title: Multicenter evaluation of a synthetic single-crystal diamond detector for CyberKnife small field size output factors.
abstract: OBJECTIVE
  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.
authors.affiliation: Medical Physics Unit of Radiation Oncology Dept, Azienda Sanitaria Firenze, I-50012 Firenze, Italy. Electronic address: serenella.russo@asf.toscana.it.
authors.forename: Serenella
authors.initials: S
authors.lastname: Russo
authors.affiliation: Department of Medical Physics and Radiation Oncology, IFCA, I-50139 Firenze, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Masi
authors.affiliation: Department of Radiation Oncology, Ospedale Di Vicenza, I-36100 Vicenza, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Francescon
authors.affiliation: Radiotherapy Department, Mater Dei Hospital, Città di Bari Hospital spa, I-70124 Bari, Italy.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Frassanito
authors.affiliation: Radiotherapy Department, Istituto Neurologico Besta, I-20133 Milano, Italy.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Fumagalli
authors.affiliation: Università di Roma 'Tor Vergata', I-00133 Roma, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Marinelli
authors.affiliation: Università di Roma 'Tor Vergata', I-00133 Roma, Italy.
authors.forename: Maria Daniela
authors.initials: MD
authors.lastname: Falco
authors.affiliation: Radiotherapy Department, Centro Diagnostico Italiano, I-20147 Milano, Italy.
authors.forename: Anna Stefania
authors.initials: AS
authors.lastname: Martinotti
authors.affiliation: Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA-INMRI C R Casaccia, I-00123 Roma, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Pimpinella
authors.affiliation: Medical Physics Unit of Radiation Oncology Dept., Humanitas Research Hospital, I-20089 Milano, Italy.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Reggiori
authors.affiliation: Università di Roma 'Tor Vergata', I-00133 Roma, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Verona Rinati
authors.affiliation: Radiotherapy Department, Istituto Europeo Oncologia, I-20141 Milano, Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Vigorito
authors.affiliation: Medical Physics Unit of Radiation Oncology Dept., Humanitas Research Hospital, I-20089 Milano, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Mancosu
mesh_terms: D003627:Data Interpretation, Statistical; D018130:Diamond / Q000737:chemistry; D006801:Humans; D011874:Radiometry / Q000379:methods; D016634:Radiosurgery / Q000295:instrumentation* / Q000379:methods; D012825:Silicon / Q000737:chemistry
chemical_list: D018130:Diamond; D012825:Silicon
keywords: CyberKnife; Multicenter evaluation; Output factor; Single microDiamond detector; Small beam dosimetry