International Journal of Radiation Research
Volume:6 Issue: 1, Jan 2008

The paper discusses the results of 30 years of radon indoor entry research. While some progress has been made, many discrepancies between current theories and experimental data still remain. Misconceptions of radon transport mechanisms in homes are analyzed. The role of US Environmental Protection Agency in radon indoor entry research is examined and the agency''s policies are criticized. The need to include thermotranspiration gas transport in the general model of radon indoor entry is substantiated..

A study on the migration characteristics of 238U, 210Po, 232Th and 40K within the soil to the wild plants in the Western Ghats were carried out. Concentrations of these radionuclides were measured in different depths of soil and from different species by employing gamma ray spectrometer and alpha counter. The activity concentration of these radionuclides varied faintly within the soil but widely varied within the plant and between the species. The CR (Concentration ratio) showed wide variation in different species, while a few species of wild plants such as Evodia roxburghiana, Eleaocarpus oblangus and Glochidion neilgherense indicated preferential uptake of these radionuclides.

High level radiation areas have been recognized on various parts of the earth. Mahallat hot spring region is one of these areas. Study of exposure in these areas can be helpful in investigating the effects of ionizing radiation. Internal and external exposure to the staff was studied. Used materials and instruments include: RSS-112 ionizing chamber for environmental gamma rays measurement, pure germanium detector for measuring radioactive elements in the ground, liquid scintillation counter for measuring 222Rn gas concentration in water samples, Bubbler chamber and Locus cells for 226Ra concentration measurements as emanation method and Alfa guard detector for 222Rn concentration measurements. Considering stay period of the studied groups in indoor and outdoor environment, calculated annual external effective dose for staff has been 514.8 ± 22.7 μSv. Annual internal effective doses for staff in outdoor and indoor environment has been 21.1 mSv. Annual internal effective dose for staff due to drinking water has been 32 μSv. Measurements showed that more than 90% of the received dose in the studied groups was due to inhalation of Radon gas. External and internal effective dose for the staff was 21.6 mSv. Considering these results Mahallat hot spring region is a high level natural radiation area (HLNRA).

Synthetic radio-protective agents like aminothiols are toxic and FDA approved agent amifostine is no exception. Some Ayurvedic herbs have shown radioprotective potential. This study was carried out to test and compare the radioprotective potential of Curcuma longa (CL) Tinospora cordifolia (TC), Zizyphus mauritiana (ZM) and Ocimum sanctum (OS) against 2Gy gamma irradiation in Swiss albino mice. Adult Swiss albino mice from random breed colony were divided in to 6 groups (n=9), sham-control (SCT), radiation control (RACT), and four herb + radiation groups respectively. All except SCT were exposed to whole body 2 Gy of gamma radiation in a teletherapy unit and SCT was sham exposed on day 7 of herb pretreatment (200mg/kg-bw orally by gavage). Chromosomal studies from the bone marrow of femur by routine metaphase preparation after colchicine treatment were done in 3 animals from each group at 24, 72 and 168 hours after exposure. All four herbs showed significant radio-protective effects at 24 hrs. OS, TC and ZM showed nearly similar activity while CL showing the lowest activity. However the effects at 72 and 168 hrs showed highest protection by CL followed by ZM |“| TC > OS respectively suggesting that the well studied OS was less effective at 72 and 168 hrs. All the four herbs showed radioprotective potential with different efficacies at different time interval.

The purpose of this study was to evaluate the dependency of MAGICA polymer gel dosimeter response (R2) on different electron energies as well as on different mean dose rate for a standard clinically used linear accelerator. The sensitivity of the dosimeter was represented by the slope of calibration curve in the linear region measured for each modality. A calibration curve (in the linear region) based on 12 dosimeters (11 irradiated and one blank) was obtained for 6 MeV electron beam. Dosimeter energy dependence was studied for electron energies of 4,6,12 and 18 MeV. Dose rate dependence was studied in 10 MeV electron beam with the use of dose rates 80,160,240,320,400 and 480 cGymin-1. Evaluations of dosimeters were performed on Siemens Symphony, Germany, 1.5T Scanner in the head coil. A multiecho sequence with 32 equidistant echoes was used for the evaluation of irradiated polymer gel dosimeters. The parameters of the sequence were as follows: TR 3000ms, TE 20ms, Slice Thickness 4mm and FOV 256mm. Polymer gel dosimeter response R2 was increased with increasing electron energy. No trend in polymergel dosimeter R2 dependence was found on mean dose rate for electron beams. In MAGICA polymer gel, the sensitivity is dependant on electron energy increase, but no dependence was observed on response to dose rate. The presence of antioxidant and oxygen scavengers in the MAGICA polymer gel is believed to cause different results.

Monte Carlo and experimental relative dose determination in a water phantom, due to a high dose rate (HDR) 192Ir source is presented for real energy spectrum and monochromatic at 356 keV. The dose distribution has been calculated around the 192Ir located in the center of 30 cm ×30 cm ×30 cm water phantom using MCNP4C code by Monte Carlo method. Relative dose variation has been measured by using Gafchromic Rtqa along X and Y axis, as well. Percentage depth dose (PDD) variation along the different axis parallel and perpendicular the source were calculated. Finally, F (5cm, θ|) dosimetry parameters of TG-43 protocol were determined. The results showed that the Monte Carlo method could calculate dose deposition in high gradient region, near the source, accurately. The isodose curves and dosimetric characteristics obtained for 192Ir source are in good agreement with experimental results. The isodose curves of the 192Ir source were derived form dose calculation by MCNP code. Also, Monte Carlo and experimental PDD X=2.5 mm are in good agreement, and the both results y=10 mm, in ||x [-25mm,25mm] interval were well matched. However, out of this range Monte Carlo result was estimated to be lower. The calculated dosimetry parameters for the source were in agreement with other results.

Total Body Irradiation (TBI) is different from standard radiotherapy in many aspects, so it is not easy to predict the delivered dose to the patient under TBI treatment. Diode dosimetry procedures for surface dose reading can help to define variations of the actually delivered dose from the prescribed one. The aim of this study was to describe the measurements made to calibrate diodes in order to implement as a dosimeter for TBI tratment. An algorithm was also proposed based on diode dosimetry in order to determine the midplane dose. In this study, four p-type diodes connected to a MULTIDOSE electrometer were implemented as dosimeter. For diode calibration a water phantom with dimension of 30×30×32cm3 along with a 0.6 cc Farmer ion chamber were used. Directional dependence of diodes, the effects of thickness correction factor and complete backscatter factor were studied. Three algorithms, arithmetic, geometric mean and proposed algorithm were used to investigate midplane dose determination in TBI condition. It was found by measurements that the effect of angle incident on diode response was significant and should have been taken into account. Variation in thickness correction factor was found about 0.7%. The accuracy in midplane dose determination in the arithmetic, geometric mean and proposed algorithm was about 3.8, 12.5 and 3.3%, respectively. Diode dosimetry is very useful as a check of midplane dose delivered to patients under TBI treatment. When the calibration and correction factors are carefully determined, high precision can be obtained. The proposed algorithm by this study seems to be useful in order to midplane dose determination in TBI condition.

Immunoradiometric assay is one of the most common and precise methods for determination of prostate specific antigen (PSA) in clinical laboratories. Usual use of human serum in routine assays has many disadvantages; such as easy contamination and precipitation, instability and unavailability. Thus in order to avoid these problems the artificial matrix was used which acts similar to human serum. In order to design immunoradiometric assay for prostate specific antigen, series of standards in different concentrations were needed for special artificial matrix preparation. The influence of artificial matrix in standards was studied to determine prostate specific antigen in comparison with human serum. Some different factors, such as the amount of non-specific bonding (NSB), precision, and accuracy, conditions of storage and stability of these standards prepared by artificial matrix were investigated. The most appropriate artificial matrix (Tris-glycine (25.0 mmol/L) + NaCl (75.0 mmol/L) + Tris (12.5 mmol/L) +Triton X- 100 (0.5 ml/L) + HSA (1.2 g/L) + Urea (0.5 mol/L)) for preparing the standards was selected in comparison with human serum (HSA) and a commercial kit standards. HSA and Urea concentration have more critical influences on the properties of the standards. The amount of NSB of the selected matrix was the lowest one, so the selected matrix was the most suitable for preparing the standards. The results show the optimum condition of storage duration of our standards for one year was in refrigerator (2-8°C). It was observed that preparation of standards with selected matrix had acceptable accuracy and precision. According to the results, standards which were prepared with this matrix had suitable and appropriate properties and it could be utilized to prepare PSA standards in immunoradiometric assay.