Ultrasound imaging using apparent point-source transmt transducer

Abstract

An apparent point-source transmit transducers comprises a substantially constant-thickness shell of piezoelectric material in a shape of a spherical-section. Such transducers may be sized such that a single apparent point-source transmit transducer may produce ultrasound waveforms with substantial energy in a medium to be imaged. Use of such transducers in three-dimensional ping-based imaging may permit deeper and higher quality imaging than may be possible with conventional transducers.

What is claimed is: 
     
         1 . An ultrasound imaging system comprising:
 a first apparent point-source transmit transducer shaped as a spherical section having a spherical center point, the first apparent point-source transmit transducer configured to transmit a three-dimensional semi-spherical pulse into a target object to be imaged;   a first plurality of receive transducer elements configured to receive echoes of the three-dimensional semi-spherical pulse;   a second plurality of receive transducer elements configured to receive echoes of the three-dimensional semi-spherical pulse;   a controller configured to control transmission of the three-dimensional semi-spherical pulse and to determine a position of reflectors within the object based on a known position of the spherical center point of the apparent point-source transmit transducer, known positions of the elements of the first and second pluralities of receive transducer elements, a time at which the three-dimensional semi-spherical pulse was transmitted, and times at which the echoes are received.   
     
     
         2 . The system of  claim 1 , wherein the first apparent point-source transmit transducer is convex relative to the target object. 
     
     
         3 . The system of  claim 1 , wherein the first apparent point-source transmit transducer is concave relative to the target object. 
     
     
         4 . The system of  claim 1 , wherein the first apparent point-source transmit transducer is shaped as a spherical section that is greater than half a sphere. 
     
     
         5 . The system of  claim 1 , wherein the first apparent point-source transmit transducer is shaped as a spherical section that is less than half a sphere. 
     
     
         6 . The system of  claim 1 , wherein the first apparent point-source transmit transducer is shaped as a spherical section that is half a sphere. 
     
     
         7 . The system of  claim 1 , wherein the first apparent point-source transmit transducer has a spherical radius of between 0.2 mm and 10 mm. 
     
     
         8 . The system of  claim 1 , wherein the first apparent point-source transmit transducer is configured to transmit ultrasound signals at a first frequency range. 
     
     
         9 . The system of  claim 1 , wherein the first apparent point-source transmit transducer comprises a shell of piezoelectric material with a constant thickness. 
     
     
         10 . The system of  claim 8  further comprising a second apparent point-source transmit transducer with a spherical radius and configured to transmit ultrasound signals at a second frequency range, the second frequency range being different than the first frequency range. 
     
     
         11 . The system of  claim 1 , wherein the apparent point-source transmit transducer comprises a shell having a constant-thickness made of a continuous piezoelectric material. 
     
     
         12 . The system of  claim 1 , wherein the apparent point-source transmit transducer comprises a shell having a constant-thickness made of a segmented piezoelectric material, 
     
     
         13 . The system of  claim 1 , wherein the apparent point-source transmit transducer comprises a plurality of segments arranged into the spherical shape, wherein all segments are configured to transmit ultrasound signals simultaneously. 
     
     
         14 . The system of  claim 1 , further comprising a computer readable memory containing data describing a position of the spherical center point of the apparent point-source transmit transducer relative to at least one element of the first plurality of receive transducer elements. 
     
     
         15 . The system of  claim 1 , further comprising a computer readable memory containing an adjustment factor representing apparent path segment equal to a distance from a surface of the first apparent point-source transmit transducer to the spherical center point. 
     
     
         16 . The system of  claim 1 , wherein each of the first plurality of receive elements and the second plurality of receive elements has a circular shape.