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

Abstract

Noninvasive detection of skin microcirculation is very sig- nificant for clinical diagnosis and therapy of peripheral vascular dis- ease. In this study, an optical clearing method enables a laser speckle contrast imaging ?LSCI? technique to image dermal blood flow through intact rat skin. The optical clearing effect of rat skin in vitro caused by a mixture of PEG-400 and Thiazone is evaluated by a com- mercially available spectrophotometer with an integrating sphere. A LSCI system is applied to image the dermal blood flow of in vivo rat skin after topical treatment of the agents. The results show that the reduced scattering coefficient ?630 nm? is down to 60% of the initial value after 40 min of topical treatment of the mixture on skin in vitro. In vivo experimental results show that a 12-min treatment of the mix- ture on the epidermis can make the skin transparent and dermal ves- sels can be observed, while treatment with pure PEG-400 cannot. The process of skin optical clearing lasts, and the skin can be recovered by treatment of saline solution. Because optical clearing decreases the temporal contrast, dermal blood flow can be obtained by the laser speckle contrast imaging technique.