Evaluation of MRI-based MAGIC polymer gel dosimeter in small photon fields

Background: Accurate small radiation field dosimetry is essential in modern radiotherapy techniques such as stereotactic radiosurgery [SRS] and intensity modulated radiotherapy [IMRT]. Precise measurement of dosimetric parameters such as beam profile, percentage depth doses and output factor of these beams are complicated due to the electron disequilibrium and the steep dose gradients. In the present work the MAGIC polymer gel was used for dosimetry of small circular photon beams. The results of MAGIC were compared with EBT2 measurements and Monte Carlo [MC] calculations. Materials and Methods: Experimental measurements were made by mentioned dosimeters in four small field sizes 5, 10, 20 and 30 mm. The BEAMnrc code based on EGSnrc was used for simulation to calculate dosimetric parameters at these small fields. The phantoms were irradiated in a 6 MV photon beam Varian 2100C linear accelerator at SSD=100 cm. gel readout performed by 3 Tesla MRI scanner. Results: The results showed that the Percent depth dose [PDD] values measured and calculated by EBT2 film and MC had maximum local differences 4% and 5% with PDD values measured by MAGIC for field size of 5mm respectively. These differences decreased for larger field sizes. The measurements of output factor and penumbra [80%-20%] and [90%-10%] showed good agreement between the measurements and MC calculation. Conclusion: This study showed that the MAGIC polymer gel based on high resolution MRI images is useful detector for small field dosimetry but its agreement with MC is less than agreement of EBT2 film with MC

Evaluating the efficiency of lettuce disinfection according to the official protocol in Iran

The objective of this study was to evaluate the efficacy of Sanitization of Lettuce according to the protocols set forth by Iranian Ministry of Health and Medical Education for reducing populations of total coliform, fecal coliform, and helminth eggs present on lettuce. In the present study, we determined the load of total coliform, fecal coliform, and parasites of lettuce. The lettuce was sanitized by protocol of Iranian Ministry of Health and Medical Education. The protocol consists of 3 levels to disinfect the fruits and vegetables. The procedure was as follows: first washing stage. The leaves of leafy vegetables washed with tap water, second stage, separation of helminth eggs by 3 to 5 droplets of detergent per liter for 5 min; third stage, disinfection of vegetables by calcium hypochlorite solution [with 200 mg/1 free chlorine] for 5 min; and finally the disinfected vegetables were washed with tap water. The average initial levels of total coliform and fecal coliform in the samples were 3.36 Iog[10]cfu/g and 2.31 log[10]cfu/g, respectively. Helminth eggs were not detected in any of the samples tested. The efficiency of total coliform and fecal coliform removal were 78.1% [0.75 Iog[10]cfu/g] and 79.6% [0.67 Iog[10]cfu/g], respectively, after washing. This increased up to 94.8[1.44 Iog[10]cfu/g] and 98.5% [1.90 log[10]cfu/g] after the use of detergent. Chlorine disinfection rose these amounts up to 98.3% [2.18 Iog[10]cfu/g] and 100% [2.31 Iog[10]cfu/g], respectively. By applying the protocol large parts of microorganisms existing on lettuce have indeed been removed

[Comparison of indoor and outdoor dose rates from environmental gamma radiation in Kurdistan province]

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. 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. 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. 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

Gonad, bone marrow and effective dose to the population of more than 90 towns and cities of Iran, arising from environmental gamma radiation

Since 1996 the assessment of environmental gamma radiation dose in residential areas of Iranian towns and cities has been accomplished for 10 counties. As a practical method and based on the results of a pilot study, in order to attribute the final results to the whole residential area of a town five stations were selected for every town. The location of individual station was studied closely to comply with recommended conditions in the literature. RDS-110 was employed to measure gamma dose rate for one hour. Average annual dose rates plus conversion coefficients were employed to estimate gonad, bone marrow, equivalent and effective dose. Minimum and maximum annual bone marrow and gonad dose equivalent attributed to environmental gamma are 0.24 mSvy[-1] [for both tissues] and 1.44 and 1.46 mSvy[-1], respectively. Average gonad and bone marrow doses for North Khorasan, Boshehr and Hormozgan provinces were less than the corresponding values for normal area