title: Rotational and translational reproducibility of newly developed Leksell frame-based relocatable fixation system.
abstract: OBJECTIVE
  The aim of this study was to evaluate three-dimensional movement of the cranium in a relocatable frame using positions of anatomical landmarks obtained from repeated quality-assurance (QA) computed tomography (CT) studies.
  
  
  METHODS
  We analyzed 17 series of QA-CT data representing five patients who underwent stereotactic radiotherapy for treatment of acoustic neurinoma. Helical-CT scans with 1-mm collimation were obtained at the time of treatment planning and during the course of treatment. The right and left short processes of the incus and the top of the crista galli were used as the three anatomical reference points.
  
  
  RESULTS
  Fluctuations in distance among the reference points were all <1 mm. The translational displacements for these points were <2 mm, with standard deviations (SD) of <2 mm. A plane that included all three reference points was defined as the reference plane. To investigate the direction of cranial rotation for each QA-CT scan, unit normal vectors of the reference plane were obtained. Three-dimensional analyses indicated that cranial rotation was greatest along the X-axis, followed by the Y-axis, with the least rotation along the Z-axis.
  
  
  CONCLUSIONS
  The result suggested that movement of the craniocaudal axis in the sagittal plane was a major factor behind displacement of the cranium.
authors.affiliation: Department of Radiology, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. kunieda-mi@umin.ac.jp
authors.forename: Etsuo
authors.initials: E
authors.lastname: Kunieda
authors.forename: Hossain M
authors.initials: HM
authors.lastname: Deloar
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kitamura
authors.forename: Osamu
authors.initials: O
authors.lastname: Kawaguchi
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Shiba
authors.forename: Atsuya
authors.initials: A
authors.lastname: Takeda
authors.forename: Takatsugu
authors.initials: T
authors.lastname: Kawase
authors.forename: Satoshi
authors.initials: S
authors.lastname: Seki
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Shigematsu
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kubo
mesh_terms: D000328:Adult; D019583:Dose Fractionation, Radiation; D004867:Equipment Design; D005260:Female; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D007103:Immobilization / Q000295:instrumentation*; D008297:Male; D008875:Middle Aged; D009068:Movement; D009464:Neuroma, Acoustic / Q000000981:diagnostic imaging / Q000532:radiotherapy; D011786:Quality Control; D011879:Radiotherapy Dosage; D013238:Stereotaxic Techniques / Q000295:instrumentation*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*