Hora Kavarian; Armin Mosayebi; Hamideh Daneshvar
Abstract
In this research work, commercial beta-tricalcium phosphate powder is converted into tablets by pressure-less sintering method. Thermoluminescence responses of tablet and powder samples in the dose range of 20 to 1500 Gy have been compared and effective factors in tablet conversion such as mass in the ...
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In this research work, commercial beta-tricalcium phosphate powder is converted into tablets by pressure-less sintering method. Thermoluminescence responses of tablet and powder samples in the dose range of 20 to 1500 Gy have been compared and effective factors in tablet conversion such as mass in the range of 30 to 60 mg, force between 1 to 3 N, concentration of granulating solution and tablet diameter in the range of 0.4 to 15 mm are investigated based on the results of dosimetric response and tablet hardness. The results show that by turning into tablets, the grain size increases, and the possibility of the first-order kinetics increases by the conversion of powders into tablets. It is possible to achieve a better dosimetric response than the it’s powder by applying suitable conditions for turning into tablets; also, the diameter of the sample can affect hardness, and it is better to make the tablets with a smaller size. Based on the results obtained from fading, reproducibility, sensitivity, peak shaping of the glow curve, and microhardness measurement, it can be seen that the samples that have been subjected to less pressure perform better and in order to achieve the desired results of converting to TLD dosimetry tablets, it is better to use more mass for tablets if more pressure is needed.
Parisa Taghipour; Farhad Zolfagharpour; Hamideh Daneshvar
Abstract
In this research work, powder hydroxyapatite samples were synthesized using a solid-state reaction method to investigate the annealing effect. The crystal structure was carried out by XRD system produced data, and the Rietveld method using MAUD software. The samples were irradiated in different radiation ...
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In this research work, powder hydroxyapatite samples were synthesized using a solid-state reaction method to investigate the annealing effect. The crystal structure was carried out by XRD system produced data, and the Rietveld method using MAUD software. The samples were irradiated in different radiation absorbed doses up to 1500Gy and their thermoluminescence properties including glow curve, response, fading effect and reproducibility were investigated from dosimetry point of view. The results showed that the annealing temperature significantly affects the crystal structure and thermoluminescence dosimetry response of hydroxyapatite samples, consequently. It was concluded that high temperature annealing process can lead to formation of β-TCP crystal phase during the synthesis of hydroxyapatite. Percentage of this formed phase increases with rising the temperature, and finally leads to increasing of the thermoluminescence response. It was concludded that in the solid state reaction method to increasing the TL response, it is better to use high annealing temperature for the synthesis of hydroxyapatite sample.
Nahid Hajiloo
Abstract
In this work, the impact of magnetic field presence on the central axis depth-dose curves of helium ion beams inside a heterogeneous phantom with air and bone layers was investigated. According to the calculations, presence of the magnetic field has a considerable impact on the dose distribution of helium ...
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In this work, the impact of magnetic field presence on the central axis depth-dose curves of helium ion beams inside a heterogeneous phantom with air and bone layers was investigated. According to the calculations, presence of the magnetic field has a considerable impact on the dose distribution of helium beams depending on the field strength and beam energy. A 32.3% abrupt increase and 92.5% reduction in dose were observed at the boundary between the water-air and the water-bone layer insert, respectively. The accuracy of the simulation was evaluated by verifying the depth dose curves of helium ion beams in a water phantom with experimental data.
Payman Rafiepour; Shahab Sheibani; Daryiush Rezaey Uchbelagh; Hossein Poorbaygi
Abstract
Radioactive stents loaded with I-125 seeds have been widely used for the treatment of advanced esophageal cancer. Understanding the dose distribution of such stents before the clinical use is essential. This study provides a dosimetric investigation of I-125 seed-loaded stents based on the seed's arrangement ...
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Radioactive stents loaded with I-125 seeds have been widely used for the treatment of advanced esophageal cancer. Understanding the dose distribution of such stents before the clinical use is essential. This study provides a dosimetric investigation of I-125 seed-loaded stents based on the seed's arrangement and activity. A cylindrical water equivalent phantom with an esophageal stent loaded with I-125 seeds, were employed. The seeds arrangements were determined based on the distance between the centers of two adjacent seeds (z) along the stent length. EBT3 films as well as Geant4 Monte Carlo toolkit were used to obtain the dose distribution around the stent. By modeling the MIRD phantom, the dose delivered to the related organs at risk was calculated. The appropriate dose distribution is achieved for z=15 mm, in which the absorbed dose at a depth of 5 mm reaches about 45% of the absorbed dose near the stent surface, thereby the therapeutic dose is delivered to the reference points. Both arrangements (z=15 and 20 mm) seemed to be clinically eligible and their utilization depends on the patient and the hospital facilities. Using esophageal stents with z>20 mm is not recommended due to the presence of cold spots in the dose distribution.
