High resolution ion chamber array delivery quality assurance for robotic radiosurgery: Commissioning and validation |
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Institution: | 1. Universitätsklinikum Schleswig-Holstein, Klinik für Strahlentherapie, Kiel, Germany;2. Saphir Radiochirurgie Zentrum, Frankfurt und Güstrow, Germany;3. IFCA, Department of Medical Physics and Radiation Oncology, Firenze, Italy;4. TuenMun Hospital, Hong Kong, Hong Kong;5. Greater Poland Cancer Centre, Medical Physics Department, Poznan, Poland;6. IntraOp Medical Corporation, Sunnyvale, USA;7. Schwarzwald-Baar-Klinikum, Klinik für Strahlentherapie, Villingen-Schwenningen, Germany;8. Technische Universität Ilmenau, Ilmenau, Germany;9. Universitätsklinikum Frankfurt am Main, Klinik für Strahlentherapie, Frankfurt, Germany;10. Universitätsklinikum Rostock, Klinik für Strahlentherapie, Rostock, Germany;11. Carl von Ossietzky Universität, Universitätsklinik für Medizinische Strahlenphysik, Campus Pius Hospital, Oldenburg, Germany |
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Abstract: | PurposeHigh 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 and materialPreliminary 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 ⩽ 2 mm, pass-rate ⩾ 90%), (3) Dose profile alignment and dose distribution shift until maximum pass-rate is found, and (4) Final evaluation with 1 mm 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.ResultsThe 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 10 cm 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 1 mm distance-to-agreement criterion while 2 mm criteria failed to reveal some of these deviations. All analyzed delivery-quality-assurance clinical patient plans were within our tight tolerance criteria.ConclusionWe 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. |
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Keywords: | Delivery quality assurance Liquid filled MicroLion ion chamber array Stereotactic body radiation therapy CyberKnife robotic radiosurgery |
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