Multispectral photoacoustic microscopy based on an optical-acoustic objective

Area of Science:

• Biomedical optics
• Microscopy
• Acoustic imaging

Background:

• Photoacoustic microscopy (PAM) offers label-free imaging capabilities.
• Existing PAM systems face challenges with chromatic aberration and alignment.
• Multispectral imaging requires broad spectral coverage and high resolution.

Purpose of the Study:

• To develop a reflection-mode multispectral photoacoustic microscopy (PAM) system.
• To overcome limitations of chromatic aberration and improve optical-acoustic alignment.
• To achieve label-free concurrent imaging of multiple tissue components at high resolution.

Main Methods:

• Developed a novel integrated optical-acoustic objective combining a custom ultrasonic transducer and a reflective microscope objective.
• Utilized a wavelength-tunable optical-parametric-oscillator laser for ultrabroad spectral range (270-1300 nm) excitation.
• Achieved confocal alignment of optical excitation and acoustic detection with zero chromatic aberration.

Main Results:

• Demonstrated a near-constant lateral resolution of approximately 2.8 μm across the ultrabroad spectral range.
• Successfully performed label-free concurrent imaging of cell nucleus (DNA/RNA contrast at 270 nm), blood vessels (hemoglobin contrast at 532 nm), and sebaceous glands (lipid contrast at 1260 nm).
• Achieved imaging in a living mouse ear model at the same spatial scale for all targeted components.

Conclusions:

• The developed reflection-mode multispectral PAM system provides high-resolution, label-free imaging across UV, visible, and NIR spectral ranges.
• The novel optical-acoustic objective design eliminates chromatic aberration and ensures precise alignment, enhancing imaging performance.
• This technology enables simultaneous visualization of diverse biological structures, offering significant potential for biomedical research and diagnostics.