ABSTRACT
The Monte Carlo method can be used to describe any technique that approximates solutions to quantitative problems through statistical sampling. This method is considered to be the most accurate method for dose calculation in radiotherapy. For complete modeling of a linear accelerator, it is required that the manufactured information covers all data, but some data such as primary electron energy must be indicated. The purpose of this study was to determine the best primary electron energy for 15 MV photon beam with varying the energy and FWHM. A Monte Carlo model for photon-beam output of a Siemens primus linear accelerator was validated by plotting the energy spectrum of photon beam and calculating the percentage depth dose [PDD] and beam profiles for 10×10 cm[2] field. Square 10×10 cm[2] field was validated by measurements in water by a farmer chamber. Linac head simulation was performed with BEAMnrc and dose calculation and 3D dose file were produced by DOSXYZnrc. The results were analyzed using MATLAB. It was found a good agreement between calculated PDD and beam profile for 15 MV photon beam using Monte Carlo simulation with primary electron energy of 11 MV and FWHM of 0.4 with maximum dose difference of 1.2% in PDD curves. In conclusion, using primary electron energy of 11 MV and FWHM of 0.4 has very good accuracy in calculating of dose distribution for 15 MV photon beam and it can be considered as a promising method for patient dose calculations
ABSTRACT
Esophageal cancer is one of the most common malignancies with a growing occurrence. It presently ranks ninth among the most frequent cancers in the world and the sixth leading cause of death from cancer. For a variety of reasons, the mainstream of patients with esophageal cancer is actually not suitable for Esophagectomy. More than 50% have locally advanced unresectable or metastatic tumors at diagnosis. Other reasons which exclude Esophagectomy include old age, comorbidity or refusal by the patient. For more advanced stages of esophageal cancers, the basis of non-surgical treatment is chemotherapy [CT] or radiotherapy [RT], either alone or in combination as chemoradiotherapy [CRT]. The purpose of this study is to summaries and judgmentally analyzes current non-surgical treatments. Although the best treatment for locally advanced esophageal cancer is still being debated, the use of neoadjuvant chemoradiotherapy has gained acceptance
ABSTRACT
PURPOSE: Mefenamic acid (MEF) as a non-steroidal anti-inflammatory drug is used as a medication for relieving of pain and inflammation. Radiation-induced inflammation process is involved in DNA damage and cell death. In this study, the radioprotective effect of MEF was investigated against genotoxicity induced by ionizing radiation in human blood lymphocytes. MATERIALS AND METHODS: Peripheral blood samples were collected from human volunteers and incubated with MEF at different concentrations (5, 10, 50, or 100 microM) for two hours. The whole blood was exposed to ionizing radiation at a dose 1.5 Gy. Lymphocytes were cultured with mitogenic stimulation to determine the micronuclei in cytokinesis blocked binucleated lymphocyte. RESULTS: A significant decreasing in the frequency of micronuclei was observed in human lymphocytes irradiated with MEF as compared to irradiated lymphocytes without MEF. The maximum decreasing in frequency of micronuclei was observed at 100 microM of MEF (38% decrease), providing maximal protection against ionizing radiation. CONCLUSION: The radioprotective effect of MEF is probably related to anti-inflammatory property of MEF on human lymphocytes.