulse artifacts detection, further comprises:

high-pass filtering the electrical signals with a cutoff frequency to remove an alpha component of cerebral electrical activity; and

identifying segments of the high-pass filtered electrical signals which include a difference between a maximum value and a minimum value that is greater than 75 μ

V.

30. The system of claim 13 or method of claim 25, wherein said significantly low amplitude signal detection comprises detecting segments of the electrical signals with a maximum mean-square energy acro one or more electrodes lower than a threshold of 12 μ

V².

14. A method for monitoring brain electrical activity, comprising:

providing an auditory stimulus to a patient, by a stimulus generator;

obtaining electrical signals representing an auditory evoked response by using a set of electrodes located on the patient after production of the auditory stimulus;

transmitting the electrical signals real-time to a signal processor;

performing a real-time artifact rejection step on the electrical signals using a plurality of automated artifact detectors working in parallel to generate artifact-free signals;

performing a non-linear denoising step on the artifact-free signals to produce denoised signals;

transforming the denoised signals to a non-linear wavelet transform domain;

automatically detecting locations of one or more peaks of the patient'"'"'s auditory evoked response in the non-linear wavelet transform domain;

extracting a set of quantitative non-linear features related to the patient'"'"'s auditory evoked response; and

comparing the set of non-linear features to one or more feature sets stored in a storage system and determining if the non-linear features are indicative of an abnormal neurologic state.

15. The method of claim 14, wherein comparing the set of non-linear features to one or more feature sets stored in a storage system includes comparing the features to a database of normal values for auditory evoked response data.

16. The method of claim 14, wherein comparing the set of non-linear features to one or more feature sets stored in a storage system includes comparing the features to a database of auditory evoked response data for a group of patients and classifying the patient'"'"'s neurologic state based on the comparison.

17. The method of claim 16, wherein the patient'"'"'s neurologic state is classified based on a similarity between one or more non-linear features of the patient'"'"'s auditory evoked response and one or more non-linear features of at least one other patient having a known neurologic state.

18. The method of claim 14, wherein comparing the set of non-linear features to one or more feature sets stored in a storage system includes comparing the non-linear features to non-linear features from prior measurements of the same patient and determining if any changes have occurred for the same patient.

19. The method of claim 14, further comprising detecting the amplitude or the timing of the one or more peaks in the patient'"'"'s auditory evoked response.

20. The method of claim 14, further including generating a signal representing the patient'"'"'s neurologic state.

21. The method of claim 20, wherein the signal is a visual display.

22. The method of claim 20, wherein the visual display indicates a deviation from a baseline measurement indicative of intracranial pressure for the patient.

23. The method of claim 14, wherein the electrode set is positioned on a head band and includes at least two electrodes positioned on the head band to allow detection of auditory evoked response signals when the headband is positioned on the patient.

24. The method of claim 14, further including transmitting data related to repeated brain electrical activity measurements to a location distant from the system.

25. The method of claim 14, wherein at least one of said automated artifact detectors is configured to detect at least one of:

horizontal eye movements, vertical eye movements, impulse artifacts, muscle activity, or significantly low amplitude signal.