Magnetic Gradient Shape Optimization for Highly Accelerated Space Imaging

Leo K. Tam¹, Jason P. Stockmann¹, Gigi Galiana², Robert Todd Constable¹

Previous research has demonstrated the utility of non-linear magnetic gradients such as the Z2 or C2 and S2 spherical harmonics for highly accelerated parallel imaging. In the present work, a systematic study of gradients shapes that are used in higher order gradients is performed via the Space Imaging (NSI) method, a technique based on designing gradients complementary to receiver coils. All combinations of spherical harmonics through the fourth order and additional combinations such as ones focused on orthogonal gradients (eg. C2 and S2 together with linears) were considered, in total 21 combinations. Simulations demonstrate that an optimal second order gradient set is composed of linear gradients and the second order in-plane gradients (C2, S2, and Z2) for NSI imaging at fixed sampling bandwidth.