NMR Based Diffusion Pore Imaging: A novel imaging concept

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Diffusion weighted imaging is a widely applied magnetic resonance technique in medical imaging, that is applied routinely in diagnostics of acute stroke. It is a technique that is often used to detect cellular structures hindering the diffusive motion, and in particular to detect the orientation of white matter tracts. For example, main white matter tracts can be reconstructed in an impressive manner. In the early 1990s, Paul Callaghan could show that nuclear magnetic resonance diffusion experiments can yield further information about the cellular structure. In particular, he could show that the magnitude spectrum of the pore space function can be measured using short diffusion gradients. The experiment can be interpreted as a scattering experiment. Unfortunately - as in x-ray crystallography - the phase information is lost, and an inverse Fourier transform cannot be performed. Thus the cell shape cannot be detected unambiguously.Recently, we could show theoretically how the shape of the pore can be measured unambiguously by modifying the temporal profile of the diffusion weighting magnetic field gradients. This is indeed a new imaging method, since the phased spectrum of the pore can be acquired, and since the inverse Fourier transform can be performed, similarly as in magnetic resonance tomography. The aim of this proposal is the experimental verification of the existing theoretical results. Therefore it is planned to- perform an in-depth analysis of the pore imaging technique in order to chose phantoms, sequence parameters etc. appropriately- perform pore imaging using hyperpolarized xenon as model for lung alveoli - perform pore imaging using water-filled capillaries as model for axonsBesides the pore imaging approach, the proposed modification of the diffusion weighting gradients yields a new magnetic resonance imaging contrast: The diffusion-weighted phase. Therefore, it is planned to analyze the properties of this new contrast, and perform magnetic resonance imaging based on it.