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Introduction: Over the last decade, exposure to non-ionizing electromagnetic waves due to base station antenna has increased. This in vivo study was planned for evaluating the effects of whole-body exposure to 950 MHz field of GSM mobile phone system on rat dentate gyrus long-term potentiation. Materials and Methods: 24 naive male Wistar rats (3 month old, 225|¡|25 g) were randomly divided in the three groups (sham-exposed, GSM and continuous field exposed). The exposure program was planned for 10 sessions at 3 days. Animals were exposed to electromagnetic field for 45 minutes in a circular plastic chamber (mean power density=0.835 mW/cm2). Immediately after end exposure, anesthesia was induced for long term potentiation (LTP) induction. Field potentials were recorded and analyzed using the population spike amplitude and EPSP slope for 60- min. Results: There were no significant differences in population spike amplitude, EPSP slope and EPSP slope maintenance among the three groups. Conclusion: This study provides no evidence indicating that long-term potentiation can be affected by the whole-body exposure to low-power density of 950 MHz field of GSM mobile phone system.

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Background: The incorporation of thallium-201 into 8-hydroxyquinoline was targeted for cell labeling due to interesting physical properties and wide availability of this nuclide as a single photon emission computed tomography (SPECT) radionuclide. Materials and Methods: Thallium-201 (T1/2=3.04 d) in Tl+ form was converted to Tl3+ cation in presence of O3/6M HCl and di-isopropyl ether, controlled by radiothin layer chromatography (RTLC) /gel electrophoresis methods. The final evaporated activity reacted with ethanolic 8-hydroxy-quinoline (oxine) solution in normal saline to yield [201Tl](III)oxinate at room temperature after 0.5 h, followed by solid phase extraction/purification using C18 Sep-Pak column and partition coefficient determination for water/lipid solubility. In vitro red blood cell (RBC) labeling was also performed. Results: A radiochemical yield of more than 95% was obtained. Radiochemical purity of 92% was obtained using RTLC (>90% using HPLC) with specific activity of about 820 GBq/mmol. The tracer was stable in the final product and in presence of human serum at 37°C up to 6h. The partition coefficient of lopP=5.5 was obtained. The labeled compound was used in RBC labeling. The cell uptake ratio was 0.47 after 240 min. Conclusion: [201Tl](III) oxinate used in this study is a widely available agent for use in RBC labeling studies in biology, medicine and various other research areas. Iran. J. Radiat. Res., 2008 6 (3): 145-150

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Background: In order to diagnose the site of thrombi, radiolabeled streptokinase can be prepared. The radiolabeled compound can be used in imaging of thrombi in many cardiovascular diseases. Materials and Methods: Streptokinase was successively labeled with [67Ga]-gallium chloride using cyclic DTPA-dianhydride. The conjugation with DTPA was optimized for concentration, time and temperature followed by size exclusion chromatography using G-50 Sephadex. The radiochemical purity of the tracer was checked using HPLC and ITLC methods. The biodistribution studies were performed in normal rats up to 167 h using tissue counting and preliminary SPECT studies up to 2 h. Results: The radiolabeled enzyme was prepared in 60 minutes after incubation at room temperature, with the radiochemical purity of >95% (HPLC) and >99% (ITLC) methods. The radioactivity was accumulated in lung, intestine and liver as shown by scarification and SPECT (Single Photon Emission Computed Tomography) methods. Conclusion: Radiolabeled Streptokinase was prepared in suitable radiochemical purity and its biodistribution is comparable to other radiolabeled proteins. Further studies are required to investigate the imaging properties of the tracer in appropriate animal model. Iran. J. Radiat. Res., 2009 6 (4): 195-200

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Background: Although ionizing radiation is widely used to diagnose many diseases, the relevant hazards are known to be as an important limitation of its application. It is believed that the awareness of ionizing radiation dose values is one of the main stages in patient's radiation protection. The purpose of this study has been to investigate the level of physicians' knowledge about radiation doses received by patients in radiological examinations. Materials and Methods: A questionnaire was designed and the most commonly requested radiological investigations were listed. Participants (155 physicians) were asked to identify the average dose of radiation received by patients when they underwent a posterior-anterior hand X-ray. Then, it was utilized to represent a single dose of radiation, and physicians were asked to estimate the equivalent doses of radiation for other radiological examinations. Several questions were also included about dose measurement's units and low exposure risk investigations. Results: The results indicated that only 58.3% of physicians know the units of radiation absorb dose measurement units. Most of them could not correctly estimate the amount of radiation dose received by patients in a routine radiography of hand and majority of them underestimated the radiation dose of other radiological examinations. Conclusion: Despite of passing medical physics course, during studentship, it does seem that most of medical doctors did not have enough knowledge about the amount of radiation received by patients led for diagnostic radiology investigations. Iran. J. Radiat. Res., 2009 6 (4): 207-212

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Background: This study was planned to examine the effects of whole-body exposure to GSM-950 MHz electromagnetic fields (EMFs) on acquisition and consolidation of spatial memory in rats using a water maze task. Materials and Methods: In experiment 1, the animals were given two blocks of five trials per day for three consecutive days in a water maze task. The interval between blocks was 4h. Before each training session, the animals were exposed to 950 MHz EMFs for 45 min with lower- (0.835 mW/cm2) or higher-power (1.166 mW/cm2) densities. In experiment 2, the animals were given two blocks of 5 trials with a 3 min interval between blocks. Immediately after the last trial, they were exposed to EMFs for 45 min with lower- or higher-power densities. In both experiments, 48 h after the last training day a 60 s probe test was done. Results: Results from experiment1 (pre-training exposure to EMFs) indicated no significant differences in performances of exposed and non-exposed groups either during acquisition (learning) or during probe test (memory retention). Results from experiment 2 (posttraining exposure to EMFs) also indicated no significant differences among groups during acquisition or probe test. Conclusion: In these experiments, no effect of exposure to 950 MHz on acquisition or consolidation of spatial navigation of rats in a water maze was detected. Iran. J. Radiat. Res., 2009 7 (1): 57-62

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Background: Oxytocin (OT) is a paracrine hormone with various biological activities and many sex organs in both sexes, as well as many tumor cells have shown to have related receptors. In this study the development of a receptor imaging tracer for possible tumor imaging has been described. Materials and Methods: OT was successively labeled with [67Ga]-gallium chloride after conjugation with freshly prepared cyclic DTPA-dianhydride. The best results of the conjugation were obtained by the addition of 1 ml of a OT pharmaceutical solution (2 mg/ml, in phosphate buffer, pH=8) to a glass tube pre-coated with DTPA-dianhydride (0.02 mg) at 25°C with continuous mild stirring for 30 min. Radiochemical purity (RCP) of the labeled compound was determined, using RTLC and ITLC followed by stability tests and animal biodistribution studies. Results: Radiolabeling took about 60 minutes with a RCP higher than 98 % at optimized conditions (specific activity = 1000 Ci/mM, labeling efficiency 80%). The stability of the tracer at room temperature was significant, up to an hour. Preliminary in vivo studies in normal female rat model showed ovary/blood and ovary/muscle ratio uptake of the tracer in 60 minutes to be 4.53 and 9.18, respectively. The result was consistent with the reported OT receptor distribution in normal female mammals. Conclusion: The radiolabeled oxytocin, prepared in this study, was a possible fast acting tracer for OT receptor imaging studies however, more studies are required to determine the best imaging conditions especially in larger mammal animals. Iran. J. Radiat. Res., 2009 7 (2): 105-111

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Background: Glioblastoma is the most common and most malignant cancer of central nervous system. Targeted radiotherapy is an effective method toward its treatment. Iododeoxyuridine (IUdR) is a halogenated thymidine analogue known to be effective as a radiosensitizer in human cancer therapy. In this study we have evaluated the combination effects of 2-Methoxyestradiol, an inhibitor of hypoxia inducible factor 1α (HIF-1α) and Methoxyaminem, an inhibitor of base excision repair (BER) pathway on radiosensitization of IUdR in glioblastoma spheroid culture. Materials and Methods: The cytotoxic damages of DNA in U87MG cell line were compared using colony formation assay. Experiments were performed in large spheroids with a diameter of approximately 350μm. Results: Evaluation of the effects of IUdR with 2ME2 and MX pretreatment on spheroid cultured cell followed by ionizing irradiation showed more enhancemented (p≤0.001) IUdR induced-radiosensitization. These results introduced a key role for 2ME2 in IUdR related studies. Conclusion: Pretreatment of tumor cells with IUdR, MX and 2ME2 before irradiation enhances tumor radiosensitization and may improve therapeutic index for IUdR and 2ME2. Iran. J. Radiat. Res., 2010 7 (4): 211-216

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Background: In recent decades many guidelines has been conducted by radiation protection organizations about radiation protection in dentistry. This study aimed to evaluate the observance of these guidelines in educational clinics of all dental schools in Iran. Material and Methods: In this cross-sectional study a self-administered questionnaire, based on National Radiation Protection Board (NRPB) and European Commission guidelines, was conducted. The radiology departments of all dental school (18 schools) were surveyed in this study. The questionnaire was consisted of 3 sections including intraoral radiography, extraoral radiography and implementation of quality control programs. Results: In the case of the existence of radiation protection facilities (such as lead apron, thyroid shield and lead impacted walls) the use of high speed films and existence of automatic processor in dental schools, there was a proper condition. The main problem was related to lack of regular quality control and quality assurance programs. Digital radiography systems were employed in none of the schools and it was occasionally used for research purposes at some of them. Conclusions: This study has emphasized on the need for further consideration of radiation protection principles in dental schools, especially on the field of quality control and quality assurance programs. Iran. J. Radiat. Res., 2010 8 (1): 51-57

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Background: In conventional radiation therapy, regarding normal tissue tolerance, the treatment of bulk tumors is one of the remaining challenges. Grid Radiation Therapy (GRT) is a technique to deliver high doses, approximately 15 – 20 Gy per fraction, to several small volumes located in a large radiation field. This can be performed using a grid block. The current work has concentrated on the dosimetric characteristics of a designed mega-voltage grid, used for a unique treatment modality. Materials and Methods: All measurements performed using a Neptune linear accelerator (9 MV photon beam). A square 16 × 16 array grid block was designed and fabricated. Several dosimetric characteristics including: depth dose, Valley To Peak (VTP) ratio, and grid out-put factor were evaluated using a calibrated diode dosimeter for a range of radiation fields. Results: The percent depth dose curves, measured in the presence of grid block, lie within those measured for the corresponding open field and a narrow beam. At the Dmax, the VTP ratio was found to be within 17% - 28%, while these ranges between 23% - 35% at a depth of 10 cm. The grid out -put factor found to be 0.78 and it slightly decreases with increasing of radiation field size. Conclusion: The VTP ratio found to be dependent strongly on the grid design and manufacturing properties. However, other parameters such as radiation field size and the depth of measurement should also be addressed as important factors. The measured dosimetric characteristics of grid block indicate that the mega-voltage grid therapy can be applied as a possible clinical modality for palliative cases. Iran. J. Radiat. Res., 2011 9(1): 49-56

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Background: The advantages of proton beam in radiation therapy- like small lateral scattering as well as absence of exit dose tail in the organs which are after the tumor- make it capable of delivering more treatment doses to the target and much lesser to the critical tissues near it. Materials and Methods: In this study, the Monte Carlo MCNPX code has been used to simulate a slab head phantom irradiated by proton pencil beams. The simplified slab has tissue compositions of the ICRU 46, and the necessary data have been taken from adult male phantom of MIRD-ORNL family series. Results: Suitable energy range of incident proton beams has been estimated in order to have the Bragg peaks inside the brain tissue. Energy straggling or, rather, range straggling, and multiple scattering which affect the lateral broadening of incident beams, have been investigated. Conclusion: The results show that the FWHM (Full Wide in Half Maximum) increases more than six times from 1.73 mm to 10.78 mm for the energy range of 50 - 135 MeV. The FWHM values of lateral dose profiles change from 1 mm in 50 MeV to 7.5 mm in 135 MeV, and it has been shown that when a pencil beam is used to irradiate a tissue, the absorbed dose in depth along the central axis does not show a Bragg peak pattern.