Near-infrared optical-resolution photoacoustic microscopy

Area of Science:

• Biomedical Optics
• Medical Imaging
• Photoacoustic Microscopy

Background:

• Visible light imaging is limited by optical attenuation in biological tissues.
• Near-infrared (NIR) light offers reduced attenuation, enabling deeper tissue penetration.
• Optical-resolution photoacoustic microscopy (OR-PAM) combines optical excitation with ultrasound detection.

Purpose of the Study:

• To demonstrate the capabilities of near-infrared optical-resolution photoacoustic microscopy (NIR-OR-PAM) using 1046 nm illumination.
• To evaluate the penetration depth and resolution of NIR-OR-PAM in biological tissues.
• To explore potential contrast mechanisms, such as lipid imaging, with NIR-OR-PAM.

Main Methods:

• Utilized a 1046 nm laser for optical excitation in OR-PAM.
• Performed ex vivo imaging in chicken breast tissue to assess penetration depth and resolution.
• Validated deep imaging in vivo using mouse ear and mouse brain models.

Main Results:

• Achieved an imaging penetration depth of 3.2 mm in chicken breast tissue within ANSI safety limits (100 mJ/cm²).
• Demonstrated superior resolution with NIR-OR-PAM compared to visible light OR-PAM (570 nm) beyond 0.6 mm depth.
• Successfully validated deep tissue imaging in mouse ear and brain models.
• Explored the potential for lipid contrast imaging using NIR-OR-PAM.

Conclusions:

• NIR-OR-PAM significantly enhances imaging depth in biological tissues compared to visible light OR-PAM.
• The 1046 nm illumination provides a valuable tool for deep-tissue biomedical imaging.
• NIR-OR-PAM shows promise for various applications, including lipid imaging and in vivo deep-tissue studies.