Devices and methods for tracking blood flow and determining parameters of blood flow

Abstract

Provided herein is a method for use in medical applications that permits (1) affordable three-dimensional imaging of blood flow using a low-profile easily-attached transducer pad, (2) real-time blood-flow vector velocity, and (3) long-term unattended Doppler-ultrasound monitoring in spite of motion of the patient or pad. The pad and associated processor collects and Doppler processes ultrasound blood velocity data in a three dimensional region through the use of a planar phased array of piezoelectric elements. The invention locks onto and tracks the points in three-dimensional space that produce the locally maximum blood velocity signals. The integrated coordinates of points acquired by the accurate tracking process is used to form a three-dimensional map of blood vessels and provide a display that can be used to select multiple points of interest for expanded data collection and for long term continuous and unattended blood flow monitoring. The three dimensional map allows for the calculation of vector velocity from measured radial Doppler. A thinned array (greater than half-wavelength element spacing of the transducer array) is used to make a device of the present invention inexpensive and allow the pad to have a low profile (fewer connecting cables for a given spatial resolution). The full aperture is used for transmit and receive so that there is no loss of sensitivity (signal-to-noise ratio) or dynamic range. Utilizing more elements (extending the physical array) without increasing the number of active elements increases the angular field of view. A further increase is obtained by utilizing a convex non-planar surface.

1 . A method for long term Doppler ultrasound monitoring using an array of ultrasound transducer elements, comprising: collecting and Doppler processing ultrasound blood velocity data in a three dimensional region; locking onto and tracking the point(s) in three-dimensional space that produce the locally maximum blood velocity signals. 
   
   
       2 . A method of  claim 1 , additionally comprising measuring radial velocity at the point(s). 
   
   
       3 . A method of  claim 1 , additionally comprising forming a three-dimensional map of at least one blood vessel based on integrating coordinates of points acquired by the tracking process. 
   
   
       4 . A method of  claim 1 , wherein the ultrasound blood velocity data is radial Doppler data, and additionally comprising calculating vector velocity from the Doppler ultrasound blood velocity data. 
   
   
       5 . A method of  claim 1 , additionally comprising providing a display that allows selection of multiple points of interest for expanded data collection. 
   
   
       6 . A method of  claim 1 , additionally comprising forming a broad ultrasound transmit beam encompassing a plurality of narrow receive beams and initially acquiring the blood velocity data by insonating a large region. 
   
   
       7 . A method of  claim 1 , additionally comprising applying post Doppler sub-resolution processing to locate the point(s) being tracked to an accuracy that is finer than the resolution. 
   
   
       8 . A method of  claim 1 , additionally comprising tracking and maintaining focus on multiple blood vessels. 
   
   
       9 . A method of  claim 1 , additionally comprising performing color velocity imaging. 
   
   
       10 . A method of  claim 1 , additionally comprising forming and displaying a choice of projection, slice or perspective views. 
   
   
       11 . A method of  claim 1 , additionally comprising displaying at least one of instantaneous blood flow velocity and average blood flow velocity and estimated average blood flow volume. 
   
   
       12 . A method of  claim 1 , additionally comprising maintaining a multi-day history and displaying average blood flow velocity versus time for each monitored vessel over a time period. 
   
   
       13 . A method of  claim 1 , additionally comprising sounding an alarm when at least one of a maximum blood flow velocity, a minimum blood flow velocity, and an emboli count is high. 
   
   
       14 . A method of  claim 1 , additionally comprising electronically rotating the array or portions of the array using digital processing techniques. 
   
   
       15 . A transcranial Doppler device for long term Doppler ultrasound monitoring comprising an array of ultrasound transducer elements and processing electronics that produce and digitally analyze data composed of ultrasound signal return amplitude as a function of depth, azimuth, elevation, radial blood velocity and time and that automatically locates and locks onto the point(s) with the maximum volume of blood having a significant radial velocity. 
   
   
       16 . An ultrasound device comprising an array of ultrasound transducer elements and additionally comprising processing electronics programmed to operate the array differently in transmit and receive modes, to form a transmit beam encompassing a plurality of receive beams for initially acquiring a signal by insonating a target region comprising multiple receive beam positions simultaneously, to receive and Doppler process data from the multiple receive beam positions of the array, and to lock onto and track the point(s) in three-dimensional space that produce the locally maximum blood velocity signals. 
   
   
       17 . A device of  claim 16 , wherein the processing electronics are programmed to steer the receive beams using a phase steering or time-delay steering technique. 
   
   
       18 . A device of  claim 16 , wherein the processing electronics are additionally programmed to correct for motions in the target region by periodically forming multiple receive beams and re-acquiring a peak signal. 
   
   
       19 . A device of  claim 16 , wherein the array of ultrasound transducer elements is provided on a low-profile easily-attached transducer pad. 
   
   
       20 . A device of  claim 16 , wherein the processing electronics are additionally programmed to determine spatial coordinates of received data. 
   
   
       21 . A device of  claim 20 , additionally comprising a display device, and wherein the processing electronics are additionally programmed to form and display a 3D map based on the spatial coordinates of received data.