Hybrid CARS technology images label-free biopsies

Compiled by EuroPhotonics staff

A new technique takes the sting out of skin biopsies – in fact, it allows doctors to look for disease with no skin contact at all.

The label-free, in vivo 3-D optical biopsy uses a hybrid multiphoton tomography and coherent anti-Stokes Raman scattering (MPT-CARS) technique to glean information on skin morphology at a subcellular level; it also determines lipid and water content.

CARS images of psoriasis at the skin surface. Courtesy of JenLab GmbH.

The MPT-CARS instrument combines the clinical multiphoton tomograph DermaInspect from JenLab GmbH and an add-on CARS module based on APE GmbH’s optical parametric oscillator (OPO). The OPO provides the required second laser beam for CARS imaging. The CARS signal relies on the wavelength difference between DermaInspect’s tunable femtosecond pump laser beam and the OPO’s Stokes laser beam, which must be tuned to match vibrational modes of the molecule of interest.

To image the intratissue lipid distribution in patients who suffer from psoriasis, cancer and other skin diseases, the tomography MPT-CARS wavelengths were tuned to 811 and 1053 nm, respectively. The combined mean power of both beams did not exceed 50 mW. Standard acquisition time for an optical section was 7 s. Using a piezo-driven, high-numerical-aperture objective, the scientists obtained up to 20 sections per region of interest at various tissue depths.

They also investigated, in time-lapse studies, the distribution of topically applied lipid-water emulsions that are of interest to companies in the cosmetics and pharmaceutical industries.

Clinical studies are being conducted at the Charité hospital in Berlin as part of the German BMBF project ChemoPraevent to evaluate the potential of the device for early diagnosis of skin diseases, optimization of treatment procedures, evaluation of the efficacy of cosmetics and investigation of the side effects of drugs such as chemotherapy agents.

The findings were published online March 1, 2011, by Laser Physics Letters (doi: 10.1002/lapl.201110014).