جستجوی مقالات مرتبط با کلیدواژه « دز نوترون » در نشریات گروه « فیزیک »

Given that neutron is a non-load-bearing particle that quickly responds to environmental elements and leads to ionization of elements, as well as dispersion that affects neutron spectrum due to environmental factors. Dosage of dispersed neutrons, as well as minimizing dispersion factors is the goal of this research. Calibration can be defined as a set of operations under specified conditions that measure the relationship between the values measured by the measuring instrument or system and the Similarly known well known values of a value.

The 252Cf brachytherapy source is a spontaneous fission decay source, which is used as a neutron-emitting source. In addition to neutrons emitted from this source, gamma rays are also emitted with the average energy of 1 MeV. In this study, using the Monte Carlo N-Particle code (MCNPX), the absorbed dose rates of the neutrons, the primary gamma and the secondary gamma that generated by thermal neutron capture in the hydrogen of the water were calculated at different distances from the source in the water phantom. Also, the equivalent dose rates of the total, the neutrons, and the gammas were obtained at different intervals from the source. The results indicate that gamma rays from this source can provide significant energy at distances close to the source, so the contribution of these rays to total absorption doses should be calculated. The neutron dose rate and total gamma decrease with increasing distance from the source and at the distances close to the source are deposited the most energy. The equivalent dose of neutrons at distances close to the source (lower than 2cm) with differences to gamma rays has the highest effect at the equivalent total dose. So, the values at the distances of 0.5 to 2.0 cm from the source reach the value of 46.30 cSv/h.µg to 2.95 cSv/h.µg, while the equivalent dose rate of gamma at distances of 0.5 to 2.0 cm from the source is 4.30 cSv/h.µg to 0.272 cSv/h.µg.

This research aimed to measure the received photon and thermal neutron doses to contralateral breast (CB) surface in breast cancer radiation therapy for different field sizes in presence of dynamic and physical wedges. The photon and thermal neutron doses were measured by thermo uminescent dosimeter (TLDs) chips for 11 × 13, 11 × 17 and 11 × 21 cm2 field sizes in presence of physical and dynamic wedges. The findings of current study demonstrated that the received doses (both of the photon and thermal neutron) to CB surface in presence of physical wedge for 11 × 13, 11 × 17 and 11 × 21 cm2 field sizes were 12.06, 15.75 and 33.40% of the prescribed dose, respectively, as well as for dynamic wedge were 9.18, 12.92 and 29.26% of the prescribed dose, respectively. The received photon and thermal neutron doses to CB surface increased with increment of field sizes. In addition, the received photon and thermal neutron doses to CB surface in presence of dynamic wedge were less than physical wedge. Similar to recommendations of previous conducted studies, in breast radiation therapy with wedge technique, the using a dynamic wedge is preferable than a physical wedge, especially for medial tangential field.