Seizure detection methods, apparatus, and systems using a wavelet transform maximum modulus algorithm

Abstract

Methods for detecting a seizure, by use of a wavelet transform maximum modulus (WTMM) algorithm applied to body data. A non-transitive, computer-readable storage device for storing data that when executed by a processor, perform such a method.

1 . A non-transitory computer readable program storage unit encoded with instructions that, when executed by one or more medical devices, performs a method, comprising:
 receiving via the one or more medical devices a time series of a first body signal of a patient obtained from one or more sensors;   determining a sliding foreground time window and a sliding background time window for the time series of the first body signal;   applying a spectral filter having a defined power spectral density to each of the sliding foreground time window and the sliding background time window;   determining a ratio of a spectral power between the sliding foreground time window and the sliding background time window;   determining a seizure onset in response to a first determination that the ratio reaches an onset threshold;   initiating an electrical therapy based on the seizure onset determination;   determining a seizure termination in response to a second determination that the ratio reaches a termination threshold; and   wherein the method further comprises at least one of:   determining a seizure occurrence based on a first output of a STA/LTA algorithm on at least one second body signal;   determining the seizure occurrence based on a second output of at least one second algorithm on the first body signal; and   determining the seizure occurrence based on a third output of at least one second algorithm on the at least lease one second body signal;   wherein the second body signal is selected from an EKG signal, an accelerometer signal, or a signal indicative of a loss of responsiveness.   
     
     
         2 . The non-transitory computer readable program storage unit of  claim 1 , including data that when executed by the one or more medical devices perform the method of  claim 1 , wherein:
 a number of samples in the sliding foreground time window (N STA ) is 16;   a number of samples in the sliding background time window (N LTA ) is 360;   the time of seizure onset (T onset ) corresponds to a time fulfilling a condition   
       
         
           
             
               
                 
                   STALTA 
                   ⁡ 
                   
                     ( 
                     
                       τ 
                       + 
                       
                         
                           N 
                           STA 
                         
                         / 
                         2 
                       
                     
                     ) 
                   
                 
                 ≥ 
                 
                   T 
                   
                     onset 
                     , 
                   
                 
               
               ⁢ 
               
                   
               
             
           
         
         
           
             
               wherein 
               ⁢ 
               
                   
               
             
           
         
         
           
             
               
                 STALTA 
                 ⁡ 
                 
                   ( 
                   τ 
                   ) 
                 
               
               = 
               
                 
                   
                     ∑ 
                     
                       t 
                       = 
                       
                         τ 
                         - 
                         
                           N 
                           STA 
                         
                         + 
                         1 
                       
                     
                     τ 
                   
                   ⁢ 
                   
                     
                       
                         X 
                         2 
                       
                       ⁡ 
                       
                         ( 
                         t 
                         ) 
                       
                     
                     / 
                     
                       N 
                       STA 
                     
                   
                 
                 
                   
                     ∑ 
                     
                       t 
                       = 
                       
                         τ 
                         - 
                         
                           N 
                           LTA 
                         
                         + 
                         1 
                       
                     
                     τ 
                   
                   ⁢ 
                   
                     
                       
                         X 
                         2 
                       
                       ⁡ 
                       
                         ( 
                         t 
                         ) 
                       
                     
                     / 
                     
                       N 
                       LTA 
                     
                   
                 
               
             
           
         
       
       and τ is a common right-hand end of both the sliding foreground time window and the sliding background time window;
 a time of the seizure termination (T end ) corresponds to a second time fulfilling a second condition of max {STALTA(s),τ−N STA ≤s≤τ}≤T end ; and 
 a filter's spectral density corresponds to a Daubechies wavelet order 4, level 3. 
 
     
     
         3 . The non-transitory computer readable program storage unit of  claim 1 , including data that when executed by the one or more medical devices perform the method of  claim 1 , wherein at least one parameter selected from the sliding foreground time window, the sliding background time window, the spectral filter, the onset threshold, or the termination threshold is selected based on at least one of: a level of safety risk associated with an activity; at least one of an age, a physical state, or a mental state of the patient; a length of a window available for a warning; a degree of circadian and ultradian fluctuations of a patient's seizure activity; a performance of a detection method as a function of a patient's sleep/wake cycle or vigilance level; a dependence of a patient's seizure activity on at least one of a level of consciousness, a level of cognitive activity, or a level of physical activity; a site of a seizure origin; or a seizure type. 
     
     
         4 . The non-transitory computer readable program storage unit of  claim 3 , including data that when executed by the one or more medical devices perform the method of  claim 3 , wherein the method further comprises adaptively establishing the at least one parameter. 
     
     
         5 . The non-transitory computer readable program storage unit of  claim 1 , including data that when executed by one or more medical devices perform the method of  claim 1 , wherein the second body signal comprises at least one of: a measurement of a patient's heart activity, a measurement of a patient's respiratory activity, a measurement of a patient's kinetic activity, a measurement of a patient's brain electrical activity, a measurement of a patient's oxygen consumption, a measurement of a patient's oxygen saturation, a measurement of an endocrine activity of the patient, a measurement of a metabolic activity of the patient, a measurement of an autonomic activity of the patient, a measurement of a cognitive activity of the patient, and a measurement of a tissue stress marker of the patient. 
     
     
         6 . The non-transitory computer readable program storage unit of  claim 1 , including data that when executed by the one or more medical devices perform the method of  claim 1 , wherein the method further comprises:
 initiating the electrical therapy by delivering the electrical therapy for the seizure at a particular time, wherein at least one of the electrical therapy, the particular time, or both is based upon the determination of the seizure onset;   determining an efficacy of the electrical therapy; or   issuing a warning for the seizure, wherein the warning is based upon the determination of the seizure onset.   
     
     
         7 . The non-transitory computer readable program storage unit of  claim 1 , including data that when executed by the one or more medical devices perform the method of  claim 1 , wherein the method further comprises determining at least one of:
 a timing of a delivery of the electrical therapy, a type of the electrical therapy, at least one parameter of the electrical therapy, a timing of sending a warning, a type of the warning, a duration of the warning, or an efficacy index based upon the seizure onset, the seizure termination, or both.   
     
     
         8 . The non-transitory computer readable program storage unit of  claim 1 , including data that when executed by the one or more medical devices perform the method of  claim 1 , wherein the method further comprises:
 determining at least one value selected from a duration of the seizure, a severity of the seizure, an intensity of the seizure, an extent of spread of the seizure, an inter-seizure interval between the seizure and a prior seizure, a patient impact of the seizure, and a time of the seizure occurrence; and   logging the at least one value in a memory.   
     
     
         9 . The non-transitory computer readable program storage unit of  claim 1 , including data that when executed by one or more medical devices perform the method of  claim 1 , wherein the method further comprises estimating a degree of nonstationarity of the first body signal. 
     
     
         10 . A non-transitory computer readable program storage unit encoded with instructions that, when executed by a computer via one or more processors and computer readable media, perform a method, comprising:
 receiving a time series of a first body signal of a patient;   determining at least two sliding adjacent time windows for the time series of the first body signal comprising a foreground window and a background window;   determining one or more long chains for the foreground window and the background window based on a parameter that defines which chains are long;   extracting at least one first long chain from the foreground window and at least one second long chain from the background window;   applying a continuous wavelet transform to each of the one first long chain and the one second long chain, to yield a wavelet transform maximum modulus (WTMM) skeleton for each window;   determining a first variance of the WTMIM skeleton from the foreground window and a second variance of the WTMM skeleton from the background window;   generating a stepwise approximation of changes in the variances;   determining a seizure onset in response to a determination that an output of the stepwise approximation of changes in the first variance has reached an onset threshold;   initiating via a therapy device one or more therapies to treat the seizure onset; and   determining a seizure termination in response to a determination that an output of the stepwise approximation of changes in the second variance has reached a termination threshold;   wherein the method further comprises at least one responsive action selected from:   delivering a therapy for said seizure at a particular time, wherein at least one of said therapy, said particular time, or both is based upon said determination of said seizure onset;   determining an efficacy of said therapy; or   issuing a warning for said seizure, wherein said warning is based upon a determination of said seizure onset, a determination of duration of said seizure, a determination of a type of said seizure, or two to more thereof.   
     
     
         11 . The non-transitory computer readable program storage unit of  claim 10 , including data that when executed by a processor performs the method of  claim 10 , wherein at least one of the delivered therapy or the issued warning is based at least in part on at least one of the type of activity engaged in by the patient at the time of seizure onset, the seizure type, the seizure severity, or the time elapsed from the last seizure. 
     
     
         12 . The non-transitory computer readable program storage unit of  claim 10 , including data that when executed by a processor performs the method of  claim 10 , wherein the method further comprises determining at least one of:
 a time delivery of therapy, a duration of a therapy, a type of therapy, at least one parameter of the therapy, a timing of sending a warning, a type of warning, or a duration of the warning;   based upon said seizure onset, said seizure termination, or both.   
     
     
         13 . The non-transitory computer readable program storage unit of  claim 10 , including data that when executed by a processor performs the method of  claim 10 , wherein the method further comprises:
 determining at least one value selected from the duration of said seizure, the severity of said seizure, the intensity of said seizure, the extent of spread of said seizure, an inter-seizure interval between said seizure and a prior seizure, a patient impact of said seizure, or a time of occurrence of said seizure and   logging said at least one value.   
     
     
         14 . A medical device for detecting a seizure onset and a seizure termination of an epileptic seizure event from a patient body signal using a multi time-period averaging algorithm, comprising:
 a body data processing module for receiving via one or more processors a body signal of a patient during a first time series from one or more sensors; and   a seizure onset/termination unit configured to:   select a first time window and a second time window within the first time series;   apply a spectral filter having a predetermined power spectral density to each of the first time window and the second time window;   determine a ratio of a spectral power between the first time window and the second time window;   determine that the seizure onset has occurred in response to a first determination that the ratio reaches an onset threshold;   initiating an electrical therapy based on the seizure onset determination; and   determine that the seizure termination has occurred in response to a second determination that the ratio reaches a termination threshold;   wherein the time window control module uses parameters selected based on at least one of: a clinical application of at least one the determination; a level of safety risk associated with an activity; at least one of an age, a physical state, or a mental state of the patient; a length of a window available for a warning; a degree of efficacy of the electrical therapy and of the electrical therapy's latency; a degree of a seizure control; a degree of circadian and ultradian fluctuations of a patient's seizure activity; a performance of the detection method as a function of a patient's sleep/wake cycle or vigilance level; a dependence of the patient's seizure activity on at least one of a level of consciousness, a level of cognitive activity, or a level of physical activity; a site of seizure origin; a seizure type, a desired sensitivity of the detection of the seizure, a desired specificity of the detection of the seizure, a desired speed of the detection of the seizure, an input provided by the patient, or an input provided by the one or more sensors.   
     
     
         15 . The medical device of  claim 14 , wherein the body data processing module comprises:
 a body data interface for receiving the body signal, the body data interface comprising:   a buffer to perform buffering function upon the body signal;   an amplifier for performing an amplification of the body signal;   an analog-to-digital (A/D) converter for converting the body signal from an analog signal to a digital signal; and   a filter for performing a filtering function upon the body signal;   and   a body data memory to store the digital signal.   
     
     
         16 . The medical device of  claim 15 , wherein the seizure onset/termination unit comprises:
 a time window control module capable of selecting the first time window and the second time window;   a spectral filter module for applying the spectral filter to the first time window and the second time window;   a ratio determination unit for determining the ratio of the spectral power; and   a ratio threshold comparison unit for comparing the ratio of the spectral power to a first threshold to determine whether the seizure onset has occurred, and for comparing the ratio of the spectral power to a second threshold to determine whether the seizure termination has occurred.   
     
     
         17 . The medical device of  claim 16 , wherein the first time series body signal comprises at least one of a measurement of a patient's heart activity, a measurement of a patient's respiratory activity, a measurement of a patient's kinetic activity, a measurement of a patient's brain electrical activity, a measurement of a patient's oxygen consumption, a measurement of a patient's oxygen saturation, a measurement of an endocrine activity of the patient, a measurement of a metabolic activity of the patient, a measurement of an autonomic activity of the patient, a measurement of a cognitive activity of the patient, or a measurement of a tissue stress marker of the patient.