Optimization of multi-pulse sequences for nonlinear contrast agent imaging using a cMUT array.

Area of Science:

• Ultrasound Imaging
• Biomedical Engineering
• Medical Physics

Background:

• Capacitive micromachined ultrasonic transducer (cMUT) technology offers wide bandwidth for contrast agent imaging.
• Traditional multi-pulse imaging schemes like pulse inversion (PI) have limited efficiency with cMUTs due to their nonlinear characteristics.
• A new bias voltage modulation sequence (BVM) was developed to mitigate cMUT nonlinearities.

Purpose of the Study:

• To optimize contrast agent detection in cMUT imaging.
• To evaluate the combination of BVM with PI and/or chirp reversal (CR) for improved imaging performance.

Main Methods:

• Lipid encapsulated microbubbles were imaged in vitro using a 9-element cMUT linear array (4 MHz center frequency).
• Multiple imaging sequences were tested, including combinations of BVM, PI, and CR.
• Chirp excitations were used with a custom compression filter to extract nonlinear microbubble responses.

Main Results:

• Combining BVM with PI and CR effectively canceled nonlinear signals from the transducer.
• Sequences incorporating BVM increased contrast-to-tissue ratio by 10.0 dB (vs. PI) and 4.6 dB (vs. CR).
• The combination of BVM with CR and PI significantly improved contrast-to-noise ratio by +29 dB.

Conclusions:

• The integration of BVM with PI and CR offers superior contrast agent detection in cMUT imaging.
• The use of chirp signals and preserved nonlinear components contributes to enhanced imaging performance.
• This optimized multi-pulse sequence holds promise for advanced ultrasound contrast imaging applications.