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Lübeck, Germany

Horstmann J.,Medical Laser Center Lubeck | Brinkmann R.,Medical Laser Center Lubeck | Brinkmann R.,University of Lubeck
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2014

We introduce an innovative detection approach for photoacoustic tomography. The pressure induced surface displacement is obtained in 2D by Electronic Speckle Pattern Interferometry (ESPI) in a repetitive measurement with a variable time delay between excitation- and detection pulses. The detection approach works without any physical contact to the object surface and is very versatile in terms of an adjustable object surface area and an adjustable temporal sampling rate. Furthermore, the approach is potentially very fast by the use of a high speed camera and a high repetition laser excitation and detection. In a proof of concept measurement, transparent silicone cubes with black silicone sphere absorbers are measured. In order to validate the acquired displacement data, the pressure is measured using a lipstick needle hydrophone and correlated to the measured displacement. © 2014 SPIE.

Horstmann J.,Medical Laser Center Lubeck | Brinkmann R.,Medical Laser Center Lubeck | Brinkmann R.,University of Lubeck
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2013

An innovative very fast non-contact imaging technique for Photoacoustic Tomography is introduced. It is based on holographic optical speckle detection of a transiently altering surface topography for the reconstruction of absorbing targets. The surface movement is obtained by parallel recording of speckle phase changes known as Electronic Speckle Pattern Interferometry. Due to parallelized 2-D camera detection and repetitive excitation with variable delay with respect to the image acquisition, data recording of whole volumes for Photoacoustic Imaging can be completed in times far below one second. The size of the detected area is scalable by optical magnification. As a proof of concept, an interferometric setup is realized, capable of surface displacement detection with an axial resolution of less than 3 nm. The potential of the proposed method for in vivo Photoacoustic Imaging is discussed.

Rohde I.,University of Lubeck | Brinkmann R.,University of Lubeck | Brinkmann R.,Medical Laser Center Lubeck
Journal of Optics (United Kingdom) | Year: 2014

An intracavity frequency doubled, Q-switched Nd:YLF emitting at a wavelength of 527 nm was designed with the goal to temporally stretch the Q-switched pulses up to some microseconds at pulse energies of several millijoules. With different resonator configurations pulse durations between 12 μs and 3 μs with energies of 1 mJ-4.5 mJ have been achieved, which is demanded for an application in ophthalmology. For tighter intracavity foci and high pump power, however, strong power modulations by trains of picosecond pulses on the rear flank of the microsecond pulses were observed, indicating the occurrence of cascading nonlinearities and mode-locking. Simultaneously a significant increase of the fundamental spectrum up to 5 nm was found. A similar effect, which is referred to as gain broadening, has previously been observed by using ppKTP for intracavity second harmonic generation. This is, to the best of our knowledge, the first observation of this effect with unpoled second harmonic media. © 2014 IOP Publishing Ltd.

Hagen-Eggert M.,Medical Laser Center Lubeck | Hillmann D.,Thorlabs GmbH Lubeck | Koch P.,Thorlabs GmbH Lubeck | Huttmann G.,Institute of Biomedical Optics Lubeck
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2011

Diffusion-sensitive optical coherence tomography (DS-OCT) is presented as a functional extension to OCT. Fluctuations of signal intensity and phase, which are caused by Brownian motion, are analysed by an autocorrelation function similar to dynamic light scattering measurements. Based on an ultra-fast Fourier-domain OCT, DS-OCT can determine quantitatively diffusion properties with high depth resolution, e.g. the hydrodynamic diameter of colloidal suspensions. Performance of DS-OCT is demonstrated with polystyrene particle suspensions and compared to conventional DLS measurements. Applications for DS-OCT may be found in the measurement of particle size distributions of inhomogeneous samples or measurements of diffusion properties at boundary surfaces. Additionally, the method has the capability to become a useful benefit in clinical diagnostics, especially in ophthalmology, where the molecular compositions and pathological changes of anterior eye components could be detected. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Rohde I.,University of Lubeck | Masch J.-M.,University of Lubeck | Theisen-Kunde D.,Medical Laser Center Lubeck | Marczynski-Buhlow M.,University of Kiel | And 3 more authors.
Journal of Cardiac Surgery | Year: 2015

Background Transcatheter aortic valve implantation (TAVI) can result in paravalvular leakage and stent deformation in the presence of severe calcification. This study was undertaken to determine the efficacy of laser-assisted resection of calcific aortic valve leaflets as a method to minimize the effects of calcium on perivalvular leakage during TAVI. Methods A Q-switched Tm:YAG laser emitting at a wavelength of 2.01-μm was used to evaluate the cutting efficiency on highly calcified human aortic leaflets in vitro (N-=-10). A pulse energy of 4.3-mJ, a pulse duration of 0.8-1-μs, and a repetition rate of 1-kHz were used. The radiation was transmitted via a 200-μm core diameter quartz fiber. Resection was performed in a fiber-tissue contact mode on water-covered samples in a dish. The remnant particles were analyzed with respect to quantity and size by light microscopy. Results A resection rate of 40.4-±-22.2-mg/min on highly calcified aortic leaflets was achieved. This corresponds to a cutting speed of approximately 1-cm/min; a laser dissection time of 3-min per leaflet is expected. The majority of the remnant particles (85.4%) were <6-μm in diameter, with only 0.1% exceeding 300-μm. Conclusions The Q-switched Tm:YAG laser system showed promising results in cutting calcified aortic valves, by transmitting sufficient energy through a small flexible fiber. Catheter-based removal of aortic valve calcification may help to improve TAVI technology. doi: 10.1111/jocs.12481 (J Card Surg 2015;30:157-162) © 2014 Wiley Periodicals, Inc.

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