title: A g-factor metric for k-t SENSE and k-t PCA based parallel imaging.
abstract: OBJECTIVE
  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 gxf -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 gxf values (gx (avg) ) in static regions when compared with k-t PCA, k-t PCA yielded lower gx (avg) values in dynamic regions. Temporal transfer was better preserved with k-t PCA for increasing undersampling factors.
  
  
  CONCLUSIONS
  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.
authors: Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.
authors: Christian
authors: C
authors: Binter
authors: Department of Diagnostic Radiology, Medical Physics, University Medical Center, Freiburg, Germany.
authors: Rebecca
authors: R
authors: Ramb
authors: Department of Diagnostic Radiology, Medical Physics, University Medical Center, Freiburg, Germany.|Institute for Diagnostic, Interventional and Pediatric Radiology, University Hospital Berne, Switzerland.
authors: Bernd
authors: B
authors: Jung
authors: Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.|Imaging Sciences and Biomedical Engineering, King's College London, United Kingdom.
authors: Sebastian
authors: S
authors: Kozerke
mesh_terms: D000465:Algorithms; D016477:Artifacts; D006321:Heart / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*
keywords: g-factor; k-t PCA; k-t SENSE; noise estimation; parallel imaging; temporal filtering