title: Calibrationless parallel imaging reconstruction based on structured low-rank matrix completion.
abstract: OBJECTIVE
  A calibrationless parallel imaging reconstruction method, termed simultaneous autocalibrating and k-space estimation (SAKE), is presented. It is a data-driven, coil-by-coil reconstruction method that does not require a separate calibration step for estimating coil sensitivity information.
  
  
  METHODS
  In SAKE, an undersampled, multichannel dataset is structured into a single data matrix. The reconstruction is then formulated as a structured low-rank matrix completion problem. An iterative solution that implements a projection-onto-sets algorithm with singular value thresholding is described.
  
  
  RESULTS
  Reconstruction results are demonstrated for retrospectively and prospectively undersampled, multichannel Cartesian data having no calibration signals. Additionally, non-Cartesian data reconstruction is presented. Finally, improved image quality is demonstrated by combining SAKE with wavelet-based compressed sensing.
  
  
  CONCLUSIONS
  Because estimation of coil sensitivity information is not needed, the proposed method could potentially benefit MR applications where acquiring accurate calibration data is limiting or not possible at all.
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California at San Francisco, San Francisco, California, USA; The UC Berkeley-UCSF Graduate Program in Bioengineering, California, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Shin
authors.forename: Peder E Z
authors.initials: PE
authors.lastname: Larson
authors.forename: Michael A
authors.initials: MA
authors.lastname: Ohliger
authors.forename: Michael
authors.initials: M
authors.lastname: Elad
authors.forename: John M
authors.initials: JM
authors.lastname: Pauly
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Vigneron
authors.forename: Michael
authors.initials: M
authors.lastname: Lustig
mesh_terms: D000465:Algorithms; D016477:Artifacts; D002138:Calibration; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D057054:Molecular Imaging / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio
keywords: GRAPPA; SPIRiT; compressed sensing; parallel imaging; rapid MRI; structured low-rank matrix completion