ARTICLE IN PRESSCongress Abstracts / Medical Laser Application 24 (2009) 120–142 125

120 fs) and a fiber-based system (Toptica, 90MHz,1090 nm, 20 fs) were used in combination with variousfiber bundles (Sumitomo Electrics Industries). Twominiaturized objectives were examined, a GRIN-lenssystem (GRINTECH) and a custom made system(Storz), with a numerical aperture of 0.75 and 0.6,respectively. The fluorescent dyes, fluorescein and cresylviolet acetate, were used on sample materials andexcised bladder wall tissue. Simulations of short-pulsepropagation in the fiber materials were done withLAB2-A.Results: First measurements with our two-photon micro-endoscope showed that it is possible to detect fluores-cence signals without compensating for linear and non-linear pulse broadening. The outer diameter is alreadycompatible with the working channel of a conventionalcystoscope. Furthermore, the optical performanceshowed a good image quality at high axial resolution.Consequently, intracellular details could be resolvedfrom bulky tissue with high-speed performance. Forfuture optimizations, the simulations indicate an effec-tive decrease of linear and non-linear pulse distortionsby mainly quadratic pre-chirping, which may beimplemented for example, using a simple gratingcompressor.Conclusion: The current microendoscope for two-photonimaging shows the potential to resolve intracellulardetails and can be integrated into a commercialendoscope. Two-photon endoscopy may be the possiblenext step to effectively overcome the limitations ofconfocal microendoscopy. In particular, the higherpenetration depth may contribute to a broader accep-tance for in-vivo tissue diagnostics.Acknowledgement: The work was carried out with thesupport of the ‘‘Bundesministerium fur Bildung undForschung (BMBF)’’ and the DFG Cluster of Excel-lence ‘‘Munich-Centre for Advanced Photonics’’.

doi: 10.1016/j.mla.2009.02.010

[2.04] Multiphoton imaging of skin

Karsten Koniga,b

aFaculty of Mechatronics and Physics, Saarland Uni-

versity, Campus, 66123 Saarbruecken, GermanybJenLab GmbH, Schillerstraße 1, 07745 Jena, Germany

Clinical multiphoton tomography and two-photonmicroendoscopy provide clinicians and researchers withhigh-resolution in-vivo optical biopsies based on two-photon autofluorescence, second harmonic generation,and fluorescence lifetime imaging. This review reflectsstate-of-the-art technology and reports on applicationsin the fields of early stage melanoma detection, skin

aging, nanoparticle imaging, tissue engineering, andin-situ screening of pharmaceutical and cosmetic pro-ducts. So far, more than 500 patients and volunteers inEurope, Asia, and Australia have been investigatedusing these novel molecular imaging tools.

The femtosecond multiphoton tomograph DermaIn-spects is the first multiphoton imaging system in clinicaluse. The novel tissue tomograph has a 0.5m long flexiblemirror arm in combination with piezo-driven focusingoptics and multiple single-photon-counting PMT detec-tors. The photodetectors are particularly useful forobtaining information about the extracellular matrix asthey simultaneous measure the two-photon autofluores-cence of elastin as well as the second harmonicgeneration of collagen. A major application is thein-vivo determination of the age index of the skin.

Multiphoton tomography has the potential to providenovel, non-invasive, high-resolution diagnostic tools ona cellular level under physiological conditions.

doi: 10.1016/j.mla.2009.02.011

[2.05] Optical monitoring of tissue coagulation during

MRI-assisted interstitial laser thermotherapy (ILTT)

Michael Pellera, Maximilian F. Reisera, Ronald Srokab

aJosef Lissner Laboratory for Biomedical Imaging,

Department of Clinical Radiology, University Hospital

of Munich, Marchioninistr.15, 81377 Munich, GermanybLaser Research Laboratory, LIFE Center, Ludwig

Maximilian University, Großhadern Medical Campus,

Marchioninistr. 23, 81377 Munich, Germany

Objective: Thermally altered tissue can be distinguishedfrom native tissue by its optical parameters. Thus, adevice, monitoring the evolution of diffuse backscat-tered test-light intensity, could detect this transition. Thepurpose of this study was to demonstrate technicalfeasibility of such a device, characterize its signalresponse during interstitial laser thermotherapy (ILTT)in comparison with MRI and to identify a switch-offparameter for ILTT.Material and methods: The backscattering light detector(BLD) is based on the interstitial measurement of adiffuse backscattered test light (HeNe laser: l=632 nm,P=5mW) describing optical changes depending onthe time at a certain position. The ILTT-inducedspread of the coagulation zones, in muscle and livertissue samples, were determined by macroscopicexamination and MRI (1.5 T). MRI monitoring in-cluded temperature-sensitive parameter maps and post-ILTT T2-weighted images. The results were thencorrelated with the position and the time-dependentBLD signal.