title: Quantification of respiration-induced esophageal tumor motion using fiducial markers and four-dimensional computed tomography.
abstract: OBJECTIVE
  Respiration-induced tumor motion is an important geometrical uncertainty in esophageal cancer radiation therapy. The aim of this study was to quantify this motion using fiducial markers and four-dimensional computed tomography (4DCT).
  
  
  METHODS
  Twenty esophageal cancer patients underwent endoscopy-guided marker implantation in the tumor volume and 4DCT acquisition. The 4DCT data were sorted into 10 breathing phases and the end-of-inhalation phase was selected as reference. We quantified for each visible marker (n=60) the motion in each phase and derived the peak-to-peak motion magnitude throughout the breathing cycle. The motion was quantified and analyzed for four different regions and in three orthogonal directions.
  
  
  RESULTS
  The median(interquartile range) of the peak-to-peak magnitudes of the respiration-induced marker motion (left-right/anterior-posterior/cranial-caudal) was 1.5(0.5)/1.6(0.5)/2.9(1.4) mm for the proximal esophagus (n=6), 1.5(1.4)/1.4(1.3)/3.7(2.6) mm for the middle esophagus (n=12), 2.6(1.3)/3.3(1.8)/5.4(2.9) mm for the distal esophagus (n=25), and 3.7(2.1)/5.3(1.8)/8.2(3.1) mm for the proximal stomach (n=17).
  
  
  CONCLUSIONS
  The variations in the results between the three directions, four regions, and patients suggest the need of individualized region-dependent anisotropic internal margins. Therefore, we recommend using markers with 4DCT to patient-specifically adapt the internal target volume (ITV). Without 4DCT, 3DCTs at the end-of-inhalation and end-of-exhalation phases could be alternatively applied for ITV individualization.
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, The Netherlands. Electronic address: p.jin@amc.uva.nl.
authors.forename: Peng
authors.initials: P
authors.lastname: Jin
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, The Netherlands.
authors.forename: Maarten C C M
authors.initials: MC
authors.lastname: Hulshof
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, The Netherlands.
authors.forename: Rianne
authors.initials: R
authors.lastname: de Jong
authors.affiliation: Department of Gastroenterology and Hepatology, Academic Medical Center, University of Amsterdam, The Netherlands.
authors.forename: Jeanin E
authors.initials: JE
authors.lastname: van Hooft
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, The Netherlands.
authors.forename: Arjan
authors.initials: A
authors.lastname: Bel
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, The Netherlands.
authors.forename: Tanja
authors.initials: T
authors.lastname: Alderliesten
mesh_terms: D004938:Esophageal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D057918:Fiducial Markers; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D009038:Motion; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015656:Respiratory Mechanics / Q000502:physiology*; D012189:Retrospective Studies
keywords: 4DCT; Esophageal cancer; Fiducial marker; Radiation therapy; Respiration-induced motion