Null Space Imaging: a Novel Gradient Encoding Strategy for Highly Efficient Parallel Imaging

Introduction: The current work proposes a novel encoding scheme that makes use of nonlinear magnetic encoding gradients designed to be maximally complementary to coil sensitivities in parallel MRI. In parallel MRI, multiple receiver coils collect signal locally sensitive to limited regions within the field of view. Coil sensitivity profiles, which map the spatial dependence of electromagnetic signal induction, are used in methods such as SENSE and SMASH to reconstruct images. Traditionally, advances in parallel imaging acceleration have not considered the encoding magnetic gradient fields used for localizing spins but have focused more on the receiver coil hardware.