title: Development of a video image-based QA system for the positional accuracy of dynamic tumor tracking irradiation in the Vero4DRT system.
abstract: OBJECTIVE
  To develop and evaluate a new video image-based QA system, including in-house software, that can display a tracking state visually and quantify the positional accuracy of dynamic tumor tracking irradiation in the Vero4DRT system.
  
  
  METHODS
  Sixteen trajectories in six patients with pulmonary cancer were obtained with the ExacTrac in the Vero4DRT system. Motion data in the cranio-caudal direction (Y direction) were used as the input for a programmable motion table (Quasar). A target phantom was placed on the motion table, which was placed on the 2D ionization chamber array (MatriXX). Then, the 4D modeling procedure was performed on the target phantom during a reproduction of the patient's tumor motion. A substitute target with the patient's tumor motion was irradiated with 6-MV x-rays under the surrogate infrared system. The 2D dose images obtained from the MatriXX (33 frames/s; 40 s) were exported to in-house video-image analyzing software. The absolute differences in the Y direction between the center of the exposed target and the center of the exposed field were calculated. Positional errors were observed. The authors' QA results were compared to 4D modeling function errors and gimbal motion errors obtained from log analyses in the ExacTrac to verify the accuracy of their QA system. The patients' tumor motions were evaluated in the wave forms, and the peak-to-peak distances were also measured to verify their reproducibility.
  
  
  RESULTS
  Thirteen of sixteen trajectories (81.3%) were successfully reproduced with Quasar. The peak-to-peak distances ranged from 2.7 to 29.0 mm. Three trajectories (18.7%) were not successfully reproduced due to the limited motions of the Quasar. Thus, 13 of 16 trajectories were summarized. The mean number of video images used for analysis was 1156. The positional errors (absolute mean difference + 2 standard deviation) ranged from 0.54 to 1.55 mm. The error values differed by less than 1 mm from 4D modeling function errors and gimbal motion errors in the ExacTrac log analyses (n = 13).
  
  
  CONCLUSIONS
  The newly developed video image-based QA system, including in-house software, can analyze more than a thousand images (33 frames/s). Positional errors are approximately equivalent to those in ExacTrac log analyses. This system is useful for the visual illustration of the progress of the tracking state and for the quantification of positional accuracy during dynamic tumor tracking irradiation in the Vero4DRT system.
authors.affiliation: Joetsu General Hospital, 616 Daido-Fukuda, Joetsu-shi, Niigata 943-8507, Japan.
authors.forename: Kazuyu
authors.initials: K
authors.lastname: Ebe
authors.affiliation: Juntendo University Graduate School of Medicine, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Sugimoto
authors.affiliation: Graduate School of Medical and Dental Sciences, Niigata University, Niigata 951-8510, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Utsunomiya
authors.affiliation: Graduate School of Medical and Dental Sciences, Niigata University, Niigata 951-8510, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kagamu
authors.affiliation: Graduate School of Medical and Dental Sciences, Niigata University, Niigata 951-8510, Japan.
authors.forename: Hidefumi
authors.initials: H
authors.lastname: Aoyama
authors.affiliation: The University of Texas MD Anderson Cancer Center, Houston, Texas 77030-4009.
authors.forename: Laurence
authors.initials: L
authors.lastname: Court
authors.affiliation: Joetsu General Hospital, 616 Daido-Fukuda, Joetsu-shi, Niigata 943-8507, Japan.
authors.forename: Katsuichi
authors.initials: K
authors.lastname: Tokuyama
authors.affiliation: Joetsu General Hospital, 616 Daido-Fukuda, Joetsu-shi, Niigata 943-8507, Japan.
authors.forename: Ryuta
authors.initials: R
authors.lastname: Baba
authors.affiliation: Joetsu General Hospital, 616 Daido-Fukuda, Joetsu-shi, Niigata 943-8507, Japan.
authors.forename: Yoshisada
authors.initials: Y
authors.lastname: Ogihara
authors.affiliation: Joetsu General Hospital, 616 Daido-Fukuda, Joetsu-shi, Niigata 943-8507, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Ichikawa
authors.affiliation: Joetsu General Hospital, 616 Daido-Fukuda, Joetsu-shi, Niigata 943-8507, Japan.
authors.forename: Joji
authors.initials: J
authors.lastname: Toyama
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D057918:Fiducial Markers; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008175:Lung Neoplasms / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D009038:Motion; D019047:Phantoms, Imaging; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation / Q000379:methods*; D012984:Software; D014741:Video Recording / Q000379:methods*