Biocompatibility studies of percutanous implants in animal models usually involve numerous lethal biopsies for
subsequent morphometric analysis of the implant-tissue interface. A common drawback of the study protocol is
the restriction of the analysis to one final time point. In this study optical coherence tomography (OCT) was used
to visualize and enable quantification of the local skin anatomy in the vicinity of a percutaneous implant in an
animal model using hairless mice. Non invasive in vivo optical biopsies were taken on predetermined time points
after implantation and ex vivo in situ at the day of noticeable inflammation. The custom made Fourier-domain
OCT system was programmed for imaging with different scanning schemes. A spoke-pattern of 72 cross-sectional
scans which was centred at the midpoint of the circular shaped implants was acquired and worked best for the
in-vivo situation. Motion-artefact-free three-dimensional tomograms were obtained from the implant site before
excision and preparation for histology. Morphometric parameters such as epithelial downgrowth, distance
to normal growth and tissue thickness were extracted from the images with a simple segmentation algorithm.
Qualitatively, the OCT B-Scans are in good agreement with histological sections. Therefore, OCT can provide
additional valuable information about the implant-tissue interface at freely selectable time points before the
lethal biopsy. Locally confined quantitative assessments of tissue-implant interaction for in vivo postoperative
monitoring can be carried out.
The hearing performance with conventional hearing aids and cochlear implants is dramatically reduced in noisy environments and for sounds more complex than speech (e. g. music), partially due to the lack of localized sensorineural activation across different frequency regions with these devices. Laser light can be focused in a controlled manner and may provide more localized activation of the inner ear, the cochlea. We sought to assess whether visible light with parameters that could induce an optoacoustic effect (532 nm, 10-ns pulses) would activate the cochlea. Auditory brainstem responses (ABRs) were recorded preoperatively in anesthetized guinea pigs to confirm normal hearing. After opening the bulla, a 50-µm core-diameter optical fiber was positioned in the round window niche and directed toward the basilar membrane. Optically induced ABRs (OABRs), similar in shape to those of acoustic stimulation, were elicited with single pulses. The OABR peaks increased with energy level (0.6 to 23 µJ/pulse) and remained consistent even after 30 minutes of continuous stimulation at 13 µJ, indicating minimal or no stimulation-induced damage within the cochlea. Our findings demonstrate that visible light can effectively and reliably activate the cochlea without any apparent damage. Further studies are in progress to investigate the frequency-specific nature and mechanism of green light cochlear activation.
Fs-lasers are widely used for microsurgery and micromachining. Due to nonlinear interaction of ultrashort pulses with tissue or matter precisions of a few μm can be achieved. But particularly in the field of surgery this precision can not be obtained as the devices for diagnostics and treatment have to be changed due to separate systems. We show a combined system of a fs-laser and a Fourier-Domain optical coherence tomography (FD-OCT) enabling to cut and image the region of interest alternately. The FD-OCT offers non-invasive imaging at an axial resolution of 6, 2 μm and a transverse resolution of 3 μm in air which is comparable to the interaction zone of the fslaser-pulses. OCT-aided subsurface cutting is successfully demonstrated on biological ex-vito samples of porcine
cornea and larynx. Furthermore it appeared that in situ OCT imaging enables to monitor cuts produced with pulse energies close to the energy threshold. In conclusion, this setup demonstrates the potential of a system combining cutting and OCT imaging within the same optical setup without the need of changing devices.
Due to nonlinear interaction with optical transparent and scattering samples the femtosecond technology is a
very useful tool for high precision micro surgery on biological tissues. At the same time femtosecond lasers are
ideal light sources for imaging methods such as optical coherence tomography (OCT) due to the broad spectrum
of the laser, which is necessary for creating ultra short pulses. Using OCT structures within biological tissues
can be imaged non invasive with a resolution within the low m-range.
The combined use of an ultra short pulse laser for cutting of biological tissues as well as imaging via OCT is a
very interesting tool. It opens up a wide range of new surgery techniques and improves many existing methods
due to high precision and high flexibility of the cutting process.
Therefore we combined a femtosecond cutting system and a fourier domain OCT. In this attempt the OCT is
operated with an SLD and is used alternately to the cutting system. The OCT is integrated into the optical
path which enables in situ imaging of the surgery area before and after treatment.
Due to nonlinear interaction with optical transparent samples the femtosecond technology is a very useful tool
for high precision micro surgery on biological tissues. At the same time femtosecond lasers are ideal light sources
for imaging methods such as optical coherence tomography (OCT) due to the broad spectrum of the laser, which
is necessary for creating ultra short pulses. Using OCT structures within biological tissues can be imaged non
invasive with a resolution within the low μm-range. The combined use of an ultra short pulse laser for cutting of
biological tissues as well as imaging via OCT is a very interesting tool. It opens up a wide range of new surgery
techniques and improves many existing methods due to high precision and high flexibility of the cutting process.
Therefore we combined a femtosecond cutting system and a fourier domain OCT. In a first attempt the OCT is
driven with an SLD and is used alternately to the cutting system. The OCT is integrated into the optical path
which enables in situ imaging of the surgery area.
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