Material simulation for scatter and degrader plates construction

There are many radiosensitive diseases associated to the skin such as mycosis fungoids and the syndrome of Sezary that are part of a sub-group of cutaneous diseases type T-cell lymphoma. Several studies indicate the eradication of the disease when treated with linear accelerators emitting electron beams with energies between 4 to 10 MeV. However, this treatment technique presents innumerable technical challenges since the disease in general reaches all patient's body, becoming necessary a very large field size radiation beam, and also, it should deliver superficial doses limited to the skin depth. To reach the uniformity in the dose distribution, many techniques had already been developed. Based on these previous studies and guided by the report nr. 23 of the AAPM (American Association of Physicists in Medicine), the present study will develop an energy scattering and degrading plates, supplying subsidies for a future installation for skin treatment at the 'Servico de Radioterapia do Hospital das Clinicas de Sao Paulo'. As part of the plates design, first of all, the energy spectrum of the 6 MeV electron beam of the VARIAN 2100C accelerator was reconstructed through Monte Carlo simulations using the MCNP4C code and based on experimental data. Once the spectrum is built the design of the plates has been performed analyzing several materials, on the basis of radial and axial dose distribution, production of rays-x and dose attenuation. The simulations was validated with experimental measurements using copper and aluminum. (author)