title: Comparison of respiratory-gated and respiratory-ungated planning in scattered carbon ion beam treatment of the pancreas using four-dimensional computed tomography.
abstract: OBJECTIVE
  We compared respiratory-gated and respiratory-ungated treatment strategies using four-dimensional (4D) scattered carbon ion beam distribution in pancreatic 4D computed tomography (CT) datasets.
  
  
  METHODS
  Seven inpatients with pancreatic tumors underwent 4DCT scanning under free-breathing conditions using a rapidly rotating cone-beam CT, which was integrated with a 256-slice detector, in cine mode. Two types of bolus for gated and ungated treatment were designed to cover the planning target volume (PTV) using 4DCT datasets in a 30% duty cycle around exhalation and a single respiratory cycle, respectively. Carbon ion beam distribution for each strategy was calculated as a function of respiratory phase by applying the compensating bolus to 4DCT at the respective phases. Smearing was not applied to the bolus, but consideration was given to drill diameter. The accumulated dose distributions were calculated by applying deformable registration and calculating the dose-volume histogram.
  
  
  RESULTS
  Doses to normal tissues in gated treatment were minimized mainly on the inferior aspect, which thereby minimized excessive doses to normal tissues. Over 95% of the dose, however, was delivered to the clinical target volume at all phases for both treatment strategies. Maximum doses to the duodenum and pancreas averaged across all patients were 43.1/43.1 GyE (ungated/gated) and 43.2/43.2 GyE (ungated/gated), respectively.
  
  
  CONCLUSIONS
  Although gated treatment minimized excessive dosing to normal tissue, the difference between treatment strategies was small. Respiratory gating may not always be required in pancreatic treatment as long as dose distribution is assessed. Any application of our results to clinical use should be undertaken only after discussion with oncologists, particularly with regard to radiotherapy combined with chemotherapy.
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan. shinshin@nirs.go.jp
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Mori
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yanagi
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Hara
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Sharp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Asakura
authors.forename: Motoki
authors.initials: M
authors.lastname: Kumagai
authors.forename: Riwa
authors.initials: R
authors.lastname: Kishimoto
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yamada
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Kato
authors.forename: Susumu
authors.initials: S
authors.lastname: Kandatsu
authors.forename: Tadashi
authors.initials: T
authors.lastname: Kamada
mesh_terms: D002244:Carbon / Q000627:therapeutic use*; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D063193:Heavy Ion Radiotherapy; D006801:Humans; D008875:Middle Aged; D009068:Movement; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012119:Respiration; D047368:Tumor Burden
chemical_list: D002244:Carbon