Ultrasound imaging using apparent point-source transmit transducer
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.
1. A method of imaging an object with ultrasound energy, the method comprising the steps of:
transmitting an un-focused ultrasound signal into a target medium from apparent point-source transmit transducer comprising a shell of piezoelectric material shaped as a spherical section with a spherical center point;
receiving echoes reflected by a reflector in the target medium with an omnidirectional receive transducer element that is different than the apparent point-source transmit transducer;
determining a position of the reflector within the target medium by obtaining element position data describing a position of the spherical center point of the apparent point-source transmit transducer and a position of the receive transducer element, calculating a total path distance as a sum of a first distance between the spherical center point and the reflector and a second distance between the reflector and the receive transducer element, wherein calculating the total path distance comprises adding an apparent path segment representing a distance from a convex transmit transducer surface of the apparent point-source transmit transducer to the spherical center point, and determining a locus of possible points at which the reflector may lie; and
producing an image of the reflector.
2. The method of claim 1 , wherein the receive transducer element comprises a shell of piezoelectric material shaped as a spherical section with a second spherical center point and wherein the position of the receive transducer element is a position of the second spherical center point.
3. The method of claim 1 , wherein the position of the receive transducer element lies on a surface of the receive transducer element.
4. The method of claim 1 , further comprising repeating the receiving, determining, and producing steps with a plurality of receive transducer elements in a common receive aperture.
5. The method of claim 4 , further comprising repeating the receiving, determining, and producing with elements of a plurality of receive apertures.
6. The method of claim 1 , further comprising repeating the transmitting step with a separate second, apparent point-source transmit transducer.
7. The method of claim 1 , wherein a straight-line distance between the apparent point-source transmit transducer and the receive transducer element is greater than a maximum coherent aperture length for an intended imaging application.
8. The method of claim 1 , wherein the receive transducer element has a circular shape.
9. A method of imaging an object with ultrasound energy, the method comprising the steps of:
transmitting an un-focused ultrasound signal into a target medium from apparent point-source transmit transducer comprising a shell of piezoelectric material shaped as a spherical section with a spherical center point;
receiving echoes reflected by a reflector in the target medium with an omnidirectional receive transducer element that is different than the apparent point-source transmit transducer;
determining a position of the reflector within the target medium by obtaining element position data describing a position of the spherical center point of the apparent point-source transmit transducer and a position of the receive transducer element, calculating a total path distance as a sum of a first distance between the spherical center point and the reflector and a second distance between the reflector and the receive transducer element, wherein calculating the total path distance comprises subtracting an apparent path segment representing a distance from a concave transmit transducer surface of the apparent point-source transmit transducer to the spherical center point, and determining a locus of possible points at which the reflector may lie; and
producing an image of the reflector.
10. The method of claim 9 , wherein the receive transducer element comprises a shell of piezoelectric material shaped as a spherical section with a second spherical center point and wherein the position of the receive transducer element is a position of the second spherical center point.
11. The method of claim 9 , wherein the position of the receive transducer element lies on a surface of the receive transducer element.
12. The method of claim 9 , further comprising repeating the receiving, determining, and producing steps with a plurality of receive elements in a common receive aperture.
13. The method of claim 12 , further comprising repeating the receiving, determining, and producing with elements of a plurality of receive apertures.
14. The method of claim 9 , further comprising repeating the transmitting step with a separate second, apparent point-source transmit transducer.
15. The method of claim 9 , wherein a straight-line distance between the apparent point-source transmit transducer and the receive transducer element is greater than a maximum coherent aperture length for an intended imaging application.
16. The method of claim 9 , wherein the receive transducer element has a circular shape.