Imaging dermal blood flow through the intact rat skin with an optical clearing method

Area of Science:

• Biomedical Optics
• Microcirculation Imaging
• Peripheral Vascular Disease Diagnostics

Background:

• Noninvasive detection of skin microcirculation is crucial for diagnosing and treating peripheral vascular diseases.
• Current imaging techniques are often limited by light scattering in the skin.
• Optical clearing offers a potential solution to enhance imaging depth and resolution.

Purpose of the Study:

• To evaluate the efficacy of an optical clearing method using a PEG-400 and Thiazone mixture for noninvasive imaging of dermal blood flow.
• To assess the optical clearing effect on rat skin in vitro and in vivo.
• To demonstrate the application of laser speckle contrast imaging (LSCI) post-optical clearing.

Main Methods:

• Optical clearing effect evaluated using a spectrophotometer with an integrating sphere on ex vivo rat skin.
• A mixture of PEG-400 and Thiazone applied topically to rat skin.
• Laser speckle contrast imaging (LSCI) system used to image dermal blood flow in vivo.
• Reduced scattering coefficient measured at 630 nm to quantify optical clearing.

Main Results:

• The mixture reduced the skin's scattering coefficient by 40% within 40 minutes in vitro.
• In vivo, a 12-minute topical application rendered the skin transparent, allowing visualization of dermal vessels.
• Pure PEG-400 did not achieve significant optical clearing.
• Optical clearing enhanced LSCI by decreasing temporal contrast, facilitating blood flow imaging.

Conclusions:

• A topical mixture of PEG-400 and Thiazone effectively clears rat skin, significantly reducing scattering.
• This optical clearing method enables noninvasive in vivo imaging of dermal microcirculation using LSCI.
• The technique holds promise for improved diagnosis and monitoring of peripheral vascular conditions.