In-Vivo Quantification of Brain Microstructure: a Preliminary Analysis using SHORE Diffusion Model L. Brusini1, M. Zucchelli1, G.K. Ricciardi2, F. Pizzini2, S. Montemezzi2, G. Menegaz1 1 Dept. of Computer Science, University of Verona 2 Dept. of Neuroradiology, AOUI of Verona From Diffusion Signal to Water Molecules PDF E(q) 2/8 From Diffusion Signal to Water Molecules PDF E(q) The Ensemble Average Propagator (EAP) represents the probability of a net displacement r in the unit time P(r) 2/8 From Diffusion Signal to Water Molecules PDF E(q) The Ensemble Average Propagator (EAP) represents the probability of a net displacement r in the unit time P(r) ODF(u) The Orientation Distribution Function (ODF) represents the probability of diffusion in each direction u 2/8 Diffusion Tensor Imaging (DTI) 3/8 Diffusion Tensor Imaging (DTI) ✓ Fast acquisition ✓ Efficient reconstruction 3/8 Diffusion Tensor Imaging (DTI) ✓ Fast acquisition ✓ Efficient reconstruction ☓ Since the EAP is modeled as a single tensor, DTI is not able to resolve complex fibers architectures like fannings and crossings 3/8 Simple Harmonic Oscillator based Reconstruction and Estimation (SHORE) Signal approximated using a combination of orthonormal functions which are the solutions of the 3D quantum mechanical harmonic oscillator 4/8 Simple Harmonic Oscillator based Reconstruction and Estimation (SHORE) Signal approximated using a combination of orthonormal functions which are the solutions of the 3D quantum mechanical harmonic oscillator Continuous analytical basis ✓ Continuous analytical signal representation in q-space independently from the acquisition sampling scheme ✓ Possibility to calculate the EAP and the ODF analytically, obtaining an exact solution for all the computations 4/8 Propagator Anisotropy (PA) and Mean Squared Displacement (MSD) GFA 5/8 Propagator Anisotropy (PA) and Mean Squared Displacement (MSD) PA GFA Measure of the angular similarity between the propagator and its isotropic part 5/8 Propagator Anisotropy (PA) and Mean Squared Displacement (MSD) PA Measure of the angular similarity between the propagator and its isotropic part GFA MSD Degree of diffusivity of the water molecules in the voxel 5/8 Measures of Zero Net Displacement ● Restricted diffusion in pores ● gradient duration very small ● time between gradients is large figure refers to L. Avram et al., NMR Biomed. 2008; 21: 888–898 6/8 Measures of Zero Net Displacement ● Restricted diffusion in pores ● gradient duration very small ● time between gradients is large figure refers to L. Avram et al., NMR Biomed. 2008; 21: 888–898 Return To the Origin Probability (RTOP) 6/8 Measures of Zero Net Displacement ● Restricted diffusion in pores ● gradient duration very small ● time between gradients is large figure refers to L. Avram et al., NMR Biomed. 2008; 21: 888–898 Return To the Origin Probability (RTOP) Return To the Axis Probability (RTAP) 6/8 Measures of Zero Net Displacement ● Restricted diffusion in pores ● gradient duration very small ● time between gradients is large figure refers to L. Avram et al., NMR Biomed. 2008; 21: 888–898 Return To the Origin Probability (RTOP) Return To the Plane Probability (RTPP) Return To the Axis Probability (RTAP) 6/8 From RTOP, RTAP and RTPP to Physical Measures Probability for molecules to undergo no net displacement between the application of the two diffusion sensitizing gradients RTOP reciprocal of the volume 7/8 From RTOP, RTAP and RTPP to Physical Measures Probability for molecules to undergo no net displacement between the application of the two diffusion sensitizing gradients RTAP reciprocal of the mean crosssectional area RTOP reciprocal of the volume 7/8 From RTOP, RTAP and RTPP to Physical Measures Probability for molecules to undergo no net displacement between the application of the two diffusion sensitizing gradients RTAP reciprocal of the mean crosssectional area RTOP reciprocal of the volume RTPP reciprocal of the mean length of the pores 7/8 Conclusions and Future Works 8/8 Conclusions and Future Works 8/8 Conclusions and Future Works 8/8 Conclusions and Future Works 8/8

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