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HARDI (High Angular Resolution Diffusion Imaging) is a recent magnetic resonance imaging (MRI) technique for imaging water diffusion processes in fibrous tissues such as brain white matter and muscles. In this article we study left-invariant diffusion on the group of 3D rigid body movements (i.e. 3D Euclidean motion group) SE(3) and its application to(More)
We provide the explicit solutions of linear, left-invariant, diffusion equations and the corresponding resolvent equations on the 2D-Euclidean motion group SE(2) = R 2 T. These parabolic equations are forward Kolmogorov equations for well-known stochastic processes for contour enhancement and contour completion. The solutions are given by group convolution(More)
By means of a special type of wavelet unitary transform we construct an orientation score from a grey-value image. This orientation score is a complex-valued function on the 2D Euclidean motion group SE(2) and gives us explicit information on the presence of local orientations in an image. As the transform between image and orientation score is unitary we(More)
From an image we construct an invertible orientation score, which provides an overview of local orientations in an image. This orientation score is a function on the group SE(2) of both positions and orientations. It allows us to diffuse along multiple local line segments in an image. The transformation from image to orientation score amounts to(More)
A permanent hole burning study on the Fenna-Matthews-Olson, or FMO, antenna complex of the green sulfur bacterium Prosthecochloris aestuarii was carried out at 6 K. Excitation resulted not only in relatively sharp features resonant with the burn wavelength but also in broad absorbance changes in the wavelength region of 800-820 nm. The shape of the latter(More)
Our EPIDs have recently been equipped with Peltier-cooled CCD cameras. The CCD cooling dramatically reduced deteriorating effects of radiation damage on image quality. Over more than 600 days of clinical operation, the radiation induced noise contribution has remained stable at a very low level (1 SD < or = 0.15% of the camera dynamic range), in marked(More)
Many medical image processing problems require enhancement of crossing elongated structures. This problem can not easily be solved by commonly used coherence-enhancing diffusion methods. Therefore we propose a method for coherence-enhancing diffusion in the invertible orientation score of an image. In an orientation score, the local orientation is made an(More)
We have developed new methods for contrast transfer function (CTF) correction of tilted and/or thick specimens. In order to achieve higher resolutions in cryo-electron tomography (CryoET), it is necessary to account for the defocus gradient on a tilted specimen and possibly the defocus gradient within a thick specimen. CTF correction methods which account(More)
Defocus and twofold astigmatism are the key parameters governing the contrast transfer function (CTF) in transmission electron microscopy (TEM) of weak phase objects. We present a new algorithm to estimate these aberrations and the associated uncertainties. Tests show very good agreement between simulated and estimated defocus and astigmatism. We evaluate(More)
Cardiac catheter ablation is a minimally invasive medical procedure to treat patients with heart rhythm disorders. It is useful to know the positions of the catheters and electrodes during the intervention, e.g. for the automatization of cardiac mapping. Our goal is therefore to develop a robust image analysis method that can detect the catheters in X-ray(More)