It is expected that this work will be utilized in the analysis of three-dimensional gel volumes irradiated using complex radiotherapy treatments.

No abstract

In this work, soft‐tissue equivalence of water, polystyrene, PMMA and water equivalence of polystyrene, and PMMA has been assessed for multiple megavoltage photon beams and field sizes. EGSnrc based Monte Carlo (MC) codes, BEAMnrc and DOSXYZnrc are used for the linac head modeling and the phantom dose calculations, respectively. Percentage depth doses (PDDs) are scored for two field sizes (5×5 cm2, 10×10 cm2) and photon energies (6 MV and 10 MV) in water, polystyrene, PMMA, and soft tissue. The comparisons of PDDs show that soft‐tissue equivalence of various materials varies with the depth in the phantom, field size, and photon energy. Water and PMMA are found to be the closest soft‐tissue and water substitutes, respectively. Soft‐tissue and water equivalence of dosimetry materials need to be evaluated for a range of photon energies and field sizes before their application in complex radiation beams.PACS numbers: 87.55.Gh, 87.55.K‐

This work is focussed on developing a commissioning procedure so that a Monte Carlo model, which uses BEAMnrc's standard VARMLC component module, can be adapted to match a specific BrainLAB m3 micro-multileaf collimator (microMLC). A set of measurements are recommended, for use as a reference against which the model can be tested and optimized. These include radiochromic film measurements of dose from small and offset fields, as well as measurements of microMLC transmission and interleaf leakage. Simulations and measurements to obtain microMLC scatter factors are shown to be insensitive to relevant model parameters and are therefore not recommended, unless the output of the linear accelerator model is in doubt. Ultimately, this note provides detailed instructions for those intending to optimize a VARMLC model to match the dose delivered by their local BrainLAB m3 microMLC device.