Ultrasonic Method and Apparatus for Measuring or Detecting Flow Behavior of a Non-Sinusoidal Periodicity

Abstract

A method and apparatus for automated detection of a general, non-sinusoidal type of periodicity in ultrasound Doppler signals from pulsatile blood flow is described. The method computes a pulsation index, which is a sum of the normalized powers of the fundamental and several harmonic components in the frequency spectrum of the banded Doppler signal. A weighting function may be applied to the power from each harmonic component in order to suppress contributions due to spurious peaks, as in the case when pulsatile flow is absent.

1 . An ultrasonic method for detecting and/or measuring pulsatile flow comprising:
 acquiring ultrasonic Doppler signal information from a flow site;   determining from the Doppler signal information a power spectrum within a specific frequency band;   identifying fundamental and harmonic peaks of the power spectrum;   determining the power in bands including the identified fundamental and harmonic peaks; and   determining a measure of pulsatility from the power in the bands.   
   
   
       2 . The method of  claim 1 , wherein identifying further comprises identifying a fundamental and a plurality of harmonic peaks of the power spectrum. 
   
   
       3 . The method of  claim 2 , wherein identifying further comprises identifying a fundamental and four harmonic peaks of the power spectrum. 
   
   
       4 . The method of  claim 1 , wherein determining the power further comprises calculating the normalized power in each band including a fundamental or harmonic peak. 
   
   
       6 . The method of  claim 1 , further comprising weighting the power in the bands as a function of noise. 
   
   
       7 . The method of  claim 6 , wherein weighting the power in the bands further comprises weighting the power in the bands with a sigmoidal weighting function. 
   
   
       8 . The method of  claim 1 , wherein determining a measure of pulsatility comprises combining the power in the bands to form a pulsation index. 
   
   
       9 . The method of  claim 8 , further comprising comparing the pulsation index with a threshold. 
   
   
       10 . The method of  claim 1 , further comprising determining a measure of noise from the spectrum between the peaks. 
   
   
       11 . The method of  claim 10 , further comprising normalizing the measure of noise to total spectral power. 
   
   
       12 . A defibrillator comprising:
 a pair of electrodes;   a shock delivery circuit coupled to the electrodes;   an ultrasonic Doppler transducer;   a Doppler processor, coupled to the Doppler transducer, which operates to produce a Doppler spectrum;   a peak detector operable to detect a fundamental and at least one harmonic peak in the Doppler spectrum;   a pulsatility processor, responsive to the detected peaks, which acts to produce a measure of pulsatility from the Doppler power in the vicinity of the detected peaks.   
   
   
       13 . The defibrillator of  claim 12 , further comprising an ECG signal processor coupled to the electrodes and to the shock delivery circuit. 
   
   
       14 . The defibrillator of  claim 12 , further comprising a Doppler signal transmitter coupled to the Doppler transducer. 
   
   
       15 . The defibrillator of  claim 12 , wherein the Doppler processor further comprises means for producing a banded Doppler signal. 
   
   
       16 . The defibrillator of  claim 12 , further comprising a noise detector operable to immunize the pulsatility processor against the effect of noise.