title: Tracking accuracy of a real-time fiducial tracking system for patient positioning and monitoring in radiation therapy.
abstract: OBJECTIVE
  In radiation therapy there is a need to accurately know the location of the target in real time. A novel radioactive tracking technology has been developed to answer this need. The technology consists of a radioactive implanted fiducial marker designed to minimize migration and a linac mounted tracking device. This study measured the static and dynamic accuracy of the new tracking technology in a clinical radiation therapy environment.
  
  
  METHODS
  The tracking device was installed on the linac gantry. The radioactive marker was located in a tissue equivalent phantom. Marker location was measured simultaneously by the radioactive tracking system and by a Microscribe G2 coordinate measuring machine (certified spatial accuracy of 0.38 mm). Localization consistency throughout a volume and absolute accuracy in the Fixed coordinate system were measured at multiple gantry angles over volumes of at least 10 cm in diameter centered at isocenter. Dynamic accuracy was measured with the marker located inside a breathing phantom.
  
  
  RESULTS
  The mean consistency for the static source was 0.58 mm throughout the tested region at all measured gantry angles. The mean absolute position error in the Fixed coordinate system for all gantry angles was 0.97 mm. The mean real-time tracking error for the dynamic source within the breathing phantom was less than 1 mm.
  
  
  CONCLUSIONS
  This novel radioactive tracking technology has the potential to be useful in accurate target localization and real-time monitoring for radiation therapy.
authors.affiliation: Navotek Medical, Ltd., Yokneam, Israel.
authors.forename: Tal
authors.initials: T
authors.lastname: Shchory
authors.forename: Dan
authors.initials: D
authors.lastname: Schifter
authors.forename: Rinat
authors.initials: R
authors.lastname: Lichtman
authors.forename: David
authors.initials: D
authors.lastname: Neustadter
authors.forename: Benjamin W
authors.initials: BW
authors.lastname: Corn
mesh_terms: D003199:Computer Systems; D004867:Equipment Design; D006801:Humans; D008297:Male; D056888:Patient Positioning; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D019736:Prostheses and Implants; D011834:Radiation Monitoring / Q000295:instrumentation / Q000379:methods; D011851:Radioactivity; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012119:Respiration