Retrospective correction of second‐order concomitant fields in 3D axial stack‐of‐spirals imaging on a high‐performance gradient system.

Purpose: MRI using 3D stack‐of‐spirals (SoS) readout on a high‐performance gradient system is subject to strong second‐order, spatially varying concomitant fields, which can lead to signal dropout and blurring artifacts that become more significant at locations farther from the gradient isocenter. A method for compensating for second‐order concomitant fields in 3D axial SoS image reconstruction is described. Methods: We retrospectively correct for second‐order concomitant field–induced phase error in the 3D SoS data by slice‐dependent k‐space phase compensation based on the nominal spiral readout trajectories. The effectiveness of the method was demonstrated in phantom and healthy volunteer scans in which 3D pseudo‐continuous arterial spin labeling imaging was performed with SoS fast spin‐echo readout at 3 T. Results: Substantial reduction in blurring was observed with the proposed method. In phantom scans, blurring was reduced by about 53% at 98 mm from the gradient isocenter. In the in vivo 3D pseudo‐continuous arterial spin labeling scans, differences of up to 10% were observed at 78 mm from the isocenter, especially around the white‐matter and gray‐matter interfaces, between the corrected and uncorrected proton density images, perfusion‐weighted images, and cerebral blood flow maps. Conclusions: The described retrospective correction method provides a means to correct erroneous phase accruals due to second‐order concomitant fields in 3D axial stack‐of‐spirals imaging. [ABSTRACT FROM AUTHOR]