High acoustic numerical aperture photoacoustic microscopy with improved sensitivity

Area of Science:

• Biomedical Optics
• Acoustic Imaging
• Photoacoustic Microscopy

Background:

• Optical resolution photoacoustic microscopy (OR-PAM) sensitivity is limited by ultrasonic detection numerical aperture.
• Existing OR-PAM systems struggle to achieve optimal performance due to these limitations.

Purpose of the Study:

• To develop a novel OR-PAM system with a high acoustic numerical aperture (HNA-OR-PAM) to overcome sensitivity limitations.
• To enhance imaging performance, including sensitivity, penetration depth, and view angle.

Main Methods:

• Engineered an acoustic lens to achieve the highest possible acoustic numerical aperture (approximately 0.74) for a spherical concave lens.
• Developed a high acoustic numerical aperture OR-PAM (HNA-OR-PAM) system.

Main Results:

• Achieved a sensitivity improvement of approximately 160% compared to state-of-the-art OR-PAM.
• Enabled in vivo imaging of oxygen saturation with only 10-nJ pulse energy without averaging.
• Increased the photoacoustic view angle to 51.8 degrees, improving visibility of tilted features.
• Demonstrated enhanced imaging of weaker absorbers and deeper penetration.

Conclusions:

• The HNA-OR-PAM system significantly enhances sensitivity and imaging capabilities.
• The improved system allows for high-quality in vivo imaging with reduced energy requirements and an augmented view angle.
• This technology holds promise for advanced biomedical imaging applications.