“…New developments in radiotherapy have been concerned with the study of equivalent gel dosimeters for tissues containing active chemical sensors to measure the absorbed radiation dose [ 1 , 2 , 3 , 4 , 5 , 6 ]. Gel dosimeters such as polymer gels have a range of properties like biological tissues, and are suitable alternatives compared with conventional dosimeters due to their ability in resolving three-dimensional (3D) dose distributions [ 7 , 8 , 9 , 10 , 11 ].…”
The impact of calcium chloride (CaCl2) on the performance of N-(hydroxymethyl)acrylamide (NHMA) polymer gel dosimeter is studied in this article. The dosimeter was exposed to doses of up to 10 Gy with radiation beam-energy of 10 MV and dose-rates of 300 cGy/min. The relaxation rate (R2) parameter was utilized to explore the performance of irradiated NHMAGAT gels. The dose response in terms of R2 increased from 0.29 to 0.63 Gy−1·s−1 with increasing calcium chloride concentration from 0 to 1000 mM. The results show no substantial impact of dose-rates as well as radiation energies on NHMAGAT samples. For the steadiness of irradiated NHMAGAT dosimeters, it was found that there is no apparent variation in R2 (less than ±3%; standard deviation) up to 3 days. The overall uncertainty of the gel dosimeter with calcium chloride is 4.96% (double standard deviation, 95% confidence level).
“…New developments in radiotherapy have been concerned with the study of equivalent gel dosimeters for tissues containing active chemical sensors to measure the absorbed radiation dose [ 1 , 2 , 3 , 4 , 5 , 6 ]. Gel dosimeters such as polymer gels have a range of properties like biological tissues, and are suitable alternatives compared with conventional dosimeters due to their ability in resolving three-dimensional (3D) dose distributions [ 7 , 8 , 9 , 10 , 11 ].…”
The impact of calcium chloride (CaCl2) on the performance of N-(hydroxymethyl)acrylamide (NHMA) polymer gel dosimeter is studied in this article. The dosimeter was exposed to doses of up to 10 Gy with radiation beam-energy of 10 MV and dose-rates of 300 cGy/min. The relaxation rate (R2) parameter was utilized to explore the performance of irradiated NHMAGAT gels. The dose response in terms of R2 increased from 0.29 to 0.63 Gy−1·s−1 with increasing calcium chloride concentration from 0 to 1000 mM. The results show no substantial impact of dose-rates as well as radiation energies on NHMAGAT samples. For the steadiness of irradiated NHMAGAT dosimeters, it was found that there is no apparent variation in R2 (less than ±3%; standard deviation) up to 3 days. The overall uncertainty of the gel dosimeter with calcium chloride is 4.96% (double standard deviation, 95% confidence level).
“…The presence of paramagnetic Fe 3+ alters the proton relaxation times of water and these changes can be measured by means of Nuclear Magnetic Resonance (NMR) relaxometry [12] and Magnetic Resonance Imaging (MRI) [10,13]. Furthermore, the spatial distribution of Fe 3+ can be used to produce a 3D dose map by optical imaging [14,15] if a suitable metallic ion indicator is added to the gel matrix [16][17][18][19].…”
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“…MTB is a sensitive but non-selective metallochromic indicator, and interacts with more than twenty MIs, depending on the pH value of solution 15 – 18 . It has been used as a chelator for iron in ferrous/Fricke gel dosimeters for 3-dimensional dosimetry in cancer radiotherapy 19 , 20 . Figure 1 Molecular structure for the 6-protonated form of MTB.…”
In this study, we determine the acidity constants of methylthymol blue (MTB) and association constants of its complexes with the ZnII, CuII, and FeII metal ions (MIs), through theoretical and experimental means. The complexes were characterized using UV–Visible absorption spectroscopy combined with soft/hard chemometrics methods and quantum chemical calculations. Quantum chemical calculations revealed that electronic transitions in the UV–Visible spectra of MTB have mixed n → π* and π → π* characters. The results of molar ratio and multivariate curve resolution alternating least squares (MCR-ALS) revealed the formation of successive 1:2 and 1:1 complexes (MI:MTB) for the ZnII and CuII systems. However, the formation of successive 1:1 and 2:1 complexes are suggested for FeII by the molar ratio and MCR-ALS. The majority of transitions observed in the UV–Visible spectra of the Zn(MTB) and Cu(MTB) complexes have ligand-to-ligand charge transfer (LLCT) characters. However, the transitions in the UV–Visible spectrum of the Fe(MTB) complex have LLCT and metal-to-ligand charge transfer (MLCT) characters. For the Fe2(MTB) complex, the lowest energy transition of has an LLCT character. However, its higher energy transitions are a mixture of LLCT, MLCT, and metal-to-metal charge transfer (MMCT) characters. The correlation between experimental and computed wavelengths revealed that the 1:1 complexes of ZnII and CuII prefer square pyramidal geometries. However, the FeII complexes always show octahedral geometry.
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