Analytical parameterization of Bragg curves for proton beams in muscle, bone, and polymethylmethacrylate.

Proton dose calculation in media other than water may be of interest for either research purposes or clinical practice. Current study aims to quantify the required parameters for analytical proton dosimetry in muscle, bone, and PMMA. Required analytical dosimetry parameters were extracted from ICRU-49 report and Janni study. Geant4 Toolkit was also used for Bragg curve simulation inside the investigated media at different proton energies. Calculated and simulated dosimetry data were compared using gamma analysis. Simulated and calculated Bragg curves are consistent, a fact that confirms the validity of reported parameters for analytical proton dosimetry inside considered media. Furthermore, derived analytical parameters for these media are different from those of water. Listed parameters can be reliably utilized for analytical proton dosimetry inside muscle, bone, and PMMA. Furthermore, accurate proton dosimetry inside each medium demands dedicated analytical parameters and one is not allowed to use the water coefficients for non-water media.

In-field radiation contamination during intraoperative electron radiation therapy with a dedicated accelerator.

The in-field radiation contamination including photons and neutrons originated from a dedicated intraoperative electron radiotherapy (IOERT) accelerator, LIAC12, at different electron energies (6-12 MeV) and applicator sizes (3, 5 and 10 cm diameter) were quantitatively evaluated in the current study. A validated MC model of LIAC12 head in conjunction with different applicator diameters was employed for this purpose. The results showed that the fluence of in-field photon contamination is highly dependent on the electron energy and field size so that it would be increased by the factors of about 3 and 10 with an increment of electron energy and decrement of field size, respectively. Neutron contamination was found only at 12 MeV electron energy and zero neutron fluence was obtained at lower electron energies. The same trend with the field size was observed for neutron contamination fluence that increased about 7 times by decreasing the applicator diameter from 10 cm to 3 cm. The maximum contaminant neutron dose and photon dose per one Gy delivered electron dose were obtained about 0.3 µSv and 7.24 mSv, respectively. The produced neutron contamination by this dedicated IOERT accelerator was approximately 10-3 times lower than those originated from a conventional radiotherapy accelerator.