Monte Carlo study of Si diode response in electron beams

Journal Article · Tue May 15 04:00:00 EDT 2007 · Medical Physics

DOI:https://doi.org/10.1118/1.2722720· OSTI ID:20951304

Wang, Lilie L. W.; Rogers, David W. O. ^[1]

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1. Physics Department, Carleton University, Ottawa K1S 5B6 (Canada)

Silicon semiconductor diodes measure almost the same depth-dose distributions in both photon and electron beams as those measured by ion chambers. A recent study in ion chamber dosimetry has suggested that the wall correction factor for a parallel-plate ion chamber in electron beams changes with depth by as much as 6%. To investigate diode detector response with respect to depth, a silicon diode model is constructed and the water/silicon dose ratio at various depths in electron beams is calculated using EGSnrc. The results indicate that, for this particular diode model, the diode response per unit water dose (or water/diode dose ratio) in both 6 and 18 MeV electron beams is flat within 2% versus depth, from near the phantom surface to the depth of R{sub 50} (with calculation uncertainty <0.3%). This suggests that there must be some other correction factors for ion chambers that counter-balance the large wall correction factor at depth in electron beams. In addition, the beam quality and field-size dependence of the diode model are also calculated. The results show that the water/diode dose ratio remains constant within 2% over the electron energy range from 6 to 18 MeV. The water/diode dose ratio does not depend on field size as long as the incident electron beam is broad and the electron energy is high. However, for a very small beam size (1x1 cm{sup 2}) and low electron energy (6 MeV), the water/diode dose ratio may decrease by more than 2% compared to that of a broad beam.

• OSTI ID: 20951304
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 5 Vol. 34; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
COMPUTERIZED SIMULATION
DOSIMETRY
ELECTRON BEAMS
IONIZATION CHAMBERS
MONTE CARLO METHOD
PHANTOMS
PHOTONS
RADIATION DOSES
SILICON DIODES