title: Four-dimensional MRI using three-dimensional radial sampling with respiratory self-gating to characterize temporal phase-resolved respiratory motion in the abdomen.
abstract: OBJECTIVE
  To develop a four-dimensional MRI (4D-MRI) technique to characterize the average respiratory tumor motion for abdominal radiotherapy planning.
  
  
  METHODS
  A continuous spoiled gradient echo sequence was implemented with 3D radial trajectory and 1D self-gating for respiratory motion detection. Data were retrospectively sorted into different respiratory phases based on their temporal locations within a respiratory cycle, and each phase was reconstructed by means of a self-calibrating CG-SENSE program. Motion phantom, healthy volunteer and patient studies were performed to validate the respiratory motion detected by the proposed method against that from a 2D real-time protocol.
  
  
  RESULTS
  The proposed method successfully visualized the respiratory motion in phantom and human subjects. The 4D-MRI and real-time 2D-MRI yielded comparable superior-inferior (SI) motion amplitudes (intraclass correlation = 0.935) with up-to one pixel mean absolute differences in SI displacements over 10 phases and high cross-correlation between phase-resolved displacements (phantom: 0.985; human: 0.937-0.985). Comparable anterior-posterior and left-right displacements of the tumor or gold fiducial between 4D and real-time 2D-MRI were also observed in the two patients, and the hysteresis effect was shown in their 3D trajectories.
  
  
  CONCLUSIONS
  We demonstrated the feasibility of the proposed 4D-MRI technique to characterize abdominal respiratory motion, which may provide valuable information for radiotherapy planning.
authors.affiliation: Biomedical Imaging Research Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Department of Bioengineering, University of California, Los Angeles, California, USA.
authors.forename: Zixin
authors.initials: Z
authors.lastname: Deng
authors.affiliation: Biomedical Imaging Research Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Department of Radiology and Biomedical Engineering, Northwestern University, Chicago, Illinois, USA.
authors.forename: Jianing
authors.initials: J
authors.lastname: Pang
authors.affiliation: Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Wensha
authors.initials: W
authors.lastname: Yang
authors.affiliation: Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Yue
authors.affiliation: Biomedical Imaging Research Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Behzad
authors.initials: B
authors.lastname: Sharif
authors.affiliation: Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Tuli
authors.affiliation: Biomedical Imaging Research Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Department of Bioengineering, University of California, Los Angeles, California, USA.
authors.forename: Debiao
authors.initials: D
authors.lastname: Li
authors.affiliation: Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Benedick
authors.initials: B
authors.lastname: Fraass
authors.affiliation: Biomedical Imaging Research Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Zhaoyang
authors.initials: Z
authors.lastname: Fan
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging*; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009068:Movement; D019047:Phantoms, Imaging; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D055815:Young Adult
keywords: 3D radial sampling; 4D-MRI; hysteresis; radiotherapy planning; respiratory motion; self-gating