Trond Varslot

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PURPOSE We present an iterative framework for CT reconstruction from transmission ultrasound data which accurately and efficiently models the strong refraction effects that occur in our target application: Imaging the female breast. METHODS Our refractive ray tracing framework has its foundation in the fast marching method (FNMM) and it allows an accurate(More)
PURPOSE In this paper we show that optimization-based autofocus may be used to overcome the instabilities that have, until now, made high-resolution theoretically-exact tomographic reconstruction impractical. To our knowledge, this represents the first successful use of theoretically-exact reconstruction in helical micro computed tomography (micro-CT)(More)
In this paper we develop a method for synthetic-aperture radar (SAR) imaging through a dispersive medium. We consider the case when the sensor and scatterers are embedded in a known homogeneous dispersive material, the scene to be imaged lies on a known surface and the radar antenna flight path is an arbitrary but known smooth curve. The scattering is(More)
A simulation study is performed to present results concerning 3D aberration correction for harmonic imaging. Two different correction schemes (a pure time-delay correction and a time-delay and amplitude correction) are employed along with estimation based on either the received firstor second-harmonic frequency. An aberrating body wall is implemented as a(More)
In this paper we analyze the problem of optimal waveform design for syntheticaperture radar (SAR) imaging through a dispersive medium. We use a scalar model for wave propagation, together with the single-scattering approximation, and we assume that measurements are polluted with thermal noise whose statistics are known. For image formation, we use a(More)
PURPOSE The authors present a robust algorithm that removes the blurring and double-edge artifacts in high-resolution computed tomography (CT) images that are caused by misaligned scanner components. This alleviates the time-consuming process of physically aligning hardware, which is of particular benefit if components are moved or swapped frequently. (More)
Triphilic star-polyphiles are short-chain oligomeric molecules with a radial arrangement of hydrophilic, hydrocarbon and fluorocarbon chains linked to a common centre. They form a number of liquid crystalline structures when mixed with water. In this contribution we focus on a hexagonal liquid crystalline mesophase found in star-polyphiles as compared to(More)
A fast implementation of bilateral filtering is presented, which is based on an optimal expansion of the filter kernel into a sum of factorized terms. These terms are computed by minimizing the expansion error in the mean-square-error sense. This leads to a simple and elegant solution in terms of eigenvectors of a square matrix. In this way, the bilateral(More)
We report that a specific realization of Schwarz's triply periodic hexagonal minimal surface is isotropic with respect to the Doi-Ohta interface tensor and simultaneously has minimal packing and stretching frustration similar to those of the commonly found cubic bicontinuous mesophases. This hexagonal surface, of symmetry P6(3)/mmc with a lattice ratio of(More)