title: Four-dimensional computed tomographic analysis of esophageal mobility during normal respiration.
abstract: BACKGROUND
  Chemo-radiotherapy for thoracic tumors can result in high-grade radiation esophagitis. Treatment planning to reduce esophageal irradiation requires organ motion to be accounted for. In this study, esophageal mobility was assessed using four-dimensional computed tomography (4DCT).
  
  
  METHODS
  Thoracic 4DCT scans were acquired on a 16-slice CT scanner in 29 patients. The outer esophageal wall was contoured in two extreme phases of respiration in 9 patients with nonesophageal malignancies. The displacement of the center of contour was measured at 2-cm intervals. In 20 additional patients with Stage I lung cancer, the esophagus was contoured in all 10 phases of each 4DCT at five defined anatomic levels. Both approaches were then applied to 4DCT scans of 4 patients who each had two repeat scans performed. A linear mixed effects model was constructed with fixed effects: measurement direction, measurement type, and measurement location along the cranio-caudal axis.
  
  
  RESULTS
  Measurement location and direction were significant descriptive parameters (Wald F-tests, p < 0.001), and the interaction term between the two was significant (p = 0.02). Medio-lateral mobility exceeded dorso-ventral mobility in the lower half of the esophagus but was of a similar magnitude in the upper half. Margins that would have incorporated all movement in medio-lateral and dorso-ventral directions were 5 mm proximally, 7 mm and 6 mm respectively in the mid-esophagus, and 9 mm and 8 mm respectively in the distal esophagus.
  
  
  CONCLUSIONS
  The distal esophagus shows more mobility. Margins for mobility that can encompass all movement were derived for use in treatment planning, particularly for stereotactic radiotherapy.
authors.affiliation: Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Edith M T
authors.initials: EM
authors.lastname: Dieleman
authors.forename: Suresh
authors.initials: S
authors.lastname: Senan
authors.forename: Andrew
authors.initials: A
authors.lastname: Vincent
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Lagerwaard
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Slotman
authors.forename: John R
authors.initials: JR
authors.lastname: van Sörnsen de Koste
mesh_terms: D004947:Esophagus; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D009068:Movement; D015203:Reproducibility of Results; D012119:Respiration; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*