background: monte carlo (mc) modeling of a linear accelerator is a prerequisite for monte carlo dose calculations in external beam radiotherapy. in this study, a simple and efficient model was developed for elekta sl-25 linear accelerator using mcnp4c monte carlo code materials and methods: the head of elekta sl-25 linac was simulated for 6 and 18 mv photon beams using mcnp4c mc code. energy sp...

ionization radiation caused to incidence of complications in the exposed organs. in prostate radiotherapy, rectum and bladder have been radiated unwantedly and indicated some complications during and after treatment. the purpose of present study is to consider and to compare clinical complications of rectum and bladder in custom block and mlc for 3- d conformal radiotherapy, in order to determi...

 Background: To analyze the dosimetric and radio biologic advantages between intensity modulated radiotherapy (IMRT) and 3 dimensional conformal radiotherapy (3DCRT) and selection of optimal photon energy for IMRT treatments. Material and methods: 24 patients with localized prostate carcinoma were planned for 3DCRT and IMRT techniques. Radiation dose of 54 Gy with 2 Gy/fraction, was planned to ...

Background: Breast conserving surgery (BCS) followed by radiotherapy (RT) has been widely accepted as the standard treatment in early stages of invasive breast cancer. The standard technique of RT includes whole breast irradiation (WBI). Additional tumor bed boost irradiation has also an important role in the local tumor control. But there are various controversial delivery methods. The aim of ...

Stereotactic ablative radiotherapy is being increasingly adopted in the treatment of lung tumors. The use of proton beam therapy can further reduce dose to normal structures. However, uncertainty exists in proton-based treatment plans, including range uncertainties, large sensitivity to position uncertainty, and calculation of dose deposition in heterogeneous areas. This study investigated the ...

Background: Monte Carlo (MC) modeling of a linear accelerator is a prerequisite for Monte Carlo dose calculations in external beam radiotherapy. In this study, a simple and efficient model was developed for Elekta SL-25 linear accelerator using MCNP4C Monte Carlo code Materials and methods: The head of Elekta SL-25 linac was simulated for 6 and 18 MV photon beams using MCNP4C MC code. Energ...

Background: In radiotherapy, low-energy photon beams are better adapted to the treated volume, and the use of high-energy beams can reduce hot spots in the radiation therapy. Therefore, mixing low and high energies with different ratios can control the rate of hotspots, as well as the dose distribution of the target volume.Material and Methods: The percentage depth doses (PDDs) were calculated ...

We compute the one loop vacuum polarization from massless, minimally coupled scalar QED in a locally de Sitter background. Gauge invariance is maintained through the use of dimensional regularization, whereas conformal invariance is explicitly broken by the scalar kinetic term as well as through the conformal anomaly. A fully renormalized result is obtained. The one loop corrections to the line...