International Journal of Radiation Research
Volume:11 Issue: 1, Jan 2013

Some Areas of Ramsar, a city in northern Iran are among the world’s wellknown inhabited areas with highest levels of natural radiation. Annual exposure levels in these areas are up to 260 mGy y‐1 and the mean exposure rate is about 10 mGy y‐1 for a population of about 2000 residents. If elevated levels of natural radiation as high as a few hundred mSv per year is detrimental to health and leads to higher risks of genetic abnormalities and cancer, it should be evident in the residents of areas such as Ramsar. However, it has been reported that no detrimental biological effects have ever been detected in high natural background radiation areas. Some studies indicate that Ramsar residents not only show a significant increase in DNA repair but also demonstrate induction of radioadaptive response. There is currently a great debate over the shape of the dose‐response curve for stochastic effects such as mutations and cancer after exposure to low doses of ionizing radiation. Linear‐no‐threshold (LNT) model predicts that every dose, no matter how low, carries some cancer risk. Lack of any proven detrimental effect in the residents of high natural background radiation areas of Ramsar may be due to the induction of nonlinear dose‐response relationships which are not compatible with the widely accepted LNT hypothesis.

Exposure to ionizing radiation results in genotoxicity and the unrepaired lesions in cellular DNA results in cell cycle arrest, reproductive death, interphase death, division delay, chromosome aberrations, mutations, etc. leading to the intensive destruction of cells and violation of their proliferative capacity there by adversely affecting the mammalian system. Since ionizing radiation is widely used in medicine, industry, agriculture and research, an effective radioprotector is a must to protect living beings. This work aims to identify the ability of dietary supplements, curcumin and ascorbic acid in offering protection from radiation induced genomic insult to human peripheral blood leukocytes. Alkaline single cell gel electrophoresis was performed on human peripheral blood leukocytes exposed to 2 doses of gamma radiation in presence and absence of curcumin and ascorbic acid (in vitro). The same technique was also applied to blood leukocytes of volunteers before consumption of these supplements and 5 days after (ex vivo). The comet parameters such as % DNA in tail, tail length, tail moment and olive tail moment were determined. The comet parameters of leukocytes increased upon exposure to ionizing radiation indicating DNA damage, in vitro or ex vivo. The extent of DNA damage was found significantly decreased either in the presence or following the intake of curcumin and ascorbic acid. Curcumin offered higher protection than ascorbic acid. Intake of dietary antioxidants such as curcumin or ascorbic acid could offer protection against ionizing radiation induced cellular DNA damage in peripheral blood leukocytes.

Treatment of ionizing radiation combined with chemical agents can enhance the inactivation of cells. The aim of this study was to determine the parameters involved in the inhibition of cell recovery. A mathematical model describing the process of recovery as a decrease in the effective radiation dose was used. The model includes two parameters, recovery constant and irreversible component. Both parameters were estimated quantitatively by using experimental survival and recovery data reported by others. The inhibition of cell recovery might be done via either the damage of the mechanism of the recovery itself or via the formation of irreversible damage which could not be repaired at all. Both these processes could take place at the same time. Another mechanism was the higher probability to produce primary radiation damage without changing the recovery process. The results indicate the opportunity to search agents, selectively or simultaneously acting on the probability of recovery and the yield of irreversible radiation damage. The results obtained may have a practical use, rather than being concerned only with theoretical position.

Decrease of economically accessible uranium resources motivates consideration of breeding of fertile elements such as thorium. Thorium oxide fuel burn up calculation of a simulated research reactor cooled heavy water has been proposed in the present work using MCNPX 2.6 code. Two 233U and 235U isotopes have been used as fissile element of thorium oxide fuel. 135Xe and 149Sm reactivity variations has been studied in the core loaded (Th- 233U)O2 or (Th- 235U)O2 fuel matrixes during 3 months burn up process. Thorium oxide having 4% 233U burned 1 MW power results in less 149Sm reactivity than thorium oxide having 4% 235U burned in 0.5 MW power. 135Xe reactivity has an overestimated shift by 15 days in the core operated in 0.5 MW than the other, after 15 days both the cores behave similarly. 480 g of 235U burns into the core using 0.5 MW power and 364 g of 233U invents after 3 months. Burn up calculation of the modeled core of (Th-233U)O2 fuel shows a fissile mass reduction by 60 days while the consumed fissile mass reaches to its initial value after 120 days. The core flux is constant during 3 months for both modeled cores. A considerable negative reactivity occurs up to 15 days in both cores which can be refer to xenon inventory during this time and then neutron multiplication factor is steadier up 3 months. Breeder thorium fuel enriched 233U make several advantages of good neutronic economy, 233U inventory and less inventory of long-lived alpha emitter wastes.

β-glucans are glucose polymers with a variety of stimulatory effects on the immune system. The objective of this study was to evaluate the immune-enhancing activities of low molecular weight gamma irradiated β-glucan (Iβ-g) extracted from Pleurotus ostreatus in response to Pseudomonas aeruginosa infection in rats. β-glucan (β-g) powder was exposed to 50 kGy of gamma radiation. For experimental study, healthy male rats were divided in six groups. Group I: did not receive any treatment. Group 2: infected group was injected once with P. aeruginosa. Group 3: were orally administrated with β-g for 15 days at a dose of 65 mg/Kg body weight/day. Group 4: were orally administrated with Iβ-g for 15 days at a dose of 65 mg/Kg body weight/day. Group 5: rats were treated with β-g and injected once with P. aeruginosa. Group 6: rats were treated with Iβ-g and injected once with P. aeruginosa. Rats were sacrificed 24 h post bacterial infection. β-g and Iβ-g were characterized using FTIR spectra and SEM, showed breakdown of the glycosidic bonds with deformation and splitting of β-g molecule. Oral ingestion of β-g markedly enhanced the production of lymphocytes and leucocytes and CD8 compared to that of Iβ-g, although Iβ-g was more effective in stimulating CD4 count compared to that of β-g and ameliorated CD4/CD8 ratio. Iβ-g enhanced GPx and CAT activity, elevated zinc concentration in the blood compared to that of β-g, although both Iβ-g and β-g elevated GSH and caused no effect on MDA level in post infected groups. In conclusion Iβ-g improves antioxidant state and enhances immune system in particular CD4 count against bacterial infections which is an important marker of immune system.

Broca’s and Wernicke’s areas, which are important language areas of brain, are commonly irradiated in patients with right frontal lobe glioblastomamultiforme (GBM). We aimed to compare two different treatment planning techniques in terms of the doses in the Broca’s and Wernicke’s areas for the patients with right frontal GBM. Two different treatment planning techniques of right frontal GBM were generated for Rando phantom: two field technique using parallel opposed beams and three field techniques. Both plans were compared for doses in planning target volume (PTV), Broca’s and Wernicke’s areas. Additionally to test the accuracy of treatment planning system (TPS) dose calculation; thermoluminescent dosimeters (TLD) were used. The three field technique allowed the lower doses in the Broca’s and Wernickes’s areas. The doses calculated in the Broca’sand Wernicke’s areas were 0.98% ± 0.03 and 0.09% ± 0.06 of the isocenter dose with three field and 1.06% ± 0.04 and 0.133% ± 0.03 of the isocenter dose with two field techniques respectively. When the doses measured by TLD and calculated with TPS were compared; the differences were 3.23% and 2.92 % for Broca’s area, and 4.12 % and 3.95% for Wernicke’s area for two field and three field techniques respectively. There was a good agreement between TPS and TLD calculations for both techniques. Three field techniques seem to be more advantageous than two field technique with respect to doses of Broca’s and Wernicke’s areas. However this finding should be clarified with further clinical studies.

7-LiF: Mg,Cu,P (GR-207A) is one kind of thermo-luminescent dosimeters (TLD) which can be used in diagnostic radiology and radiotherapy applications. Because of having suitable properties such as good sensitivity, small size and being tissue equivalent, thermo-luminescent dosimetry has been one of the most important techniques in medicine over many years. Choosing a correct energy for TLDs’ calibration is one of the most important factors in the accuracy of the absorbed dose In order to evaluate the effect of calibration energy on the response of GR-207A TLDs, calibration of the TLDs were done with 120kVp, 200kVp, 6MV, 18MV and 60Co beams. Then the responses of TLDs were normalized to 60Co and energy dependence was calculated for each dose step. The results confirmed that this kind of TLD dose not have the same response in different energies and reference dose affects on the amount of energy dependence. Energy dependence of this type of TLDs is more significant at lower energies compared to megavoltage beams. Relative response to 60Co illustrates that GR-207A dose not have uniform response to different steps of energies and the amount of energy dependence is totally different in various dose levels.

Radiation-sensitive polymer gels are among the most promising three-dimensional dose verification tools and tissue-like developed to date. Among the special features of this type of dosimeters, is be doped with other elements or chemicals which made them appropriate for investigating of dose enhancement with contrast agents, by high atomic number. In this study, To evaluate dose characteristic of the normoxic polymer gel (MAGICA) such as dose response, dose sensitivity and dose resolution And To find the gold nanoparticles (50 nm) effects of the normoxic polymer gel such as a DEF in mega voltage radiation therapy (18 MV-X ray). Also it is compared by method of Monte Carlo simulation with MCNPX Code. The results shown that the MAGICA polymer gel dose response in dose range of 0 to 600 cGy is linear and dose resolution in this range, is less than 0.7 Gy. MAGICA Polymer gel dosimeter response R2 was increased by added gold nanoparticles. Absorbed dose enhancement factor by adding of gold nanoparticles with the 0.1, 0.2, 0.4 mM concentrations was 10%, 2% and 4% respectively. In this study, Shielding effect or self absorption happened on 0.2 mM & 0.4 mM. And optimum gold nanopartiles concentration to achieved maximum absorbed doe is 0.1mM, so that is useable for clinical studies.