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Radiation therapy aims to maximize doses to cancer cells while minimizing damage to normal tissues. Today, nanoparticles containing high-atomic-number elements, such as gold, gadolinium, and silver, have proven effective as radiosensitizers in radiotherapy to enhance dose delivery for cancer treatment. In this study, we used the Geant4-DNA toolkit to investigate the effects of multiple nanoparticles (NPs) with varying sizes (radius= 3.15 to 5 nm) on DNA damage when exposed to monoenergetic photons with energies of 15, 40, 50, and 68 keV. Direct and indirect single-strand breaks (SSBs), double-strand breaks (DSBs), and hybrid double-strand breaks (Hybrid DSBs) were calculated in the presence and absence of 1 to 4 nanoparticles (NPs) of the same total volume of gold, gadolinium, and silver nanoparticles for the 1ZBB model (selected from the Protein Data Bank (PDB) library). The results show that increasing the number of gold, gadolinium, and silver NPs and decreasing the photon beam energy increases the total number of strand breaks. Furthermore, gold nanoparticles (GNPs) are more effective options than gadolinium nanoparticles (GdNPs), and silver nanoparticles (SNPs) for inhibiting and controlling cancer cells. [ABSTRACT FROM AUTHOR]

Gamma radiation indicators are appropriate tools for monitoring visually whether or not the irradiation process has been carried out properly. Among chemical radiation indicators available worldwide, a few are suitable for monitoring low dose ranges (especially for blood irradiation, below 50 Gy). Addressing this scope, PVA Fricke gel was proposed in this work. Irradiation of the prepared PVA Fricke gel samples was performed by Co-60 gamma cell unit up to a dose of 80 Gy. Color change of the samples was observed from orange to purple proportional to increasing absorbed dose. Prepared samples were divided into three groups, kept at different environmental conditions, to investigate stability of the gel against temperature and light. Results revealed that the irradiated samples kept at dark and refrigerator were stable for seven days. Optical absorbance measurement of the samples also estimated pre- and post-irradiation color stability. The gel can be easily used to identify processed and unprocessed products in blood irradiation. Although the gel is designed to be a qualitative indicator, it is also a good quantitative dosimeter for gamma rays. [ABSTRACT FROM AUTHOR]

Low energy I-125- seeds are considered as a common source in different brachytherapy techniques for treatment of different cancers. In this study, at first, we simulated and validated I-125 (model 6711) seed according to the TG-43U1 recommendation, by GEANT4 Monte Carlo toolkit. Moreover, we simulated new seeds containing cylindrical Ag+Al2O3 markers with different ratio of Ag and Al2O3 in the final composition of the marker and compared the radial dose functions and anisotropy functions of the sources. For validation and evaluation purposes, the radial dose function and anisotropy function were calculated at various distances from the center of the different simulated sources. The source validation results show that GEANT4 Monte Carlo toolkit produces accurate results for dosimetric parameters of the I-125 seed by choosing the appropriate physics list. On the other hand, results show a similarity between calculated dosimetric parameters of the I-125 seed (6711) and other sources, with a percentage difference of about 5%. [ABSTRACT FROM AUTHOR]

BACKGROUND: Recently, the treatment efficiency of Yttrium 90 (Y-90) and providing reliable estimates of activity by single photon emission computed tomography (SPECT) imaging of bremsstrahlung radiation released during beta therapy have been evaluated. In the Y-90 bremsstrahlung SPECT imaging, the resulting energy spectrum is very complex and continuous, which creates many difficulties in the imaging protocol and image reconstruction. Furthermore, image quality and quantitative accuracy in the bremsstrahlung SPECT imaging are affected by collimator penetration and scatter. So, the collimator type and its geometry have impressive effects on the spatial resolution, system sensitivity and image contrast. MATERIAL AND METHODS: Hereby, in this paper, we evaluated the effect of the energy window (three energy windows: 60 to 160 keV, 160 to 400 keV, and 60 to 400 keV) and the commercial parallel-hole collimators with different geometric parameters on the Y-90 bremsstrahlung spectrum and the image quality of the liver tumors based on criteria such as system sensitivity and image contrast. SIMIND Monte Carlo simulation code was used to generate the Y-90 bremsstrahlung SPECT images of the liver tumor with different diameters: 1.36, 2.04, 2.72, 3.4, 4.08, and 4.76 cm by use of the digital Zubal phantom. Furthermore, the tumor size was estimated by evaluating pixel intensity profile on the line drawn through the activity distribution image. RESULTS: Our results showed that the collimator choice and energy window setting in the bremsstrahlung SPECT imaging have significant effects on the image quality and tumor size estimation. Optimal image quality could be acquired by the energy window of 60 to 400 keV and the SPECT system equipped with a Medium-Energy General-Purpose (MEGP) collimator of Millennium VG Kameran (GV) Company. Moreover, the estimation of distribution size was close to the actual value for tumor sizes larger than 2.04 cm, especially by using the SPECT system equipped with the GV-MEGP collimator in the wide energy window. CONCLUSIONS: We found an optimal collimator to be more appropriate for improving the imaging quality of Y-90 bremsstrahlung photons, which can be used for reliable activity distribution estimates after radiation therapy. [ABSTRACT FROM AUTHOR]

Purpose: Dosimetric characterization of a new 32P brachytherapy source was studied and the validity of the FLUKA code to reproduce the dosimetric parameters in a water phantom was evaluated. In addition, dose rate distributions around the 32P source sheathed by a catheter and unsheathed source were investigated in different tissue phantoms. Material and methods: The new 32P source was modeled using FLUKA Monte Carlo code. According to the AAPM TG-60 recommendations, reference of absorbed dose rate, radial dose function, anisotropy function, and an away-along table for quality assurance purposes inside water phantom were calculated. Moreover, the results of the radial dose function and dose rate were obtained for the sheathed source and unsheathed sources at radial distances in different tissue phantoms: liver, fat tissue, 9-component soft tissue, and 4-component soft tissue. Results: The calculated dosimetric parameters of the new 32P source by FLUKA code in water phantom agreed well with that of the GEANT4 calculation. The 2D away-along dose results were similar to the GEANT4 simulation for distances less than 0.25 cm, small differences were apparent at long distances from the source. Dose rate evaluation for the sheathed source shows that the presence of a catheter increases the dose values up to 2.11% in comparison with the unsheathed source in water phantom. Our results show that the radial dose function calculated in water, as generalized by AAPM TG-60, differed in tissue, especially at large distances from the source. Conclusions: This work fully characterizes dosimetric parameters of the sheathed and unsheathed new 32P brachytherapy sources in water and different tissue phantoms by using FLUKA code. The results demonstrate that the dose distribution in water differed from the calculated ones in tissue phantoms due to the densities and atomic composition for tissues that are not taken account by the TG-60 formalism. [ABSTRACT FROM AUTHOR]

Knowledge of the energy deposition in different eye components is a critical decision-making to the overall effectivity of ocular melanoma treatment with plaques loaded with low-energy sources. The aim of this study is using the GATE 8.2 Monte Carlo code to calculate the 3D dose distribution in a realistic eye model. At first, we validated the GATE simulation for 125 I, 103 Pd, and 131 Cs seeds by calculating the dose rate constant, radial dose function, and anisotropy function of the three radioactive sources. Then, a 12-mm Collaborative Ocular Melanoma Study (COMS) eye plaque was simulated in the eye phantoms to evaluate dose distribution due to low-energy gamma emitters on the three simulated medium-sized tumors. The findings of this study indicate that the estimated doses received by different eye substructures strongly depend on the source type. The results show that the type of seeds used in the plaque, as well as the size of the eye tumor, have significant effects on the dose deposition in the different structures of the eye and dose deposition uniformity. Moreover, comparing different radionuclides showed that the COMS plaque fully loaded with 103 Pd presents a higher dose delivery to the tumor and a lower one to the critical structures for medium-sized tumors, while the plaque fully loaded with 131 Cs produces the most uniform dose distribution in the tumor., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Purpose: Dosimetric characterization of a new 32P brachytherapy source was studied and the validity of the FLUKA code to reproduce the dosimetric parameters in a water phantom was evaluated. In addition, dose rate distributions around the 32P source sheathed by a catheter and unsheathed source were investigated in different tissue phantoms., Material and Methods: The new 32P source was modeled using FLUKA Monte Carlo code. According to the AAPM TG-60 recommendations, reference of absorbed dose rate, radial dose function, anisotropy function, and an away-along table for quality assurance purposes inside water phantom were calculated. Moreover, the results of the radial dose function and dose rate were obtained for the sheathed source and unsheathed sources at radial distances in different tissue phantoms: liver, fat tissue, 9-component soft tissue, and 4-component soft tissue., Results: The calculated dosimetric parameters of the new 32P source by FLUKA code in water phantom agreed well with that of the GEANT4 calculation. The 2D away-along dose results were similar to the GEANT4 simulation for distances less than 0.25 cm, small differences were apparent at long distances from the source. Dose rate evaluation for the sheathed source shows that the presence of a catheter increases the dose values up to 2.11% in comparison with the unsheathed source in water phantom. Our results show that the radial dose function calculated in water, as generalized by AAPM TG-60, differed in tissue, especially at large distances from the source., Conclusions: This work fully characterizes dosimetric parameters of the sheathed and unsheathed new 32P brachytherapy sources in water and different tissue phantoms by using FLUKA code. The results demonstrate that the dose distribution in water differed from the calculated ones in tissue phantoms due to the densities and atomic composition for tissues that are not taken account by the TG-60 formalism., Competing Interests: Authors report no conflict of interest.

Background: Recently, the treatment efficiency of Yttrium 90 (Y-90) and providing reliable estimates of activity by single photon emission computed tomography (SPECT) imaging of bremsstrahlung radiation released during beta therapy have been evaluated. In the Y-90 bremsstrahlung SPECT imaging, the resulting energy spectrum is very complex and continuous, which creates many difficulties in the imaging protocol and image reconstruction. Furthermore, image quality and quantitative accuracy in the bremsstrahlung SPECT imaging are affected by collimator penetration and scatter. So, the collimator type and its geometry have impressive effects on the spatial resolution, system sensitivity and image contrast., Material and Methods: Hereby, in this paper, we evaluated the effect of the energy window (three energy windows: 60 to 160 keV, 160 to 400 keV, and 60 to 400 keV) and the commercial parallel-hole collimators with different geometric parameters on the Y-90 bremsstrahlung spectrum and the image quality of the liver tumors based on criteria such as system sensitivity and image contrast. SIMIND Monte Carlo simulation code was used to generate the Y-90 bremsstrahlung SPECT images of the liver tumor with different diameters: 1.36, 2.04, 2.72, 3.4, 4.08, and 4.76 cm by use of the digital Zubal phantom. Furthermore, the tumor size was estimated by evaluating pixel intensity profile on the line drawn through the activity distribution image., Results: Our results showed that the collimator choice and energy window setting in the bremsstrahlung SPECT imaging have significant effects on the image quality and tumor size estimation. Optimal image quality could be acquired by the energy window of 60 to 400 keV and the SPECT system equipped with a Medium-Energy General-Purpose (MEGP) collimator of Millennium VG Kameran (GV) Company. Moreover, the estimation of distribution size was close to the actual value for tumor sizes larger than 2.04 cm, especially by using the SPECT system equipped with the GV-MEGP collimator in the wide energy window., Conclusions: We found an optimal collimator to be more appropriate for improving the imaging quality of Y-90 bremsstrahlung photons, which can be used for reliable activity distribution estimates after radiation therapy.