title: [Method for evaluating the positional accuracy of a six-degrees-of-freedom radiotherapy couch using high definition digital cameras].
abstract: OBJECTIVE
  In this study, we proposed and evaluated a positional accuracy assessment method with two high-resolution digital cameras for add-on six-degrees-of-freedom radiotherapy (6D) couches.
  
  
  METHODS
  Two high resolution digital cameras (D5000, Nikon Co.) were used in this accuracy assessment method. These cameras were placed on two orthogonal axes of a linear accelerator (LINAC) coordinate system and focused on the isocenter of the LINAC. Pictures of a needle that was fixed on the 6D couch were taken by the cameras during couch motions of translation and rotation of each axis. The coordinates of the needle in the pictures were obtained using manual measurement, and the coordinate error of the needle was calculated. The accuracy of a HexaPOD evo (Elekta AB, Sweden) was evaluated using this method.
  
  
  RESULTS
  All of the mean values of the X, Y, and Z coordinate errors in the translation tests were within ±0.1 mm. However, the standard deviation of the Z coordinate errors in the Z translation test was 0.24 mm, which is higher than the others. In the X rotation test, we found that the X coordinate of the rotational origin of the 6D couch was shifted.
  
  
  CONCLUSIONS
  We proposed an accuracy assessment method for a 6D couch. The method was able to evaluate the accuracy of the motion of only the 6D couch and revealed the deviation of the origin of the couch rotation. This accuracy assessment method is effective for evaluating add-on 6D couch positioning.
authors.affiliation: Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Takemura
authors.forename: Shinichi
authors.initials: S
authors.lastname: Ueda
authors.forename: Kimiya
authors.initials: K
authors.lastname: Noto
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kurata
authors.forename: Saori
authors.initials: S
authors.lastname: Shoji
mesh_terms: D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D010781:Photography / Q000295:instrumentation*; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation* / Q000379:methods; D012680:Sensitivity and Specificity