Reflection-mode acousto-optic imaging using plane wave ultrasound pulses.

Area of Science:

• Biomedical optics
• Acoustic imaging
• Medical physics

Background:

• Acousto-optic imaging system performance is constrained by light fluence and acoustic pressure fields.
• Optimization of system geometry is often limited in clinical settings due to single-sided sample access and water tank infeasibility.

Purpose of the Study:

• Investigate performance enhancement of reflection-mode acousto-optic imaging.
• Compare plane wave ultrasound pulses against focused pulses using a linear ultrasound transducer array.

Main Methods:

• Numerical and experimental determination of acoustic pressure field distributions for varied transducer excitation patterns.
• Acquisition of acousto-optic images using laser speckle contrast measurements with plane wave and focused ultrasound pulses.
• Evaluation of different apodization patterns for transducer excitation.

Main Results:

• Nonsteered plane wave ultrasound pulses effectively reduce the influence of residual acoustic pressure field components on light modulation.
• Clear two-dimensional reconstructions of light fluence rate maps were achieved by shifting transducer apodization laterally.
• Plane wave ultrasound pulses demonstrated a mitigation of unwanted acoustic field effects compared to focused pulses.

Conclusions:

• Nonsteered plane wave ultrasound pulses offer superior imaging performance compared to focused pulses in the studied acousto-optic system geometry.
• This approach enhances contrast and resolution in optically scattering media.
• The findings suggest a viable method for improving acousto-optic imaging in challenging clinical scenarios.