Dosimetric Study Of Genipin Gelatin-Chemical Additives Polymer Gel Using 6 Mv And 10 Mv Therapeutic Facilities
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Date
2015-05
Authors
Aljarrah, Amer Mahmoud Mohammad
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Abstract
Gold nanoparticles AuNPs of high-Z materials, inorganic salts and glucose have been used in this study to enhance physical and radiological properties of genipin gel dosimeter for different clinical applications. The effectiveness of these additives were investigated for optimum visible absorption dose response, transparency, melting points, density, and water equivalency for 3D dose measurements. A reliable new gel formulation (GP -Gl-AuNPs) was formulated and evaluated for 3D dosimetry using optical evaluation and CT scanning techniques for dose readout. The addition of glucose with optimum concentration of 10% (w/w) was found to improve the thermal stability of the genipin gel and increase its melting point (Tm) by 6°C. Furthermore, glucose helps to adjust the gel mass density to obtain the desired tissue-equivalent properties. A drop of Tm and the gel strength were observed when salt was used as additives. As the salt concentration increase, gel strength and Tm decreased. The radiological water equivalence of each genipin gel dosimeters was determined by evaluating the densities, effective atomic numbers, and the linear attenuation coefficients. All of these values were compared with water and muscle values, proving that the radiological properties of the new gel approximate muscle values and could be considered as a water equivalent gel. The maximum optical dose responses of genipin gel at 6 and 10 MV photon beams were –0.00526 and –0.00522 (cm–1Gy–1) respectively. The addition of AuNPs (optimum concentration, 200 ppm) has resulted in a slight increment of the optical dose response of less than 10%. According to the density calibration curve obtained from CT scan, the gel sample densities were extracted using the corresponding CTNs. The result displayed an increment of gel density approximately in the order of 0.5 mg cm–3Gy–1 due to irradiation. The dose resolutions calculations were also indicated that GP–Gl–AuNPs gel enhanced dose resolution (~0.05 Gy).The percent depth doses (PDDs) and dose profiles of 6 MV photon beams using an ionization chamber (IC), GP–Gl–AuNPs, and EBT3 films of field sizes (100 × 100 mm2) were investigated for comparison and verification purpose. According to the results, the maximum absolute percentage difference between the PDD measurements of GP–Gl–AuNPs with IC and EBT3 films were 4% and 6%. The flatness of the IC, GP–Gl–AuNPs and EBT3 films were 2.2%, 2.1% and 1.8%, respectively, while the symmetry of the IC, GP–Gl–AuNPs and EBT3 films were 0.9% 1.0% and 0.8% respectively. This study provides a significant contribution toward the development and successful implementation of gel dosimetry towards clinical radiotherapy.
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Keywords
Ionizing radiation , Radiotherapy