Comparison of Indoor and Outdoor Dose Rates from Environmental Gamma Radiation in Kurdistan Province

Abstract: Background & Aims: Studying about background radiation is important because human beings are continuously exposed to these radiations which leave energy in tissues and the transferred energy leads to undesirable biologic effects. The level of background radiation differs in indoor and outdoor places. Since, people spend more time indoors, in this research environmental gamma dose rate for indoor and outdoor places of Kurdistan towns was determined and compared. Methods: To estimate dose rate at outdoors, four stations in the length of main directions and one in the center of each city were selected. To estimate dose rate at indoors, two stations in each town according to the type of buildings were selected. In each station gamma dose rate was measured for one hour by RDS-110 servimeter at one meter height from the earth. Results: The average of outdoor and indoor environmental gamma dose rate for Kurdistan towns obtained as follows: Baneh 134 (SD=5), 166 (SD=25) nSv/h, Bijar 113 (SD=17), 141 (SD=8) nSv/h, Divandareh 110 (SD=8), 134 (SD=12) nSv/h, Saqez 105 (SD=12), 134 (SD=11) nSv/h, Sanandaj 110 (SD=12), 133 (SD=4) nSv/h, Qorve 114 (SD=20), 160 (SD=4) nSv/h, Kamyaran 92 (SD=4), 115 (SD=14) nSv/h, Marivan 110 (SD=9), 122 (SD=18) nSv/h. Conclusion: Data shows that indoor dose rates in Baneh (%24), Bijar (%24), Divandareh (%22), Saqez (%28), Sanandaj (%21), Qorveh (%40), Kamyaran (%25) and Marivan (%11) exceed outdoor dose rate in these towns. Keywords: Environmental gamma, Dose rate, Indoor, Outdoo

Quality assurance program for prototype stereotactic system developed for Neptun 10 PC linac

Background: A prototype stereotactic radiosurgery set was designed and constructed for a Neptun 10 PC linac that is currently being used at Imam Reza hospital in Mashhad. Materials and Methods: A complete qualit y assurance program was designed and performed for the constructed system including isocentric accuracy test, localization accuracy test, dose delivery accuracy test and leakage radiation test. Target simulator, control alignment device and plexiglass phantom which were parts of the developed hardware were used to fulfill quality assurance program. Results: The average isocentric shift resulted from the gantry rotation and couch turning were respectively obtained to be 1.4 and 2 mm. The average localization error in the three coordinates was found to be 2.2 mm. The total treatment uncertainty due to all of the probable errors in the system was equal to 4.32 mm. The dose delivery accuracy test was carried out, the result indicated a 3-7% difference between the given and measured dose. Conclusion: The quality assurance tests showed consistent performance of the constructed system within the accepted limits; however, some inconsistency might exist in certain cases. The safety of SRS method is increased when the overall uncertainty is minimized and the treatment of the lesions adjacent to critical organs is avoided

Assessment of skin dose in breast cancer radiotherapy: on-phantom measurement and Monte Carlo simulation

Aim: The main purpose of the present study is assessment of skin dose in breast cancer radiotherapy. Background: Accurate assessment of skin dose in radiotherapy can provide useful information for clinical considerations. Materials and methods: A RANDO phantom was irradiated using a 6 MV Siemens Primus linac with medial and tangential radiotherapy fields for simulating breast cancer treatment. Dosimetry was also performed on various positions across the fields using an EBT3 radiochromic film. Similar conditions of measurement on the RANDO phantom including field size, irradiation angle, number of fields, etc. were subsequently simulated via the Monte Carlo N-Particle Transport code (MCNP). Ultimately, dose values for corresponding points from both methods were compared. Results: Considering dosimetry using radiochromic films on the RANDO phantom, there were points having underdose and overdose based on the prescribed dose and skin tolerance levels. In this respect, 81.25 and 18.75 of the points had underdose and overdose, respectively. In some cases, several differences were observed between the measurement and the MCNP simulation results associated with skin dose. Conclusion: Based on the results of the points which had underdose, it was suggested that a bolus should be used for the given points. With regard to overdose points, it was advocated to consider skin tolerance dose in treatment planning. Differences between the measurement and the MCNP simulation results might be due to voxel size of tally cells in simulations, effect of beam's angle of incidence, validation time of linac's head, lack of electronic equilibrium in the build-up region, as well as MCNP tally type. © 2020 Greater Poland Cancer Centr