ABSTRACT
Since the first cross-sectional images of the human skin in vivo by high-frequency ultrasound were published in the early 1980s, numerous imaging techniques have been proposed for improving our knowledge of the morphology and physiology of the different skin layers in vivo. Ultrasound imaging at 20 to 25 MHz is nowadays the most widespread method (1-3), whereas ultra high-resolution ultrasound scanners operating in the 100 to 150 MHz range are still prototypes (4,5). Optical techniques, such as confocal microscopy, have provided new insight into the microscopic level of the outermost part of the skin (6-9); more recently, optical coherence tomography, with a 1 to 10 mm resolution range, seems very promising (10-12). The next key step in skin imaging is just starting: the combination of microscopic images coupled with localized spectroscopy as proposed with confocal Raman microscopy (13,14) or multiphoton microscopy (15,16).
