title: Free-breathing pediatric MRI with nonrigid motion correction and acceleration.
abstract: OBJECTIVE
  To develop and assess motion correction techniques for high-resolution pediatric abdominal volumetric magnetic resonance images acquired free-breathing with high scan efficiency.
  
  
  METHODS
  First, variable-density sampling and radial-like phase-encode ordering were incorporated into the 3D Cartesian acquisition. Second, intrinsic multichannel butterfly navigators were used to measure respiratory motion. Lastly, these estimates are applied for both motion-weighted data-consistency in a compressed sensing and parallel imaging reconstruction, and for nonrigid motion correction using a localized autofocusing framework. With Institutional Review Board approval and informed consent/assent, studies were performed on 22 consecutive pediatric patients. Two radiologists independently scored the images for overall image quality, degree of motion artifacts, and sharpness of hepatic vessels and the diaphragm. The results were assessed using paired Wilcoxon test and weighted kappa coefficient for interobserver agreements.
  
  
  RESULTS
  The complete procedure yielded significantly better overall image quality (mean score of 4.7 out of 5) when compared to using no correction (mean score of 3.4, P < 0.05) and to using motion-weighted accelerated imaging (mean score of 3.9, P < 0.05). With an average scan time of 28 seconds, the proposed method resulted in comparable image quality to conventional prospective respiratory-triggered acquisitions with an average scan time of 91 seconds (mean score of 4.5).
  
  
  CONCLUSIONS
  With the proposed methods, diagnosable high-resolution abdominal volumetric scans can be obtained from free-breathing data acquisitions.
authors.affiliation: Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA.|Department of Radiology, Stanford University, Stanford, California, USA.
authors.forename: Joseph Y
authors.initials: JY
authors.lastname: Cheng
authors.affiliation: Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA.|Department of Radiology, Stanford University, Stanford, California, USA.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Nichanan
authors.initials: N
authors.lastname: Ruangwattanapaisarn
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA.
authors.forename: Marcus T
authors.initials: MT
authors.lastname: Alley
authors.affiliation: Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Uecker
authors.affiliation: Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Pauly
authors.affiliation: Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Lustig
authors.affiliation: Department of Radiology, Stanford University, Stanford, California, USA.
authors.forename: Shreyas S
authors.initials: SS
authors.lastname: Vasanawala
mesh_terms: D000054:Acceleration; D000465:Algorithms; D016477:Artifacts; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009038:Motion; D015588:Observer Variation; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D012680:Sensitivity and Specificity
keywords: autofocus; compressed sensing; nonrigid motion; parallel imaging; pediatric abdominal MRI; soft-gating