A numerical analysis of NMR spin echo attenuation due to variations in magnetic susceptibility

Abstract

Variations in the susceptibility of a heterogeneous sample will produce background microscopic field gradients when the sample is inserted into a magnetic field. These field gradients frequently alter the signal intensity observed in a nuclear magnetic resonance (NMR) image. A random walk simulation of the NMR spin echo experiment, with several model geometries, has been performed using Mathematica. Using this procedure a qualitative/ quantitative study has been done in an attempt to examine the role of diffusion in diminishing the observed signal intensity. The simulations will be compared to several MRI images of materials containing varying magnetic susceptibility, and various applications of this technique will be discussed.