The results showed that while the SOBP designed by the Bortfeld model has a homogeneity of 92-97%, the SOBP designed by the numerical method in the present study is above 99%, which in some cases even closed to 100%.

In this paper, we aim to provide a theoretical study of thermal entanglement of two qubits coupled to a spin chain with considering multiple-spin correlations which accompanies decay in multiple quantum nuclear magnetic resonance (MQ NMR) system. We show an explicit connection between the coherence factor and entanglement, and numerically and analytically study the dynamical process of entanglement in weak coupling cases for dipolar ordered initial states. We provide results that the entanglement evolution depends not only on the coupling constant between central two qubits and the system-environment couplings but also on temperature and the number of spins in chain.

Aim: The purpose of this study is to optimize treatment planning in carbon ion radiotherapy, taking into account the effect of tumour hypoxia. Background: In conventional hadron therapy, the goal is to create a homogenous dose in the tumour area and, thus, achieve a uniform cell survival level. Since the induction of a specific damage to cells is directly influenced by the level of hypoxia in the tissue, the varying oxygen pressure in the different regions of hypoxic tumours would disrupt the uniformity of the cell survival level. Materials and methods: Using the Geant4 Monte Carlo Code, the physical dose profile and dose-averaged linear energy transfer were calculated in the tumour. Then, the oxygen enhancement ratio in different areas of the tumour were compared with different pressures. Results: Modulations of radiation intensities as well as energies of ion beams were calculated, both considering and disregarding the effect of hypoxia, and the required dose profiles were compared with each other. Cell survival levels were also compared between the two methods. An equation was obtained for re-modulating the beams in the presence of hypoxia, and radiation weighting factors were extracted for the beam intensities. Conclusion:The results show that taking the effect of hypoxia into account would cause the reduction of average doses delivered to the tumour tissues up to 1.54 times. In this regard, the required dose is reduced by 1.63 times in the healthy tissues before the tumour. This will result in an effective protection of healthy tissues around the tumour.

Introduction: Recently, the use of various sensitizers has been used to increase photon-induced doses in brachytherapy. One of these cases is the addition of heavy metal nanoparticles such as gold in the target area, which increases the production of ionizing electrons by increasing the possibility of photoelectric effects, and increases the efficacy of the treatment. In this study, the target of the irradiation was the endothelial cell in the wall of blood capillaries located inside the tumor, which, if destroyed, would result in abnormal blood cell counts and tumor cell death. Methods: The effect of using nanoparticles of gold, silver, bismuth and copper has been evaluated by calculating the dose increase ratio using Geant4 tool that was based on Monte Carlo method. These calculations were performed on two microscopic (cellular) and macroscopic (tumor dimensions) scale and the effects of different concentrations of these nanoparticles were compared. Also, the dose increase ratio has been evaluated to determine the most appropriate photon energy range. Results: As the concentration of nanoparticles increases, the dose enhancement factor increased in photon energy. In addition, for energies less than 70 keV, with increasing energy, dose enhancement factor increased and for energies above 80 keV, this quantity decreased with increasing energy. Conclusion: In terms of dose, gold is the best option, and in terms of the dose enhancement factor, silver and bismuth are better alternative among the four elements studied. Also, the most suitable photon energy range is 70 keV to 80 keV.