Bubble-based acoustic radiation force using chirp insonation to reduce standing wave effects

Area of Science:

• Biomedical Engineering
• Acoustics
• Medical Imaging

Background:

• Bubble-based acoustic radiation force (ARF) is a technique used to measure local viscoelastic properties of biological tissues.
• High-intensity acoustic waves interacting with laser-generated bubbles cause displacements that are inversely proportional to the tissue's Young's modulus.
• Long acoustic pulse durations are often desirable for ARF measurements but are prone to standing wave artifacts that compromise displacement accuracy.

Purpose of the Study:

• To investigate the efficacy of chirp pulse acoustic radiation force (ARF) as a method to mitigate standing wave artifacts.
• To compare the performance of chirp pulses against traditional tone burst pulses in ARF measurements under varying standing wave conditions.

Main Methods:

• Chirp pulses with linear frequency sweeps (100, 200, 300 kHz) centered at 1.5 MHz were applied to glass beads in gelatin phantoms and laser-generated bubbles in porcine lenses.
• An ultrasound transducer was axially translated to systematically alter standing wave conditions.
• Bubble displacements were measured and compared between chirp pulses and 1.5 MHz tone burst pulses of identical duration and peak rarefactional pressure.

Main Results:

• Chirp pulse ARF demonstrated a significant reduction in standing wave artifacts compared to tone burst pulses.
• Bubble displacements were found to be proportional to acoustic intensity and bubble size, consistent with theoretical predictions.
• The chirp pulse method maintained measurement integrity across varied standing wave conditions.

Conclusions:

• Chirp pulse ARF is a promising technique for overcoming standing wave artifacts in viscoelastic property measurements.
• This approach enhances the reliability of bubble-based ARF, offering improved accuracy for tissue characterization.
• The findings support the use of chirp pulses for more robust ultrasound-based mechanical property assessments.