A method for spatial mapping of gradient field nonlinearity in magnetic resonance imaging

D. Wang, G. Cowin, K. McMahon, D. M. Doddrell Centre for Magnetic Resonance, The University of Queensland, Brisbane, Qld, Australia Introduction Gradient coils in magnetic resonance imaging (MRI) play an increasingly important role as many advanced imaging sequences developed in recent years normally require faster and stronger gradients. To meet this demand, gradient designers employed different design strategies using shorter gradient coil structure with a compromise in gradient field linearity. Increased gradient field nonlinearity in MRI scanners equipped with shorter gradient coils has been shown to cause a range of undesirable imaging errors such as geometric distortions [1], errors in diffusion-weighted imaging and diffusion tensor imaging [2] and in phase contrast MRI [3]. Recently, a comprehensive approach employing a 3-dimensional phantom has been developed for investigating the geometric distortions principally caused by the gradient field nonlinearity [4]. In this presentation, we describe a method that provides a spatial mapping of the gradient field nonlinearity derived indirectly from the measured geometric distortion.