title: Magnetic resonance imaging assessment of spinal cord and cauda equina motion in supine patients with spinal metastases planned for spine stereotactic body radiation therapy.
abstract: OBJECTIVE
  To assess motion of the spinal cord and cauda equina, which are critical neural tissues (CNT), which is important when evaluating the planning organ-at-risk margin required for stereotactic body radiation therapy.
  
  
  METHODS
  We analyzed CNT motion in 65 patients with spinal metastases (11 cervical, 39 thoracic, and 24 lumbar spinal segments) in the supine position using dynamic axial and sagittal magnetic resonance imaging (dMRI, 3T Verio, Siemens) over a 137-second interval. Motion was segregated according to physiologic cardiorespiratory oscillatory motion (characterized by the average root mean square deviation) and random bulk shifts associated with gross patient motion (characterized by the range). Displacement was evaluated in the anteroposterior (AP), lateral (LR), and superior-inferior (SI) directions by use of a correlation coefficient template matching algorithm, with quantification of random motion measure error over 3 separate trials. Statistical significance was defined according to P<.05.
  
  
  RESULTS
  In the AP, LR, and SI directions, significant oscillatory motion was observed in 39.2%, 35.1%, and 10.8% of spinal segments, respectively, and significant bulk motions in all cases. The median oscillatory CNT motions in the AP, LR, and SI directions were 0.16 mm, 0.17 mm, and 0.44 mm, respectively, and the maximal statistically significant oscillatory motions were 0.39 mm, 0.41 mm, and 0.77 mm, respectively. The median bulk displacements in the AP, LR, and SI directions were 0.51 mm, 0.59 mm, and 0.66 mm, and the maximal statistically significant displacements were 2.21 mm, 2.87 mm, and 3.90 mm, respectively. In the AP, LR, and SI directions, bulk displacements were greater than 1.5 mm in 5.4%, 9.0%, and 14.9% of spinal segments, respectively. No significant differences in axial motion were observed according to cord level or cauda equina.
  
  
  CONCLUSIONS
  Oscillatory CNT motion was observed to be relatively minor. Our results support the importance of controlling bulk patient motion and the practice of applying a planning organ-at-risk margin.
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Chia-Lin
authors.initials: CL
authors.lastname: Tseng
authors.affiliation: Department of Medical Imaging, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Marshall S
authors.initials: MS
authors.lastname: Sussman
authors.affiliation: Department of Biostatistics, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Eshetu G
authors.initials: EG
authors.lastname: Atenafu
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Daniel
authors.initials: D
authors.lastname: Letourneau
authors.affiliation: Department of Radiation Oncology, University of California San Francisco, San Francisco, California.
authors.forename: Lijun
authors.initials: L
authors.lastname: Ma
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Hany
authors.initials: H
authors.lastname: Soliman
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Thibault
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: B C John
authors.initials: BC
authors.lastname: Cho
authors.affiliation: Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Anna
authors.initials: A
authors.lastname: Simeonov
authors.affiliation: Department of Medical Imaging, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Eugene
authors.initials: E
authors.lastname: Yu
authors.affiliation: Department of Neurosurgery and Spine Program, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Fehlings
authors.affiliation: Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada. Electronic address: arjun.sahgal@sunnybrook.ca.
authors.forename: Arjun
authors.initials: A
authors.lastname: Sahgal
mesh_terms: D000465:Algorithms; D002420:Cauda Equina / Q000502:physiology*; D002555:Cerebrospinal Fluid / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009068:Movement / Q000502:physiology*; D058958:Organs at Risk / Q000502:physiology*; D056888:Patient Positioning; D016634:Radiosurgery / Q000379:methods*; D012119:Respiration; D013116:Spinal Cord / Q000502:physiology*; D013125:Spinal Neoplasms / Q000556:secondary* / Q000601:surgery*; D016683:Supine Position / Q000502:physiology