Measuring the Diffusion of Nuclei in Biological Systems by Magnetic Resonance Methods: Checking the Quality of Gradient Magnetic Fields

Imaging techniques based on the principle of nuclear magnetic resonance (MRI) can be used in the study of molecular transport phenomena in biological systems such as self-diffusion processes. The precision of determining the diffusion constants depends on generating the gradient pulse with high precision. For the purpose of determining the characteristics of time behaviour of gradient pulses a simple measuring method was developed and experimentally tested on a 4.7 T tomograph. The method is based on the principle of measuring the instantaneous frequency of MR signal in the presence of gradient pulse after the excitation of a thin defined layer of the examined specimen placed outside the gradient field centre. Using the above method, errors were found in the amplitude and time integral of generated gradient fields and in determining the diffusion constants for biological tissues.