title: Effect of patient positioning on carbon-ion therapy planned dose distribution to pancreatic tumors and organs at risk.
abstract: OBJECTIVE
  Pancreatic tumor treatment dose distribution variations associated with supine and prone patient positioning were evaluated.
  
  
  METHODS
  A total of 33 patients with pancreatic tumors who underwent CT in the supine and prone positions were analyzed retrospectively. Gross tumor volume (GTV), planning target volume (PTV), and organs at risk (OARs) (duodenum and stomach) were contoured. The prescribed dose of 55.2Gy (RBE) was planned from four beam angles (0°, 90°, 180°, and 270°). Patient collimator and compensating boli were designed for each field. Dose distributions were calculated for each field in the supine and prone positions. To improve dose distribution, patient positioning was selected from supine or prone for each beam field.
  
  
  RESULTS
  Compared with conventional beam angle and patient positioning, D2cc of 1st-2nd portion of duodenum (D1-D2), 3rd-4th portion of duodenum (D3-D4), and stomach could be reduced to a maximum of 6.4Gy (RBE), 3.5Gy (RBE), and 4.5Gy (RBE) by selection of patient positioning. V10 of D1-D2, D3-D4, and stomach could be reduced to a maximum of 7.2cc, 11.3cc, and 11.5cc, respectively. D95 of GTV and PTV were improved to a maximum of 6.9% and 3.7% of the prescribed dose, respectively.
  
  
  CONCLUSIONS
  Optimization of patient positioning for each beam angle in treatment planning has the potential to reduce OARs dose maintaining tumor dose in pancreatic treatment.
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.
authors.forename: Mai
authors.initials: M
authors.lastname: Fukahori
authors.affiliation: Particle Therapy Division, Research Center for Innovative Oncology, National Cancer Center East, 6-5-1 Kashiwa, Chiba 277-8577, Japan.
authors.forename: Motoki
authors.initials: M
authors.lastname: Kumagai
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
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
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; 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 / Q000532:radiotherapy*; D056888:Patient Positioning; D016684:Prone Position; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies; D016683:Supine Position
keywords: Carbon ion radiotherapy; Dose distribution; Pancreatic cancer; Patient positioning