ABSTRACT
Background: polyethylene composites including boron can be used as an effective neutron shield. Our investigation focuses on manufacturing borated polyethylene nano-composite. The purpose of this study is to design a radiation shield for use in both neutron and gamma fields
Materials and Methods: borated polyethylene shields containing 2%, and 5% weight percentage of Boron nano-particles were constructed and their neutron attenuation was compared with pure polyethylene. Polycarbonate films were used to find the attenuation of Am-Be neutrons after passing the shields. Mechanical properties of the shields were finally compared
Results: mean [+/- SD] number of alpha tracks induced by neutrons passing through the shields, were found to be 1.0488×10[3]+/-128.98, 1.1972×10[3]+/-289.56and 1.5340×10[3]+/-206.52 for polyethylene with 5% by weight, polyethylene with 2% by weight boron nano-particles, and pure polyethylene, respectively. The neutron spectrum after each shield was also obtained by MCNP4C Monte Carlo simulations. On the other hand, borated polyethylene nano-composites showed higher tensile strength compared to that of pure polyethylene. Attenuation of neutrons measured in experiments and the result of MCNP simulation were in good agreement
Conclusion: a statistically significant difference was found between neutron attenuation by borated polyethylene nanocomposite made of 5% by weight boron and pure polyethylene. However, the difference between borated polyethylene nano-composite with 5% weight and 2% wt boron was not statistically significant
ABSTRACT
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
ABSTRACT
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
Subject(s)
Radiometry , Iodine , Monte Carlo MethodABSTRACT
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
ABSTRACT
Different menopausal manifestations may be due to low level of sex hormones. Considering the important side effects of hormone replacement therapy [HRT] provides more attention to the other modalities of treatment like phytoestrogens. So, this study was done to compare the therapeutic effect of soy protein with hormone therapy in decreasing of menopausal manifestations. In this trial, 73 women, recently entered to menopausal state were studied in three groups for 4 months. The first group was 20 women, who underwent HRT. The second and third groups, each one including 24 and 29 women respectively, were treated by 60 gr and 10Qgr of soya per day. Some of the menopausal manifestations, consisting: sleep disorder, hot flush, recent memory loss, vaginal mucosal maturation index [MI], dysparonia and mean arterial blood pressure were evaluated before and after treatment. Four and nine patients from second and third group have respectively dropped out of study due to discontinuation of therapy. After therapy, hot flush improved 55%, 60% and 65% in HRT, soya 60gr and soya 100gr groups, respectively. Also sleep disorder improved by 40%, 50%, and 60% at the same groups, respectively. Increasing memory was seen by 60%, 40% and 65% in first, second and third groups. Vaginal MI improved 90% in first, 80% in second and 55% in third groups. Dysparonia decreased 45%, 25% and 50% in first, second, third groups, respectively. Mean arterial pressure decreased 5.6 mmHg in HRT, 1.3 mmHg in soya 60gr and 2.4 mmhg in soya 100gr groups. All findings were significant after therapy by all modalities [p<0.05]. But there was no significant difference between different modalities of treatments. The result of the study showed, soya with a little difference, like HRT could improve menopausal symptoms, and its effect increases dose dependently. So considering the HRT dangers, soybeans could be a suitable treatment substitute for relief of menopausal symptoms