title: Simultaneous orthogonal plane imaging.
abstract: Intrafraction motion can result in a smearing of planned external beam radiation therapy dose distributions, resulting in an uncertainty in dose actually deposited in tissue. The purpose of this paper is to present a pulse sequence that is capable of imaging a moving target at a high frame rate in two orthogonal planes simultaneously for MR-guided radiotherapy.
  
  
  
  By balancing the zero gradient moment on all axes, slices in two orthogonal planes may be spatially encoded simultaneously. The orthogonal slice groups may be acquired with equal or nonequal echo times.
  
  
  
  A Cartesian spoiled gradient echo simultaneous orthogonal plane imaging (SOPI) sequence was tested in phantom and in vivo. Multiplexed SOPI acquisitions were performed in which two parallel slices were imaged along two orthogonal axes simultaneously. An autocalibrating phase-constrained 2D-SENSE-GRAPPA (generalized autocalibrating partially parallel acquisition) algorithm was implemented to reconstruct the multiplexed data.
  
  
  
  SOPI images without intraslice motion artifacts were reconstructed at a maximum frame rate of 8.16 Hz. The 2D-SENSE-GRAPPA reconstruction separated the parallel slices aliased along each orthogonal axis.
  
  
  
  The high spatiotemporal resolution provided by SOPI has the potential to be beneficial for intrafraction motion management during MR-guided radiation therapy or other MRI-guided interventions. Magn Reson Med 78:1700-1710, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Nikolai J
authors.initials: NJ
authors.lastname: Mickevicius
authors.affiliation: Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.|Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.|Department of Radiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Paulson
mesh_terms: D000465:Algorithms; D016477:Artifacts; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009038:Motion; D019047:Phantoms, Imaging; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D060726:Torso / Q000000981:diagnostic imaging
keywords: MR-guided radiation therapy; SMS; simultaneous multislice; simultaneous orthogonal slice