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Monte carlo dose calculation

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https://www.readbyqxmd.com/read/30326386/dietary-intake-of-4-nonylphenol-and-bisphenol-a-in-taiwanese-population-integrated-risk-assessment-based-on-probabilistic-and-sensitive-approach
#1
Wei-Hsiang Chang, Shou-Chun Liu, Hsiu-Ling Chen, Ching-Chang Lee
4-Nonylphenol (NP) and bisphenol A (BPA) are high-production and high-volume chemicals used to manufacture various commercial products. They are also ubiquitous contaminants that disrupt endocrine systems in wildlife and humans. We collected, from Taiwan cities with the highest food production, and analyzed, using high performance liquid chromatography tandem mass spectrometry (HPLC/MS/MS), 278 food samples for NP and BPA from 11 categories. We found background levels of 100% for NP and 72% for BPA in total samples...
October 10, 2018: Environmental Pollution
https://www.readbyqxmd.com/read/30320027/the-influence-of-brass-compensator-thickness-and-field-size-on-neutron-contamination-spectrum-in-18mv-elekta-sl-75-25-medical-linear-accelerator-with-and-without-flattening-filter-a-monte-carlo-study
#2
A S Talebi, M Maleki, P Hejazi, M Jadidi, R Ghorbani
Background: One of the most significant Intensity Modulated Radiation Therapy treatment benefits is a high target to normal tissue dose ratio. To improve this advantage, an additional accessory such as a compensator is used to deliver doses. Compensator-based IMRT treatment is usually operated with an energy higher than 10 MV. Photoneutrons, which have high linear energy transfer and radiobiological effectiveness, are produced by colliding high-energy photon beams with linear accelerator structures, then they deliver the unwanted doses to patients and staff...
September 2018: Journal of Biomedical Physics & Engineering
https://www.readbyqxmd.com/read/30320026/evaluation-of-aaa-and-xvmc-algorithms-for-dose-calculation-in-lung-equivalent-heterogeneity-in-photon-fields-a-comparison-of-calculated-results-with-measurements
#3
N Singh, N K Painuly, L N Chaudhari, A Chairmadurai, T Verma, D Shrotiya, C P Bhatt
Aims: The aims of the present work are (1) to evaluate dose calculation accuracy of two commonly used algorithms for 15 MV small photon fields in a medium encompassing heterogeneity and (2) to compare them with measured results obtained from gafchromic film EBT2. Materials and Methods: Authors employed kailwood (Pinus Wallichiana) to mimic lung. Briefly, seven Kailwood plates, each measuring 25x25 cm2 of varying thicknesses totaling 13 cm equivalent to the mean thickness of an adult human lung, were sandwiched between 5 cm tissue equivalent material from top and 10 cm below...
September 2018: Journal of Biomedical Physics & Engineering
https://www.readbyqxmd.com/read/30315873/dvh-based-inverse-planning-using-monte-carlo-dosimetry-for-ldr-prostate-brachytherapy
#4
Konstantinos A Mountris, Dimitris Visvikis, Julien Bert
PURPOSE: Inverse planning is an integral part of modern low-dose-rate (LDR) brachytherapy. Current clinical planning systems do not exploit the total dose information and largely use the AAPM TG-43 dosimetry formalism to ensure clinically acceptable planning times. Thus, sub-optimal plans may be derived due to TG-43-related dose overestimation and non-conformity with dose distribution requirements. The purpose of this study was to propose an inverse planning approach that can improve planning quality by combining dose-volume information and precision without compromising the overall execution times...
October 10, 2018: International Journal of Radiation Oncology, Biology, Physics
https://www.readbyqxmd.com/read/30314732/normalized-glandular-dose-coefficients-in-mammography-digital-breast-tomosynthesis-and-dedicated-breast-ct
#5
A Sarno, G Mettivier, F Di Lillo, R M Tucciariello, K Bliznakova, P Russo
PURPOSE: To provide mean glandular dose (MGD) estimates via Monte Carlo (MC) simulations as a function of the breast models and scan parameters in mammography, digital breast tomosynthesis (DBT) and dedicated breast CT (BCT). METHODS: The MC code was based on GEANT4 toolkit. The simulated compressed breast was either a cylinder with a semi-circular section or ad hoc shaped for oblique view (MLO). In DBT we studied the influence of breast models and exam parameters on the T-factors (i...
October 9, 2018: Physica Medica: PM
https://www.readbyqxmd.com/read/30311639/implementation-of-planar-proton-minibeam-radiation-therapy-using-a-pencil-beam-scanning-system-a-proof-of-concept-study
#6
Ludovic De Marzi, Annalisa Patriarca, Catherine Nauraye, Eric Hierso, Rémi Dendale, Consuelo Guardiola, Yolanda Prezado
PURPOSE: Proton minibeam radiation therapy (pMBRT) is an innovative approach that combines the advantages of minibeam radiation therapy with the more precise ballistics of protons to further reduce the side effects of radiation. One of the main challenges of this approach is the generation of very narrow proton pencil beams with an adequate dose-rate to treat patients within a reasonable treatment time (several minutes) in existing clinical facilities. The aim of this study was to demonstrate the feasibility of implementing pMBRT by combining the pencil beam scanning (PBS) technique with the use of multislit collimators...
September 22, 2018: Medical Physics
https://www.readbyqxmd.com/read/30310294/integrated-pharmacokinetic-pharmacodynamic-modeling-to-evaluate-empiric-carbapenem-therapy-in-bloodstream-infections
#7
Tze-Peng Lim, Reyna Wang, Gang Quan Poh, Tse-Hsien Koh, Thean-Yen Tan, Winnie Lee, Jocelyn Qi-Min Teo, Yiying Cai, Thuan-Tong Tan, Pui Lai Rachel Ee, Andrea L Kwa
Objectives: Treatment for nosocomial bloodstream infections (BSI) caused by multidrug-resistant (MDR) Gram-negative bacteria (GNB) is challenging. Rising antimicrobial resistance, especially in extended spectrum beta-lactamase production, inadvertently increases empiric carbapenem consumption. Three antipseudomonal carbapenems (imipenem, meropenem [MER], and doripenem [DOR]) are available commercially against MDR GNB in Singapore. The study aims to determine the most optimal empiric carbapenem dosing regimens (CDR) and evaluate their cost-effectiveness for GNB-BSI in the face of increasing MDR GNB...
2018: Infection and Drug Resistance
https://www.readbyqxmd.com/read/30305777/optimization-of-variance-reduction-techniques-used-in-egsnrc-monte-carlo-codes
#8
Sangeetha Shanmugasundaram, Sureka Chandrasekaran
Monte Carlo (MC) simulations are often used in calculations of radiation transport to enable accurate prediction of radiation-dose, even though the computation is relatively time-consuming. In a typical MC simulation, significant computation time is allocated to following non-important events. To address this issue, variance reduction techniques (VRTs) have been suggested for reducing the statistical variance for the same computation time. Among the available MC simulation codes, electron gamma shower (National Research Council of Canada) (EGSnrc) is a general-purpose coupled electron-photon transport code that also features an even-handed, rich set of VRTs...
July 2018: Journal of Medical Physics
https://www.readbyqxmd.com/read/30305773/comparison-of-measured-and-monte-carlo-calculated-dose-distributions-from-indigenously-developed-6-mv-flattening-filter-free-medical-linear-accelerator
#9
Bibekananda Mishra, Subhalaxmi Mishra, T Palani Selvam, S T Chavan, S N Pethe
Purpose: Monte Carlo simulation was carried out for a 6 MV flattening filter-free (FFF) indigenously developed linear accelerator (linac) using the BEAMnrc user-code of the EGSnrc code system. The model was benchmarked against the measurements. A Gaussian distributed electron beam of kinetic energy 6.2 MeV with full-width half maximum of 1 mm was used in this study. Methods: The simulation of indigenously developed linac unit has been carried out by using the Monte Carlo-based BEAMnrc user-code of the EGSnrc code system...
July 2018: Journal of Medical Physics
https://www.readbyqxmd.com/read/30295950/validation-and-application-of-a-fast-monte-carlo-algorithm-for-assessing-the-clinical-impact-of-approximations-in-analytical-dose-calculations-for-pencil-beam-scanning-proton-therapy
#10
Sheng Huang, Kevin Souris, Siyang Li, Minglei Kang, Ana Maria Barragan Montero, Guillaume Janssens, Alexander Lin, Elizabeth Garver, Christopher Ainsley, Paige Taylor, Ying Xiao, Liyong Lin
PURPOSE: Monte Carlo (MC) dose calculation is generally superior to analytical dose calculation (ADC) used in commercial TPS to model the dose distribution especially for heterogeneous sites, such as lung and head/neck patients. The purpose of this study is to provide a validated, fast and open-source MC code, MCsquare, to assess the impact of approximations in ADC on clinical pencil beam scanning (PBS) plans covering various sites. METHODS: First, MCsquare was validated using tissue-mimicking IROC lung phantom measurements as well as benchmarked with the general-purpose Monte Carlo TOPAS for patient dose calculation...
October 8, 2018: Medical Physics
https://www.readbyqxmd.com/read/30294066/irradiation-effects-in-monazite-ce-and-zircon-raman-and-photoluminescence-study-of-au-irradiated-fib-foils
#11
Lutz Nasdala, Shavkat Akhmadaliev, Andreas Artac, Chutimun Chanmuang N, Gerlinde Habler, Christoph Lenz
Lamellae of 1.5 µm thickness, prepared from well-crystallised monazite-(Ce) and zircon samples using the focused-ion-beam technique, were subjected to triple irradiation with 1 MeV Au+ ions (15.6% of the respective total fluence), 4 MeV Au2+ ions (21.9%) and 10 MeV Au3+ ions (62.5%). Total irradiation fluences were varied in the range 4.5 × 1012  - 1.2 × 1014 ions/cm2 . The highest fluence resulted in amorphisation of both minerals; all other irradiations (i.e. up to 4.5 × 1013 ions/cm2 ) resulted in moderate to severe damage...
2018: Physics and Chemistry of Minerals
https://www.readbyqxmd.com/read/30292957/simulating-the-radial-dose-distribution-for-charged-particles-in-water-medium-by-a-semi-empirical-model-an-analytical-approach
#12
E M Awad, I El Masady, Y S Rammah, M Abu-Shady
A computational semi-empirical model based on electronic radiation damage to medium has been presented to simulate the radial dose distribution. An analytical approach was used to calculate the deposited energy in water per unit mass within a cylindrical shell of unit length around the ion path at a radial distance between r and r + dr, the so-called radial dose distribution, RDD. Detail steps were given and the final radial dose integration over the electron range between Rmin and Rmax was solved numerically using the Mid-Point Method...
September 26, 2018: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/30291717/a-five-compartment-biokinetic-model-for-90y-dotatoc-therapy
#13
Marija Z Jeremic, Milovan D Matovic, Dragana Z Krstic, Suzana B Pantovic, Dragoslav R Nikezic
PURPOSE: Neuroendocrine tumours (NETs) are now routinely treated by radiopeptide targeted therapy using somatostatin receptor-binding peptides such as 90 Y- and 177 Lu-DOTATOC. The objective of this work was to develop a biokinetics model of 90 Y labelled DOTATOC, which is applied in the therapy of NETs in order to estimate doses in kidney and tumour. METHODS: A multi-compartment model described by two sets of differential equations, one set for the actual thirty-minutes infusion and the other set for the post-infusion period was developed and activities were measured by liquid scintillation counting in blood (compartment 1) and the urine (compartment 3)...
October 6, 2018: Medical Physics
https://www.readbyqxmd.com/read/30287930/fast-robust-dose-calculation-on-gpu-for-high-precision-1-h-4-he-12-c-and-16-o-ion-therapy-the-frog-platform
#14
Stewart Mein, Kyungdon Choi, Benedikt Kopp, Thomas Tessonnier, Julia Bauer, Alfredo Ferrari, Thomas Haberer, Jürgen Debus, Amir Abdollahi, Andrea Mairani
Radiotherapy with protons and heavier ions landmarks a novel era in the field of high-precision cancer therapy. To identify patients most benefiting from this technologically demanding therapy, fast assessment of comparative treatment plans utilizing different ion species is urgently needed. Moreover, to overcome uncertainties of actual in-vivo physical dose distribution and biological effects elicited by different radiation qualities, development of a reliable high-throughput algorithm is required. To this end, we engineered a unique graphics processing unit (GPU) based software architecture allowing rapid and robust dose calculation...
October 4, 2018: Scientific Reports
https://www.readbyqxmd.com/read/30281330/the-potential-impact-of-ultrathin-filter-design-on-dosimetry-and-relative-biological-effectiveness-in-modern-image-guided-small-animal-irradiators
#15
Yannick Poirier, Christopher Daniel Johnstone, Charles Kirkby
OBJECTIVE: Modern image-guided small animal irradiators like the Xstrahl Small Animal Radiation Research Platform (SARRP) are designed with ultrathin 0.15  mm Cu filters, which compared with more heavily filtrated traditional cabinet-style biological irradiators, produce X-ray spectra weighted toward lower energies, impacting the dosimetric properties and the relative biological effectiveness (RBE). This study quantifies the effect of ultrathin filter design on relative depth dose profiles, absolute dose output, and RBE using Monte Carlo techniques...
October 3, 2018: British Journal of Radiology
https://www.readbyqxmd.com/read/30278982/monte-carlo-dose-verification-of-vmat-treatment-plans-using-elekta-agility-160-leaf-mlc
#16
Ryota Onizuka, Fujio Araki, Takeshi Ohno
In this study, we verified volumetric modulated arc therapy (VMAT) plans in an Elekta Synergy system with an integrated Agility 160-leaf multileaf collimator (MLC) by comparing them with Monte Carlo (MC)-calculated dose distributions using the AAPM TG-119 structure sets. The head configuration of the linear accelerator with the integrated MLC was simulated with the EGSnrc/BEAMnrc code. Firstly, the dosimetric properties of the MLC were evaluated with the MC technique and film measurements. Next, VMAT plans were created with the Pinnacle3 treatment planning system (TPS) for four regions in the AAPM TG-119 structures...
July 2018: Physica Medica: PM
https://www.readbyqxmd.com/read/30277221/peripheral-dose-around-a-mobile-linac-for-intraoperative-radiotherapy-radiation-protection-aspects
#17
Francisco García-Cases, Jose Perez-Calatayud, Facundo Ballester, Javier Vijande, Domingo Granero
The aim of this work is to analyse the scattered radiation produced by the mobile accelerator Mobetron 1000. To do so, detailed Monte Carlo simulations using two different codes, Penelope2008 and Geant4, were performed. Measurements were also done.
 To quantify the attenuation due to the internal structures, present in the accelerator head, on the scattered radiation produced, some of the main structural shielding in the Mobetron 1000 has been incorporated into the geometry simulation.
 Results are compared with measurements...
October 2, 2018: Journal of Radiological Protection: Official Journal of the Society for Radiological Protection
https://www.readbyqxmd.com/read/30273996/monte-carlo-and-60-co-based-kilovoltage-x-ray-dosimetry-methods
#18
Michael J Lawless, Lianna Dimaso, Benjamin Palmer, John Micka, Wesley S Culberson, Larry A DeWerd
PURPOSE: This work seeks to investigate new methods to determine the absorbed dose to water from kilovoltage x-rays. Current methods are based on measurements in-air and rely on correction factors in order to account for differences between the photon spectrum in air and at depth in phantom, between the photon spectra of the calibration beam and the beam of interest, or in the radiation absorption properties of air and water. This work aims to determine the absorbed dose to water in the NIST-matched x-ray beams at the University of Wisconsin Accredited Dosimetry Calibration Laboratory (UWADCL)...
October 1, 2018: Medical Physics
https://www.readbyqxmd.com/read/30272222/analytical-model-to-estimate-equivalent-dose-from-internal-neutrons-in-proton-therapy-of-children-with-intracranial-tumors
#19
Kyle J Gallagher, Phillip J Taddei
This study developed a computationally efficient and easy-to-implement analytical model to estimate the equivalent dose from secondary neutrons originating in the bodies ('internal neutrons') of children receiving intracranial proton radiotherapy. A two-term double-Gaussian mathematical model was fit to previously published internal neutron equivalent dose per therapeutic absorbed dose versus distance from the field edge calculated using Monte Carlo simulations. The model was trained using three intracranial proton fields of a 9-year-old girl...
October 1, 2018: Radiation Protection Dosimetry
https://www.readbyqxmd.com/read/30260003/technical-note-experimental-verification-of-egsnrc-calculated-depth-dose-within-a-parallel-magnetic-field-in-a-lung-phantom
#20
Andrei Ghila, B Gino Fallone, Satyapal Rathee
PURPOSE: The calculation of depth doses from a 6 MV photon beam in polystyrene using EGSnrc Monte Carlo, within a parallel magnetic field, has been previously verified against measured data. The current work experimentally investigates the accuracy of EGSnrc calculated depth doses in lung within the same parallel magnetic field. METHODS: Two cylindrical bore electromagnets produced a magnetic field parallel to the central axis of a Varian Silhouette beam. A Gammex lung phantom was used, along with a parallel plate ion chamber, for the depth dose measurements...
September 27, 2018: Medical Physics
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