Selective microstructural images by modulated gradients in diffusion weighted imaging

ANALIA ZWICK; MILENA CAPIGLIONI; GONZALO A. ALVAREZ

Buenos Aires

Workshop; IV Taller de Resonancia Magnética; 2018

Taller de Resonancia Magnética

Diffusion weighted imaging in Magnetic Resonance (MRI) is a powerful non-invasivetechnique for microstructure characterization. However, attaining microstructure resolution is stilla challenge as the MRI resolution is much larger. Resorting to tools from quantum informationtheory, we analytically derive the ultimate precision limits for estimating microstructure sizes asthe one given by restriction lengths in diffusion processes with diffusion weighted MRIsequences. We provide the control conditions, exemplifying with routinely gradient waveformsand with generic geometries of the microstructures, to achieve this precision limit in theestimation considering limitations imposed by T 2 relaxation. On the other hand, we optimize ofthe sequence control named "selective dynamical recoupling" (SDR) 1,2 developed to enhancethe sensitivity to pore sizes determination in restricted diffusion process due to its robustnessagainst unavoidable noises which detriment the echo signal. We designed selective pore-sizefilters by optimally choosing experimental control variables. We characterize the filterperformances under experimental limitations. These results offer a new mechanism to performquantitative 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-uniformOscillating-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.