Multicenter evaluation of a synthetic single-crystal diamond detector for CyberKnife small field size output factors

Serenella Russo, Laura Masi, Paolo Francescon, Maria Cristina Frassanito, Maria Luisa Fumagalli, Marco Marinelli, Maria Daniela Falco, Anna Stefania Martinotti, Maria Pimpinella, Giacomo Reggiori, Gianluca Verona Rinati, Sabrina Vigorito, Pietro Mancosu

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
JournalPhysica Medica
Publication statusAccepted/In press - Dec 16 2015


  • CyberKnife
  • Multicenter evaluation
  • Output factor
  • Single microDiamond detector
  • Small beam dosimetry

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging
  • Physics and Astronomy(all)


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