title: Dosimetric characterization of a microDiamond detector in clinical scanned carbon ion beams.
abstract: OBJECTIVE
  To investigate for the first time the dosimetric properties of a new commercial synthetic diamond detector (PTW microDiamond) in high-energy scanned clinical carbon ion beams generated by a synchrotron at the CNAO facility.
  
  
  METHODS
  The detector response was evaluated in a water phantom with actively scanned carbon ion beams ranging from 115 to 380 MeV/u (30-250 mm Bragg peak depth in water). Homogeneous square fields of 3 × 3 and 6 × 6 cm(2) were used. Short- and medium-term (2 months) detector response stability, dependence on beam energy as well as ion type (carbon ions and protons), linearity with dose, and directional and dose-rate dependence were investigated. The depth dose curve of a 280 MeV/u carbon ion beam, scanned over a 3 × 3 cm(2) area, was measured with the microDiamond detector and compared to that measured using a PTW Advanced Markus ionization chamber, and also simulated using fluka Monte Carlo code. The detector response in two spread-out-Bragg-peaks (SOBPs), respectively, centered at 9 and 21 cm depths in water and calculated using the treatment planning system (TPS) used at CNAO, was measured.
  
  
  RESULTS
  A negligible drift of detector sensitivity within the experimental session was seen, indicating that no detector preirradiation was needed. Short-term response reproducibility around 1% (1 standard deviation) was found. Only 2% maximum variation of microDiamond sensitivity was observed among all the evaluated proton and carbon ion beam energies. The detector response showed a good linear behavior. Detector sensitivity was found to be dose-rate independent, with a variation below 1.3% in the evaluated dose-rate range. A very good agreement between measured and simulated Bragg curves with both microDiamond and Advanced Markus chamber was found, showing a negligible LET dependence of the tested detector. A depth dose curve was also measured by positioning the microDiamond with its main axis oriented orthogonally to the beam direction. A strong distortion in Bragg peak measurement was observed, confirming manufacturer recommendation on avoiding such configuration. Very good results were obtained for SOBP measurements, with a difference below 1% between measured and TPS-calculated doses. The stability of detector sensitivity in the observation period was within the experimental uncertainty.
  
  
  CONCLUSIONS
  Dosimetric characterization of a PTW microDiamond detector in high-energy scanned carbon ion beams was performed. The results of the present study showed that this detector is suitable for dosimetry of clinical carbon ion beams, with a negligible LET and dose-rate dependence.
authors.affiliation: INFN-Dipartimento di Ingegneria Industriale, Università di Roma "Tor Vergata," Via del Politecnico 1, Roma 00133, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Marinelli
authors.affiliation: INFN-Dipartimento di Ingegneria Industriale, Università di Roma "Tor Vergata," Via del Politecnico 1, Roma 00133, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Prestopino
authors.affiliation: INFN-Dipartimento di Ingegneria Industriale, Università di Roma "Tor Vergata," Via del Politecnico 1, Roma 00133, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Verona
authors.affiliation: INFN-Dipartimento di Ingegneria Industriale, Università di Roma "Tor Vergata," Via del Politecnico 1, Roma 00133, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Verona-Rinati
authors.affiliation: Fondazione CNAO, Strada Campeggi 53, Pavia 27100, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Ciocca
authors.affiliation: Fondazione CNAO, Strada Campeggi 53, Pavia 27100, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Mirandola
authors.affiliation: Fondazione CNAO, Strada Campeggi 53, Pavia 27100, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Mairani
authors.affiliation: INFN-Laboratori Nazionali del Sud, Via S. Sofia 62, Catania 95123, Italy and Fondazione CNAO, Strada Campeggi 53, Pavia 27100, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Raffaele
authors.affiliation: INFN-Dipartimento di Fisica, Università degli Studi di Pavia, Via U. Bassi 6, Pavia 27100, Italy and Fondazione CNAO, Strada Campeggi 53, Pavia 27100, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Magro
mesh_terms: D002244:Carbon / Q000627:therapeutic use*; D016014:Linear Models; D017785:Photons; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation* / Q000379:methods
chemical_list: D002244:Carbon