Modeling of the Characteristics of Electron Beams and Generated Photon Fluxes on the M-30 Microtron

Electron and photon beams demonstrate extraordinary characteristics useful for the treatment of cancer. These characteristics are essential to analyze before the calibration of the linear accelerator with dual energies. This study focused on the dosimetric characteristics of the different energies of electron beam for different field sizes. The basic objective of this work was to calculate the dosimetric parameters and characteristics of the electron beam, especially depth dose characteristics along the central axis. In this work, 6 MeV, 9 MeV, 12 MeV, 15 MeV and 18 MeV of electron beam and 6 MV and 15 MV of photon beam with different field sizes were used. The characteristics of the depth dose of electron and photon beams in water were analyzed to optimize the radiation quality for radiation treatment planning. The different beam characteristics are due to different interactions that occur between electron beams giving them a definite range, whereas photon beams are attenuated leading to dose deposition and a much larger range with no definite end. Depth dose characteristics of electron and photon beams are not similar since the interaction of these beams with matter depends on their quality. Attenuation and penetration factors change with changing dosimetric parameters. A complete analysis of the dosimetric characteristics of electron and photon beams helps to choose the more accurate beam for the treatment of cancer. This work helps to increase accuracy in the treatment of cancer with radiotherapy. Copyright(c) The Authors

In external beam radiation therapy, electron and photon beams have extraordinary characteristics in the treatment of cancer. The electron and photon beam characteristic are essential to study before calibration of machine. This study focused on the dosimetric characteristics of different energies of electron beams for different field size. The basic objective of this work is, to calculate dosimetric parameters and characteristics of electron beam, specially depth dose characteristics along central axis. In this work, 6 MeV, 9 MeV, 12 MeV, 15 MeV and 18 MeV of electron beam and 6 MV and 15 MV of photon beam with different field size is used. Characteristics of depth dose of electron and photon beam in water have analyzed to provide better quality of radiation therapy treatment planning. The different beam characteristics are due to different interactions that occurs between electron beams giving them a definite range whereas photon beams are attenuated leading to dose deposition and much larger range with no definite end. Depth dose characteristics of electron and photon beams do not show same characteristics as interaction of beam with matter depends on the quality of beam. Attenuation and penetration factors change with changing dosimetric parameters. Complete analysis of dosimetric characteristics of electron and photon beam help to choose more accurate beam for the treatment of cancer. This work will help to increase accuracy in treatment of cancer with radiotherapy.

Introduction: Radiotherapy uses high-energy radiation to shrink tumors and kill cancer cells. The radiation may be delivered by a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (brachytherapy). Many types of external-beam radiation therapy are delivered using a machine called a linear accelerator (also called a LINAC). The process of commissioning a linac for clinical use includes comprehensive measurements of dosimetric parameters that are necessary to validate the treatment planning systems used to select optimal radiation modality and treatment technique for individual patients. In the present study, clinically pertinent data for both the available photon and electron energies were investigated. Methods: For making measurements in water, a three dimensional radiation field analyzer RFA-300 (Scanditronix Wellhofer) and for absolute dosimetry and other measurements like relative output factors, wedge factors etc., a DOSE1 electrometer (Scanditronix Wellhofer) in a white polystyrene were employed. Results: The percentage depth dose data, wedge factors, output factors and cross beam profiles have been measured and compared with the other studies for photon beams and isodose plots, virtual source to surface distance, uniformity index for electron beams. Conclusion: All these measured data were utilized as input to the ECLIPSE treatment planning system for further clinical use. The characteristics of the electron beams are found to follow the trends experimentally observed by others, generally found to be different from the others theoretically predicted and depend on the model of the machine.

Exploration of new treatment modalities offered by high energy (up to 50 MeV) electrons and photons

The specific design of the mobile dedicated intraoperative radiotherapy (IORT) accelerators and different electron beam collimation system can change the dosimetric characteristics of electron beam with respect to the conventional accelerators. The aim of this study is to measure and compare the dosimetric characteristics of electron beam produced by intraoperative and conventional radiotherapy accelerators. To this end, percentage depth dose along clinical axis (PDD), transverse dose profile (TDP), and output factor of LIAC IORT and Varian 2100C/D conventional radiotherapy accelerators were measured and compared. TDPs were recorded at depth of maximum dose. The results of this work showed that depths of maximum dose, R90,R50, and RP for LIAC beam are lower than those of Varian beam. Furthermore, for all energies, surface doses related to the LIAC beam are substantially higher than those of Varian beam. The symmetry and flatness of LIAC beam profiles are more desirable compared to the Varian ones. Contrary to Varian accelerator, output factor of LIAC beam substantially increases with a decrease in the size of the applicator. Dosimetric characteristics of beveled IORT applicators along clinical axis were different from those of the flat ones. From these results, it can be concluded that dosimetric characteristics of intraoperative electron beam are substantially different from those of conventional clinical electron beam. The dosimetric characteristics of the LIAC electron beam make it a useful tool for intraoperative radiotherapy purposes.PACS number: 87.56.‐v, 87.56.bd

Reliable information on the characteristics (spectral, integral, spatial distributions) of electron and secondary photons beams falling into the plane of sample potential placement during their irradiation using electron accelerators is necessary to ensure the optimization procedure (creation of homogeneous particle fields in the plane of sample placement) and prediction of experimental results (estimation of the absorbed dose during interaction with electrons and the contribution of additional dose from interaction with secondary photons). The results of simulations of the influence of air layers (1…5000 mm) between the electron output node of the M-30 microtron and the plane (1000 x 1000 mm) on the characteristics of the primary electron beam with an energy of 17.5 MeV and the generated secondary bremsstrahlung photons are presented. When modeling with the GEANT4 tool, the technical characteristics of the M-30 microtron were taken into account.

This thesis presents the results of two investigations into the characteristics of electron beams for application in radiation therapy. The first involves modeling the interactions between the applicator of a Siemens Mevatron KD2 linear accelerator, and the accelerator's electron beam. EGS4 Monte Carlo code is used to simulate narrow beams incident on sections of applicator trimming plate edges in order to investigate the characteristics of scattering off these edges. A model for scatter from irregular apertures is developed based on a superposition of scatter kernels from edge elements. This model is found to give central‐axis depth dose and profile data consistent with measured results. The model is also used to obtain detailed information of the characteristics of particles scattered from the electron applicator. In the second investigation, optimal electron beam properties are determined by inversion of desired dose distributions using a simulated annealing optimization method. This technique is used for several regular desired dose distributions, and various intuitive results are obtained regarding the effects electron energy and angular modulation have on resulting dose distributions. The technique is also used for several complex desired dose distributions, indicating the relative influence energy and angular modulation can have on dose conformation with electrons.

Influence of particle fluxes from a target on the characteristics of intense electron beams

The least known parameters in a Monte Carlo simulation of a linear accelerator treatment head are often the properties of the initial electron beam directed onto the exit vacuum window. Several initial beams with different spatial fluence distributions, angular divergences and energy spectra have been transported through the geometry of a scattering foil accelerator. The electron beam characteristics (energy spectrum and angular distribution) at the phantom surface and the subsequent relative absorbed dose distribution in a water phantom were calculated. The dose distribution was found to be insensitive to the geometrical properties of the initial beam. Furthermore, the lateral dose profiles are unaffected by the energy spectrum of the initial beam. The effect on the depth–dose curve is negligible if the initial energy spectrum is symmetric (e.g., Gaussian shaped) and its full width at half maximum (FWHM) is less than approximately 10% of the most probable energy. A larger FWHM will decrease the normalized dose gradient, but will not affect the dose in the build-up region. An asymmetric wedge shaped spectrum with a low-energy extension simultaneously increases the dose in the build-up region and decreases the dose gradient. The relationship between the energy spectral width and the normalized dose gradient is, however, smaller than published analytical expressions indicate. Some well-established energy-range relationships were shown to be accurate for most of the initial beams studied. The energy spectrum at the phantom surface was also derived from a measured depth–dose curve through different methods. The extracted spectrum depends on the beam model and the spectral reconstruction algorithm. Even though the depth–dose curve is fairly independent of initial beam characteristics, a correct description of the low-energy tail of the energy spectrum is important to obtain good agreement between measured and Monte Carlo calculated doses in the build-up region.

Studies on the inhibition effectiveness of the initial degree of inoculation of the Salmonella microorganism were carried out. In this paper, the irradiation efficiency of model systems with electron beams with beam energy of 6.5 and 10 MeV was studied. The investigations were carried out at UELV-10-10-C-70 accelerator at Frumkin Institute of Physical Chemistry and Electrochemistry of Russian Academy of Sciences (IPCE RAS) with an average beam power of 6.5 MeV and at radiation-technological center with an electron accelerator UELR-10-10-40 at A.I. Burnazyan Federal Medical Biophysical Centre of Federal Medical Biological Agency with an average electron energy of 10 MeV. The conducted researches on studying and revealing the dependence of inhibition of pathogenic microflora, irradiation with different intensity, on the structure (density) of the studied samples, which model liquid and solid nutrient media. The study used a strain Salmonella enterica subsp. Enterica serovar Typhimurium. The results of the effective inhibition of the initial degree of contamination for the two plants were obtained. Studies have shown that the effectiveness of inhibition of Salmonella culture can vary depending on the characteristics of electron beams. For example, when samples were irradiated with electrons with energy of 6.5 and 10 MeV at doses from 3 to 7 kGy, various results of the inhibition effectiveness of Salmonella culture on media with different work were obtained. When processing samples with studied strains of cultures in the dose range from 4 to 5 kGy, there is an increase in the growth of microorganisms for all processing conditions. In the remaining studied ranges their inhibition are observed. It is important to take into account not only the effectiveness of the oppression of microflora on specific products, but also the efficiency of the installation for a specific sample.

Electron beam characteristics at extended source to surface distance for a Clinac-DHX linear accelerator A uniform dose to the target site is required with a knowledge of delivered dose, central axis depth dose and beam flatness for successful electron treatment at an extended source to surface distance (SSD). In an extended SSD treatment under dosage of the lateral tissue may occur due to reduced beam flatness. To study the changes in beam characteristics, the depth dose curves, beam flatness and isodose distributions were measured at different SSDs from 100 to 120 cm for clinically used field sizes from (4×4) to (25×25) cm2 and beam energies ranging from 6 MeV to 20 MeV. Our results suggest that the change in depth dose is minimal except in the buildup region for most energy. In general surface dose is decreased as the SSD increased moderately. It was observed that the loss in beam flatness is significant for smaller fields, higher isodose lines, and lower energies. The penumbra enlarged and the uniformity index reduced with increasing SSD.

Integrated numerical modeling of free electron laser oscillators

Experimental and Monte Carlo absolute characterization of a medical electron beam using a magnetic spectrometer

The investigation on focus and transport characteristics of sheet electron beam has been a key technique for the development of high-power microwave and millimeter-wave vacuum electronic devices. Compared with the period permanent magnetic system to transport the sheet electron beam, the uniform magnetic focusing system has many advantages, such as easily adjusting and matching the magnet with the beam, focusing the intensity electron beam, no cut off beam voltage restriction, etc. However, the Diocotron instability of the sheet electron beam in the uniform magnetic field can produce the distortion, deformation, vortex and oscillation to destroy the beam transportation. In this paper, the single-particle model and the cold-fluid model theory and calculation are used to indicate that if the electron optics system parameters of the sheet beam are designed more carefully, the magnitude of uniform magnetic field and the filling factor of the beam in transport tunnel are increased appropriately, the Diocotron instability can be reduced, even vanished completely to transport the sheet beam effectively in a long distance. To verify the above conclusion, the electron gun with the ellipse cathode and the electron optics system are designed and optimized with the three-dimensinal simulation software in detail. After the complex assembly and weld process with the small geometry and high precision, the W-band sheet electron beam tube is manufactured and tested. The sheet beam cross section of 10 mm0.7 mm is achieved experimentally with the one-dimensional compression and formation of electron gun. Also, with a beam voltage of 2080 kV, and beam current of 0.644.60 A,the experimental transmission rate of sheet beam electron tube manufactured is more than 95% with a drift length of 90 mm, which is higher than the periodic cusp magnetic field transport experiment result of 92% obtained recently.

The purpose of this study is to perform a comparison and on analysis of measured dose factor values by using various commercially available high-energy electron beam detectors to measure dose profiles and energy property data. By analyzing the high-energy electron beam data from each detector, we determined the optimal detector for measuring electron beams in clinical applications. The dose linearity, dose-rate dependence, percentage depth dose, and dose profile of each detector were measured to evaluate the dosimetry characteristics of high-energy electron beams. The dose profile and the energy characteristics of high-energy electron beams were found to be different when measured by different detectors. Through comparison with other detectors based on the analyzed data, the microdiamond detector was found to have outstanding dose linearity, a low dose-rate dependency, and a small effective volume. Thus, this detector has outstanding spatial resolution and is the optimal detector for measuring electron beams. Radiation therapy results can be improved and related medical accidents can be prevented by using the procedure developed in this research in clinical practice for all beam detectors when measuring the electron beam dose.