System and method of operating microfabricated ultrasonic transducers for harmonic imaging

• US 20050124882A1
• Filed: 10/04/2004
• Published: 06/09/2005
• Est. Priority Date: 02/14/2003
• Status: Active Grant

• Current Assignee: Siemens Medical Solutions USA Incorporated (Siemens AG)
• Original Assignee: Siemens Medical Solutions USA Incorporated (Siemens AG)
• Inventors: Ladabaum, Igal, Panda, Satchi
• Granted Patent: US 7,635,332 B2
• Time in Patent Office: Days
• US Class Current: 600/437
• CPC Class Codes: B06B 1/0215 for generating pulses, e.g. bursts of oscillations, envelopes
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type
• CPC Class Codes: B06B 2201/51 Electrostatic transducer
• CPC Class Codes: B06B 2201/76 Medical, dental
• CPC Class Codes: G01S 15/8925 the array being a two-dimensional transducer configuration, i.e. matrix or orthogonal linear arrays
• CPC Class Codes: G01S 15/8959 using coded signals for correlation purposes
• CPC Class Codes: G01S 15/8963 using pulse inversion
• CPC Class Codes: G01S 7/52038 involving non-linear properties of the propagation medium or of the reflective target
• CPC Class Codes: G01S 7/52085 Details related to the ultrasound signal acquisition, e.g. scan sequences control of medical diagnostic ultrasound devices A61B8/54

Abstract

A capacitive microfabricated ultrasonic transducer (cMUT) is operated to improve its performance during harmonic imaging in non-linear media, such as in contrast agents or in human tissue. The cMUT is operated by inverting the transmit waveform to adjacently spaced azimuth elements, and combining at least two additional firings without adjacent inversion, for each transmit vector, thereby canceling the second harmonic generation of the cMUT; and thus, the performance of harmonic imaging using the cMUTs can achieve improvement.

Claims

1. A method of ultrasonically imaging an object that reduces undesired transmitted harmonic distortion comprising the steps of:

generating a plurality of transmit waveforms centered around a predetermined fundamental frequency from a plurality of microfabricated ultrasonic transducer transmit elements that are within a microfabricated transducer array, wherein at least one of the plurality of transmit waveforms generated contains the fundamental frequency and certain harmonic frequencies;

detecting return waveforms associated with the transmit waveforms that are received by microfabricated ultrasonic transducer receive elements within the microfabricated transducer array and generating return signals corresponding thereto; and

combining the return signals such that the transmitted fundamental frequency and the transmitted certain harmonic frequencies are minimized, thereby providing data which represents a harmonic image of the object having reduced transmitted harmonic distortion therein.

2. The method according to claim 1 wherein:

the step of generating the plurality of transmit waveforms applies a transmit signal to different transducer transmit elements, the transmit signal applied to the different transducer transmit elements differing in a delay profile; and

harmonic frequencies of the transmit waveforms with greatly reduced fundamental frequency component are generated by alternating the polarity of the transmit signal applied to adjacent transducer transmit elements.

3. The method according to claim 1, wherein the step of generating the plurality of transmit waveforms includes the steps of:

repeating the steps of generating, detecting, and combining for each of a plurality of vectors, each vector formed from three transmit waveforms and three associated return signals.

4. The method according to claim 3, wherein the three transmit waveforms include:

a first transmit waveform;

a second transmit waveform that is inverted from the first transmit waveform; and

a third transmit waveform that contains a greatly reduced fundamental frequency component.

5. The method according to claim 4, wherein the first, second and third transmit waveforms are sequentially generated.

6. The method according to claim 5, wherein the step of combining implements the algorithm F1+F2−

(2*F3), wherein F1 is the received voltage v. time data from the first transmit waveform, F2 is the received voltage v. time data from the second transmit waveform, and F3 is the received voltage v. time data from the third transmit waveform.

7. The method according to claim 1, wherein the step of generating the plurality of transmit waveforms includes the step of generating arbitrary signals that are applied to different transducer transmit elements;

and

the step of detecting detects the return waveform corresponding to the generated arbitrary signals and generates return signals corresponding thereto; and

the step of combining the return signals includes combining the return signals to minimize inherent asymmetries and distortions of the microfabricated transducer array.

8. The method according to claim 1 wherein the steps of generating and detecting are applied to multiple focal zones to improve cancellation of the fundamental frequency.

9. The method according to claim 1, wherein the steps of generating and receiving are performed independent of bias applied to the transducer transmit elements and the transducer receive elements.