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Introduction: Environmental and occupational human exposure from neutron source can lead to the serious biologic effects. The aim of this study is to evaluate the cancer incidence risk for various human organs at different neutron dose levels due to exposure from an Americium-241/Beryllium (Am-241/Be), a standard neutron source for calibration purposes. Material and Methods: We measured ambient dose equivalent H*(10) at different distances from Am-241/Be mixed neutron source by Berthold LB 6411 detector and determined cancer incidence risk for different organs of both male and female subjects at different neutron exposure levels by BEIR VII model. Results: Exposure age had a reverse impact on cancer incidence risk of different organs. We found that as H*(10) increases, cancer incidence risk increments as well. Colon (for men) and bladder (for women) had the highest sensitivity to neutron exposure, while prostate and uterus showed the lowest risk of cancer incidence among male and female subjects, respectively. Conclusion: Older exposed persons are at a lower risk of cancer incidence. The risk of cancer incidence for various organs is considerably associated with gender, such that radiation sensitivity of female organs was higher at all the measured neutron dose levels. [ABSTRACT FROM AUTHOR]

Introduction The first medical intervention for many breast cancer patients is breast conserving surgery (BCS) and/or modified radical mastectomy (MRM). Most of these patients undergo radiation therapy, following surgery. The most common side-effect of breast radiotherapy is skin damage. In the present study, the severity of acute skin changes and the underlying causes were investigated in patients undergoing BCS and radiotherapy. Materials and Methods This prospective, cohort study was performed on 31 female patients, undergoing breast surgery therapy at Shahid Rajaie Babolsar Radiotherapy Center from September 2011 to July 2012. A questionnaire was designed, including the patient's characteristics, details of radiotherapy technique, and skin damage; the questionnaire was completed for each patient. The obtained results were analysed by performing ANOVA and Fisher's exact tests. Complications were graded using the radiation therapy oncology group (RTOG) scale. Results Grade 0 or 4 of skin damage was observed in none of the patients. Among the evaluated patients, 58%, 35.5%, and 6.5% of the patients had grade 1, grade 2, and grade 3 of skin damage, respectively. There was no statistically significant relationship between regional skin burns and factors such as average tangential field size, internal mammary field, chemotherapy, prior history of diseases, tamoxifen use, previous radiotherapy in breast area, or skin type (p>0.05). However, there was a significant relationship between skin burns and presence of supraclavicular field (p=0.05). Conclusion Considering the significant relationship between skin burn and supraclavicular field, special attention needs to be paid to factors affecting the treatment planning of supraclavicular field such as field size and photon energy. [ABSTRACT FROM AUTHOR]

Introduction In this study, we aimed to calculate dose enhancement factor (DEF) for gold (Au) and iron (Fe) nanoparticles (NPs) in brachytherapy and teletherapy, using Monte Carlo (MC) method. Materials and Methods In this study, a new algorithm was introduced to calculate dose enhancement by AuNPs and FeNPs for Iridium-192 (Ir-192) brachytherapy and Cobalt-60 (Co-60) teletherapy sources, using the MC method. In this algorithm, the semi-random distribution of NPs was used instead of the regular distribution. Diameters were assumed to be 15, 30, and 100 nm in brachytherapy and 15 and 30 nm in teletherapy. Monte Carlo MCNP4C code was used for simulations, and NP density values were 0.107 mg/ml and 0.112 mg/ml in brachytherapy and teletherapy, respectively. Results AuNPs significantly enhanced the radiation dose in brachytherapy (approximately 60%), and 100 nm diameter NPs showed the most uniform dose distribution. AuNPs had an insignificant effect on teletherapy radiation field, with a dose enhancement ratio of 3% (about the calculation uncertainty) or less. In addition, FeNPs had an insignificant effect on both brachytherapy and teletherapy radiation fields. FeNPs dose enhancement was 3% in brachytherapy and 6% (about the calculation uncertainty) or less in teletherapy. Conclusion It can be concluded that AuNPs can significantly increase the absorbed dose in brachytherapy; however, FeNPs do not have a noticeable effect on the absorbed dose. Overall, AuNPs and FeNPs cannot increase the absorbed dose for the Co-60 teletherapy source. [ABSTRACT FROM AUTHOR]