Reflectance confocal microscopy of human skin using near infrared femtosecond laser pulses

Abstract

The optical properties of the skin including reflectance are affected by aging, dehydration, and diseases and, therefore, can be used for non-invasive diagnosis. Multiphoton tomography (MPT) based on near-infrared (NIR) femtosecond (fs) lasers provide 3D optical biopsies with high-resolution (~300 nm). MPT has been used as a rapid diagnostic tool e.g., for the detection of malignant melanoma, the optimization of treatments as well as the investigation of the live 3D architecture of skin under various clinical conditions. So far, imaging is based on endogenous fluorophores e.g., elastin and metabolic coenzymes NAD(P)H and FAD as well as second harmonic generation (SHG) of the extracellular matrix protein collagen. The new tomograph MPTcompact is a multimodal high-resolution optical imaging tomograph with a reflectance confocal microscopy (RCM) module. The system employs 80 MHz NIR femtosecond laser pulses at 780 nm. In contrast to conventional RCM with a continuous wave NIR laser, the new tomograph provides the possibility of RCM with femtosecond laser pulses. The use of these ultrashort laser pulses has the advantage of confocal one-photon imaging (RCM) as well as two-photon autofluorescence and SHG imaging. This paper demonstrates clinical high-resolution reflectance confocal imaging of in vivo skin of volunteers and patients with dermatological disorders, in particular, malignant pigmented lesions.