title: The effects of SENSE on PROPELLER imaging.
abstract: OBJECTIVE
  To study how sensitivity encoding (SENSE) impacts periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) image quality, including signal-to-noise ratio (SNR), robustness to motion, precision of motion estimation, and image quality.
  
  
  METHODS
  Five volunteers were imaged by three sets of scans. A rapid method for generating the g-factor map was proposed and validated via Monte Carlo simulations. Sensitivity maps were extrapolated to increase the area over which SENSE can be performed and therefore enhance the robustness to head motion. The precision of motion estimation of PROPELLER blades that are unfolded with these sensitivity maps was investigated. An interleaved R-factor PROPELLER sequence was used to acquire data with similar amounts of motion with and without SENSE acceleration. Two neuroradiologists independently and blindly compared 214 image pairs.
  
  
  RESULTS
  The proposed method of g-factor calculation was similar to that provided by the Monte Carlo methods. Extrapolation and rotation of the sensitivity maps allowed for continued robustness of SENSE unfolding in the presence of motion. SENSE-widened blades improved the precision of rotation and translation estimation. PROPELLER images with a SENSE factor of 3 outperformed the traditional PROPELLER images when reconstructing the same number of blades.
  
  
  CONCLUSIONS
  SENSE not only accelerates PROPELLER but can also improve robustness and precision of head motion correction, which improves overall image quality even when SNR is lost due to acceleration. The reduction of SNR, as a penalty of acceleration, is characterized by the proposed g-factor method.
authors.affiliation: Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA.
authors.forename: Yuchou
authors.initials: Y
authors.lastname: Chang
authors.affiliation: Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA.
authors.forename: James G
authors.initials: JG
authors.lastname: Pipe
authors.affiliation: Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Karis
authors.affiliation: Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA.
authors.forename: Wende N
authors.initials: WN
authors.lastname: Gibbs
authors.affiliation: Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA.
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Zwart
authors.affiliation: Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, USA.|Philips Healthcare, Cleveland, Ohio, USA.|Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Schär
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009038:Motion; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio
keywords: PROPELLER; SENSE; g-factor; motion correction; parallel imaging; sensitivity map extrapolation and rotation