title: Displacement of hepatic tumor at time to exposure in end-expiratory-triggered-pulse proton therapy.
abstract: OBJECTIVE
  This study is to evaluate reproducibility of hepatic tumors in end-expiration and end-inspiration on free-breathing, also measure shift of hepatic tumor location in pulsed proton beams exposure in end-expiration in order to estimate feasible planning target volume (PTV) margin.
  
  
  METHODS
  Pairs (1232) of anterior and lateral radiographs from 30 patients (628 end-expiration and 604 end-inspiration phases) were analyzed using fiducial markers adjacent to the tumors. By using the co-ordinates of the marker centroid of mass related to the isocenter, intrafractional variation was compared in end-expiration and end-inspiration, and a feasible PTV margin was generated using the measured motion.
  
  
  RESULTS
  The average internal motion in end-expiration was 1.1mm, which was significantly smaller than that in end-inspiration. The mean deviation from the plan was -0.1, 0.3, and 0.1mm in the left-right (LR), cranio-cepharal (CC), and anterior-posterior (AP) directions, respectively. The estimated PTV margins were 3.2, 3.5, and 4.6mm, in the LR, CC, and AP directions, respectively.
  
  
  CONCLUSIONS
  It was indicated that localization of the targets was more reproducibility in end-expiration than that in end-inspiration. Also, feasible and practical margin values were obtained. These should contribute accuracy of respiration synchronized proton radiotherapy for liver tumors.
authors.affiliation: Department of Radiation Oncology and Proton Medical Research Center, Tsukuba University, Ibaraki, Japan. ooyoshiko@pmrc.tsukuba.ac.jp
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Oshiro
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Okumura
authors.forename: Masaya
authors.initials: M
authors.lastname: Ishida
authors.forename: Shinji
authors.initials: S
authors.lastname: Sugahara
authors.forename: Masashi
authors.initials: M
authors.lastname: Mizumoto
authors.forename: Takayuki
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Yasuoka
authors.forename: Koji
authors.initials: K
authors.lastname: Tsuboi
authors.forename: Takeji
authors.initials: T
authors.lastname: Sakae
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Sakurai
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D005260:Female; D057918:Fiducial Markers; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D061766:Proton Therapy; D011880:Radiotherapy Planning, Computer-Assisted; D015203:Reproducibility of Results; D012119:Respiration; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D011522:Protons
chemical_list: D011522:Protons