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Poster — Thur Eve — 47: Monte Carlo Simulation of Scp, Sc and Sp
Author(s) -
Zhan Lixin,
Jiang Runqing,
Osei Ernest K.
Publication year - 2014
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4894907
Subject(s) - monte carlo method , imaging phantom , kerma , physics , computational physics , linear particle accelerator , beam (structure) , scattering , dosimetry , photon , field (mathematics) , percentage depth dose curve , optics , ionization chamber , nuclear medicine , mathematics , statistics , ionization , medicine , ion , quantum mechanics , pure mathematics
The in‐water output ratio ( Scp ), in‐air output ratio ( Sc ), and phantom scattering factor ( Sp ) are important parameters for radiotherapy dose calculation. Experimentally, Scp is obtained by measuring the dose rate ratio in water phantom, and Sc the water Kerma rate ratio in air. There is no method that allows direct measurement of Sp . Monte Carlo (MC) method has been used to simulate Scp and Sc in literatures, similar to experimental setup, but no MC direct simulation of Sp available yet to the best of our knowledge. We propose in this report a method of performing direct MC simulation of Sp . Starting from the definition, we derived that Sp of a clinical photon beam can be approximated by the ratio of the dose rates contributed from the primary beam for a given field size to the reference field size. Since only the primary beam is used, any Linac head scattering should be excluded from the simulation, which can be realized by using the incident electron as a scoring parameter for MU. We performed MC simulations for Scp , Sc and Sp . Scp matches well with golden beam data. Sp obtained by the proposed method agrees well with what is obtained using the traditional method, Sp = Scp/Sc . Since the smaller the field size, the more the primary beam dominates, our Sp simulation method is accurate for small field. By analyzing the calculated data, we found that this method can be used with no problem for large fields. The difference it introduced is clinically insignificant.