Optical coherence tomography (OCT) has been developed during the last 10 years as a new noninvasive imaging tool and has been applied to diagnose different ocular and skin diseases. This technique has been modified for cross–sectional imaging of dental structures. In this first preliminary study the technique was applied to obtain tomographic images of extracted sound and decayed human teeth in order to evaluate its possible diagnostic potential for dental applications. Classical OCT images based on reflectivity measurements and phase retardation images using polarization–sensitive OCT were recorded. It was demonstrated that polarization–sensitive OCT can provide additional information which is probably related to the mineralization status and/or the scattering properties of the dental material. One of the attractive features of OCT is that it uses near–infrared light instead of ionizing radiation. Furthermore, high transversal and depth resolution on the order of 10 μm can be obtained. Present limitations, e.g. the limited penetration depth, and possible solutions are discussed.

We propose a new approach for automatic road extraction from aerial imagery with a model and a strategy mainly based on the multi-scale detection of roads in combination with geometry-constrained edge extraction using snakes. A main advantage of our approach is, that it allows for the rst time a bridging of shadows and partially occluded areas using the heavily disturbed evidence in the image. Additionally, it has only few parameters to be adjusted. The road network is constructed after extracting crossings with varying shape and topology. We show the feasibility of the approach not only by presenting reasonable results but also by e v aluating them quantitatively based on ground truth.A revised version of this paper will appear in Machine Vision and Applications, 2000.

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Non-invasive biometry of the anterior structures of the human eye can be performed with unprecedented precision of 8-10 microns and a resolution of approximately 9 microns by partial coherence interferometry, which has the potential to assess the effect of cycloplegia on the ocular components of the anterior eye segment, to further improve the precision to 1-2 microns by the use of these agents and to quantify the amount of residual accommodations in different states of cycloplegia. In addition, the anterior chamber depth, the thickness of the crystalline lens, their changes during accommodation, as well as the movement of the anterior and posterior lens pole during accommodation can be quantified objectively and accurately to investigate the mechanism of accommodation.

In nondispersive media, the minimum distance that can be resolved by partial coherence interferometry (PCI) and optical coherence tomography (OCT) is inversely proportional to the source spectral bandwidth. Dispersion tends to increase the signal width and to degrade the resolution. We analyze the situation for PCI ranging and OCT imaging of ocular structures. It can be shown that for each ocular segment an optimum source bandwidth yielding optimum resolution exists. If the resolution is to be improved beyond this point, the group dispersion of the ocular media has to be compensated. With the use of a dispersion compensating element, and employing a broadband superluminescent diode, we demonstrate a resolution of 5 μm in the retina of both a model eye and a human eye in vivo. This is an improvement by a factor of 2-3 as compared to currently used instruments. © 1999 Society of Photo-Optical Instrumentation Engineers.

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Our data suggest that rebound of MS disease activity affects a subgroup of patients (11.9%), especially those with low disease activity before natalizumab therapy and a longer treatment gap after its withdrawal.