title: Impact of using different four-dimensional computed tomography data sets to design proton treatment plans for distal esophageal cancer.
abstract: OBJECTIVE
  To study the impact of selecting different data sets from four-dimensional computed tomography (4D CT) imaging during proton treatment planning in patients with distal esophageal cancer.
  
  
  METHODS
  We examined the effects of changes in 4D CT data set and smearing margins in proton treatment planning for 5 patients with distal esophageal cancer whose diaphragms were in the beam path and could move several centimeters during respiration. Planning strategies based on (1) average, (2) inspiration, and (3) expiration CT were evaluated in terms of their coverage on the internal clinic target volume (ICTV) at the prescribed dose.
  
  
  RESULTS
  For Strategy 1, increasing the smearing margin caused an increase in the ICTV prescription dose coverage (PDC) at the end-exhalation phase for all patients, whereas the ICTV PDC decreased for some patients at the end-inhalation phase. For Strategy 2, a smearing margin in the range of 1.0 to 3.5 cm caused the ICTV PDC to remain essentially unchanged, regardless of which phase of 4D CT was used for dose calculation, for all patients. For Strategy 3, the ICTV coverage was adequate for 2 of the 5 patients when a smearing margin of less than 1.0 cm was used, but was not adequate for the other 3 patients regardless of the smearing margin.
  
  
  CONCLUSIONS
  Using the inspiration CT plus a smearing margin can lead to adequate ICTV coverage in treatment plans for patients with distal esophageal tumors surrounded by tissue that is subject to large changes in density during a proton treatment.
authors.affiliation: Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA.
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Pan
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zhang
authors.forename: Yupeng
authors.initials: Y
authors.lastname: Li
authors.forename: Radhe
authors.initials: R
authors.lastname: Mohan
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Liao
mesh_terms: D003964:Diaphragm / Q000000981:diagnostic imaging; D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D005260:Female; D006801:Humans; D001239:Inhalation; D008297:Male; D009068:Movement; D061766:Proton Therapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012119:Respiration; D014057:Tomography, X-Ray Computed / Q000379:methods*; D011522:Protons
chemical_list: D011522:Protons