title: [Dose reconstruction using respiratory signals and machine parameters during treatment in stereotactic body radiotherapy].
abstract: OBJECTIVE
  Volumetric modulated arc therapy (VMAT) is a rotational intensity-modulated radiotherapy (IMRT) technique capable of acquiring projection images during treatment. The purpose of this study was to reconstruct the dose distribution from respiratory signals and machine parameters acquired during stereotactic body radiotherapy (SBRT).
  
  
  METHODS
  The treatment plans created for VMAT-SBRT included the constraint of 1 mm/degree in multileaf collimator (MLC) for a moving phantom and three patients with lung tumors. The respiratory signals were derived from projection images acquired during VMAT delivery, while the machine parameters were derived from machine logs. The respiratory signals and machine parameters were then linked along with the gantry angle. With this data, the dose distribution of each respiratory phase was calculated on the planned four-dimensional CT (4D CT). The doses at the isocenter, the point of max dose and the centroid of the target were compared with those of the corresponding plans.
  
  
  CONCLUSIONS
  In the phantom study, the maximum dose difference between the plan and "in-treatment" results was -0.4% at the centroid of the target. In the patient study, the difference was -1.8 ± 0.4% at the centroid of the target. Dose differences of the evaluated points between 4 and 10 phases were not significant.
  
  
  CONCLUSIONS
  The present method successfully reconstructed the dose distribution using the respiratory signals and machine parameters acquired during treatment. This is a feasible method for verifying the actual dose for a moving target.
authors.affiliation: Department of Radiology, University of Tokyo Hospital.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Imae
authors.forename: Akihiro
authors.initials: A
authors.lastname: Haga
authors.forename: Naoya
authors.initials: N
authors.lastname: Saotome
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kida
authors.forename: Masahiro
authors.initials: M
authors.lastname: Nakano
authors.forename: Shigeharu
authors.initials: S
authors.lastname: Takenaka
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Takeuchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Shiraki
authors.forename: Keiichi
authors.initials: K
authors.lastname: Yano
authors.forename: Hideomi
authors.initials: H
authors.lastname: Yamashita
authors.forename: Keiichi
authors.initials: K
authors.lastname: Nakagawa
authors.forename: Kuni
authors.initials: K
authors.lastname: Ohtomo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000532:radiotherapy; D008297:Male; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D014057:Tomography, X-Ray Computed / Q000295:instrumentation