title: Separation of parallel encoded complex-valued slices (SPECS) from a single complex-valued aliased coil image.
abstract: OBJECTIVE
  Achieving a reduction in scan time with minimal inter-slice signal leakage is one of the significant obstacles in parallel MR imaging. In fMRI, multiband-imaging techniques accelerate data acquisition by simultaneously magnetizing the spatial frequency spectrum of multiple slices. The SPECS model eliminates the consequential inter-slice signal leakage from the slice unaliasing, while maintaining an optimal reduction in scan time and activation statistics in fMRI studies.
  
  
  METHODS
  When the combined k-space array is inverse Fourier reconstructed, the resulting aliased image is separated into the un-aliased slices through a least squares estimator. Without the additional spatial information from a phased array of receiver coils, slice separation in SPECS is accomplished with acquired aliased images in shifted FOV aliasing pattern, and a bootstrapping approach of incorporating reference calibration images in an orthogonal Hadamard pattern.
  
  
  RESULTS
  The aliased slices are effectively separated with minimal expense to the spatial and temporal resolution. Functional activation is observed in the motor cortex, as the number of aliased slices is increased, in a bilateral finger tapping fMRI experiment.
  
  
  CONCLUSIONS
  The SPECS model incorporates calibration reference images together with coefficients of orthogonal polynomials into an un-aliasing estimator to achieve separated images, with virtually no residual artifacts and functional activation detection in separated images.
authors.affiliation: Department of Mathematics, Statistics, and Computer Science, Marquette University, Milwaukee WI, USA; Department of Biophysics, Medical College of Wisconsin, Milwaukee WI, USA. Electronic address: daniel.rowe@marquette.edu.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Rowe
authors.affiliation: Duke/UNC Brain Imaging and Analysis Center, Duke University, Durham, NC, USA.
authors.forename: Iain P
authors.initials: IP
authors.lastname: Bruce
authors.affiliation: Department of Biophysics, Medical College of Wisconsin, Milwaukee WI, USA.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Nencka
authors.affiliation: Department of Biophysics, Medical College of Wisconsin, Milwaukee WI, USA.
authors.forename: James S
authors.initials: JS
authors.lastname: Hyde
authors.affiliation: Department of Mathematics, Statistics, and Computer Science, Marquette University, Milwaukee WI, USA.
authors.forename: Mary C
authors.initials: MC
authors.lastname: Kociuba
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000000981:diagnostic imaging* / Q000502:physiology; D001931:Brain Mapping / Q000379:methods; D002138:Calibration; D003198:Computer Simulation; D017352:Echo-Planar Imaging; D005583:Fourier Analysis; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging; D019047:Phantoms, Imaging
keywords: MRI; Multiband; Parallel slice; SPECS; Simultaneous multi-slice (SMS); fMRI