title: Assessment of spatial uncertainty in computed tomography-based Gamma Knife stereotactic radiosurgery process with automated positioning system.
abstract: BACKGROUND
  In this study, we assessed the geometric accuracy of an automated positioning system in Gamma Knife (GK) surgery. Specifically, we looked at the total spatial uncertainty over the entire treatment range of GK stereotactic radiosurgery (SRS) procedures in both the GK model C and the Perfexion (PFX).
  
  
  METHODS
  An originally-developed phantom and a radiochromic film were used for obtaining actual dose distributions. The phantom, with inserted films on different axial planes (z = 60, 75, 100, 125, 140 mm), sagittal planes (x = 60, 75, 100, 125, 140 mm), and coronal planes (y = 60, 75, 100, 125, 140 mm), was placed on a Leksell skull frame. Computed tomography (CT) was then performed with a stereotactic localizer box attached to the frame, and dose planning was made using the Leksell GammaPlan treatment planning system. The phantom finally received beam delivery using a single shot of a 4-mm collimator helmet. The discrepancy between the planned shot position and the irradiated center position was evaluated by a dedicated film analysis software.
  
  
  RESULTS
  The total uncertainty of CT-based GK SRS was less than 1 mm for almost all measured points over the stereotactic space in both the model C and the PFX. In addition, the geometric accuracy of the automated positioning system was estimated to be less than 0.1 mm and equal to 0.5 mm in the central and peripheral areas, respectively.
  
  
  CONCLUSIONS
  We confirmed that the total spatial uncertainties of both the GK model C and the PFX are acceptable for clinical use.
authors.affiliation: Department of Radiological Sciences, Nagoya University Graduate School of Medicine, 1-1-20 Daikominami Higashiku, Nagoya, Aichi, 461-8673, Japan, hnakazawa@kaikou.or.jp.
authors.forename: Hisato
authors.initials: H
authors.lastname: Nakazawa
authors.forename: Masataka
authors.initials: M
authors.lastname: Komori
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Oguchi
authors.forename: Yuta
authors.initials: Y
authors.lastname: Shibamoto
authors.forename: Takahiko
authors.initials: T
authors.lastname: Tsugawa
authors.forename: Yukio
authors.initials: Y
authors.lastname: Uchiyama
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kobayashi
mesh_terms: D001331:Automation / Q000295:instrumentation / Q000379:methods; D006801:Humans; D019047:Phantoms, Imaging; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods*; D012886:Skull / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D035501:Uncertainty