Selective microstructural images by modulated gradients in diffusion weighted imaging

A. ZWICK, M. CAPIGLIONI; GONZALO A. ALVAREZ

Taller; IV Taller de Resonancia Magnética; 2018

Diffusion weighted imaging in Magnetic Resonance (MRI) is a powerful non-invasive technique for microstructure characterization. However, attaining microstructure resolution is still a challenge as the MRI resolution is much larger. Resorting to tools from quantum information theory, we analytically derive the ultimate precision limits for estimating microstructure sizes as the one given by restriction lengths in diffusion processes with diffusion weighted MRI sequences. We provide the control conditions, exemplifying with routinely gradient waveforms and with generic geometries of the microstructures, to achieve this precision limit in the estimation considering limitations imposed by T2 relaxation. On the other hand, we optimize of the sequence control named "selective dynamical recoupling" (SDR)1,2 developed to enhance the sensitivity to pore sizes determination in restricted diffusion process due to its robustness against unavoidable noises which detriment the echo signal. We designed selective pore-size filters by optimally choosing experimental control variables. We characterize the filter performances under experimental limitations. These results offer a new mechanism to perform quantitative images selective on microstructural sizes.References:1- ?Coherent dynamical recoupling of diffusion-driven decoherence in magnetic resonance''. G.A. Álvarez, N. Shemesh, and L. Frydman. Phys. Rev. Lett. 111, 080404 (2013).2- ?Measuring small compartment dimensions by probing diffusion dynamics via Non-uniform Oscillating-Gradient Spin-Echo (NOGSE) NMR''. N. Shemesh, G.A. Álvarez, and L. Frydman. J. Magn. Reson. 237, 49 (2013). dami, S.M.; Orquera, P. B. Org. Lett. 2012, 34, 590-678.