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F-FYS-Naturvitenskap, fysikk

Correction of geometrical and intensity distortions in medical magnetic resonnance images with applications to neuroimaging

Tildelt: kr 1,3 mill.

MR images are degraded by a series of factors. The significance of these degradations increase with the speed of the pulse sequence. Surprisingly, for the chemical shift artifact of fat, degradations and loss of anatomical information is substantial for a ll pulse sequences, even for spin echo images. Intensity variations caused by magnetic field inhomogeneties are pronounced for rapid pulse sequences, with additional geometrical distortions in ultrafast pulse sequences. The aim of the thesis is to develop new methods to reduce or remove artifacts in images of spin echo, gradient echo and ultrafast pulse sequences. The methods will be tested in neuroimaging applications. The thesis work will start with the simplest case, which is removal of degradations in spin echo images. The aim is to remove geometrical distortions, chemical shift and intensity variations caused by susceptibility artifacts. The second major aim is to r educe the same artifacts in gradient echo images. This is much harder than in spin ec ho images because signal degradations caused by susceptibility artfacts are not reversed during image acquisition. The final goal is to implement and test promising methods for correction of geometrical distortions in echo planar images. Based on this exp erience, improved algorithms shall be developed.

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F-FYS-Naturvitenskap, fysikk

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