Experimental evaluation of a non-linear coded excitation method for contrast imaging

Area of Science:

• Ultrasound imaging
• Acoustics
• Biomedical engineering

Background:

• Ultrasound contrast agents (UCAs) are microbubbles used to enhance image quality.
• Traditional pulse excitation signals can lead to suboptimal UCA detection.
• Chirp excitation has shown promise for improving UCA response in prior single-bubble studies.

Purpose of the Study:

• To evaluate the effectiveness of chirp excitation signals for detecting randomly distributed UCA bubbles.
• To compare the performance of chirp excitation against traditional pulse excitation for UCA imaging.

Main Methods:

• Computer simulations of randomly distributed UCA bubbles subjected to pulse and chirp excitations.
• Analysis of UCA echo response, including signal-to-noise ratio (SNR) and second harmonic generation.
• Experimental validation using SonoVue contrast agent in a water tank setup.

Main Results:

• Chirp excitation demonstrated a 10-13 dB increase in response compared to pulse excitation for distributed UCA bubbles in simulations.
• Second harmonic compression of simulated bubble echoes showed lower side-lobe levels with chirp excitation.
• Experimental results confirmed increased SNR and approximately 12 dB higher second harmonic signal with chirp excitation.

Conclusions:

• Chirp excitation offers a significant improvement over pulse excitation for UCA detection, enhancing both signal strength and image quality.
• The findings suggest chirp signals are beneficial for UCA-based ultrasound imaging, improving diagnostic capabilities.
• Both simulations and experimental data support the superiority of chirp excitation for UCA applications.