International Journal of Radiation Research
Volume:10 Issue: 1, Jan 2012

Ionizing radiation induces the production of reactive oxygen species (ROS), which play an important causative role in cell death. Wholebody exposure of mice to gamma radiation leads to diminution of tissue antioxidant defense systems; increases the peroxidative damage to membrane lipids and damages the haematopoietic and gastrointestinal systems. Tempol (TPL), a cell membranepermeable amphilite nitroxide, shown to protect against cell injury caused by ROS was studied for its radioprotective effects. Animals were administered with TPL at doses of 100 or 200 mg/kg body weight p.o 10 minutes prior to sub- lethal doses (4 or 6 Gy) of whole body gamma radiation exposure. Tempol prevented the radiation induced depletion in RBC and total WBC counts, glutathione content in blood and bone marrow cellularity. TPL also protected the tissue antioxidant system and membrane lipids from the radiation-induced damages. An enhanced spleen colony formation and spleen weight recovery were also observed in radiation exposed mice administered with TPL. The compound also protected the epithelial cells of the gastrointestinal tract from the radiation-induced structural alterations. These preclinical data indicate that TPL may have its potential as a radioprotector during radiation exposure scenarios.

Gemcitabine (2′, 2′-difluoro-2′- deoxycytidine, an analogue of deoxycytidine) is a relatively new drug with wide range of anti-cancer activity. In this study, radiosensitizing effects of gemcitabine was investigated on HeLa and MRC5 human originated cell lines under both chronically hypoxic and normoxic conditions using the micronucleus (MN) assay. For induction of chronic hypoxia, the cell culture flasks were saturated with N2 gas. To evaluate the radiosensitizing effects, in the presence of the non-genotoxic concentration (1ng/ml) of gemcitabine, cells were exposed to different doses (0.5, 1, 2 Gy) of X-ray in both chronically hypoxic and normoxic conditions. Results showed that there was no significant difference in MN induction under chronically hypoxic and normoxic condition when using 1 ng/ml gemcitabine alone, however in the absence of drug, MN induction was significantly different in irradiated cells (P<0.01). Radiosensitizing effects of gemcitabine in chronic hypoxic condition was greater than normoxic condition in both cell lines (P<0.01), although more pronounced in HeLa cells. Radiosensitizing effects and greater dose modifying factor of gemcitabine under depleted oxygen condition is not clearly understood. It might be due to depletion of deoxynocleotides pools via inhibition of ribonucleotide reductase and mismatched nucleosides incorporation into DNA after radiation exposure.

Several epidemiological studies conducted on underground miner’s show that exposure to elevated levels of radioactive radon gas is expected to increase the risk of lung cancer. Relative risk of lung cancer is almost linear with radon exposure. Elevated concentrations of radon are not only reported within mines but also for closed indoor environment of general public houses. Measurements of radon play a serious role in scrutinizing public health and safety in homes. Indoor radon measurements were taken over a period of year, using CR-39 detectors. Measured indoor radon concentrations, was converted in to excess relative risk (ERR) factors by using the risk model reported in the Biological Effects of Ionizing Radiation (BEIR VI) report. ERR was calculated for age groups of 35 and 55 years. A careful selection of occupancy factor based on interviews with house occupants has been made. Using this local occupancy factor, average excess lung cancer risk for the age group of 35 and 54 y peoples was found to 0.51±0.03 and 0.42±0.03. Similarly average values of ERR for local occupancy factor with ages 35 and 55 years was found as 0.59±0.03 and 0.45±0.03. The overall average excess lung cancer risk for the studied area was 0.46±0.03. The study suggested that United State Environmental Protection Agency (US EPA) occupancy factor gave a higher excess lung cancer risk as compared with the local occupancy factor used for studied areas. The ERR due to indoor radon is within the standard limits and does not pose any serious threat to the occupants of the houses under investigation.

The South-west coast of India is known to have very high levels of natural background radiation due to the monazite beach sand. Uranium is the heaviest trace element found in all terrestrial substances at varying levels with chemical and radio toxicities. It supports several short-lived radioisotopes in its decay series including radium. Uranium in drinking water is important in terms of the ingestion dose. The present study reports the results of uranium analysis of 346 drinking water samples from the three costal districts of Kerala using fission track registration technique. Results obtained show that uranium concentrations vary from 0.31 μg/l to 4.92 μg/l equivalent to the specific activity of 3.9 Bq/m3 and 62 Bq/m3, respectively. The estimated daily intake of uranium through drinking water is lower than the recommended limits. The distribution of uranium in water bodies shows a heterogeneous nature of distribution.

Radon concentration was measured in 50 drinking water samples in Mashhad - Iran. b The tap water used for drinking and other household usages can increase the indoor radon level. Drinking water samples were collected from various places and supplies of public water used in Mashhad. Then radon concentration has been measured by portable radon gas surveyor SILENA (PRASSI) system. The results showed that about 70% of water samples had radon concentration greater than 11Bq/l the level recommended USA environmental protection agency (EPA). The arithmetic mean of radon concentration for all samples was 16.238 ± 9.322 Bq/l. Also the annual effective dose in stomach and lung per person were estimated in this research, with the mean value of 0.040 mSv and 0.043 mSv per year for these two organs for all samples, respectively. The results indicate that radon concentrations in public drinking water samples of Mashhad are mostly low enough and below the proposed concentration limits. The mean radon level was 16.238 Bq/l for all samples; which is not much greater than 11Bq/l as EPA advised level. Further, only two samples induced the total annual effective dose greater than 0.1 mSv per year.

Two protocols of AAPM TG-51 and IAEA TRS-398 were compared followed by a measurement and Monte Carlo simulation of beam quality correction factor, KQ, AAPM TG-51 and IAEA TRS-398 protocols were compared for the absorbed dose to water for DW, and KQ parameters. Dose measurements by either protocols were performed with cylindrical and plane parallel chambers for 6 and 18 MV photons, and 6, 9, 12, 15, 18 MeV electron clinical beams were traced to the calibration factor of Iranian secondary standard dosimetry laboratory. MCNP-4C simulation of depth doses, beam profiles and KQ factors were validated typically for 18 MV and 12 MeV beams by experimental measurements. The differences between simulation and measurements were 0.07% for beam profile, -2.60% and 1.19% for 12 MeV build up and linear portion of the depth dose curve, respectively. The figures of merit for 18 MV were about -4.17%, - 1.62% and 0.38%. The differences of KQ's between simulation and measurement of 12 MeV, and 18 MV beams for TG-51 were -0.194% and 0.169%, and for TRS-398, they were about -0.465% and 0.097%, respectively. These differences between the two dosimetry protocols (IAEA TRS-398 & AAPM TG-51) from the point of absolute dosimetry were not significant at least when they were used under the same calibration procedure. The good agreement between Monte Carlo and measurement may also be even more important regarding the contribution into the development of radiotherapy treatment planning system, based on Monte Carlo procedures.

Sentinel node biopsy (SLNB) is the standard of care for breast cancer treatment and it is getting wide acceptance in Iran. The radiation safety of the procedure has been investigated under controlled conditions, but the standard dose of radiotracer and techniques are not always observed in the community setting. The aim of this study was to assess the magnitude of the absorbed doses of radiation to the hands of operating surgeons. Twenty consecutive SLNB procedures were studied. Radiation dose to the hands of the surgeons was measured by placing lithium fluoride thermoluminescent dosimeters (TLDs) in the surgeon's glove. The radiation dose to the abdomen and thyroid area was measured by placing TLDs at these areas. The injected dose of radiotracer, the time interval to the surgery and the duration of the surgery were recorded. The injected dose of radiotracer ranged from 0.1 to 5 mCi. The highest absorbed dose was recorded by TLD, placed on the non-dominant hand third finger (189.1 μSv). Mean recorded doses were higher for non-dominant hand second finger (53.49 ± 24.60 μSv). The measured absorbed doses for the abdominal and thyroid area were lower than those for the fingers. This study has confirmed the procedure safety, even with high dose of radiotracer. Nevertheless, it is advisable to use the lowest dose of the radiotracer to avoid the waste of resources.

The 153Sm-[tris(1,10-phenanthroline) Samarium(III)]complex (153Sm-PL3) was prepared in view of development of targeting therapeutic compounds for malignancies, and interesting in-vitro anti-tumor activities of lanthanide phenanthroline complexes,. Sm-153 chloride was obtained by thermal neutron flux (4 × 1013 n.cm-2.s-1) of enriched 152Sm2O3 sample, dissolved in acidic media. The labeling was performed in ethanol in 24h, controlled by ITLC (1.0mM DTPA, pH.5, as mobile phase). The partition coefficient for the labeled compound was also determined. A radiochemical yield of more than 95% was obtained. Radiochemical purity of 96% was obtained using ITLC with specific activity of about 27.75 GBq/mg. The radio-labeled complex was stable in aqueous solution at least 24 hours and no significant amount of free 153Sm was released from the complex. The partition coefficient for the labeled compound was determined (log P. 3.4). The complex was stable in final formulation for 66h. The biological evaluation of the compound is under investigation. The radiolabeled compound used in this study was a very inexpensive and useful agent for the use as a therapeutic compound.

As bremsstrahlung photon beam fluence is important parameter to be known in a photonuclear reaction experiment as the number of produced particle is strongly depends on photon fluence. Photon production yield from different thickness of aluminum target has been estimated using artificial neural network (ANN) model. Target thickness and incoming electron energy has been used as input in ANN model and the photon fluence was output. The results were estimated using ANN model for three different thickness and compared with the results obtained by EGS (Electron Gamma Shower) simulation. It can be concluded from this work that the bremsstrahlung photon fluence can be obtained using ANN model.