ULTRASOUND IMAGING USING APPARENT POINT-SOURCE TRANSMIT TRANSDUCER

• US 20150080727A1
• Filed: 05/15/2014
• Published: 03/19/2015
• Est. Priority Date: 09/13/2013
• Status: Active Grant

• Current Assignee: Maui Imaging, Inc.
• Original Assignee: Donald F. Specht, Josef R. Call
• Inventors: SPECHT, Donald F., CALL, Josef R.
• Granted Patent: US 9,883,848 B2
• Time in Patent Office: Days
• US Class Current: 600/443
• CPC Class Codes: A61B 8/4461 Features of the scanning mechanism, e.g. for moving the transducer within the housing of the probe
• CPC Class Codes: A61B 8/4483 characterised by features of the ultrasound transducer
• CPC Class Codes: A61B 8/483 involving the acquisition of a 3D volume of data
• CPC Class Codes: A61B 8/5207 involving processing of raw data to produce diagnostic data, e.g. for generating an image reconstruction G06T11/00
• CPC Class Codes: G01S 15/8913 using separate transducers for transmission and reception
• CPC Class Codes: G01S 15/8915 using a transducer array
• CPC Class Codes: G01S 15/8929 using a three-dimensional transducer configuration
• CPC Class Codes: G01S 15/8993 Three dimensional imaging systems
• CPC Class Codes: G01S 15/8995 Combining images from different aspect angles, e.g. spatial compounding
• CPC Class Codes: G01S 15/8997 using synthetic aperture techniques
• CPC Class Codes: G01S 7/52077 with means for elimination of unwanted signals, e.g. noise or interference
• CPC Class Codes: G01S 7/52079 Constructional features constructional features of transducers B06B; mounting transducers G10K11/00; constructional features of ultrasonic medical diagnostic devices A61B8/44

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.

Claims

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 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 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 element, 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 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 element is a position of the second spherical center point.

3. The method of claim 1, wherein the position of the receive element lies on a surface of the receive element.

4. The method of claim 1, further comprising repeating the receiving, determining, and producing steps with a plurality of receive 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 element is greater than a maximum coherent aperture length for an intended imaging application.

8. The method of claim 1, wherein calculating the total path distance comprises adding apparent path segment representing a distance from a convex transmit transducer surface of the apparent point-source transmit transducer to the spherical center point.

9. The method of claim 1, wherein calculating the total path distance comprises subtracting apparent path segment representing a distance from a concave transmit transducer surface of the apparent point-source transmit transducer to the spherical center point.

10. The method of claim 1, wherein the receive element has a circular shape.

11. 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.

12. The system of claim 11, wherein the first apparent point-source transmit transducer is convex relative to the target object.

13. The system of claim 11, wherein the first apparent point-source transmit transducer is concave relative to the target object.

14. The system of claim 11, wherein the first apparent point-source transmit transducer is shaped as a spherical section that is greater than half a sphere.

15. The system of claim 11, wherein the first apparent point-source transmit transducer is shaped as a spherical section that is less than half a sphere.

16. The system of claim 11, wherein the first apparent point-source transmit transducer is shaped as a spherical section that is half a sphere.

17. The system of claim 11, wherein the first apparent point-source transmit transducer has a spherical radius of between 0.2 mm and 10 mm.

18. The system of claim 11, wherein the first apparent point-source transmit transducer is configured to transmit ultrasound signals at a first frequency range.

19. The system of claim 11, wherein the first apparent point-source transmit transducer comprises a shell of piezoelectric material with a constant thickness.

20. The system of claim 18 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.

21. The system of claim 11, wherein the apparent point-source transmit transducer comprises a shell having a constant-thickness made of a continuous piezoelectric material.

22. The system of claim 11, wherein the apparent point-source transmit transducer comprises a shell having a constant-thickness made of a segmented piezoelectric material,

23. The system of claim 11, 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.

24. The system of claim 11, 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.

25. The system of claim 11, 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.

26. The system of claim 11, wherein each of the first plurality of receive elements and the second plurality of receive elements has a circular shape.

27-33. -33. (canceled)

36-56. -56. (canceled)