Motion correction for functional MRI with three-dimensional hybrid radial-Cartesian EPI

Purpose Subject motion is a major source of image degradation for functional MRI, especially when using multi-shot sequences like 3D EPI. We present a hybrid radial-Cartesian 3D EPI trajectory enabling motion correction in k-space for functional MRI. Methods The EPI “blades” of the 3D hybrid radial-Cartesian EPI sequence (TURBINE) are rotated about the phase-encoding axis to fill out a cylinder in 3D k-space. Angular blades are acquired over time using a golden angle rotation increment, allowing reconstruction at flexible temporal resolution. The self-navigating properties of the sequence are used to determine motion parameters from a high temporal resolution navigator time-series. The motion is corrected in k-space as part of the image reconstruction and evaluated for experiments with both cued and natural motion. Results We demonstrate that the motion correction works robustly and that we can achieve substantial artifact reduction as well as improvement in temporal SNR and fMRI activation in the presence of both severe and subtle motion. Conclusion We show the potential for hybrid radial-Cartesian 3D EPI to substantially reduce artifacts for application in fMRI, especially for subject groups with significant head motion. The motion correction approach does not prolong the scan and no extra hardware is required.</p

Motion correction for functional MRI with three-dimensional hybrid radial-Cartesian EPI

Purpose Subject motion is a major source of image degradation for functional MRI, especially when using multi-shot sequences like 3D EPI. We present a hybrid radial-Cartesian 3D EPI trajectory enabling motion correction in k-space for functional MRI. Methods The EPI “blades” of the 3D hybrid radial-Cartesian EPI sequence (TURBINE) are rotated about the phase-encoding axis to fill out a cylinder in 3D k-space. Angular blades are acquired over time using a golden angle rotation increment, allowing reconstruction at flexible temporal resolution. The self-navigating properties of the sequence are used to determine motion parameters from a high temporal resolution navigator time-series. The motion is corrected in k-space as part of the image reconstruction and evaluated for experiments with both cued and natural motion. Results We demonstrate that the motion correction works robustly and that we can achieve substantial artifact reduction as well as improvement in temporal SNR and fMRI activation in the presence of both severe and subtle motion. Conclusion We show the potential for hybrid radial-Cartesian 3D EPI to substantially reduce artifacts for application in fMRI, especially for subject groups with significant head motion. The motion correction approach does not prolong the scan and no extra hardware is required.</p