Serenella Russo1, Laura Masi2, Paolo Francescon3, Maria Cristina Frassanito4, Maria Luisa Fumagalli5, Marco Marinelli6, Maria Daniela Falco6, Anna Stefania Martinotti7, Maria Pimpinella8, Giacomo Reggiori9, Gianluca Verona Rinati6, Sabrina Vigorito10, Pietro Mancosu9. 1. Medical Physics Unit of Radiation Oncology Dept, Azienda Sanitaria Firenze, I-50012 Firenze, Italy. Electronic address: serenella.russo@asf.toscana.it. 2. Department of Medical Physics and Radiation Oncology, IFCA, I-50139 Firenze, Italy. 3. Department of Radiation Oncology, Ospedale Di Vicenza, I-36100 Vicenza, Italy. 4. Radiotherapy Department, Mater Dei Hospital, Città di Bari Hospital spa, I-70124 Bari, Italy. 5. Radiotherapy Department, Istituto Neurologico Besta, I-20133 Milano, Italy. 6. Università di Roma 'Tor Vergata', I-00133 Roma, Italy. 7. Radiotherapy Department, Centro Diagnostico Italiano, I-20147 Milano, Italy. 8. Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA-INMRI C R Casaccia, I-00123 Roma, Italy. 9. Medical Physics Unit of Radiation Oncology Dept., Humanitas Research Hospital, I-20089 Milano, Italy. 10. Radiotherapy Department, Istituto Europeo Oncologia, I-20141 Milano, Italy.
Abstract
PURPOSE: The aim of the present work was to evaluate small field size output factors (OFs) using the latest diamond detector commercially available, PTW-60019 microDiamond, over different CyberKnife systems. OFs were measured also by silicon detectors routinely used by each center, considered as reference. METHODS: Five Italian CyberKnife centers performed OFs measurements for field sizes ranging from 5 to 60mm, defined by fixed circular collimators (5 centers) and by Iris(™) variable aperture collimator (4 centers). Setup conditions were: 80cm source to detector distance, and 1.5cm depth in water. To speed up measurements two diamond detectors were used and their equivalence was evaluated. MonteCarlo (MC) correction factors for silicon detectors were used for comparing the OF measurements. RESULTS: Considering OFs values averaged over all centers, diamond data resulted lower than uncorrected silicon diode ones. The agreement between diamond and MC corrected silicon values was within 0.6% for all fixed circular collimators. Relative differences between microDiamond and MC corrected silicon diodes data for Iris(™) collimator were lower than 1.0% for all apertures in the totality of centers. The two microDiamond detectors showed similar characteristics, in agreement with the technical specifications. CONCLUSIONS: Excellent agreement between microDiamond and MC corrected silicon diode detectors OFs was obtained for both collimation systems fixed cones and Iris(™), demonstrating the microDiamond could be a suitable detector for CyberKnife commissioning and routine checks. These results obtained in five centers suggest that for CyberKnife systems microDiamond can be used without corrections even at the smallest field size.
PURPOSE: The aim of the present work was to evaluate small field size output factors (OFs) using the latest diamond detector commercially available, PTW-60019 microDiamond, over different CyberKnife systems. OFs were measured also by silicon detectors routinely used by each center, considered as reference. METHODS: Five Italian CyberKnife centers performed OFs measurements for field sizes ranging from 5 to 60mm, defined by fixed circular collimators (5 centers) and by Iris(™) variable aperture collimator (4 centers). Setup conditions were: 80cm source to detector distance, and 1.5cm depth in water. To speed up measurements two diamond detectors were used and their equivalence was evaluated. MonteCarlo (MC) correction factors for silicon detectors were used for comparing the OF measurements. RESULTS: Considering OFs values averaged over all centers, diamond data resulted lower than uncorrected silicon diode ones. The agreement between diamond and MC corrected silicon values was within 0.6% for all fixed circular collimators. Relative differences between microDiamond and MC corrected silicon diodes data for Iris(™) collimator were lower than 1.0% for all apertures in the totality of centers. The two microDiamond detectors showed similar characteristics, in agreement with the technical specifications. CONCLUSIONS: Excellent agreement between microDiamond and MC corrected silicon diode detectors OFs was obtained for both collimation systems fixed cones and Iris(™), demonstrating the microDiamond could be a suitable detector for CyberKnife commissioning and routine checks. These results obtained in five centers suggest that for CyberKnife systems microDiamond can be used without corrections even at the smallest field size.