Free-breathing and ungated cardiac cine using navigator-less spiral SToRM
Purpose: To develop a free-breathing and ungated cardiac MRI scheme using an iterative kernel low-rank algorithm and self-gated spiral sequence. Methods: The data were acquired continuously over 8-16 seconds per slice without ECG gating or breath holding using a golden-angle gradient echo spiral sequence. The reconstruction scheme relies on the manifold structure of a dynamic data to recover it from the highly undersampled measurements. An iterative kernel low-rank algorithm is introduced to estimate the manifold structure of the images, or equivalently the manifold Laplacian matrix, from the central k-space regions. The iterative algorithm, coupled with the non-Cartesian acquisitions, eliminates the need for dedicated navigators to estimate the manifold Laplacian, unlike previous manifold methods, thus improving sampling efficiency. Results: The proposed method is demonstrated in patients with different breathing patterns and cardiac rates. The experiments show the ability of our proposed iterative strategy to reduce spatial and temporal blurring compared to state-of-the-art methods. Conclusion: The iterative SToRM algorithm facilitates the extension of manifold regularization to navigator-less spiral acquisitions, thus improving sampling efficiency. The proposed scheme eliminates the need for breath-holding and ECG gating, while facilitating the imaging of the cardiac function in different respiratory phases.
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