Radiation attenuation properties of shields containing micro and Nano WO3 in diagnostic X-ray energy range

Background: It has recently been shown that the particle size of materials used for radiation shielding can affect the magnitude of radiation attenuation. Over the past years, application of nano-structured materials in radiation shielding has attracted attention world-wide. The purpose of this study was to investigate the shielding properties of the lead-free shields containing micro and nano-sized WO3 against low energy x-rays. Materials and Methods: The radiation shields were constructed using nano and micro WO3 particles incorporated into an EPVC polymer matrix. The attenuation coefficients of the designed shields were evaluated for low energy x-rays [diagnostic radiology energy range]. Results: The results indicate that nano-structured WO3/PVC shields have higher photon attenuation properties compared to those of the micro-sized samples. Conclusion: Our experiment clearly shows that the smaller size of nano-structured WO3 particles can guarantee a better radiation shielding property. However, it is too early to draw any conclusion on the possible mechanisms of enhanced attenuation of nano-sized WO3 particles

Calibration and optimization of a low cost diffusion chamber for passive separated measurements of radon and thoron in soil by Lexan PC SSNTD

Separate radon and thoron measurements in soil are very important in assessment of internal exposure due to inhalation of such radioactive gases. In this study, a low cost, small size, passive diffusion chamber has been developed for simple measurement of Radon-222 and Radon-220[Thoron] gases separately in soil. The diffusion chamber consists of two films and two fiber glass filters. Lexan polycarbonate films were used as Solid State Nuclear Track Detectors [SSNTDs] and optimized film to filter distance was obtained. Calibration factors for the designed diffusion chamber were measured using flow through method which was 16.85[track.cm[-2] [kBq. m-3d] [-1]] and 17.25 [track.cm[-2][kBq.m[-3]d][-1]] for radon for the lower and upper Lexan films, respectively and 1.76 [track.cm[-2] [kBq.m[-3] d][-1]] for thoron. The designed chamber is an economic, applicable and efficient detector for measurement of radon and thoron separately in soil

Natural ventilation considerations for radon prone areas of Ramsar

In Iran, architectures are often unaware of the risk of radon inhalation and how to reduce radon levels. Furthermore, radon considerations are not implemented in construction methods, construction materials and building utilization by regulatory authorities. In this study after reviewing the meteorological changes of Ramsar over the past 50 years [1955-2005], a novel design for constructing dwellings in radon prone areas is introduced. Out of building interventions such as planting wind-tunnel-making trees will be discussed in another paper. Ramsar soil samples with 4 levels of specific activities [extremely hot, severely hot, very hot, and hot] were placed in a model house. Radon level monitoring was performed by using a PRASSI portable radon gas survey meter. For extremely hot soil samples, the radon levels inside the model house when windows were closed for 24 hours were 1615 +/- 516 Bq/m3. When windows which were in the wind direction or opposite the wind direction were opened for 24 h, the radon level decreased to 89 +/- 286 and 139 +/- 314 Bq/m3, respectively. Interestingly, when crossed windows were opened for the same duration, Radon level was 144 +/- 92 Bq/m3. In cold seasons, when windows are usually closed, Chimney effect reduced the radon level to 323 +/- 641. For severely hot, very hot and hot soil samples, natural ventilation-based interventions effectively reduced the radon level. Results obtained in this study clearly show that natural ventilation-based simple cost-effective interventions can significantly reduce the radon concentration in radon prone areas of Ramsar

effects of internal wall covering materials on hazards of indoor radon concentrations in houses of Iran

Radon gas emanating from underground can concentrate indoor and reach levels, which represent a risk to people's health. According to WHO [World Health Organization] and ERA [Environmental Protection Agency], radon is the second leading cause of lung cancer in the world. Due to the direct correlation of lung cancer and radon exposure, it is ideal to evaluate the hazards of radon accumulation in the Iran dwellings with different materials by direct measurement of the radon concentrations using accurate, simple and fast method. The aim of this study was to measure variation of radon concentrations with different covering materials on internal building surfaces including walls, which are used in Iran dwellings. A special chamber with changeable walls of different covering materials [gypsum, wallpaper, oil dye, plastic dye, wood board, and Belka] was made. Radioactive lantern mantles were used for elevating the radon [220]Rn] levels in the chamber artificially. Ventilation in the chamber had been such way that accumulation of radon could be possible. Active measurement by Prassi portable radon gas surveyor was performed for staging purposes. The average radon concentration for wood and plastic dye was 869.0 +/- 66.7 and 936.8_60.6 [bq/m[3]], respectively, while that for wallpaper and gypsum was 449.2 +/- 101.7, 590.9 +/- 49.0 [bq/m[3]], significantly lower than other covers. The average radon concentration for oil dye and Belka cover was 668.3 +/- 42.3, 697.2 +/- 136.7 [bq/m[3]], respectively. Individuals living in a house with internal wall covering materials of gypsum and wallpaper receive an average annual dose smaller than one living in a house with internal wall covering materials of wood board and plastic dye. Using wallpaper and gypsum as an internal cover for the dwellings suggested

Evaluation of the changes in the shape and location of the prostate and pelvic organs due to bladder filling and rectal distension

A steep dose gradient between prostate and organs at risk [rectum and bladder] is ideal in treatment modality, so prostate displacement and deformation due to bladder filling and rectal distension play an important role in critical organs dose. This study aims to evaluate the changes in the shape and location of the prostate and pelvic organs due to bladder filling and rectal distension. Three patients who referred for transrectal prostatic biopsy [Shahid Faghihi Hospital, Shiraz, Iran] with different prostate sizes were enrolled. A 1.5-Tesla MRI system [Avanto, Siemens, Germany] and an ultrasound system [Logiq 500, GE medical systems, USA] were used to collect images of patients prostate at different stages of bladder and rectum fullness. The mean displacement of the prostate after bladder filling in the supine and left decubitus positions along the Anterior-Posterior [AP] axis was posterior by 4.9 mm [range: 0.7-6.3 mm] and along the Superior-Inferior [SI] axis was inferior by 3.4 mm [range: 1.4-5 mm]. Prostate displacement in the Left-Right [LR] axis was negligible. The mean prostate displacement after rectal distension was anterior by 7.1 mm in the supine position, 5.1 mm anterior in the left decubitus position and along the SI axis was inferior by 2.5 mm in the supine and left decubitus positions. The maximum prostate deformation due to rectal distension and bladder filling in the supine position was as large as 3.2 mm, 1.9 mm and 1.2 mm in the AP, SI and LR directions respectively. While in the left decubitus position, it was 2.6 mm, 1.2 mm and 1.3 mm in the AP, LR and SI axis respectively. It is probably of importance to evaluate the influence of the changes in the shape and location of the prostate due to bladder filling, rectal distension and patient position in post-implant brachytherapy dosimetry. Using images of the patients in the left decubitus position with full bladder and distended rectum for planning a treatment are suggested

Comparison of dosimetry parameters of two commercially available Iodine brachytherapy seeds using Monte Carlo calculations

Iodine brachytherapy sources with low photon energies have been widely used in treating cancerous tumors. Dosimetric parameters of brachytherapy sources should be determined according to AAPM TG-43U1 recommendations before clinical use. Monte Carlo codes are reliable tools in calculation of these parameters for brachytherapy sources. Dosimetric parameters [dose rate constant, radial dose function, and anisotropy function] of two I-125 brachytherapy sources [models LS-1 and Intersource] were calculated with MCNP4C Monte Carlo code following task group number 43 [TG-43U1] recommendations of American Assossiation of Physicists in Medicine. The simulations were done inside a spherical water phantom because of its tissue equivalent properties. The Monte Carlo simulations for radial dose function were performed at distances ranging from 0.25 to 10 cm from the source center. The anisotropy functions F[r, theta], for both sources, were calculated at distances of 1, 2, 3, 5 and 7 cm from the source center for angles ranging from 15 to 90 degree. The results of the Monte Carlo simulation indicated a dose rate constant of 0.952 cGyh -1U-1 and 0.986 cGyh -1U-1 for models LS-1 and Intersource, respectively. The tabulated data and fifth order polynomial coefficients for radial dose functions along the source are described in this paper .The results indicated that the anisotropy in dose distribution increased along the source axis. The obtained results were in good agreement with measurements and calculations of other investigators, using other Monte Carlo codes

Simulation of the shielding effects of an applicator on the AAPM TG-43 parameters of CS-137 Selectron LDR brachytherapy sources

The dose rate distribution delivered by a low dose rate [137]Cs pellet source, a spherical source used within the source trains of the Selectron gynecological brachytherapy system, was investigated using the MCNP4C Monte Carlo code. The calculations were performed in both water and Plexiglas and the absolute dose rate distribution for a single pellet source and the AAPM TG-43 parameters were computed. A spherical phantom with dimensions large enough [60 cm] was used to provide full scattering conditions. In order to score dose at different distances from the source centre, this sphere was divided into a set of 600 concentric spherical shells of 0.05 cm thickness. The calculations were performed up to a distance of 10 cm from the source centre. To calculate the effect of the applicator and dummy pellets on dose rate constant and radial dose function, a single pellet source was simulated inside the vaginal applicator, and spherical tally cells with radius of 0.05 cm were used in the simulations. The F6 tally was used to score the absolute dose rate at a given point in the phantom. The dose rate constant for a single active pellet was found to be 1.102 +/- 0.007 cGyh[-1]U[-1], and the dose rate constant for an active pellet inside the applicator was 1.095 +/- 0.009 cGyh[-1]U[-1]. The tabulated data and 5th order polynomial fit coefficients for the radial dose function along with the dose rate constant are provided for both cases. The effect of applicator and dummy pellets on anisotropy function of the source was also investigated. The error resulting from ignoring the applicator was reduced using the data of a single pellet. The results indicate that F[r, theta] decreases towards the applicator