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Title: Why diamond dimensions and electrode geometry are crucial for small photon beam dosimetry

Recent use of very small photon beams (down to 4 mm) in stereotactic radiotherapy requires new detectors to accurately determine the delivered dose. Diamond detectors have been presented in the literature as an attractive candidate for this application, due to their small detection volume and the diamond atomic number (Z = 6) which is close to water effective atomic number (Zeff ∼ 7.42). However, diamond exhibits a density 3.51 times greater than that of water and recent studies using Monte Carlo simulations have demonstrated the drawback of a high-density detector on small beam output factors. The current study focuses on geometrical parameters of diamond detector, namely, the diamond dimensions and the electrode geometry, in order to solve the dosimetric issues still observed in small photon beams with diamond detectors. To give better insights to these open questions, we have used both computational method and experimental analysis. This study highlighted that reducing diamond dimensions is crucial for small beam output factor measurements and to limit the influence of its high density. Furthermore, electrodes covering the whole diamond surface were essential for a dose rate independence of the diamond detector. The optimal dosimeter derived from this work presented small diamond dimensions of approximately 1 × 1 × 0.15 mm{sup 3}, with diamond-like-carbonmore » electrodes covering the whole diamond surface. A dose rate independence of this diamond detector (better than 0.5% over a wide range of dose rates available on a stereotactic dedicated facility) was obtained due to the electrode geometry. Concerning the output factor measurements, a good agreement (better than 1.1%) was observed between this carbon material detector and two types of passive dosimeters (LiF microcubes and EBT2 radiochromic films) for all beam sizes except the smallest field of 0.6 × 0.6 cm{sup 2} with a deviation of 2.6%. This new study showed the high performance of this diamond detector in small photon beams, in comparison with various commercially available passive and active dosimeters.« less
Authors:
; ; ; ;  [1] ; ;  [2] ;  [3] ; ; ;  [4] ; ;  [5] ; ;  [6] ; ;  [7]
  1. CEA, LIST, Diamond Sensors Laboratory, 91191 Gif-sur-Yvette (France)
  2. IRSN, PRP-HOM/SDE/LDRI, 31 Av. de la Division Leclerc, 92260 Fontenay-aux-Roses (France)
  3. IRSN, PRP-HOM/SER/UEM, 31 Av. de la Division Leclerc, 92260 Fontenay-aux-Roses (France)
  4. Pitié Salpêtrière Hospital, 47-83 Blvd de l'Hôpital, 75013 Paris (France)
  5. Institut de Cancérologie de Lorraine, 6 Av. de Bourgogne, 54500 Vandoeuvre-lès-Nancy (France)
  6. Institut de Cancérologie de l'Ouest, Blvd Prof. Jacques Monod, 44805 Saint-Herblain (France)
  7. CEA, LIST, LM2S, 91191 Gif-sur-Yvette (France)
Publication Date:
OSTI Identifier:
22493067
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 23; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 62 RADIOLOGY AND NUCLEAR MEDICINE; ATOMIC NUMBER; BEAM PRODUCTION; COMPUTERIZED SIMULATION; DIAMONDS; DOSE RATES; DOSEMETERS; DOSIMETRY; ELECTRODES; GEOMETRY; LITHIUM FLUORIDES; MONTE CARLO METHOD; PHOTON BEAMS; RADIOTHERAPY; WATER