Method of characterizing molecular diffusion within a body from a set of diffusion-weighted magnetic resonance signals and apparatus for carrying out such a method

A diffusion-weighted magnetic resonance apparatus comprising:

• at least a magnet for generating a static magnetic field, called longitudinal magnetic field, uniform within a volume of interest;
• at least a magnetic field gradient generator, for generating magnetic field gradients along a plurality of directions within said volume of interest;
• at least a radio-frequency pulse generator for emitting radio-frequency pulses within said volume of interest;
• at least a radio-frequency receiver for acquiring magnetic-resonance signals emitted by a body inside said volume of interest;
• at least one processor;
• one or more computers and/or electronic circuits comprising the at least one processor;
• and
• a non-transitory computer-implemented program embodied on a computer readable medium configured to be executed on the at least one processor such that:
• the at least one processor is configured for controlling said or each said magnetic field gradient generator, radio-frequency pulse generator and radio-frequency receiver and for processing said magnetic-resonance signals;
• the at least one processor is configured to control said or each said magnetic field gradient generator, radio-frequency pulse generator and radio-frequency receiver to expose a body situated within said volume of interest to a magnetic resonance imaging process, wherein a plurality of magnetic gradients are applied to said body and, for each said magnetic gradient, acquiring a plurality of diffusion-weighted magnetic resonance signals for a plurality of voxels;
• the at least one processor is configured to fit a plurality of nested multi-compartment diffusion models with an increasing number of compartments to said magnetic resonance signals, each said model being associated to a respective diffusion profile;
• the at least one processor is configured to compute a weight, representative of a performance criterion, for each of said models;
• the at least one processor is configured to convert said models into respective extended models having a same number of compartments by replicating each compartment of each model a predetermined number of times;
• the at least one processor is configured to determine an averaged model by computing said weighted average of said extended models using the corresponding computed weights;
• the at least one processor is configured to fit a plurality of nested multi-compartment diffusion models with an increasing number of compartments to said signals, each said model being associated to a respective diffusion profile;
• the at least one processor is configured to compute a weight, representative of a performance criterion, for each of said models;
• the at least one processor is configured to convert said models into respective extended models having a same number of compartments by replicating each compartment of each model a predetermined number of times;
• the at least one processor is configured to determine an averaged model by computing said weighted average of said extended models using corresponding computed weights;
• and
• the at least one processor is configured to determine a voxel-dependent water diffusion profile within the biological tissue from the weighted average of a plurality of multi-compartment diffusion models.