The aim of this study is a defined, visually based and camera controlled bone removal by a navigated CO2 laser on the
promontory of the inner ear. A precise and minimally traumatic opening procedure of the cochlea for the implantation of
a cochlear implant electrode (so-called cochleostomy) is intended. Harming the membrane linings of the inner ear can
result in damage of remaining organ functions (e.g. complete deafness or vertigo). A precise tissue removal by a laser-based
bone ablation system is investigated. Inside the borehole the pulsed laser beam is guided automatically over the
bone by using a two mirror galvanometric scanner. The ablation process is controlled by visual servoing. For the
detection of the boundary layers of the inner ear the ablation area is monitored by a color camera. The acquired pictures
are analyzed by image processing. The results of this analysis are used to control the process of laser ablation. This
publication describes the complete system including image processing algorithms and the concept for the resulting
distribution of single laser pulses. The system has been tested on human cochleae in ex-vivo studies. Further
developments could lead to safe intraoperative openings of the cochlea by a robot based surgical laser instrument.
Drilling and surface processing of bone and tooth tissue belongs to standard medical procedures (bores and embeddings
for implants, trepanation etc.). Small circular bores can be generally quickly produced with mechanical drills. However
problems arise at angled drilling, the need to execute drilling procedures without damaging of sensitive soft tissue
structures underneath the bone or the attempt to mill small non-circular cavities in hard tissue with high precision. We
present investigations on laser hard tissue "milling", which can be advantageous for solving these problems.
The processing of bone is done with a CO2 laser (10.6 &mgr;m) with pulse durations of 50 - 100 &mgr;s, combined with a PC-controlled
fast galvanic laser beam scanner and a fine water-spray, which helps keeping the ablation process effective
and without thermal side-effects.
Laser "milling" of non-circular cavities with 1 - 4 mm width and about 10 mm depth can be especially interesting for
dental implantology. In ex-vivo investigations we found conditions for fast laser processing of these cavities without
thermal damage and with minimised tapering. It included the exploration of different filling patterns (concentric rings,
crosshatch, parallel lines, etc.), definition of maximal pulse duration, repetition rate and laser power, and optimal water
spray position. The optimised results give evidence for the applicability of pulsed CO2 lasers for biologically tolerable
effective processing of deep cavities in hard tissue.
Drilling of bone and tooth tissue belongs to recurrent medical procedures (screw- and pin-bores, bores for implant inserting, trepanation etc.). Small round bores can be in general quickly produced with mechanical drills. Problems arise however by angled drilling, by the necessity to fulfill the drilling without damaging of sensitive soft tissue beneath the bone, or by the attempt to mill precisely noncircular small cavities. We present investigations on laser hard tissue "milling", which can be advantageous for solving these problems.
The "milling" is done with a CO2 laser (10.6 &mgr;m) with pulse duration of 50 - 100 &mgr;s, combined with a PC-controlled galvanic beam scanner and with a fine water-spray, which helps to avoid thermal side-effects. The damaging of underlying soft tissue can be prevented through control of the optical or acoustical ablation signal. The ablation of hard tissue is accompanied with a strong glowing, which is absent during the laser beam action on soft tissue. The acoustic signals from the diverse tissue types exhibit distinct differences in the spectral composition. Also computer image analysis could be a useful tool to control the operation.
Laser "milling" of noncircular cavities with 1 - 4 mm width and about 10 mm depth is particularly interesting for dental implantology. In ex-vivo investigations we found conditions for fast laser "milling" of the cavities without thermal damage and with minimal tapering. It included exploration of different filling patterns (concentric rings, crosshatch, parallel lines and their combinations), definition of maximal pulse duration, repetition rate and laser power, optimal position of the spray. The optimized results give evidences for the applicability of the CO2 laser for biologically tolerable "milling" of deep cavities in the hard tissue.
Non-contact laser osteotomy brings new opportunities in maxillofacial and other surgical fields, since it allows very precise pre-programmed incisions of arbitrary geometries. Laser osteotomy is however difficult, because bone is a tough composite material, which is at the same time sensitive to a temperature increase. Besides thermal side effects, practical laser applicability was limited until now because of very low cutting rates and limited incision depths. We discuss how to overcome these disadvantages by means of an optimal arrangement of thermo-mechanical ablation with a pulsed CO2 laser and with a water-spray as an assisting media. To the arrangement belong optimal duration, intensity and energy density of the laser pulses, as well as a multi-pass cutting procedure. We show that effective ablation of hard tissue with minor thermal damage is possible with relatively long CO2 laser pulses of 80 μs duration and average laser power up to 40 - 50 W. To overcome the depth limit we have developed a special scanning technique, which allows cutting of massive multilayer bones with a feasible rate.
Systems for automated image analysis are useful for a variety of tasks and their importance is still increasing due to technological advances and an increase of social acceptance. Especially in the field of driver assistance systems the progress in science has reached a level of high performance. Fully or partly autonomously guided vehicles, particularly for road-based traffic, pose high demands on the development of reliable algorithms due to the conditions imposed by natural environments. At the Institut fur Neuroinformatik, methods for analyzing driving relevant scenes by computer vision are developed in cooperation with several partners from the automobile industry. We introduce a system which extracts the important information from an image taken by a CCD camera installed at the rear view mirror in a car. The approach consists of a sequential and a parallel sensor and information processing. Three main tasks namely the initial segmentation (object detection), the object tracking and the object classification are realized by integration in the sequential branch and by fusion in the parallel branch. The main gain of this approach is given by the integrative coupling of different algorithms providing partly redundant information.
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