scholarly journals Estimation of Dose Enhancement for Inhomogeneous Distribution of Nanoparticles: A Monte Carlo Study

2021 ◽  
Vol 11 (11) ◽  
pp. 4900
Author(s):  
Fouad Abolaban ◽  
Eslam Taha ◽  
Abdulsalam Alhawsawi ◽  
Fathi Djouider ◽  
Essam Banoqitah ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Metal Nanoparticles ◽  
Beam Energy ◽  
Positive Impact ◽  
Monte Carlo Study ◽  
Nanoparticle Concentration ◽  
Dose Enhancement ◽  
Hypoxic Conditions ◽  
Innermost Layer ◽  
Necrotic Region

High atomic number nanoparticles are of increasing interest in radiotherapy due to their significant positive impact on the local dose applied to the treatment site. In this work, three types of metal nanoparticles were utilized to investigate their dose enhancement based on the GATE Monte Carlo simulation tool. Gold, gadolinium, and silver were implanted at three different concentrations to a 1 cm radius sphere to mimic a cancerous tumor inside a 10 × 10 × 30 cm3 water phantom. The innermost layer of the tumor represents a necrotic region, where the metal nanoparticles uptake is assumed to be zero, arising from hypoxic conditions. The nanoparticles were defined using the mixture technique, where nanoparticles are added to the chemical composition of the tumor. A directional 2 × 2 cm2 monoenergetic photon beam was used with several energies ranging from 50 keV to 4000 keV. The dose enhancement factor (DEF) was measured for all three metal nanoparticles under all beam energies. The maximum DEF was ~7 for silver nanoparticles with the 50 keV beam energy at the highest nanoparticle concentration of 30 mg/g of water. Gold followed the same trend as it registered the highest DEF at the 50 keV beam energy with the highest concentration of nanoparticles at 30 mg/g, while gadolinium registered the highest at 100 keV.

scholarly journals DNA Dosimetry with Gold Nanoparticle Irradiated by Proton Beams: A Monte Carlo Study on Dose Enhancement

2021 ◽  
Vol 11 (22) ◽  
pp. 10856
Author(s):  
Ngoc Han Huynh ◽  
James C. L. Chow
Keyword(s):  
Monte Carlo ◽  
Gold Nanoparticle ◽  
Proton Beam ◽  
Beam Energy ◽  
Heavy Atom ◽  
Monte Carlo Study ◽  
Nanoparticle Size ◽  
Proton Radiation ◽  
Dose Enhancement ◽  
Proton Beam Energy

Heavy atom nanoparticles, such as gold nanoparticles, are proven effective radiosensitizers in radiotherapy to enhance the dose delivery for cancer treatment. This study investigated the effectiveness of cancer cell killing, involving gold nanoparticle in proton radiation, by changing the nanoparticle size, proton beam energy, and distance between the nanoparticle and DNA. Monte Carlo (MC) simulation (Geant4-DNA code) was used to determine the dose enhancement in terms of dose enhancement ratio (DER), when a gold nanoparticle is present with the DNA. With varying nanoparticle size (radius = 15–50 nm), distance between the gold nanoparticle and DNA (30–130 nm), as well as proton beam energy (0.5–25 MeV) based on the simulation model, our results showed that the DER value increases with a decrease of distance between the gold nanoparticle and DNA and a decrease of proton beam energy. The maximum DER (1.83) is achieved with a 25 nm-radius gold nanoparticle, irradiated by a 0.5 MeV proton beam and 30 nm away from the DNA.

Monte Carlo study on mucosal dose in oral and naval cavity using photon beams with small field

2011 ◽  
Vol 10 (4) ◽  
pp. 261-271 ◽  
Author(s):  
James C.L. Chow ◽  
Amir M. Owrangi
Keyword(s):  
Monte Carlo ◽  
Beam Energy ◽  
Field Size ◽  
Small Field ◽  
Beam Angle ◽  
Photon Beams ◽  
Dose Ratio ◽  
Dose Enhancement ◽  
Bone Interface ◽  
Energy Beam

AbstractWe study how mucosal dose in the oral or nasal cavity depends on the irradiated small segmental photon fields varying with beam energy, beam angle and mucosa thickness. Dose ratio (mucosal dose with bone underneath to dose at the same point without bone) reflecting the dose enhancement due to the bone backscatter was determined by Monte Carlo simulation (EGSnrc-based code), validated by measurements. Phase space files based on the 6 and 18 MV photon beams with small field size of 1 × 1 cm2, produced by a Varian 21 EX linear accelerator, were generated using the BEAMnrc Monte Carlo code. Mucosa phantoms (mucosa thickness = 1, 2 and 3 mm) with and without a bone under the mucosa were irradiated by photon beams with gantry angles varying from 0 to 30°. Doses along the central beam axis in the mucosa and the dose ratio were calculated with different mucosa thicknesses. For the 6 MV photon beams, the dose at the mucosa-bone interface increased by 44.9–41.7%, when the mucosa thickness increased from 1 to 3 mm for the beam angle ranging from 0 to 30°. These values were lower than those (58.8–53.6%) for the 18 MV photon beams with the same beam angle range. For both the 6 and 18 MV photon beams, depth doses in the mucosa were found to increase with an increase of the beam angle. Moreover, the dose gradient in the mucosa was greater for the 18 MV photon beams compared to the 6 MV. For the dose ratio, it was found that the dose enhancement due to the bone backscatter increased with a decrease of mucosa thickness, and was more significant at both the air-mucosa and mucosa-bone interface. Mucosal dose with bone was investigated by Monte Carlo simulations with different experimental configurations, and was found vary with the beam energy, beam angle and mucosa thickness for a small segmental photon field. The dosimetric information in this study should be considered when searching for an optimized treatment strategy to minimize the mucosal complications in the head-and-neck intensity-modulated radiation therapy.

scholarly journals A Monte Carlo study on dose enhancement and photon contamination production by various nanoparticles in electron mode of a medical linac

Nukleonika ◽  
2015 ◽  
Vol 60 (3) ◽  
pp. 489-496 ◽  
Author(s):  
Mohammad Taghi Bahreyni Toossi ◽  
Mahdi Ghorbani ◽  
Leila Sobhkhiz Sabet ◽  
Fateme Akbari ◽  
Mohammad Mehrpouyan
Keyword(s):  
Monte Carlo ◽  
Electron Beams ◽  
Monte Carlo Study ◽  
Monte Carlo Code ◽  
Dose Enhancement ◽  
Electron Dose ◽  
Additional Advantage ◽  
Photon Dose ◽  
Electron Mode ◽  
Medical Linac

Abstract The aim of this study is the evaluation of electron dose enhancement and photon contamination production by various nanoparticles in the electron mode of a medical linac. MCNPX Monte Carlo code was used for simulation of Siemens Primus linac as well as a phantom and a tumor loaded with nanoparticles. Electron dose enhancement by Au, Ag, I and Fe2O3 nanoparticles of 7, 18 and 30 mg/ml concentrations for 8, 12 and 14 MeV electrons was calculated. The increase in photon contamination due to the presence of the nanoparticles was evaluated as well. The above effects were evaluated for 500 keV and 10 keV energy cut-offs defined for electrons and photons. For 500 keV energy cut-off, there was no significant electron dose enhancement. However, for 10 keV energy cut-off, a maximum electron dose enhancement factor of 1.08 was observed for 30 mg/ml of gold nanoparticles with 8 MeV electrons. An increase in photon contamination due to nanoparticles was also observed which existed mainly inside the tumor. A maximum photon dose increase factor of 1.07 was observed inside the tumor with Au nanoparticles. Nanoparticles can be used for the enhancement of electron dose in the electron mode of a linac. Lower energy electron beams, and nanoparticles with higher atomic number, can be of greater benefit in this field. Photons originating from nanoparticles will increase the photon dose inside the tumor, and will be an additional advantage of the use of nanoparticles in radiotherapy with electron beams.

scholarly journals Study of Radiation Dose Enhancement to Capillary Endothelial Cells Due to the Presence of Heavy Metal Nanoparticles in Two Cell and Tumor Scales by Monte Carlo Method

2020 ◽  
Author(s):  
Aghdas Sohayli-Jabbareh-Naseroo ◽  
Ladan Rezaee
Keyword(s):  
Heavy Metal ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Energy Range ◽  
Metal Nanoparticles ◽  
Photon Energy ◽  
Enhancement Factor ◽  
Photon Energy Range ◽  
Dose Increase ◽  
Dose Enhancement

Introduction: Recently, the use of various sensitizers has been used to increase photon-induced doses in brachytherapy. One of these cases is the addition of heavy metal nanoparticles such as gold in the target area, which increases the production of ionizing electrons by increasing the possibility of photoelectric effects, and increases the efficacy of the treatment. In this study, the target of the irradiation was the endothelial cell in the wall of blood capillaries located inside the tumor, which, if destroyed, would result in abnormal blood cell counts and tumor cell death. Methods: The effect of using nanoparticles of gold, silver, bismuth and copper has been evaluated by calculating the dose increase ratio using Geant4 tool that was based on Monte Carlo method. These calculations were performed on two microscopic (cellular) and macroscopic (tumor dimensions) scale and the effects of different concentrations of these nanoparticles were compared. Also, the dose increase ratio has been evaluated to determine the most appropriate photon energy range. Results: As the concentration of nanoparticles increases, the dose enhancement factor increased in photon energy. In addition, for energies less than 70 keV, with increasing energy, dose enhancement factor increased and for energies above 80 keV, this quantity decreased with increasing energy. Conclusion: In terms of dose, gold is the best option, and in terms of the dose enhancement factor, silver and bismuth are better alternative among the four elements studied. Also, the most suitable photon energy range is 70 keV to 80 keV.

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