Reduction of ringing artifacts induced by diaphragm drifting in free‐breathing dynamic pulmonary MRI using 3D koosh‐ball acquisition.

Purpose: To reduce the ringing artifacts of the motion‐resolved images in free‐breathing dynamic pulmonary MRI. Methods: A golden‐step based interleaving (GSI) technique was proposed to reduce ringing artifacts induced by diaphragm drifting. The pulmonary MRI data were acquired using a superior–inferior navigated 3D radial UTE sequence in an interleaved manner during free breathing. Successive interleaves were acquired in an incoherent fashion along the polar direction. Four‐dimensional images were reconstructed from the motion‐resolved k‐space data obtained by retrospectively binning. The reconstruction algorithms included standard nonuniform fast Fourier transform (NUFFT), Voronoi‐density‐compensated NUFFT, extra‐dimensional UTE, and motion‐state weighted motion‐compensation reconstruction. The proposed interleaving technique was compared with a conventional sequential interleaving (SeqI) technique on a phantom and eight subjects. Results: The quantified ringing artifacts level in the motion‐resolved image is positively correlated with the quantified nonuniformity level of the corresponding k‐space. The nonuniformity levels of the end‐expiratory and end‐inspiratory k‐space binned from GSI data (0.34 ± 0.07, 0.33 ± 0.05) are significantly lower with statistical significance (p < 0.05) than that binned from SeqI data (0.44 ± 0.11, 0.42 ± 0.12). Ringing artifacts are substantially reduced in the dynamic images of eight subjects acquired using the proposed technique in comparison with that acquired using the conventional SeqI technique. Conclusion: Ringing artifacts in the motion‐resolved images induced by diaphragm drifting can be reduced using the proposed GSI technique for free‐breathing dynamic pulmonary MRI. This technique has the potential to reduce ringing artifacts in free‐breathing liver and kidney MRI based on full‐echo interleaved 3D radial acquisition. [ABSTRACT FROM AUTHOR]