Nonlinear Microscopy Applied to Dermatology

Abstract

Abstract The application of nonlinear optical microscopy for tissue imaging has an early start in dermatology and is the subject of an increasing number of studies that are based on nonlinear optical microscopy. The term “dermatology” (Greek derma [skin] Greek logos [study]) was created in the late 1700s (Holubar & Schmidt, 1992). The early adaptation of nonlinear microscopy in dermal studies originates from two factors. First, unlike many internal organs, the accessibility of skin allows nonlinear microscopic imaging in the format of standard laboratory microscopes and does not require surgery or the use of endoscopic technology. Second, skin is a highly scattering tissue with large layer-by-layer variation in refractive index. Therefore, while there is good progress in noninvasive skin imaging using linear optical technology, the superior performance of nonlinear microscopy in highly scattering materials enables more rapid progress to be made in this field. For biomedical applications, the ideal case is to study in vivo human skin using minimally invasive optical imaging and spectroscopy techniques. In practice, this is not always possible, as in vivo imaging techniques do not provide resolution and biochemical information content comparable to that of traditional histology. Furthermore, some measurements, such as the determination of tissue genetic expression profiles, inevitably require specimen excision. When optical imaging can be obtained together with histological skin preparations from the same body region, very good comparison can still be made (Rajadhyaksha, González, et al., 1999). Alternatively, a better understanding of skin physiology can also be obtained by using two different in vivo optical techniques, including nonlinear optical microscopy methods, to study the same region of human in vivo skin (Masters & So, 1999, 2001). In this chapter, we are discussing human skin unless otherwise stated.