MRI method of diffusion measurement in heterogeneous materials

. This paper describes a newly proposed magnetic resonance (MR) method and the processing of signals being measured, with the aim of establishing the diffusion coefficients in heterogeneous materials. The pulsed field gradient stimulated-echo methods have reduced coupling between the applied magnetic field gradient and a constant internal magnetic field gradient caused by different susceptibilities throughout the sample. When studying systems where it is necessary to keep the duration of the pulse sequence to a minimum or to study diffusion as a function of observation time, the spin-echo method should be chosen. The basic idea is to acquire the spin-echo amplitude with pulsed field gradient of opposite signs and to add/subtract the NMR signals measured in a suitable way. The measuring method and the digital signal processing enable the elimination of the effect of static magnetic field on the accuracy of measurement. The method proposed can be used to measure diffusion-weighted images of liquids found in porous materials and in the development of new MR tomography measuring methods at the Institute of Scientific Instruments of the Academy of Sciences of the Czech Republic, v. v. i.