scholarly journals A study on a dental device for the prevention of mucosal dose enhancement caused by backscatter radiation from dental alloy during external beam radiotherapy

2016 ◽  
Vol 57 (6) ◽  
pp. 709-713 ◽  
Author(s):  
Kouji Katsura ◽  
Satoru Utsunomiya ◽  
Eisuke Abe ◽  
Hironori Sakai ◽  
Naotaka Kushima ◽  
...  
Keyword(s):  
External Beam Radiotherapy ◽  
Ethylene Vinyl Acetate ◽  
Field Size ◽  
Dental Alloy ◽  
Dose Enhancement ◽  
Effective Prevention ◽  
Depth Dose ◽  
Physical Density ◽  
Significant Difference ◽  
Backscatter Radiation

Abstract The changes in dose distribution caused by backscatter radiation from a common commercial dental alloy (Au–Ag–Pd dental alloy; DA) were investigated to identify the optimal material and thicknesses of a dental device (DD) for effective prevention of mucositis. To this end, 1 cm3 of DA was irradiated with a 6-MV X-ray beam (100 MU) in a field size of 10 × 10 cm2 using a Novalis TX linear accelerator. Ethylene vinyl acetate copolymer, polyolefin elastomer, and polyethylene terephthalate (PET) were selected as DD materials. The depth dose along the central axis was determined with respect to the presence/absence of DA and DDs at thicknesses of 1–10 mm using a parallel-plate ionization chamber. The dose in the absence of DDs showed the lowest value at a distance of 5 mm from the DA surface and gradually increased with distance between the measurement point and the DA surface for distances of ≥5 mm. Except for PET, no significant difference between the DA dose curves for the presence and absence of DDs was observed. In the dose curve, PET showed a slightly higher dose for DA with DD than for DA without DD for thicknesses of ≥4 mm. The findings herein suggest that the optimal DD material for preventing local dose enhancement of the mucosa caused by DA backscatter radiation should have a relatively low atomic number and physical density and that optimal DD thickness should be chosen considering backscatter radiation and percentage depth dose.

scholarly journals Electron contamination for 6 MV photon beams from an Elekta linac: Monte Carlo simulation

2020 ◽  
Vol 2 (2) ◽  
pp. 97-101
Author(s):  
Choirul Anam ◽  
Djarwani S Soejoko ◽  
Freddy Haryanto ◽  
Sitti Yani ◽  
Geoff Dougherty
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Intensity Distribution ◽  
External Beam Radiotherapy ◽  
Absorbed Dose ◽  
Field Size ◽  
Photon Beams ◽  
Initial Electron ◽  
Depth Dose ◽  
Air Column

In external beam radiotherapy, the photons from a linear accelerator (linac) machine undergo multiple interactions, not only in the patient but also in the linac head and the air column between the linac head and the patient. Electrons are released from these interactions and contaminate the beams. The current study evaluates electron contamination for 6 MV photon beams from an Elekta linac using Monte Carlo simulation. The linac head was simulated by the BEAMnrc code and the absorbed dose in a phantom was calculated using the DOSXYZnrc code. The parameters of the initial electron beams on the target, such as mean energy and radial intensity distribution, were determined by matching the calculated dose distributions with the measured dose (at 10 x 10 cm2 field size and 90 cm source-skin distance). The central axis depth-dose curves of electron contamination were calculated for various field sizes from 5 x 5 cm2 to 40 x 40 cm2. We investigated the components that generated the electron contamination for a field size of 10 x 10 cm2. The optimal initial electron beam energy was 6.3 MeV with a full-width half maximum (FWHM) of the radial intensity distribution of 1.0 mm. These parameters were found to be in good agreement with the measured data. Electron contamination increased as the field size increased. At a depth of 1.0 mm and field sizes of 5 x 5, 10 x 10, 20 x 20, 30 x 30, and 40 x 40 cm2, the doses from electron contamination were 3.71, 5.19, 14.39, 18.97 and 20.89 %, respectively. Electron contamination decreased with increased depth. At a depth of 15 mm, the electron contamination was about 1 %. It was mainly generated in the air column between the linac head and the phantom (3.65 %), the mirror (0.99 %), and the flattening filter (0.59 %) (for the depth of 1.0 mm and the field size of 10 x 10 cm2).

scholarly journals Metallized Carbon Nanotubes for Radiation Therapy Enhancement

2020 ◽  
Author(s):  
Sarah Ashmeg ◽  
Michael Fasullo ◽  
Edward Holupka ◽  
Eric Eisenbraun
Keyword(s):  
Carbon Nanotubes ◽  
Radiation Dose ◽  
External Beam Radiotherapy ◽  
Field Size ◽  
In Vivo Studies ◽  
Water Medium ◽  
Dose Enhancement ◽  
Energy Beam ◽  
Ion Chamber

Abstract Background: Carbon nanotubes have been the focus of many in-vitro and in-vivo studies where they serve as cargo delivery vehicles. In this preliminary work, multi-walled carbon nanotube were impregnated with copper, to study the effect of metallized carbon nanotubes on enhancing radiation dose in external beam radiotherapy.Methods: Using a 6x6x6 cm3 cube, filled with water or with water plus partially filled or unfilled carbon nanotubes, the dose enhancement effects of megavoltage photon beams were determined. Ion chamber readings were collected at 1 cm below the water cube. The beams were delivered from a TrueBeam Linac, at a 100 cm source to surface distance and 20x20cm2 field size. In addition, film measurements were taken just below the water cube (i.e. at 0 cm distance) and compared to the ion chamber dose enhancement at 1 cm below, for 6 MV energy beam.Results: For all studied photon energies, the ion chamber readings showed a dose increase when copper filled carbon nanotubes were added to the water medium. With copper filled CNTs concentration in water of 5 x 10-2 mg/ml, the measured dose enhancement ratios (DER) were 1.025, 1.016, 1.017, 1.011 and 1.013for 2.5MV, 6MV, 6MV FFF, 10MV and 10MV FFF energies, respectively. Furthermore, when copper filled MWCNTs are added to water, the film measurements (at 0 cm distance from the water cube) have also shown a dose enhancement ratio of 1.022 in comparison to 1.012 for ion chamber (1 cm away from the water cube). Conclusion: The results show an increase of the radiation dose enhancement, with a DER up to 1.025 at 1 cm below the studied medium, when metallized carbon nanotubes are added to water versus when the beam is delivered to just water. This increase in DER decreases with the increase of x-ray beam energy. It also decreases with increasing the distance of the point of measurement from the medium where the metalized carbon nanotubes were added.

Rheological studies of SBS/EVA blends modified with bio-based cashew nut shell liquid

2021 ◽  
pp. 009524432199040
Author(s):  
Isabela Pinto Ferreira ◽  
Alex da Silva Sirqueira ◽  
Taiane Andre dos Santos ◽  
Monica Feijo Naccache ◽  
Bluma Guenther Soares
Keyword(s):  
Ethylene Vinyl Acetate ◽  
Rheological Parameters ◽  
Creep Recovery ◽  
Cashew Nut Shell Liquid ◽  
Cashew Nut ◽  
Curve Fit ◽  
Significant Difference ◽  
Cashew Nut Shell ◽  
S Model ◽  
Styrene Butadiene

Research on bio-plasticizers is a topic of strategic interest in polymer blends. A bio-plasticizer, cashew nut shell liquid (CNSL), was studied in blends of ethylene-vinyl acetate copolymer (EVA) and styrene-butadiene-styrene copolymer (SBS). In the literature does not report the addition of plasticizers to SBS/EVA blend. Statistical analyses showed that there was a significant difference in mechanical properties (tension at break, hardness and elongation at break) vs. the unplasticized blend. The minimum CNSL concentration required for a statistical difference was 10 phr. The Carreau-Yasuda rheological model was used to obtain rheological parameters in these blends. The plasticizing influence of CNSL was confirmed by rheology. The effects of CNSL on creep and recovery were evaluated for the SBS/EBA blends. Burger´s model explained well SBS/EVA creep compliance. Moreover, its parameters (Newtonian dashpots and Hookean springs) were evaluated as a function of the CNSL concentrations. The bio-plasticizer concentration influenced significant correlations among the rheological creep-recovery tests, thus enabling a considerable increase in the elastic phase. Experimental creep-recovery data and curve fit were in good agreement.

scholarly journals Management of neuroblastoma: a study of first- and second-line chemotherapy responses, a single institution experience

2012 ◽  
Vol 6 (1) ◽  
pp. 3 ◽  
Author(s):  
Emmad E. Habib ◽  
Amr T. El-Kashef ◽  
Ezzat S. Fahmy
Keyword(s):  
External Beam Radiotherapy ◽  
Second Line ◽  
First Line ◽  
Actuarial Survival ◽  
Term Survival ◽  
Second Line Chemotherapy ◽  
Significant Difference ◽  
Grade Malignancy ◽  
Chemotherapy Patients ◽  
Line Chemotherapy

Neuroblastoma is a high-grade malignancy of childhood. It is chemo- and radio-sensitive but prone to relapse after initial remission. The aim of the current study was to study the results of the first- and second-line chemotherapy on the short-term response and long-term survival of children, and to further describe the side effects of treatment. Ninety-five children with advanced neuroblastoma were included in the study, divided into two groups according to the treatment strategy: 65 were treated by first-line chemotherapy alone, and 30 children who were not responding or relapsed after first-line chemotherapy were treated by second-line chemotherapy. External beam radiotherapy was given to bone and brain secondary cancers when detected. Staging workup was performed before, during and after management. Response was documented after surgery for the primary tumor. Median follow up was 32 months (range 24-60 months). Chemothe rapy was continued until toxicity or disease progression occurred, indicating interruption of chemotherapy. Patients received a maximum of 8 cycles. Toxicity was mainly myelo-suppression, with grade II-III severity in 60% of the firstline and 70% of the second-line chemotherapy patients. Median total actuarial survival was nearly 51 months for the first-line chemotherapy group and 30 months for the second-line line group, with a statistically significant difference between the two groups (P<0.01).

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.

Percentage depth dose fragmentation for investigating and assessing the photon beam dosimetry quality

2018 ◽  
Vol 18 (03) ◽  
pp. 280-284 ◽  
Author(s):  
Mohamed Bencheikh ◽  
Abdelmajid Maghnouj ◽  
Jaouad Tajmouati
Keyword(s):  
Exponential Decay ◽  
Target Volume ◽  
Photon Beam ◽  
Field Size ◽  
Photon Beams ◽  
Energy Agency ◽  
Percentage Depth Dose ◽  
Depth Dose ◽  
Beam Dosimetry

AbstractAimThe purpose of this study is to introduce a new approach to assess the dosimetry quality of photon beam with energy and irradiation field size. This approach is based on percentage depth dose (PDD) fragmentation for investigating the dosimetry quality.Materials and methodsFor the investigation of the dosimetry quality of 6 and 18 MV photon beams, we have proceeded to fragment the PDD at different field sizes. This approach checks the overall PDD and is not restricted to the exponential decay regions, as per the International Atomic Energy Agency Technical Reports Series No 398 and the American Association of Physicist in Medicine Task Group 51 recommendations.Results and discussionThe 6 MV photon beam deposited more energy in the target volume than the 18 MV photon beam. The dose delivered by the 6 MV beam is greater by a factor of 1·5 than that delivered by the 18 MV beam in the build-up region and the dose delivered by the 6 MV beam is greater by a factor of 2·6 than that delivered by the 18 MV beam in the electronic equilibrium and the exponential decay regions.ConclusionThe dose measured at different points of the beam is higher for 6 MV than for 18 MV photon beam. Therefore, the 6 MV beam is more dosimetrically efficient than the 18 MV beam. Using the proposed approach, we can assess the dosimetry quality by taking into account overall PDD not only in the exponential decay region but also in the field.

scholarly journals Evaluation of The Effectiveness and Side Effects of Radiotherapy in Patients With Primary Nervous System Lymphoma. A Single Center Experience

2020 ◽  
Vol 7 ◽  
Author(s):  
Timur Koca ◽  
Aylin Fidan Korcum ◽  
Yasemin Şengün ◽  
Melek Gamze Aksu ◽  
Mine Genç
Keyword(s):  
Central Nervous System ◽  
Overall Survival ◽  
Nervous System ◽  
Side Effects ◽  
Disease Free Survival ◽  
Central Nervous System Lymphoma ◽  
Field Size ◽  
High Dose ◽  
Free Survival ◽  
Significant Difference

Aim: In this study, we aimed to evaluate the overall and progression-free survival, the radiotherapy process and the early and late adverse effects in patients who underwent radiotherapy (RT) for primary nervous system lymphoma in our clinic.Method: Between January 2010 and September 2019, 16 patients who received radiotherapy due to primary central nervous system lymphoma in our clinic were examined according to their statistically significant differences in terms of survival and side effects.Results: The median disease-free survival of the patients was 6 months, and the median overall survival was 12.5 months. 18.75% of the patients could not receive chemotherapy but only radiotherapy. Radiotherapy doses were range from 2600 to 5000 cGy. When patients were evaluated in terms of radiotherapy dose, field size and chemotherapy, no statistically significant difference in overall survival was detected. Cognitive disorders were observed as the most common late side effects while the most common acute side effects in patients were headaches.Conclusion: In the treatment of primary central nervous system lymphoma, changes in radiotherapy portals and radiotherapy doses can be predicted in patients who received high-dose methotrexate chemotherapy or not. Furthermore, it has been considered that more comprehensive studies are needed to increase the success of treatment and provide standardization in treatment, especially in patients with elderly and comorbid diseases.

scholarly journals Dosimetric Characterization of Small Radiotherapy Electron Beams Collimated by Circular Applicators with the New Microsilicon Detector

2022 ◽  
Vol 12 (2) ◽  
pp. 600
Author(s):  
Serenella Russo ◽  
Silvia Bettarini ◽  
Barbara Grilli Leonulli ◽  
Marco Esposito ◽  
Paolo Alpi ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Electron Beams ◽  
High Energy ◽  
Field Size ◽  
The Novel ◽  
Linear Accelerators ◽  
Depth Dose ◽  
Dosimetric Data ◽  
Output Factors ◽  
Dose Measurements

High-energy small electron beams, generated by linear accelerators, are used for radiotherapy of localized superficial tumours. The aim of the present study is to assess the dosimetric performance under small radiation therapy electron beams of the novel PTW microSilicon detector compared to other available dosimeters. Relative dose measurements of circular fields with 20, 30, 40, and 50 mm aperture diameters were performed for electron beams generated by an Elekta Synergy linac, with energy between 4 and 12 MeV. Percentage depth dose, transverse profiles, and output factors, normalized to the 10 × 10 cm2 reference field, were measured. All dosimetric data were collected in a PTW MP3 motorized water phantom, at SSD of 100 cm, by using the novel PTW microSilicon detector. The PTW diode E and the PTW microDiamond were also used in all beam apertures for benchmarking. Data for the biggest field size were also measured by the PTW Advanced Markus ionization chamber. Measurements performed by the microSilicon are in good agreement with the reference values for all the tubular applicators and beam energies within the stated uncertainties. This confirms the reliability of the microSilicon detector for relative dosimetry of small radiation therapy electron beams collimated by circular applicators.

scholarly journals Commissioning Measurements of Electron Beam Using Montecarlo Algorithm on Truebeam STx® and Compariaon with Clinac iX Linear Accelerator

2021 ◽  
Vol 229 ◽  
pp. 01041
Author(s):  
Kamal Saidi ◽  
Redouane El Baydaoui ◽  
Hanae El Gouach ◽  
Othmane Kaanouch ◽  
Mohamed Reda Mesradi
Keyword(s):  
Electron Beam ◽  
Electron Beams ◽  
Measured Data ◽  
University Hospital ◽  
Field Size ◽  
Large Field ◽  
Water Phantom ◽  
Depth Dose ◽  
International University ◽  
The Absolute

TrueBeam STx latest generation linear accelerators (linacs) installed at Sheikh Khalifa International University Hospital in Casablanca, Morocco. The aim of this is to present and compare the result of the Electron commissioning measurement on TrueBeam Stx and clinac iX installed at Sheikh Khalifa International University Hospital in Casablanca, Morocco. A compariaon of eMC calculations and measurements for TrueBeam Stx were evaluated. Dosimetric parameters are systematically measured using a large water phantom 3D scanning system MP3 Water Phantom (PTW, Freiburg, Germany). The data of the electron beams commissioning including depth dose curves for each applicator, depth dose curves without applicator and the profile in air for a large field size 40x 40cm2, and the Absolute Dose (cGy/MU) for each applicator. All the data were examined and compared for five electron beams (E6MeV, E9MeV, E12MeV, E16MeV and E20MeV) of Varian’s TrueBeam STx and Clinac iX machines. A comparison, between measurement PDDs and calculated by the Eclipse electron Monte Carlo (eMC) algorithm were performed to validate Truebeam Stx commissioning. All this measurements were performed with a Roos and Markus plane parallel chamber. Our measured data indicated that electron beam PDDs from the TrueBeam Stx machine are well matched to those from our Varian Clinac iX machine. Significant differences between TrueBeam and Clinac iX were found in in‐air profiles and open field output. Maximum depth dose for the TrueBeam Stx and Clinac iX for the following energies (6, 9, 12, 16, 20 MeV) are respectively (1.15; 1.89; 2.6; 3.1; and 2.35) and (1.24; 1.95; 2.70; 2.99 and 2.4cm). For the TrueBeam Stx and Clinac iX the quality index R50 for applicator 15x15 cm2 are in the tolerance intervals. Surface dose increases by increasing energy for both machines. The Absolute Dose (cGy/MU) calibrated for both machine in Dmax at 1cGy/MU for the reference field size cone 15x15 cm2. Bremsstrahlung tail Rp per energy levels as follows for the TrueBeam Stx : 6 MeV – 2.85 cm, 9 MeV – 4.28 cm, 12 MeV – 5.97 cm, 16 MeV – 7.88 cm and 20 MeV – 9.86 cm. and for the Clinac iX : 6 MeV – 2.86 cm, 9 MeV – 4.32 cm, 12 MeV – 5.96 cm, 16 MeV – 7.93 cm and 20 MeV – 10.08 cm. A good agreement between modeled and measured data is observed.

The Prevalence of Injuries among Pianists in Music Schools in Ireland

2000 ◽  
Vol 15 (4) ◽  
pp. 155-160
Author(s):  
Nora Shields ◽  
Sara Dockrell
Keyword(s):  
Risk Factors ◽  
Prevention Programs ◽  
Predisposing Factors ◽  
Lifetime Prevalence ◽  
Music Schools ◽  
Effective Prevention ◽  
Common Location ◽  
Significant Difference ◽  
Piano Playing

The purpose of this study was to determine the prevalence of injuries among pianists in music schools in Ireland. The main objectives of the study were to investigate the anatomical locations of these injuries, the most commonly reported symptoms, and possible risk factors for the development of playing-related injuries. A hand-delivered questionnaire was distributed to 182 students from seven participating music schools. The lifetime prevalence for a playing-related injury, which prevented piano playing for a period of 48 hours or longer, was 25.8%. The wrist was the most common location of injury (36.6%). Pain was the most commonly reported symptom among the respondents. No statistically significant difference in the rate of injury was found between the genders. It was concluded that further research is required into the prevalence of injury and to the predisposing factors of injury so that effective prevention programs can be put in place.

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