In vivo non-invasive Multiphoton Tomography of Human Skin
with Subcellular Spatial and Picosecond Time Resolution
Karsten König1,2, Iris Riemann1, Alexander Ehlers1, and Andrei Tchernook2
1
Fraunhofer Institute of Biomedical Technology (IBMT), D-66386 St. Ingbert
2
JenLab GmbH, Schillerstrasse 1, D-07745 Jena, Germany
We report on the near infrared laser technology multiphoton tomography based on femtosecond
lasers and the high resolution 4D imaging tool DermaInspect for non-invasive detection of
intratissue agents and their influence on cellular metabolism based on multiphoton autofluorescence
imaging (MAI) and second harmonic generation (SHG). Femtosecond laser pulses in the spectral
range of 750 nm to 850 nm have been used to image in vivo human skin with subcellular spatial and
picosecond temporal resolution. The non-linear induced autofluorescence of skin tissues originates
mainly from naturally endogenous fluorophores/protein structures like NAD(P)H, flavins, keratin,
collagen, elastin, porphyrins and melanin. Bacteria emit in the blue/green spectral range due to
NAD(P)H and flavoproteins and, in certain cases, in the red spectral range due to the biosynthesis
of Zn-porphyrins, coproporphyrin and protoporphyrin. Collagen and exogenous noncentrosymmetric molecules can be detected by SHG signals.
The system DermaInspect consists of a wavelength-tunable compact 80/90 MHz Ti:sapphire laser,
a scan module with galvo scan mirrors, piezo-driven objective, fast photon detector and timeresolved single photon counting unit. It can be used to perform optical sectioning and 3D
autofluorescence lifetime imaging (-mapping) with 1 µm spatial resolution, 10 nm spectral
resolution, and 270 ps temporal resolution. The parameter fluorescence lifetime depends on the type
of fluorophore and its microenvironment and can be used to distinguish pharmaceutical and
cosmetical agents from cellular background and to gain information on pharmacokinetics.
References.
[1] K. König, I. Riemann: High-resolution multiphoton tomography of human skin with subcellular
spatial resolution and picosecond time resolution. J. Biomed Optics 2003; 8:450-459
[2] K. König, A. Ehlers, F. Stracke, I. Riemann: In vivo Drug Screening in Human Skin Using
Femtosecond Laser Multiphoton Tomography. Skin Pharmacol Physiol 2006; 19:78-88