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The purpose of this study was to investigate acute normal tissue responses in the head and neck region following proton- or X-irradiation of a murine model. Female C57BL/6J mice were irradiated with protons (25 or 60 MeV) or X-rays (100 kV). The radiation field covered the oral cavity and the major salivary glands. For protons, two different treatment plans were used, either with the Bragg Peak in the middle of the mouse (BP) or outside the mouse (transmission mode; TM). Delivered physical doses were 41, 45, and 65 Gy given in 6, 7, and 10 fractions for BP, TM, and X-rays, respectively. Alanine dosimetry was used to assess delivered doses. Oral mucositis and dermatitis were scored using CTC v.2.0-based tables. Saliva was collected at baseline, right after end of irradiation, and at day 35. The measured dose distribution for protons (TM) and X-rays was very similar. Oral mucositis appeared earlier, had a higher score and was found in a higher percentage of mice after proton irradiation compared to X-irradiation. Dermatitis, on the other hand, had a similar appearance after protons and X-rays. Compared to controls, saliva production was lower right after termination of proton- and X-irradiation. The BP group demonstrated saliva recovery compared to the TM and X-ray group at day 35. With lower delivered doses, proton irradiation resulted in similar skin reactions and increased oral mucositis compared to X-irradiation. This indicates that the relative biological effectiveness of protons for acute tissue responses in the mouse head and neck is greater than the clinical standard of 1.1. Thus, there is a need for further investigations of the biological effect of protons in normal tissues. [ABSTRACT FROM AUTHOR]

Accurate dosimetry of ionizing radiation requires careful consideration of the absorption properties of the dosimeter material in question. The energy dependence of a dosimeter signifies the variation in dosimeter signal per absorbed dose to water with radiation type and energy. The nanophosphor BaSO 4 : Eu is a radiosensitive material for thermoluminescence (TL) dosimetry. However, the energy dependence of the material for orthovoltage X-rays and low energy protons has not previously been investigated, which is the purpose of the current work. We irradiated BaSO 4 doped with 0.5 mol% of europium with 100, 160 and 225 kV X-rays and 2 and 9 MeV protons. Co-60 γ-rays were used for reference irradiation. Absolute dose-to-water dosimetry was ensured with an ion chamber. Delivered calibration doses ranged from 0.01 to about 2 Gy. TL output was measured at a heating rate of 5 K/s, where the maximum intensity of the dominant glow peak at about 212 °C defined the dosimeter signal. The signal was found to increase linearly with absorbed dose for both radiation types and all energies. The measured energy response, defined as the ratio of the TL calibration slope at a given radiation type and energy to that following Co-60 γ-irradiation, varied between 47 and 62 for X-rays and between 0.41 and 0.61 for protons. Theoretical modelling of the energy response and proton detector efficiency gave similar trends. The findings show that BaSO 4 is an energy-dependent material, especially for X-rays, but may still prove valuable for accurate dose determination if the dosimeter is calibrated in the user beam. • The signal from BaSO 4 :Eu increased linearly with absorbed dose for all radiations. • X-irradiated BaSO 4 :Eu showed high measured energy response for all X-ray energies. • The energy response of BaSO 4 :Eu was slightly dependent on proton kinetic energy. • Theoretical energy response estimates supported the experimental findings. [ABSTRACT FROM AUTHOR]