title: Synchronous monitoring of external/internal respiratory motion: validity of respiration-gated radiotherapy for liver tumors.
abstract: OBJECTIVE
  Four-dimensional (4D) radiotherapy, in particular respiration gating for the treatment of lung tumors, is gaining popularity. Its utility for other sites, however, has not been investigated fully. The purpose of this study was to see whether 4D therapy is feasible for liver tumors.
  
  
  METHODS
  Six patients (five with hepatomas and one with metastatic liver tumor) had a fiducial, gold marker 1.5 mm in diameter implanted in the vicinity of their liver tumors. The inner and external (i.e., upper abdominal wall) respiratory movements were simultaneously recorded using a real-time tumor-tracking radiotherapy system and respiration monitor equipment applied to the mid to upper abdomen.
  
  
  RESULTS
  The fluctuations from the baseline position of liver tumors were small; the mean absolute value was 3.92 +/- 1.94 mm. The mean right-left, anteroposterior, and craniocaudal total movements were 4.19 +/- 2.46, 7.23 +/- 2.96, and 15.98 +/- 6.02 mm, respectively. The phase shift was negligible.
  
  
  CONCLUSIONS
  Liver tumors may be suitable for respiration-gated radiotherapy, and they may become curable with 4D radiotherapy.
authors.affiliation: Laboratory of Radiation Therapy, Graduate School of Health Sciences, Hokkaido University, Kita-ku, Sapporo, Japan. trout@hs.hokudai.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishioka
authors.forename: Seiko
authors.initials: S
authors.lastname: Nishioka
authors.forename: Masaki
authors.initials: M
authors.lastname: Kawahara
authors.forename: Shigeru
authors.initials: S
authors.lastname: Tanaka
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
authors.forename: Ken
authors.initials: K
authors.lastname: Nishi
authors.forename: Tadao
authors.initials: T
authors.lastname: Hiromura
mesh_terms: D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D011880:Radiotherapy Planning, Computer-Assisted; D055425:Respiratory-Gated Imaging Techniques; D014057:Tomography, X-Ray Computed / Q000379:methods*