Method and apparatus for measuring volume flow and area for a dynamic orifice

Abstract

Techniques are provided for obtaining selected instantaneous area measurements for a dynamic orifice through which blood is flowing in at least one direction, for obtaining instantaneous flow rates of blood passing through such a dynamic orifice and for obtaining flow volume for blood passing through a dynamic orifice. All of these techniques involve ensonifying a thin sample volume of blood flow exiting at the orifice, which volume is in a region of flow which is substantially laminar, such region normally being the vena contracta for the orifice, with an ultrasonic pulsed Doppler signal, receiving backscattered signal from blood within the sample volume and forming a power-velocity spectrum from the received backscattered signal. Techniques are disclosed for assuring that only laminar flow is looked at in forming the power-velocity spectrum. To obtain instantaneous area measurements, the power integral of laminar flow from the spectrum is formed, this power integral being proportional to an instantaneous cross-sectional area of the orifice. For instantaneous flow rates, the instantaneous power-velocity integral is formed from the laminar flow of the spectrum, while flow volume is obtained from the timed integral of the instantaneous flow rate.

1 . A method comprising: 
 ensonifying a sample volume of a fluid exiting an orifice with an ultrasonic signal;    receiving a backscattered signal from the sample volume; and    forming a power-velocity spectrum from the backscattered signal; and    forming an integral for the power-velocity spectrum that is proportional to a cross-sectional area of the orifice.    
     
     
         2 . The method of  claim 1 , wherein the integral is a power integral.  
     
     
         3 . The method of  claim 1 , wherein the integral is a time integral.