Extraction of depth-dependent perturbation factors for silicon diodes using a plastic scintillation detector

Journal Article · Sat Oct 15 04:00:00 EDT 2011 · Medical Physics

DOI:https://doi.org/10.1118/1.3637496· OSTI ID:22098637

Lacroix, Frederic; Guillot, Mathieu; McEwen, Malcolm; Gingras, Luc; Beaulieu, Luc ^[1]

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1. Departement de Radio-Oncologie, Centre hospitalier de l'Universite de Montreal (CHUM), 1560 Sherbrooke est, Montreal, Quebec H2L 4M1, Canada and Departement de Physique, Universite de Montreal, Pavillon Roger-Gaudry (D-428), 2900 Boul. Edouard-Montpetit, Montreal, Quebec H3T 1J4 (Canada)

Purpose: This work presents the experimental extraction of the perturbation factor in megavoltage electron beams for three models of silicon diodes (IBA Dosimetry, EFD and SFD, and the PTW 60012 unshielded) using a plastic scintillation detector (PSD). Methods: The authors used a single scanning PSD mounted on a high-precision scanning tank to measure depth-dose curves in 6-, 12-, and 18-MeV clinical electron beams. They also measured depth-dose curves using the IBA Dosimetry, EFD and SFD, and the PTW 60012 unshielded diodes. The authors used the depth-dose curves measured with the PSD as a perturbation-free reference to extract the perturbation factors of the diodes. Results: The authors found that the perturbation factors for the diodes increased substantially with depth, especially for low-energy electron beams. The experimental results show the same trend as published Monte Carlo simulation results for the EFD diode; however, the perturbations measured experimentally were greater. They found that using an effective point of measurement (EPOM) placed slightly away from the source reduced the variation of perturbation factors with depth and that the optimal EPOM appears to be energy dependent. Conclusions: The manufacturer recommended EPOM appears to be incorrect at low electron energy (6 MeV). In addition, the perturbation factors for diodes may be greater than predicted by Monte Carlo simulations.

• OSTI ID: 22098637
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 10 Vol. 38; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ACCURACY
BIOLOGICAL RADIATION EFFECTS
COMPUTERIZED SIMULATION
DEPTH DOSE DISTRIBUTIONS
DISTURBANCES
DOSIMETRY
ELECTRON BEAMS
ENERGY DEPENDENCE
EXTRACTION
MEV RANGE
MONTE CARLO METHOD
PERTURBATION THEORY
PLASTIC SCINTILLATION DETECTORS
SILICON DIODES