International Journal of Radiation Research
Volume:6 Issue: 2, Apr 2008

Humans beings are continuously exposed to ionizing radiation from natural sources. The main contributors to natural radiation are high-energy cosmic radiation and radioactive nuclides that originates in the earth’s crust. Exposure to high levels of radiation can cause serious health effects. In this study an attempt has been made to monitor the levels of environmental background radiation (gamma) in temples, historical monuments, schools and colleges, hostels, wedding halls and theaters in Mysore and Chamaraj Nagar districts and assess the possible effects on environment and human health.

Environmental radiation dosimeter is used to measure the outdoor and indoor radiation absorbed dose levels. The measurements were made 1 m above the ground level

Inside the temples it varies from 122.7 to 231.4 nGy.h–1 with a median of 130.1 nGy.h–1 outside the temples it varies from 141.8 to 340.2 nGy.h–1 with a median of 216.2 nGy.h–1. In different types of buildings in indoor atmosphere it varies from 112.2 to 197.5 nGy.h–1 with a median of 127.0 nGy.h–1 and in outdoor atmosphere it varies from 140.9 to 298.4 nGy.h–1 with a median of 216.2 nGy.h–1.

The indoor absorbed dose rate is higher than outdoors in all types of constructions. Indoor and outdoor environment of the temples has higher levels of radiation than the historical monuments and other public and private building in Mysore and Chamaraj Nagar districts. Use of additional granite materials inside or outside the building will enhance the absorbed radiation dose levels. The values observed in the study area are comparable with other values observed in different parts of the world.

To investigate the status of the nuclear medicine (NM) centers in Iran for the performance of dose calibrators, 18 out of 54 centers providing NM services in Iran were randomly selected and inspected in 1997. In the first phase of the study the selected centers were inspected for performing of quality control (QC) tests of dose calibrators. The linearity of the activity response, precision, accuracy, and the physical functions of the instruments, were studied. In the second phase of the study, carried out in 2006, 28 out of 75 NM centers were investigated for QC tests performance. The QC tests were performed by using standardized radio nuclides of Tc-99m and Cs-137 in the first phase, and Tc-99m and I-131 in the second phase of the studies. Standard procedures were used for carrying out the tests. According to the obtained results in the first phase of the study, 10 centers were found to be in unacceptable situation. Following this study, all the concerned NM centers were informed about the results, and at the same time the repair and adjustment of the dose calibrators were requested. In addition, the appropriate training courses along with the QC testing manuals were provided to the centers. Based on the data of the second phase of the study, only 6 NM centers were in unacceptable situation. The results indicated the effectiveness of the improvements carried out in the working procedures of the centers during interval between the two phases of investigation.

Prediction of the absorbed dose in irradiated volume plays an important role in the outcome of radiotherapy. Application of small fields for radiotherapy of thorax makes the dose calculation process inaccurate due to the existence of electronic disequilibrium and intrinsic deficiencies in dose calculation algorithms. To study the lung absorbed dose in radiotherapy with small fields, the central axis absorbed dose in heterogeneous thorax phantom was measured by ionization chamber and calculated for small fields by Monte Carlo (MC) method. A solid slab phantom consisting of unit and low density materials was used for dose measurements. The 6 and 18 MV photon beams of Elekta SL25 linac were simulated using MCNP4C MC Code. The model was validated by comparing the calculated depth dose and beam profiles with measurements in a water phantom. The MC model was used to calculate the depth doses in unit density and low density materials resembling the soft tissue and lung, respectively. Two small field sizes including 5×5 and 2×2 cm2 were used in this study. The measured depth dose values were in good agreement with MC results and the difference less than 2% was observed. A large dose reduction was seen in lung for field size of 2×2 cm2 due to the lateral electronic disequilibrium and it reached up to 16.2% and 33.3% for 6 and 18 MV beams, respectively. Dose build up and down at material interfaces was predicted by MC method. Our study showed that the dose reductions with small fields in lung and dose variations at interfaces was very considerable, and inaccurate prediction of absorbed dose in lung using small fields and photon beams may lead to critical consequences for patients.

Breast is one of the main radiological sensitive organs, hence it is important to evaluate absorbed dose to this organ especially to the glandular parts. It is the aim of this study to measure mean glandular dose and image contrast in terms of different mammographic parameters. In this study two mammography machines located at Said-al Shohada (Giotto) and Shahid Behesti (GE) hospitals were used. According to the recommendations of ACR and MQSA, breast phantoms were constructed and used for this study. For dose evaluation TLD dosimetry method was used. The TLD dosimeters were of LiF type and the reader was a Solaro TLD reader. To obtain a constant contrast when increasing kVp from 22 to 24, it was necessary to reduce mAs by 12 percent. The obtained relation between these two parameters is: contrast=0.2829D-0.2427. It was also found that there is a linear relationship between contrast and image quality. The relation between these two parameters is: Image quality = 28.117 Contarst + 20.134. Increasing kVp and hence decreasing mAs results a reduction to the glandular dose, especially in patients with large breast. Increasing kVp from 28 to 30 results in reduction of dose from 6.8mGy to 5mGy. It was found that there has been a linear relationship between contrast and image quality. It was also found that increasing kVp necessitate to reduce mAs for a constant contrast and hence reduction of glandular dose.

In this work investigation of the normoxic PAGAT polymer gel dosimeter such as sensitivity, the R2-dose response with post time and the percentage depth dose (PDD) of PAGAT polymer gel dosimeter have been undertaken. Using MRI, the formulation to give the maximum change in the transverse relaxation rate R2 was determined to be 4.5% N,N''-methylenbis- acrylamide ©(bis), 4.5% acrylamid(AA), 5% gelatin, 5 mM tetrakis (hydroxymethyl)phosphonium chloride (THPC), 0.01 mM hydroquinone (HQ) and 86% HPLC (Water). Irradiation of vials was performed using photon beams by Co-60 therapy unit and an Electa linear accelerator. Gel dosimeters were imaged in a Siemens Symphony 1.5 Tesla clinical MRI scanner using a head coil. Gel dosimeters were irradiated 1 day post-manufacture, and imaged 1 day post irradiation. The R2- dose response was linear up to 30 Gy. The response of the PAGAT gel is very similar in the lower dose region and the R2-dose response for doses less than 2 Gy is not exact. The R2-dose response of the PAGAT polymer gel dosimeters varies between 10 to 30 Gy with R2-dose sensitivities of 0.0905, 0.1037, 0.1023, 0.0907 and 0.123 S-1Gy-1 when imaged at 1, 8, 15, 29 and 38 days post-irradiation respectively. The percentage depth dose (PDD) of PAGAT gel dosimeter was determined and at depth of 21cm, the percentage depth dose for 1.25, 4, 6 and 18 MV photons were determined to be, 48%, 52%, 57.3% and 59.73% respectively. Calibration curve of the PAGAT polymer gel dosimeter, were found to be linear between 2-10 Gy and 10-30 Gy with different slopes of the R2-dose sensitivity also showed stability with post time imaging after 38 days. In this study, the percentage depth dose (PDD) of the PAGAT gel dosimeter was measured. It can be concluded that in case of higher energy of photon beams, higher doses can be delivered to deep-seated tumors.

Investigation on the natural radionuclides 238U, 232Th, 40K and natural fallout radionuclide 210Po in the prominent plants species of Western Ghats tropical forest near Kotagiri have been carried out as a part of baseline background radiation studies in the forest environment. The prominent plants species of the region Evodia roxburghiana and Eleaocarpus oblangus were chosen and concentrations of 238U, 232Th, 40K and 210Po were measured by employing gamma ray spectrometer and alpha counter. The radioactivity concentrations in plants and soils reflect the impact of the existence of igneous nature of rock in the area of study. Concentration ratios (CR) of these radionuclides, between plants and underlying soil, have been studied and results shows that the concentration ratios (CR) seem to be depend on radionuclides in soil. From careful analysis of the results, these plants could be used as an indicator to monitor these radonuclides.

Poorly educated people in some parts of Iran use burned mantles as a wound healing medicine. To perform surface area measurement, twenty rats were divided randomly into two groups of 10 animals each. The first group received topical burned radioactive lantern mantle powder on the first to third days after making excision wounds. The second group received non-radioactive lantern mantle powder. For histological study, 36 male rats were randomly divided into two groups of 18 animals each. Full thickness excision wound (314±31.4 mm2) was made on the dorsal neck in all animals after inducing general anesthesia. For the first three days, cases had received topical application of the radioactive lantern mantle powder. Finally, to measure the tensile strength, an incision was made on the dorsal neck of the rats. Surface area measurement of the wounds showed a progressive surface reduction in both groups. Histological study showed a significant statistically difference between cases and controls with respect to fibrinoid necrosis and neutrophilic exudate on days 3 and 14. Considering the existence of granulated tissue, a significant difference was observed between case and control groups on days 3 and 7. Tensile strength study showed no significant difference between the cases and controls. Topical use of radioactive mantle powder can accelerate the healing process of the wound in rats.

Osteoporosis is a chronic disease that contributes substantially to decrease physical activity and decline in the quality of life. Osteoporosis can be diagnosed easily with the use of dual-energy X-ray absorptiometry (DXA) equipment. The aim of this study was to investigate the magnitude of bone loss on proximal femur and lumbar spine LS in pre- and post-menopausal women from Isfahan Osteoporosis Diagnosis Center (IODC) since 2005. Bone mineral density (BMD) measurements using DXA have been performed at IODC. 185 pre-menopausal and 174 early post-menopausal women were selected randomly. A Norland XR46 system was used for the investigations. The student t-test was done to find the difference between the T-scores of the femoral neck (FN) and lumbar spine (LS) in pre- and post-menopausal women. Mean BMDs for the FN and LS in pre-menopausal women were 0.859 ± 0.136 and 1.012 ± 0.161 and in post-menopausal women were 0.816 ± 0.119 and 0.919 ± 0.140, respectively. Long-term BMD CVs of 1.0% and 1.2% for the LS and FN were found, respectively. The differences between the FN and LS for pre- and post-menopausal women were t = - 9.02, p < 0.05 and t = -3.50, p < 0.05, respectively. In spite of, the reported lower BMD T-scores for the LS compared with the FN for women, we found that the FN had significantly lower T-score than LS for both pre- and post-menopausal women.