title: High resolution ion chamber array delivery quality assurance for robotic radiosurgery: Commissioning and validation.
abstract: OBJECTIVE
  High precision radiosurgery demands comprehensive delivery-quality-assurance techniques. The use of a liquid-filled ion-chamber-array for robotic-radiosurgery delivery-quality-assurance was investigated and validated using several test scenarios and routine patient plans.
  
  
  METHODS
  Preliminary evaluation consisted of beam profile validation and analysis of source-detector-distance and beam-incidence-angle response dependence. The delivery-quality-assurance analysis is performed in four steps: (1) Array-to-plan registration, (2) Evaluation with standard Gamma-Index criteria (local-dose-difference⩽2%, distance-to-agreement⩽2mm, pass-rate⩾90%), (3) Dose profile alignment and dose distribution shift until maximum pass-rate is found, and (4) Final evaluation with 1mm distance-to-agreement criterion. Test scenarios consisted of intended phantom misalignments, dose miscalibrations, and undelivered Monitor Units. Preliminary method validation was performed on 55 clinical plans in five institutions.
  
  
  RESULTS
  The 1000SRS profile measurements showed sufficient agreement compared with a microDiamond detector for all collimator sizes. The relative response changes can be up to 2.2% per 10cm source-detector-distance change, but remains within 1% for the clinically relevant source-detector-distance range. Planned and measured dose under different beam-incidence-angles showed deviations below 1% for angles between 0° and 80°. Small-intended errors were detected by 1mm distance-to-agreement criterion while 2mm criteria failed to reveal some of these deviations. All analyzed delivery-quality-assurance clinical patient plans were within our tight tolerance criteria.
  
  
  CONCLUSIONS
  We demonstrated that a high-resolution liquid-filled ion-chamber-array can be suitable for robotic radiosurgery delivery-quality-assurance and that small errors can be detected with tight distance-to-agreement criterion. Further improvement may come from beam specific correction for incidence angle and source-detector-distance response.
authors.affiliation: Universitätsklinikum Schleswig-Holstein, Klinik für Strahlentherapie, Kiel, Germany; Saphir Radiochirurgie Zentrum, Frankfurt und 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: TuenMun Hospital, Hong Kong, Hong Kong.
authors.forename: Mark K H
authors.initials: MK
authors.lastname: Chan
authors.affiliation: Greater Poland Cancer Centre, Medical Physics Department, Poznan, Poland; IntraOp Medical Corporation, Sunnyvale, USA.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Adamczyk
authors.affiliation: Schwarzwald-Baar-Klinikum, Klinik für Strahlentherapie, Villingen-Schwenningen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Albrecht
authors.affiliation: Saphir Radiochirurgie Zentrum, Frankfurt und Güstrow, Germany; Technische Universität Ilmenau, Ilmenau, Germany.
authors.forename: Marie-Christin
authors.initials: MC
authors.lastname: Damme
authors.affiliation: Universitätsklinikum Frankfurt am Main, Klinik für Strahlentherapie, Frankfurt, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Loutfi-Krauss
authors.affiliation: Schwarzwald-Baar-Klinikum, Klinik für Strahlentherapie, Villingen-Schwenningen, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Alraun
authors.affiliation: Universitätsklinikum Rostock, Klinik für Strahlentherapie, Rostock, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Fehr
authors.affiliation: Universitätsklinikum Frankfurt am Main, Klinik für Strahlentherapie, Frankfurt, Germany.
authors.forename: Ulla
authors.initials: U
authors.lastname: Ramm
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: Tenzin Sonam
authors.initials: TS
authors.lastname: Stelljes
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: D006801:Humans; D011785:Quality Assurance, Health Care; D011874:Radiometry / Q000295:instrumentation*; D016634:Radiosurgery / Q000295:instrumentation*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012371:Robotics
keywords: CyberKnife robotic radiosurgery; Delivery quality assurance; Liquid filled MicroLion ion chamber array; Stereotactic body radiation therapy