Optical clearing agents improve photoacoustic imaging in the optical diffusive regime

Area of Science:

• Biomedical Optics
• Medical Imaging
• Acoustic Microscopy

Background:

• Acoustic resolution photoacoustic microscopy (AR-PAM) offers high-resolution imaging of microvasculature.
• Image quality and signal amplitude in AR-PAM degrade with depth due to light scattering and acoustic attenuation.
• Optical clearing techniques can improve light penetration in tissues, but their effect on AR-PAM is not well understood.

Purpose of the Study:

• To investigate the efficacy of optical clearing agents (OCAs) in enhancing AR-PAM signal amplitude and imaging depth.
• To evaluate the impact of different OCAs on photoacoustic detection in ex vivo and in vivo rat skin models.

Main Methods:

• Ex vivo study applying various OCAs to rat dorsal skin to assess photoacoustic signal changes.
• In vivo testing of selected OCAs with penetration enhancers (PEG-400, glycerol) and DMSO.
• Quantitative analysis of photoacoustic amplitude and image quality at different depths.

Main Results:

• Three OCAs demonstrated improved photoacoustic amplitude in ex vivo tests.
• PEG-400 with a penetration enhancer significantly boosted photoacoustic amplitude for deep vessel imaging in vivo.
• Glycerol alone improved image quality of superficial vessels, whereas DMSO application reduced photoacoustic amplitude.

Conclusions:

• OCAs can be effectively utilized to enhance AR-PAM performance.
• Specific OCAs like PEG-400 and glycerol show promise for improving the imaging of microvasculature at greater depths.
• The choice of OCA and penetration enhancer is crucial for optimizing AR-PAM for different imaging scenarios.