Spectral Imaging in Dermatology

This chapter will discuss the application of different optical approaches to the characterization of skin that has been taken from a patient, volunteer, or experimental animal, and studied ex vivo. Despite the fact that such samples can be prepared histologically, with fixation, thin-sectioning, and morphological or molecular staining, and subsequently studied with standard or confocal microscopes at high spatial resolution, the (patho)physiology of skin is sufficiently complex that the aid of additional optical techniques has been sought. The challenges being addressed extend from molecular, structural, and functional characterization to automated diagnosis, resolution of ambiguous or contentious classification dilemmas (typically associated with melanotic lesions), and postmortem investigations. Techniques used to help in these efforts range from conceptually simple reflectance and transmissive or fluorescence spectroscopy in the visible. +. range to imaging spectroscopy in the mid-infrared and multiphoton, lifetime, Raman, pump-probe approaches, and combinations thereof, along with the requisite analytical mathematical and image processing. In many cases, these ex vivo studies were used to generate preliminary results that would motivate applying a given technique to the task of in vivo screening, diagnosis, or surgical guidance. In addition to taking advantage of endogenous contrast, it is also possible to perform multiplexed immunostaining and utilize spectral imaging to help resolve the location and intensity of spectrally and/or spatially overlapping reporter chromogens or fluorophores. As the latter approach is not unique to skin samples, it will be discussed only briefly.