2-PHOTON DEEP TISSUE EX-VIVO IMAGING OF MOUSE DERMAL AND SUBCUTANEOUSSTRUCTURES

The non-invasive determination of deep tissue three dimensional struct ure and biochemistry is the ultimate goal of optical biopsy. Two-photo n microscopy has been shown to be a particularly promising approach. T he use of infrared radiation in two-photon microscopy is critical for deep tissue imaging since tissue absorption and scattering coefficient s for infrared light are much lower than for shorter wavelengths. Equa lly important, tissue photodamage is localized to the focal region whe re fluorescence excitation occurs. This report demonstrates that, by m eans of high resolution two-photon microscopy, skin and subcutaneous t issue structures can be imaged utilizing their endogenous fluorescence . From a freshly prepared tissue punch of a mouse ear, we were able to resolve in 3D both the living and cornified keratinocytes in the epid ermis, the collagen/elastin fibers in the dermal layer and the cartila ge in the subcutaneous layer. The ability to noninvasively acquire 3D structures of these tissue components may find application in areas su ch as non-invasive diagnosis of skin cancer and the study of wound hea ling processes. (C) 1998 Optical Society of America.