A g-Factor Metric for k-t SENSE and k-t PCA Based Parallel Imaging

Purpose: To propose and validate a g-factor formalism for k-t SENSE, k-t PCA and related k-t methods for assessing SNR and temporal fidelity. Methods: An analytical g(xf)-factor formulation in the spatiotemporal frequency domain is derived, enabling assessment of noise and depiction fidelity in both the spatial and frequency domain. Using pseudoreplica analysis of cardiac cine data the gxf-factor description is validated and example data are used to analyze the performance of k-t methods for various parameter settings. Results: Analytical gxf-factor maps were found to agree well with pseudoreplica analysis for 3x, 5x, and 7x k-t SENSE and k-t PCA. While k-t SENSE resulted in lower average g(xf) values (g(x)(avg)) in static regions when compared with k-t PCA, k-t PCA yielded lower g(x)(avg) values in dynamic regions. Temporal transfer was better preserved with k-t PCA for increasing under-sampling factors. Conclusion: The proposed gxf-factor and temporal transfer formalism allows assessing noise performance and temporal depiction fidelity of k-t methods including k-t SENSE and k-t PCA. The framework enables quantitative comparison of different k-t methods relative to frame-by-frame parallel imaging reconstruction. (C) 2015 Wiley Periodicals, Inc.