Quad-mode functional and molecular photoacoustic microscopy.

Area of Science:

• Biomedical Optics
• Photoacoustic Imaging
• Ultrasound Transducer Technology

Background:

• Conventional photoacoustic microscopy (PAM) faces limitations in balancing spatial resolution and penetration depth due to fixed system configurations.
• The single-scale imaging capability of traditional PAM restricts its utility in diverse biomedical research applications.

Purpose of the Study:

• To develop a novel quad-mode photoacoustic microscopy (QM-PAM) system capable of providing four complementary spatial resolutions and penetration depths within a single device.
• To overcome the inherent tradeoffs in conventional PAM systems for enhanced biomedical imaging.

Main Methods:

• Development of a dual-element, ring-shaped focused ultrasound transducer with central frequencies at 20 MHz and 40 MHz for complementary acoustic detection.
• Implementation of two optical excitation modes (tightly- and weakly-focused illumination) to complement the dual-element ultrasound transducer.
• Integration of dual-element acoustic detection with dual optical focusing modes to achieve four distinct imaging scales with consistent contrast and co-registered fields of view.

Main Results:

• Demonstration of a quad-mode photoacoustic microscopy (QM-PAM) system offering four imaging scales.
• Successful in vivo demonstration of multiscale morphological, functional, and molecular imaging in mouse models (head, leg, ear).
• Achieved complementary spatial resolutions and maximum penetration depths through combined optical and acoustic focusing strategies.

Conclusions:

• The developed QM-PAM system provides unprecedented scale flexibility, addressing limitations of conventional single-scale PAM.
• QM-PAM's multiscale imaging capability is expected to significantly broaden its applications in preclinical biomedical research.
• This technology offers a versatile platform for advanced in vivo imaging studies.