geant4 code

PET is a very useful and suitable imaging method in nuclear medicine. This method uses positrons with a special energy for imaging. The elements of the lanthanide are suitable for the decay of positrons with a specific energy for use in PET. Praseodymium-139 with a half-life of 4.5 hours is one of the useful elements in the group of lanthanides that can be used in PET. In this study, the 140Ce (p,2n)139Pr reaction to produce the useful radiopharmaceutical Praseodymium-139 was simulated by the TALYS code with four different models and also by the GEANT4 Monte Carlo code. The purpose of this simulation is to calculate the cross-sectional area of the reaction and the production efficiency of praseodymium-139 in the proton irradiated cerium-140 target.

The values of cross-section and production yield of Praseodymium-139 have been obtained through 140Ce(p,2n)139Pr reaction using TALYS and GEANT4 codes and the proton projectile range changes in the cerium-140 target were simulated using SRIM and GEANT4 codes.

Proton range changes are shown using the SRIM and GEANT4 codes in the Cerium-140 target for different energies of the entrance protons. The range of protons in cerium-140 at 22 MeV energy was calculated to be 1610 and 1637.5 micrometers, respectively. Then the cross-sectional values simulated using TALYS and GEANT4 codes for different energies of the entrance protons were compared with the experimental data. At the energy of 5.22 MeV, the cross section of Praseodymium-139 has the maximum amount in the reaction 140Ce(p,2n)139Pr. The thickness of the production thickness was calculated from the target of cerium-140 for different proton energies. The cross-sectional values obtained in this energy using these two codes are 1150.7 and 1350.4 bar, respectively. Also, the amount of product yield in the energy of 22 MeV was calculated using these codes, 1832.1 and 1782.83 MBqµA-1h-1, respectively.

Comparison of the simulation results for the product of praseodymium-139 radiopharmaceuticals through the 140Ce(p,2n)139Pr  reaction using the TALYS code and the GEANT4 and SRIM Monte Carlo methods show that they are in good agreement with the experimental data. It is also possible to simulate the desired reaction using these codes without spending a lot of time and money and laboratory materials and before the production of radiopharmaceuticals, and to predict the values of production efficiency and the appropriate range of energy for the production of radiopharmaceuticals.

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.

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.

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.

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.

 The most commonly used method for external radiation therapy is the use of photons, protons, neutrons, and heavy ions. Hadron therapy is used to eliminate cancerous tissues by using ionizing particles which will bring less damage to healthy tissues.The aim of this study was to evaluate the dose, energy, and flux in a cancerous tumor in the liver and also secondary particles produced by hadrons, which is using the Geant4 Monte Carlo simulation.

In this analytical and applied study by using the Geant4 Monte Carlo Codes, the human body phantom and the tumor that was inserted inside the liver tissue, were simulated. In the method of hadron therapy with different energies, dose deposit, energy, and flux, for carbon and boron were obtained and the approximate area of the target tissue was determined by extrapolation of data.

As observed, as the energy of the beam increases, the peaks become wider and their maximum value (maximum absorbed dose) decreases, because the particle path, depends only on its primary energy. In this study, according to the simulation, the best energy range to start the interaction and Bragg's peak in the tumor area, for boron, is 1805 to 2075 MeV, and for carbon is 2415 to 3015 MeV.

Hadron therapy is more accurate than conventional radiotherapy because of less damage to healthy cells around the tumor. As a result, in the calculated useful energy, the highest dose or destruction caused by radiation is only given to the tumor tissue. The results obtained from the doses, energy, and flux in the simulated liver tissue tumor showed that the hadrons after a long-distance leave the highest dose and energy in the tumor area.

In radiation therapy, oxygen ions have more biological benefits than lighter ions such as proton. Oxygen has a higher Linear Energy Transfer (LET) and a larger Relative Biological Effectiveness (RBE). To design the Spread-Out Bragg Peak (SOBP) of biological doses, we have developed a functional approach with Monte Carlo calculations and matrix computations. We have used this method for both oxygen and proton beams. After obtaining the profiles of the Bragg Peak by Geant4 code, intensity weighing factors for each beam was calculated to create a uniform SOBP. Also, the RBE value was calculated according to the Linear-uQadratic model (LQ). Biological dose, physical dose, and cell survival levels were also obtained in the radiation of both ions. The designed biological SOBP has a good uniformity. Physical dose derived from proton and oxygen beams do not differ significantly, but for biological dose, there is a sharp difference between them. Even with the modulation of the intensity of the beams to produce the same biological dosage, the cell survival levels chart will vary greatly. The biological properties and effects of oxygen in respect to the proton can be a good choice to optimize the system to maximize damage to the tumor tissue and minimize damage to surrounding healthy tissues. The existence of richer tables of experimental values for the effective parameters on the amount of relative biological effectiveness greatly increases the accuracy of this optimization.

Introdution: A careful study of the physical and biological properties of helium ion radiation on the various cell lines is essential for the treatment planning. In this study, the biological response of several different cell lines has been investigated in 4He ions. Physical dose profiles and Linear Energy Transfer (LET) calculations were performed using the Monte Carlo Geant4 code. By studying the mixed radiation field, the biological effect of 4He primary ions, 3He and 6He secondary ions, as well as secondary proton, deuteron and triton are considered in calculations. Biological doses and cell survival levels have been compared for these cell lines. The variation of relative biological effectiveness (RBE) for each cell line is calculated as a function of the phantom depth. The results have shown that the cell lines with the highest (α/β)ph levels have a higher sensitivity to damage cells against 4He radiation. Among the studied cell lines, the most appropriate treatment for 4He ion, the Colon adenocarcinoma cancer cell line has been selected. In addition, due to the large variation in RBE relative to the depth in the phantom, it is necessary to consider a variable RBE instead of a constant RBE.

Studies carried out with synchrotron radiation have shown that micro-beam radiation therapy (MRT) has unique advantages in the treatment of cancerous tumors. In this method, the determination of dose distribution and calculation of peak to valley dose ratio (PVDR) are considered as the most important steps in treatment planning. The PVDR is a criterion to evaluate the destruction of cancer cells and protection of normal cells in the tissues surrounding a tumor.   Using a multi-slit collimator, planar sliced beams were generated in an X-ray generator in order to determine dose distribution in a multilayer phantom made of plexiglass. An ionization chamber was used to measure absorbed dose. Given the large size of the sensitive area of the chamber in comparison with the narrow beams, a mono-slit collimator made of tungsten with a slit of 0.3×7.5 mm2 in its center was placed in front of the ionization chamber. Furthermore, by using Geant4 computer code, a model, including X-ray source, multi-slit collimator, phantom, mono-slit collimator, and detector, was designed to compare experimental and simulation results.

Findings: The investigation of dose distribution in the phantom with both methods indicated the presence of peaks and valleys. Given the low intensity of X-ray beam generated by the X-ray generator, and limited exposure time, the experimental errors were considerable. When using 1 mm (Air)+0.5 mm (W) collimator, PVDRs were obtained as 8.7 and 10.5 for ionization chamber and simulation, respectively, in the depth of 8 mm of the phantom. On the other hand, with a 1 mm (Air)+1 mm (W) collimator, the values obtained for this parameter were 11.1 and 13.3 for ionization chamber and simulation, respectively.

Based on the results, a multi-slit collimator made of tungsten could produce multi-slice X-ray. The estimated dose distribution using the Geant4 code was more accurate than the one obtained through ionization chamber, which can be due to the possibility of using a detector in much smaller dimensions in the Geant4 code

The Increase in cancer tissues dose while protecting the surrounding healthy tissues is regarded a great challenge in radiotherapy. Photon Activation Therapy (PAT), by introducing high-Z elements to tumor, can enhance the delivered dose in tumor tissues while reducing the dose deposited in adjacent normal tissues. In this study, the effects of various parameters such as X-ray energy, type and concentration of the activation agents in the dose distribution have been investigated to improve the quality of treatment by Geant4 simulation code.
In this study, the effects of introducing Au and Lu in targeted tissues irradiated by X-ray beam have been investigated by Geant4 code. In the designed model, the x-ray source was considered in the shape of a circular plate with the radius of 0/5cm and the phantom in cubic shape with the side of 15cm. Rectangular cubic shape detector dimensions are 3×3×7.5 cm3 and the assumed tumor in cubic shape with the side of 1cm are located inside it.
Findings:: The simulation results were obtained with different voltages of X-ray generator in labeled tumor by Au and Lu (with two concentrations of 5 and 10 wt. %). Optimum voltage of x-ray generator in order to maximum Dose Enhancement Factor (DEF) by Au was 100kV, while it was observed at 100kV and 160kV for Lutetium. Increasing the absorbed dose for tumor region could reveal the effective role of contrast agents. Furthermore, when the concentration of contrast agents was doubled, average of DEF at the optimum voltage of X-ray generator and in the tumor region, was 1.68 & 1.76 for Au and Lu, respectively.
Discussion & Based on the results, the absorbed dose in tumor region after introduction of contrast agents with specifying the optimum concentration and photon energy can be increased selectively. This approach of introducing contrast agents could improve the efficiency in the cancerous cells therapy.

Proton therapy is a treatment method for variety of tumors such as brain tumor. The most important feature of high-energy proton beams is the energy deposition as a Bragg curve and the possibility of creating the spread out Bragg peak (SOBP) for full coverage of the tumor. The aim of this study is the three dimensional (3-D) coverage of a brain tumor while healthy brain tissue absorbs less radiation.
In this study, a spherical tumor with the radius of 1 cm in the brain is considered. A SNYDER head phantom has been irradiated with 86.5 MeV proton beam energy. APMMA modulator wheel and a PMMA range compensator wheel are used for longitudinal and lateral covering of the tumor, respectively. The simulations are performed using GEANT4 code.
Findings: Using a modulator wheel, the tumor is covered longitudinally and Spread Out Bragg Peak is created. In terms of lateral, in addition to the tumor, portions of healthy brain tissue are irradiated. 3-D coverage of spherical shape tumor is performed using a range compensator wheel. In the presence of modulator and range compensator wheels, the flux and absorbed dose of secondary particles produced by nuclear interactions of protons with elements in the head are considerably small compared to protons.
Discussion & Using a modulator and a range compensator wheels the tumor can be treated accurately in the 3-D, so that the minimal damage reaches the surrounding tissues. The results show that more than 99% of the total dose of secondary particles and protons is absorbed in the tumor.

In order to increase the absorbed dose in the tumorous area, photon activation therapy via labeling of tumor by heavy contrast agents such as gadolinium (Gd) and target exposing by ortho-voltage x-rays is used. In this method, the photoelectric effect is dominant in the tumorous area which will lead to the increase of local dose. By using Geant4 computer code, dose distribution in different areas of normal tissue and Gd element tumor-activated, were obtained. In the designed model, the x-ray source was considered in the shape of a mono energetic and superficial circular plate with the radius of 15mm and the phantom (normal tissue, assumed tumor and detectors) in cubic shape with the side of 13cm. Rectangular cubic shape detector area dimensions’ are 40×40×48 mm3 which continue from phantom surface to a depth of 48.67 mm along x, y and z axes. Optimum energy of photons in order to maximum absorbed dose enhancement factor (DEF) in gadolinium smeared tumorous area is 59.6 keV. By increasing the concentration of contrast agents, the homogeneity of dose distribution in assumed tumorous area is decreased but the greatest homogeneity of dose is seen at 106.5 keV of energy. Increased fluctuations of absorbed dose relative to the contrast agents’ concentration indicate that these changes in the concentration range of 1-8 mg/ml follow the linear function. Based on the simulation results in this study, absorbed dose in tumorous area following addition of contrast agent (Gd) with specifying the concentration and photon energy, is significantly more than when the assumed tumor is not labeled.