How background noise shifts eigenvectors and increases eigenvalues in DTI |
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Authors: | Frederik Bernd Laun Lothar Rudi Schad Jan Klein Bram Stieltjes |
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Affiliation: | 1. Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany 2. Lehrstuhl für Computerunterstützte Klinische Medizin, Medizinische Fakult?t Mannheim, Universit?t Heidelberg, Mannheim, Germany 3. MeVis Research, Bremen, Germany
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Abstract: | Indroduction The signal-to-noise ratio of in vivo diffusion tensor imaging (DTI) is usually very limited, especially if high resolution
data is acquired. In a variety of settings, the signal of diffusion weighted images can drop below the background noise level
yielding an underestimated diffusion constant. In this work, we report two new artefacts in DTI that are important in this
regime.
Methods Both artifacts are described analytically and numerically and are demonstrated in DTI phantoms and in subjects in vivo.
Results First, eigenvectors are systematically shifted towards distinct ‘attractive’ orientations of the gradient scheme. Second,
certain eigenvalues can be overestimated due to the underestimation of the measured diffusion, which can result in the misordering
of eigenvalues
Discussion We show that these effects are relevant for current clinical settings of DTI. |
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Keywords: | Diffusion tensor imaging Eigenvector shift Background noise Eigenvalues Overestimation Artefacts High b value |
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