Gaussian Phase Distribution Approximation of the Square Wave Oscillating Gradient Spin-Echo (SWOGSE) Diffusion Signal

Andrada Ianus¹, Bernard Siow¹, Hui Zhang¹, Daniel C. Alexander¹

This work presents analytical formulae for both free and restricted diffusion NMR signal from a square wave oscillating gradient spin-echo (SWOGSE) sequence. The expressions are computed using the Gaussian Phase Distribution approximation and we demonstrate for cylindrical geometry. The results for different radii, frequencies, and gradient strengths are compared with the values obtained from Monte Carlo diffusion simulation. In all cases the error was less than 3% of the signal and the total computation time was reduced by several orders of magnitude, which enables model fitting applications, e.g. to generate whole brain parameter maps.