Monte-Carlo Simulation of Susceptibility Effects on the PGSE Signal and Diffusion Measures

Pim Pullens¹, ², Alard Roebroeck², Rainer Goebel², Kamil Uludag²

The susceptibility in white matter fiber is orientation-dependent and, thus, affects the gradient-echo signal. Rotating a fibrous phantom in the magnetic field, we also observed signal changes in diffusion-weighted spin-echo experiments. Consequently, diffusion parameters, such as FA and ADC, can be distorted by these orientation-dependent effects. In the study, Monte-Carlo simulations were performed to investigate the effect of susceptibility changes in a PGSE experiment. We found in our simulations that diffusion-weighted signal, FA and ADC change as a result of susceptibility differences. This could have an impact on human DW-MRI measurements especially at high and ultra-high fields.