title: Real-time free-breathing cardiac imaging with self-calibrated through-time radial GRAPPA.
abstract: Real-time free-breathing cardiac imaging with highly undersampled radial trajectories has previously been successfully demonstrated using calibrated radial generalized autocalibrating partially parallel acquisition (rGRAPPA). A self-calibrated approach for rGRAPPA is proposed that removes the need for the calibration prescan.
  
  
  
  To investigate the effect of various parameters on image quality, a comprehensive imaging study on one normal swine was performed. Root mean squared errors (RMSEs) were computed with respect to gold standard acquisitions, and several acquisition/reconstruction strategies were compared. Additionally, the method was tested on 13 human subjects, and RMSEs relative to standard through-time radial GRAPPA were computed.
  
  
  
  Real-time images with high spatiotemporal resolution were obtained. Image quality was comparable to calibrated through-time rGRAPPA with endocardial and epicardial borders clearly delineated. In the swine, the average RMSE between self-calibrated and gold-standard calibrated images was 5.18 ± 0.84%. In normal human subjects, the average RMSE between self-calibrated and calibrated through-time rGRAPPA was 3.79 ± 0.64%. For lower accelerations rates (R = 6-8) image quality was similar to comparable calibrated scans though RMSE increased for higher degrees of undersampling (R = 12-16).
  
  
  
  Highly accelerated real-time imaging with undersampled radial trajectories without additional calibration data is feasible. Image quality was acceptable for real-time cardiac MRI applications demanding high speed. Magn Reson Med 77:250-264, 2017. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Ozan
authors.initials: O
authors.lastname: Sayin
authors.affiliation: Siemens Healthcare USA, Inc., Chicago, Illinois, USA.
authors.forename: Haris
authors.initials: H
authors.lastname: Saybasili
authors.affiliation: Department of Medicine, Cardiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: M Muz
authors.initials: MM
authors.lastname: Zviman
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA.|Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Griswold
authors.affiliation: Department of Medicine, Cardiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Henry
authors.initials: H
authors.lastname: Halperin
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Seiberlich
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Herzka
mesh_terms: D000465:Algorithms; D000818:Animals; D002138:Calibration; D057791:Cardiac Imaging Techniques / Q000379:methods*; D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D012119:Respiration; D013552:Swine
keywords: cardiac magnetic resonance imaging; non-Cartesian GRAPPA; parallel imaging; real-time imaging; self-calibration