title: Feasibility of through-time spiral generalized autocalibrating partial parallel acquisition for low latency accelerated real-time MRI of speech.
abstract: OBJECTIVE
  To evaluate the feasibility of through-time spiral generalized autocalibrating partial parallel acquisition (GRAPPA) for low-latency accelerated real-time MRI of speech.
  
  
  METHODS
  Through-time spiral GRAPPA (spiral GRAPPA), a fast linear reconstruction method, is applied to spiral (k-t) data acquired from an eight-channel custom upper-airway coil. Fully sampled data were retrospectively down-sampled to evaluate spiral GRAPPA at undersampling factors R = 2 to 6. Pseudo-golden-angle spiral acquisitions were used for prospective studies. Three subjects were imaged while performing a range of speech tasks that involved rapid articulator movements, including fluent speech and beat-boxing. Spiral GRAPPA was compared with view sharing, and a parallel imaging and compressed sensing (PI-CS) method.
  
  
  RESULTS
  Spiral GRAPPA captured spatiotemporal dynamics of vocal tract articulators at undersampling factors ≤4. Spiral GRAPPA at 18 ms/frame and 2.4 mm2/pixel outperformed view sharing in depicting rapidly moving articulators. Spiral GRAPPA and PI-CS provided equivalent temporal fidelity. Reconstruction latency per frame was 14 ms for view sharing and 116 ms for spiral GRAPPA, using a single processor. Spiral GRAPPA kept up with the MRI data rate of 18ms/frame with eight processors. PI-CS required 17 minutes to reconstruct 5 seconds of dynamic data.
  
  
  CONCLUSIONS
  Spiral GRAPPA enabled 4-fold accelerated real-time MRI of speech with a low reconstruction latency. This approach is applicable to wide range of speech RT-MRI experiments that benefit from real-time feedback while visualizing rapid articulator movement. Magn Reson Med 78:2275-2282, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, USA.
authors.forename: Sajan Goud
authors.initials: SG
authors.lastname: Lingala
authors.affiliation: Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, USA.
authors.forename: Yinghua
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, USA.
authors.forename: Yongwan
authors.initials: Y
authors.lastname: Lim
authors.affiliation: Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, USA.
authors.forename: Asterios
authors.initials: A
authors.lastname: Toutios
authors.affiliation: Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA.
authors.forename: Yunhua
authors.initials: Y
authors.lastname: Ji
authors.affiliation: Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Wei-Ching
authors.initials: WC
authors.lastname: Lo
authors.affiliation: Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Seiberlich
authors.affiliation: Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, USA.
authors.forename: Shrikanth
authors.initials: S
authors.lastname: Narayanan
authors.affiliation: Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, USA.
authors.forename: Krishna S
authors.initials: KS
authors.lastname: Nayak
mesh_terms: D000465:Algorithms; D016477:Artifacts; D002138:Calibration; D004825:Epiglottis / Q000000981:diagnostic imaging; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D007830:Larynx / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging; D015233:Models, Statistical; D010614:Pharynx / Q000000981:diagnostic imaging; D011446:Prospective Studies; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D012984:Software; D013060:Speech
keywords: low latency imaging; real-time MRI; speech production