John M. Ollinger1, Andrew L. Alexander1
1Waisman Laboratory for Brain Imaging,
A model for image variance due to motion is developed and validated. It can be used minimize motion effects by optimizing EPI sequence parameters. In general, variance is minimized by minimizing the partial derivative of the steady-state magnetization along the slice axis. In particular, sidelobes contribute much of the noise at high flip angles; an optimum flip angle exists for a specified degree of motion and can be computed; and inter-slice gaps increase variance due to motion rather than decrease it.