Polar Angles Randomisation Overcomes Binning-Introduced Artefacts in 3D Radial Phyllotaxis GRE

Motivation: Sequential binning of MRI data acquired using a 3D-radial spiral phyllotaxis trajectory can introduce image artifacts, which may impact motion estimation and retrospective sequential binning —crucial for applications such as task-based fMRI. Goal(s): To propose a novel spiral phyllotaxis design aimed at minimizing artifacts and enhancing image quality for sequential binning. Approach: By randomisation of the polar angles, and uniform k-space sampling, 3D-radial data was acquired in phantoms and healthy subjects. Artifact reduction was quantified by comparison with the original trajectory. Results: We reduce artifacts in sequential binning for both phantom and in-vivo experiments, while achieving uniform phyllotaxis sampling across all non-radial directions. Impact: The flexyPhy trajectory improves 3D spiral phyllotaxis by enhancing sampling uniformity, binning flexibility, and image quality. It has potential to improve motion estimation in sequential binning applications, such as fMRI, and boost uniformity in motion-resolved techniques like cardiac MRI.