title: Film-based delivery quality assurance for robotic radiosurgery: Commissioning and validation.
abstract: OBJECTIVE
  Robotic radiosurgery demands comprehensive delivery quality assurance (DQA), but guidelines for commissioning of the DQA method is missing. We investigated the stability and sensitivity of our film-based DQA method with various test scenarios and routine patient plans. We also investigated the applicability of tight distance-to-agreement (DTA) Gamma-Index criteria.
  
  
  METHODS
  We used radiochromic films with multichannel film dosimetry and re-calibration and our analysis was performed in four steps: 1) Film-to-plan registration, 2) Standard Gamma-Index criteria evaluation (local-pixel-dose-difference ≤2%, distance-to-agreement ≤2 mm, pass-rate ≥90%), 3) Dose distribution shift until maximum pass-rate (Maxγ) was found (shift acceptance <1 mm), and 4) Final evaluation with tight DTA criteria (≤1 mm). Test scenarios consisted of purposefully introduced phantom misalignments, dose miscalibrations, and undelivered MU. Initial method evaluation was done on 30 clinical plans.
  
  
  RESULTS
  Our method showed similar sensitivity compared to the standard End-2-End-Test and incorporated an estimate of global system offsets in the analysis. The simulated errors (phantom shifts, global robot misalignment, undelivered MU) were detected by our method while standard Gamma-Index criteria often did not reveal these deviations. Dose miscalibration was not detected by film alone, hence simultaneous ion-chamber measurement for film calibration is strongly recommended. 83% of the clinical patient plans were within our tight DTA tolerances.
  
  
  CONCLUSIONS
  Our presented methods provide additional measurements and quality references for film-based DQA enabling more sensitive error detection. We provided various test scenarios for commissioning of robotic radiosurgery DQA and demonstrated the necessity to use tight DTA criteria.
authors.affiliation: Universitätsklinikum Schleswig-Holstein, Klinik für Strahlentherapie, Kiel, Germany; Saphir Radiochirurgie Zentrum Norddeutschland, Güstrow, Germany. Electronic address: oliver@blanck.de.
authors.forename: Oliver
authors.initials: O
authors.lastname: Blanck
authors.affiliation: IFCA, Department of Medical Physics and Radiation Oncology, Firenze, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Masi
authors.affiliation: Saphir Radiochirurgie Zentrum Norddeutschland, Güstrow, Germany; Technische Universität Ilmenau, Ilmenau, Germany.
authors.forename: Marie-Christin
authors.initials: MC
authors.lastname: Damme
authors.affiliation: Universitätsklinikum Rostock, Klinik für Strahlentherapie, Rostock, Germany.
authors.forename: Guido
authors.initials: G
authors.lastname: Hildebrandt
authors.affiliation: Universitätsklinikum Schleswig-Holstein, Klinik für Strahlentherapie, Kiel, Germany; University Clinic Copenhagen, Department of Radiation Oncology, Copenhagen, Denmark.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Dunst
authors.affiliation: Universitätsklinikum Schleswig-Holstein, Klinik für Strahlentherapie, Kiel, Germany.
authors.forename: Frank-Andre
authors.initials: FA
authors.lastname: Siebert
authors.affiliation: Carl von Ossietzky Universität, Universitätsklinik für Medizinische Strahlenphysik, Campus Pius Hospital, Oldenburg, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Poppinga
authors.affiliation: Carl von Ossietzky Universität, Universitätsklinik für Medizinische Strahlenphysik, Campus Pius Hospital, Oldenburg, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Poppe
mesh_terms: D002138:Calibration; D005373:Film Dosimetry; D011786:Quality Control; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated; D012371:Robotics
keywords: CyberKnife; Delivery quality assurance; Gafchromic EBT3; Radiochromic film; Stereotactic body radiation therapy; Triple channel dosimetry