title: Gated carbon-ion scanning treatment for pancreatic tumour with field specific target volume and organs at risk.
abstract: OBJECTIVE
  To assess the feasibility of treatment planning for pancreatic tumours subject to respiratory motion using field-specific target volumes (FTV) and field-specific organs at risk (FOAR) using four-dimensional computed tomography (4DCT).
  
  
  METHODS
  Fourteen pancreatic cancer patients underwent 4DCT. Radiation oncologists contoured the gross tumour volume (GTV), clinical target volume (CTV), spinal cord, duodenum, kidneys, and stomach. The gating duty cycle was set to 30 % around exhalation. FTV and FOAR were calculated using the 4DCT dataset. Planning target volumes (PTV) and planning organs at risk volumes (PRV) were defined as equal to FTV and FOAR, respectively. A dose of 55.2Gy relative biological effectiveness (RBE) was planned to target the PTV from four beam angles. A single field uniform dose (SFUD) plan was selected. The dose distribution, including intrafractional motion changes, was generated.
  
  
  RESULTS
  The mean volume of target receiving 95 % of the planned doses was 96.4±4.1 % to the GTV and 94.7±0.9 % to the CTV. The highest dose to 2cc of duodenal volume was 27.5Gy (RBE). The volume of the stomach receiving ⩾30Gy (RBE) was <7.0cc in all patients. All metrics for OARs satisfied dose constraints.
  
  
  CONCLUSIONS
  Dose to the CTV was covered sufficiently by the 4DCT-generated FTV, and dose to OARs was reduced by 4DCT-generated FOAR. This methodology may prevent adverse reactions while preserving local tumour control.
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Miki
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan. Electronic address: mori.shinichiro@qst.go.jp.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Mori
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Shiomi
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yamada
mesh_terms: D005260:Female; D056973:Four-Dimensional Computed Tomography; D063193:Heavy Ion Radiotherapy / Q000009:adverse effects* / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects*; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D055425:Respiratory-Gated Imaging Techniques; D047368:Tumor Burden / Q000528:radiation effects*
keywords: Carbon-ion radiotherapy; Organ motion; Pancreatic cancer; Scanning beam