Electron Beam Dose Research Articles

Investigating the Effects of Cut-Out Shield on High-Energy Electron Fields Using MAGIC Normoxic Polymer Gel

Introduction The use of cut-outs in electron applicators make changes on output, isodose, and percentage depth dose (PDD) curves. These changes and electron beam dose distribution in the form of three-dimensional (3D) can be measured by gel dosimeters. Materials and Methods Dosimetry was performed with and without a square shield (6×6 cm2 field). The energies were 4, 9, and 16 MeV and phantom was filled with MAGIC gel polymer. For each section, transverse relaxation rate (R2) maps were obtained from MRI images and percentage depth doses and isodose curves were plotted. Results Average energy was 3.029 MeV for the energy of 4 MeV and 8.155 MeV for the energy of 9 MeV. Surface dose was higher in shielded field compared with the open one (due to electron scattering between the phantom and lead) which increased with increasing of energy. In the open field, for energies equal to 4, 9, and 16 MeV, the surface dose was 6.40, 6.48, and 7.20 Gy and for the shielded mode, they were 6.63, 7.04, and 7.31 Gy, respectively. Also error values showed less errors and higher accuracy on curves by increasing of energy. Conclusion Investigation of an isodose pattern in the shielded mode showed scattering due to the lead, which is on the applicator. Overall, the results of this study demonstrated the value and potential of this dosimetric method with respect to characteristics such as stability, responsiveness and specially ability to show three-dimensional electron beam dose distribution.

Fungal decontamination and enhancement of shelf life of edible split beans of wild legume Canavalia maritima by the electron beam irradiation

Ripened split beans of the coastal sand dune wild legume Canavalia maritima serve as one of the traditional nutritional sources of the coastal dwellers in Southwest coast of India. Nine fungi were isolated from the unirradiated dry beans by plating on the potato dextrose agar medium. Toxigenic fungus Aspergillus niger showed the highest incidence (33–50%) followed by Aspergillus flavus (14–20%) and Penicillium chrysogenum (7–13%). Unirradiated dry beans and irradiated dry beans with electron beam doses 2.5, 5, 10 and 15kGy were monitored for occurrence of fungal species and their incidence during 0, 3 and 6 months storage period under laboratory conditions. Irradiation resulted in dose-dependent decrease in fungal species (5–7, 4–6, 3–6 and 0 on irradiation at 0, 2.5, 5 and 10 or 15kGy, respectively) as well as incidence (80–99, 19–46, 13–21 and 0%, respectively). Although aflatoxins (B1 and B2) were found below detectable level (<2ng/g) in 0, 3 and 6 months stored unirradiated and irradiated beans (2.5 and 5kGy), they were not present in beans irradiated with 10 and 15kGy. In spite of occurrence of toxigenic fungus Aspergillus ochraceus in unirradiated and irradiated beans (2.5 and 5kGy) stored for 3 and 6 months, the beans were devoid of ochratoxin-A. Electron beam irradiation dose 10kGy could be recommended for fungal decontamination and improvement of shelf life of C. maritima ripened dry split beans.

High-resolution chemical analysis on cycled LiFePO4 battery electrodes using energy-filtered transmission electron microscopy

We demonstrate an ex situ method for analyzing the chemistry of battery electrode particles after electrochemical cycling using the transmission electron microscope (TEM). The arrangement of particles during our analysis is the same as when the particles are being cycled. We start by sectioning LiFePO4 battery electrodes using an ultramicrotome. We then show that mapping of the Fe2+ and Fe3+ oxidation state using energy-filtered TEM (EFTEM) and multivariate statistical analysis techniques can be used to determine the spatial distribution of Li in the particles. This approach is validated by comparison with scanning transmission X-ray microscopy (STXM) analysis of the same samples [Chueh et al. Nanoletters, 13 (3) (2013) 866–72]. EFTEM uses a parallel electron beam and reduces the electron-beam dose (and potential beam-induced damage) to the sample when compared to alternate techniques that use a focused probe (e.g. STEM–EELS). Our analysis confirms that under the charging conditions of the analyzed battery, mixed phase particles are rare and thus Li intercalation is limited by the nucleation of new phases.

The network and properties of the NR/SBR vulcanizate modified by electron beam irradiation

A natural rubber/styrene butadiene rubber (NR/SBR) vulcanizate filled with carbon black was modified by high-energy electron beam (EB) irradiation in this work. The crosslinked structure was studied by a special chemical probe method. The influence of EB irradiation on mechanical properties, filler network, and dynamic properties including abrasion resistance, rolling resistance, and wet skid resistance was also investigated. The results revealed that the crosslink structure significantly changed after EB treatment, indicating that the amount of poly- and di-sulfide crosslinked bonds decreased and that of mono-sulfide bonds increased. The polymer–filler interaction was enhanced after EB irradiation. An EB dose of 600kGy reduced the abrasion loss of the NR/SBR vulcanizate, and one of 300kGy reduced the rolling resistance by 11.4%. Meanwhile, EB doses below 200kGy had no obvious effect on the wet skid resistance. This EB-modified NR/SBR vulcanizate can be used to prepare high-performance tires with good abrasion resistance and low rolling resistance.

Sago Starch-Mixed Low-Density Polyethylene Biodegradable Polymer: Synthesis and Characterization

This research focuses on synthesis and characterization of sago starch-mixed LDPE biodegradable polymer. Firstly, the effect of variation of starch content on mechanical property (elongation at break and Young’s modulus) and biodegradability of the polymer was studied. The LDPE was combined with 10%, 30%, 50%, and 70% of sago for this study. Then how the cross-linking with trimethylolpropane triacrylate (TMPTA) and electron beam (EB) irradiation influence the mechanical and thermal properties of the polymer was investigated. In the 2nd study, to avoid overwhelming of data LDPE polymer was incorporated with only 50% of starch. The starch content had direct influence on mechanical property and biodegradability of the polymer. The elongation at break decreased with increase of starch content, while Young’s modulus and mass loss (i.e., degradation) were found to increase with increase of starch content. Increase of cross-linker (TMPTA) and EB doses also resulted in increased Young’s modulus of the polymer. However, both cross-linking and EB irradiation processes rendered lowering of polymer’s melting temperature. In conclusion, starch content and modification processes play significant roles in controlling mechanical, thermal, and degradation properties of the starch-mixed LDPE synthetic polymer, thus providing the opportunity to modulate the polymer properties for tailored applications.

The Effect of Electron Beam Irradiation on Chemical and Morphological Properties of Hansan Ramie Fibers

The purpose of this study investigates the effects of electron beam(EB) irradiation on the chemical and morphological properties of Hansan ramie fiber. Hansan ramie fibers were irradiated with electron beam doses of 0, 1, 3, 5 and 10kGy. The effect of electron beam irradiation on the chemical components of fibers as well as the surface chemical and morphological properties were investigated using chemical component analysis methods based on TAPPI standards, XPS, and SEM. The results indicate that the surface layers can be removed under suitable EB irradiation doses. Alcohol-benzene extraction and lignin content increases gradually with an increase in EB irradiation and reaching a maximum at an EB dose of 3kGy, and decreases at 10kGy. The surface chemical changes measured by XPS corresponded to the chemical composition analysis results. The C1 peak and the O/C ratio decreased with the removal of the multi-layer and primary layer by EB irradiation. The SEM images show the inter-fibrillar structure etched by EB irradiation up to 5kGy. At 10kGy, the surface structure of the ramie fiber shows highly aligned and distinctive striations in a longitudinal direction. The removal of these exterior layers of the fiber was confirmed by changes in surface morphology as observed in SEM images.

Effect of different doses of electron beam irradiation on the structure of PAN precursor fibers and resultant stabilized fibers

Different doses of electron beam was imposed on the polyacrylonitrile(PAN) precursor fibers before the fibers were stabilized. The effect of electron beam irradiation on the chemical structure, crystallite size of PAN precursor fibers and density, oxygen content, transverse section morphology of the stabilized fibers in the stabilization process were characterized by the use of fourier transform infrared spectroscopy(FTIR), float-sink procedure, elemental analysis and scanning electron microscope(SEM), respectively. The results showed that the extent of cyclization was increased and the crystallite size was decreased. We found that electron beam irradiation could accelerate the cyclization reaction and stabilization reaction in the stabilization process through density test and elemental analysis. We also found that the effect of 200 kGy electron beam irradiated fibers with the stabilization time of 75 min was better than that of the original stabilized fibers with 90 min. These results demonstrate that electron beam irradiation can shorten the stabilization time.

Appliance of Electron Beam Technology for Disinfection of Sewage Water to Minimize Public Health Risks

First time in India, a study was aimed to establish a base- line data for electron beamradiation dose level needed to disinfect and also improve the water quality of sewage waterfor possible reuse in irrigation, industries as well as a few domestic purposes. Raw andsecondary treated sewage water samples, which were rich with microorganisms from NaviMumbai municipal sewage plant were irradiated with electron beam accelerator at doses of0.45, 0.75, 1.5, 3.0, 4.5, 6.0, 7.5, 9.0 and 10.5 kGy. Electron Beam irradiation treatment ofthe wastewater was found to be very effective in reducing the pathogenic load. ElectronBeam (EB) dose of 1.5 kGy was sufficient for complete elimination of total coli formswhereas Cryptococcus laurentii, Aspergillus fumigatus and Absidia sp. were killedby10.0 kGy and no larvae of helminthes (Ascaris lumbricoides) were recovered at thedose ≥ 1.5 kGy. The experimental findings obtained highlighted the potential of thistechnology for disinfection of wastewater.

SU‐E‐T‐513: Evaluation Output Dose of Electron Beams Based On Monte Carlo

Purpose: The purpose of this study is to investigate the influence factor of output dose for electron beams used in radiotherapy by Monte Carlo technique. Methods: MCTP code was used to calculate a group of output dose from Varian Clinac 23EX. According to the contributions, the calculated output dose was divided into four parts which can help to identify the physical reasons for the variation of output dose, dose from direct particles which was arisen from the machine head directly, dose from indirect particles which was arisen from the collimation devices, including jaws, scrapers and shielding. Results: 1. Appling same cones and same jsw settings but different field inserts, considering the 6 Mev beams, due to direct particles as well as indirect particles the output dose increases from the smallest to the largest field insert. 2. Different cones with same jaw settings and field size, for 6MeV electron beams, the use of a wider cone resulted in a higher output dose, which is mainly because of the direct particles. 3. Same field size with different cones and jaw settings, considering the 18 MeV beams, the wider cone exhibits a reduced output dose, which is attributed to indirect particles, and jaw contributes more than others. 4. Open cone, for the 6 MeV beams the wider cones that also has wider jaw settings showed an increased contribution to the output dose majorly from the indirect particles compared with the smaller cones. Similar trends were seen from the 9 MeV beams, although they were diminished. A reverse Result was indicated for the 18 MeV beams. Conclusion: The variation of output dose depends in a complicated manner on the characteristics of the beams and the modifications that the various cone‐insert combinations introduce to these characteristics.

MO‐B‐105‐01: Successes and Challenges Associated with Monte Carlo Treatment Planning in the Clinic

The availability of Monte Carlo (MC)‐based codes optimized for photon and electron beams in patient‐specific geometries has enabled the use of MC‐based dose calculations for radiotherapy treatment planning in the routine clinical setting. These codes have made it possible to perform MC‐based photon and electron beam dose calculations within minutes on typical treatment planning computational platforms. As efficient and accurate MC codes become more widely utilized in the clinic, it is important that strategies and paradigms for clinical commissioning and implementation of these systems be formulated and discussed. This lecture will focus on such strategies, challenges and successes associated with the use of MC‐based dose calculations for external photon and electron beam therapy in the clinic.Learning Objectives:1. To provide an educational review of the physics of the MC method including discussion of the approaches used for coupled photon and electron transport.2. To discuss currently available MC‐based photon and electron algorithms fast enough for clinical implementation.3. To describe the development of beam models for photon and electron beam treatment planning.4. To discuss the factors associated with MC dose calculation within the patient‐specific geometry, such as statistical uncertainties, CT‐number to material density assignments, and reporting of dose‐to‐medium versus dose‐to‐water.5. To review paradigms and approaches for commissioning and experimental verification of MC‐based photon and electron beam dose calculation algorithms.6. To summarize the approaches being used in evaluating the clinical impact of MC‐based photon dose calculations and the associated issues.NIH/NCI R01 CA106770; Varian Medical Systems, Palo Alto, CA

Effect of electron beam irradiation on the structural, thermal and optical properties of poly(vinyl alcohol) thin film

Poly(vinyl alcohol) (PVA) polymer was prepared using the casting technique. The obtained PVA thin films have been irradiated with electron beam doses ranging from 20 to 300 kGy. The resultant effect of electron beam irradiation on the structural properties of PVA has been investigated using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), while the thermal properties have been investigated using thermo-gravimetric analysis and differential thermal analysis (DTA). The onset temperature of decomposition T 0 and activation energy of thermal decomposition E a were calculated, results indicate that the PVA thin film decomposes in one main weight loss stage. Also, the electron beam irradiation in dose range 95–210 kGy led to a more compact structure of the PVA polymer, which resulted in an improvement in its thermal stability with an increase in the activation energy of thermal decomposition. The variation of transition temperatures with electron beam dose has been determined using DTA. The PVA thermograms were characterized by the appearance of an endothermic peak due to melting. In addition, the transmission of the PVA samples and any color changes were studied. The color intensity Δ E was greatly increased with increasing electron beam dose, and was accompanied by a significant increase in the blue color component.

The effect of electron beam on dates infestation

This is a commercial scale study to assess the effect of electron beam (EB) treatment on pest load, microbial load, antioxidant and free radical content of dates using different doses; 0.5, 1.0, 2.0 kGy. EB efficiency was assessed by measuring Oryzaephilus surinamensis mortality, total viable count (TVC), yeast and mold count (YMC), total antioxidants and free radicals. All doses used in EB treatment successfully eliminated all stages of O. surinamensis in dates. EB dose of 2.0 kGy had the greatest reduction in TVC to 4.35 log CFU/g in Khalas and 4.75 log CFU/g in Lulu dates. YMC was low in samples treated by EB compared with control sample. There were no significant differences in total antioxidants between treatments, except reduced antioxidants for samples treated with 2.0 kGy. The free radical content of samples treated by 2 kGy decreased by 65% after 25 days of storage. These results support the applicability of using 1.0 kGy to ensure and enhance the safety of dates.

Uniquely different PVA-xanthan gum irradiated membranes as transdermal diltiazem delivery device

This paper reports interesting differences between physical and mechanical properties of various membranes prepared from high and low molecular weight poly (vinyl alcohol) (PVA) and xanthan gum (XG) blends irradiated under low dose electron beam. The membranes were designed for sustained delivery of diltiazem hydrochloride through skin. Electron beam irradiation produced crosslinks and turned PVA into crystalline phase from its amorphous organization in the unirradiated state. PVA crystals were fibrillar at low XG content (1wt.%) when the molecular weight was high while similar orientation at higher XG content (5wt.%) when the molecular weight was low. Low molecular weight PVA–XG membranes showed equivalent physical properties under dry condition but wet-mechanical properties were superior for high molecular weight PVA–XG hybrids. Both of them showed slow and sustained diltiazem release but the later induced slightly slower release despite low drug encapsulation efficiency due to its better wet mechanical strength.

Improvement of Optical Properties of TiO&lt;SUB&gt;2&lt;/SUB&gt; Thin Film Treated with Electron Beam

Nanocrystalline titanium dioxide (TiO2) thin films on silicon wafer substrates were prepared by sol-gel spin coating process. The prepared thin films were treated with electron beam (1.1 MeV, 300 kGy) at air atmosphere. The effects of electron-beam (EB) irradiation on the structural and optical properties of the TiO2 thin films were investigated. The structures of all the TiO2 thin films by XRD analysis showed an anatase phase, and the phase remained unchanged within the investigating range of EB treatment. The thickness of the titania thin film decreased slightly with EB treatment whereas the porosity increased. The EB treatment of TiO2 thin film can increase the proportion of Ti3+ in Ti2p at the thin film surface. The optical transmittance of the film in the wavelength ranges of above 380 nm increased after the EB treatment while its refractive index decreased with increasing EB dose. Therefore, improvement of the optical properties could be due to the change in both surface chemistry and morphology of the TiO2 thin films affected by EB irradiation.

Monte Carlo investigation of the effect of small cutouts on beam profile parameters of 12 and 14 MeV electron beams

Cutouts, which are used as field-shaping shield, affect several electron beam parameters. These effects are more observable for small field sizes and high energy electron beams. Owing to the fact that small fields prevent the lateral scatter equilibrium, at higher energies larger field radius is required for the establishment of lateral equilibrium. The profile curves are derived from circular, triangular, and square cutout shapes and size placed in a 10 × 10 cm 2 electron applicator. These profile curves are obtained using parallel plane type ion chamber at the R 100 , R 90 , R 80 and R 50 depths. Correspondingly, the source surface distance is 100 cm. In this study MCNP Monte Carlo (MC) simulation was used to compare Percentage Depth Dose (PDD) and Profile of electron beams. Monte Carlo and measured results showed a good compliance for PDD and beam profile. The measurements and calculations showed that as the field width decreases, the Flatness and Penumbra Ratio also decreases. In other words, flatter plateau was available for larger fields. Also the Coverage Ratio for each of the profiles is presented. The flatness and symmetry values for triangle shapes were greater than the two other shapes. Knowledge of these changes are significant in radiation therapy. Accordingly, a comparison between the Monte Carlo data and the measured results can be beneficial for treatment simulation and development of treatment planning systems. ► Mesh Tally 1 and pedep keyword were used to calculate the PDD and profile values. ► In measurement the coverage for larger fields and fewer doses are better. ► By increasing the depth, the flatness and symmetry values were increased. ► The worst flatness and symmetry (between 3 compared shapes) belonged to triangle. ► The given Penumbra and Coverage Ratio can be helpful for PTV margin and coverage.

Reduction of aqueous Crvi using nanoscale zero-valent iron dispersed by high energy electron beam irradiation

High energy electron beam (HEEB) irradiation was used to disperse nanoscale zero-valent iron (NZVI) for reduction of CrVI to CrIII in aqueous solution. Pore size distribution, scanning electron microscopy and X-ray diffraction characterizations demonstrated that HEEB irradiation could effectively increase the dispersion of NZVI resulting in more active reduction sites of Crvi on NZVI. Batch reduction experiments indicated that the reductive capacity of HEEB irradiation-modified NZVI (IMNZVI) was significantly improved, as the reductive efficiency reached 99.79% under the optimal conditions (electron beam dose of 30 kGy at 10 MeV, pH 2.0 and 313 K) compared with that of raw NZVI (72.14%). Additionally, the NZVI was stable for at least two months after irradiation. The modification mechanism of NZVI by HEEB irradiation was investigated and the results indicated that charge and thermal effects might play key roles in dispersing the NZVI particles.

Water equivalence evaluation of PRESAGE® formulations for megavoltage electron beams: a Monte Carlo study

To investigate the radiological water equivalency of three different formulations of the radiochromic, polyurethane based dosimeter PRESAGE(®) for three dimensional (3D) dosimetry of electron beams. The EGSnrc/BEAMnrc Monte Carlo package was used to model 6-20MeV electron beams and calculate the corresponding doses delivered in the three different PRESAGE(®) formulations and water. The depth of 50% dose and practical range of electron beams were determined from the depth dose calculations and scaling factors were calculated for these electron beams. In the buildup region, a 1.0% difference in dose was found for all PRESAGE(®) formulations relative to water for 6 and 9MeV electron beams while the difference was negligible for the higher energy electron beams. Beyond the buildup region (at a depth range of 22-26mm for the 6MeV beam and 38mm for the 9MeV beam), the discrepancy from water was found to be 5.0% for the PRESAGE(®) formulations with lower halogen content than the original formulation, which was found to have a discrepancy of up to 14% relative to water. For a 16MeV electron beam, the dose discrepancy from water increases and reaches about 7.0% at 70mm depth for the lower halogen content PRESAGE(®) formulations and 20% at 66mm depth for the original formulation. For the 20MeV electron beam, the discrepancy drops to 6.0% at 90mm depth for the lower halogen content formulations and 18% at 85mm depth for the original formulation. For the lower halogen content PRESAGE(®), the depth of 50% dose and practical range of electrons differ from water by up to 3.0%, while the range of differences from water is between 6.5 and 8.0% for the original PRESAGE(®) formulation. The water equivalent depth scaling factor required for the original formulation of PRESAGE(®) was determined to be 1.07-1.08, which is larger than that determined for the lower halogen content formulations (1.03) over the entire beam energy range of electrons. All three of the PRESAGE(®) formulations studied require a depth scaling factor to convert depth in PRESAGE(®) to water equivalent depth for megavoltage electron beam dosimetry. Compared to the original PRESAGE(®) formulation, the lower halogen content formulations require a significantly smaller scaling factor and are thus recommended over the original PRESAGE(®) formulation for electron beam dosimetry.

Whole Brain Irradiation-induced Decrease of Histone H3 Acetylation in Hippocampus of Rats

The aim is to investigate the role of epigenetics in the irradiation-induced cognitive deficiency by observing the alterations of histone acetylation in the hippocampus of rats after irradiation. A signal dose of 2Gy and 30Gy 4MV electron beam were given to adult male Sprague-Dawley rats (150-200g, 4-5 weeks), this dose covered a dose range of clinical and experimental applications, and the animals were divided into 2Gy group, 30Gy group, and control group. After whole brain irradiation, the total protein was extracted from irradiated hippocampus and whole brain 30μm cryosections were cut by using a cryostat at day 7 and day 30. Western blot was performed and the brain sections were immunohistochemical stained. The alterations of histone H3 acetylation was observed and analyzed. To evaluate the consequence of whole brain irradiation on hippocampus-dependent memory formation, Morris water maze test, passive-avoidance test and open field test were performed. We show that both 2Gy and 30Gy 4MV electron beam whole brain irradiation induced significant decrease in histone H3 acetylation and different alterations of histone deacetylases (HDACs) in the hippocampus. We found a 25% reduction in histone H3 acetylation at day 7 (p < 0.01) and 5% reduction at day 30 (p < 0.05) after 2Gy irradiation. Compare to control, 30 Gy induced 5% reduction at day 7 and 13% reduction at day 30. Interestingly, we found that irradiation did not impair the expression of HDAC2, which has been indicated negatively regulates memory formation and synaptic plasticity. However, HDAC1 was increased. In Morris water maze test, passive-avoidance test and open field test, we confirmed whole brain irradiation lead to notable memory impairment at day 30 after irradiation. This study suggests that the alterations of histone H3 acetylation and HDACs after whole brain irradiation. Decreased histone H3 acetylation suggests altered hippocampal epigenetic signaling after whole brain irradiation. These results indicate epigenetics was involved in irradiation-induced memory deficiency, and alterations in chromatin structure may be a new possible molecular correlation of irradiation-induced cognitive deficiency.

Effect of crosslinkers on adhesion properties of electron beam curable polyurethane pressure sensitive adhesive

Polyurethane (PU) based pressure-sensitive adhesive (PSA) using monofunctional urethane acrylate (MFUA) and difunctional urethane acrylate (DFUA) has been cured using electron beam (e-beam) irradiation. The effect of varying e-beam doses on the adhesion properties viz. peel adhesion, shear adhesion and initial tack of PSA has been studied. Effect of various crosslinkers viz. methylene diphenyl di-isocynate (MDI), isophorone di-isocynate (IPDI) and triallyl isocynurate (TAIC) on adhesion properties as well as on moisture vapor transmission rate (MVTR) and gel content of the PSA has also been studied. It was observed that with increasing dose and concentration of crosslinkers all the adhesion properties viz. peel adhesion, shear adhesion strength and initial tack were increased and reached a plateau, and then a decline was observed with further increasing of the dose and crosslinkers concentration. Similarly, MVTR decreased and the gel content increased with increasing dose of electron beam.

Color changes in some irradiated polymers

Effects of electron beam irradiation on the color changes of the Bayfol CR 6-2 nuclear track detector have been investigated. Samples from CR 6-2 were irradiated with an electron beam at the dose range 50–400 kGy. The transmission of these samples in the wavelength range 400–800 nm, as well as any color changes, was studied. The Commission International de E'Claire (units x, y and z) methodology was used in this work for the description of colored samples. The color differences between the non-irradiated sample and those irradiated with different electron beam doses were calculated. The results indicate that the CR 6-2 detector acquires color changes under electron beam irradiation. This result is compared with those obtained from our previous work, for different polymers due to electron beam irradiation. In addition, as a review, our previous results on color changes in some irradiated polymers were collected and compared together.