Monte carlo method
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Autoři uvádějí použití metody Monte Carlo při výpočtu absorbované dávky vysokoenergetického fotonového záření při rádioterapii tkáně s kovovým materiálem. Byly použity dva materiály - železo a titan a dvě energie záření - 6 MV a 16 MV. Zvýšení dávky na proximalnim rozhraní voda-kov, způsobeném zpětným rozptylem, je maximálně 30 % a prudce Idesá se vzdáleností od rozhraní. Kromě kombinace vysoké energie a železného materiálu je ve všech ostatních případech za kovovým materiálem zřetelný stín. Vyšší energie vykazuje menší inhomogenitu dávky. Jelikož je možno tuto relativně mírnou a objemově značně omezenou nehomogenitu několika způsoby dále zmenšit, je možno indikovanou rádioterapii v podobných případech aplikovat s minimálním rizikem.
The authors applied the Monte Carlo method for the calculation of the absorbed dose of high-energy photon beam in tissue with metal material. Two materials were used - iron and titanium - and two beam energies - 6 MV and 16 MV. The dose elevation at the proximal junction water-metal is 30% at most and drops sharply within a few proximal millimetres. Except iron and high energy beam, the dose shadow developed in all other combinations. The calculated dose inhomogeneity, rather mild and limited in volume, can be further decreased by various means. The risk of properly indicated radiotherapy is therefore minimal in similar circumstances.
- MeSH
- celková dávka radioterapie metody MeSH
- kovy MeSH
- lidé středního věku MeSH
- lidé MeSH
- metoda Monte Carlo MeSH
- pacienti MeSH
- protézy a implantáty MeSH
- Check Tag
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- Publikační typ
- kazuistiky MeSH
1st ed. xvii, 486 s., grafy, tab.
- MeSH
- dávka záření * MeSH
- fantomy radiodiagnostické MeSH
- hodnotící studie jako téma MeSH
- hygiena práce MeSH
- ionizující záření MeSH
- lidé MeSH
- metoda Monte Carlo MeSH
- monitorování radiace MeSH
- nemoci štítné žlázy * MeSH
- nukleární lékařství - oddělení nemocnice MeSH
- pacienti * MeSH
- personál nemocniční MeSH
- radiační ochrana MeSH
- radioizotopy jodu škodlivé účinky toxicita účinky záření MeSH
- statistika jako téma MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- kongresy MeSH
- práce podpořená grantem MeSH
Quantitative structure - activity relationships (QSARs) for the pIC50 (binding affinity) of gamma-secretase inhibitors can be constructed with the Monte Carlo method using CORAL software (http://www.insilico.eu/coral). The considerable influence of the presence of rings of various types with respect to the above endpoint has been detected. The mechanistic interpretation and the domain of applicability of the QSARs are discussed. Methods to select new potential gamma-secretase inhibitors are suggested.
- MeSH
- Alzheimerova nemoc farmakoterapie MeSH
- kvantitativní vztahy mezi strukturou a aktivitou MeSH
- lidé MeSH
- metoda Monte Carlo MeSH
- objevování léků metody MeSH
- sekretasy * antagonisté a inhibitory chemie metabolismus MeSH
- software MeSH
- výpočetní biologie metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The presence of artificial implants complicates the delivery of proton therapy due to inaccurate characterization of both the implant and the surrounding tissues. In this work, we describe a method to characterize implant and human tissue mimicking materials in terms of relative stopping power (RSP) using a novel proton counting detector. Each proton is tracked by directly measuring the deposited energy along the proton track using a fast, pixelated spectral detector AdvaPIX-TPX3 (TPX3). We considered three scenarios to characterize the RSPs. First, in-air measurements were made in the presence of metal rods (Al, Ti and CoCr) and bone. Then, measurements of energy perturbations in the presence of metal implants and bone in an anthropomorphic phantom were performed. Finally, sampling of cumulative stopping power (CSP) of the phantom were made at different locations of the anthropomorphic phantom. CSP and RSP information were extracted from energy spectra at each beam path. To quantify the RSP of metal rods we used the shift in the most probable energy (MPE) of CSP from the reference CSP without a rod. Overall, the RSPs were determined as 1.48, 2.06, 3.08, and 5.53 from in-air measurements; 1.44, 1.97, 2.98, and 5.44 from in-phantom measurements, for bone, Al, Ti and CoCr, respectively. Additionally, we sampled CSP for multiple paths of the anthropomorphic phantom ranging from 18.63 to 25.23 cm deriving RSP of soft tissues and bones in agreement within 1.6% of TOPAS simulations. Using minimum error of these multiple CSP, optimal mass densities were derived for soft tissue and bone and they are within 1% of vendor-provided nominal densities. The preliminary data obtained indicates the proposed novel method can be used for the validation of material and density maps, required by proton Monte Carlo Dose calculation, provided by competing multi-energy computed tomography and metal artifact reduction techniques.
- MeSH
- fantomy radiodiagnostické * MeSH
- lidé MeSH
- metoda Monte Carlo * MeSH
- protézy a implantáty * MeSH
- protonová terapie přístrojové vybavení MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
An international intercomparison was organized by Working Group 7, Internal Dosimetry, of the European Radiation Dosimetry Group in collaboration with Working Group 6, Computational Dosimetry, for measurement and Monte Carlo simulation of Am in three skull phantoms. The main objectives of this combined exercise were (1) comparison of the results of counting efficiency in fixed positions over each head phantom using different germanium detector systems, (2) calculation of the activity of Am in the skulls, (3) comparison of Monte Carlo simulations with measurements (spectrum and counting efficiency), and (4) comparison of phantom performance. This initiative collected knowledge on equipment, detector arrangements, calibration procedures, and phantoms used around the world for in vivo monitoring of Am in exposed persons, as well as on the Monte Carlo skills and tools of participants. Three skull phantoms (BfS, USTUR, and CSR phantoms) were transported from Europe (10 laboratories) to North America (United States and Canada). The BfS skull was fabricated with real human bone artificially labeled with Am. The USTUR skull phantom was made from the US Transuranium and Uranium Registries whole-body donor (case 0102) who was contaminated due to an occupational intake of Am; one-half of the skull corresponds to real contaminated bone, the other half is real human bone from a noncontaminated person. Finally, the CSR phantom was fabricated as a simple hemisphere of equivalent bone and tissue material. The three phantoms differ in weight, size, and shape, which made them suitable for an efficiency study. Based on their own skull calibration, the participants calculated the activity in the three European Radiation Dosimetry Group head phantoms. The Monte Carlo intercomparison was organized in parallel with the measurement exercise using the voxel representations of the three physical phantoms; there were 16 participants. Three tasks were identified with increasing difficulty: (1) Monte Carlo simulation of the simple CSR hemisphere and the Helmholz Zentrum München high-purity germanium detector for calculating the counting efficiency for the 59.54 keV photons of Am, in established measurement geometry; (2) Monte Carlo simulation of particular measurement geometries using the BfS and USTUR voxel phantoms and the Helmholz Zentrum München high-purity germanium detector detector; and (3) application of Monte Carlo methodology to calculate the calibration factor of each participant for the detector system and counting geometry (single or multidetector arrangement) to be used for monitoring a person in each in vivo facility, using complex skull phantoms. The results of both exercises resulted in the conclusion that none of the three available head phantoms is appropriate as a reference phantom for the calibration of germanium detection systems for measuring Am in exposed adult persons. The main reasons for this are: (1) lack of homogeneous activity distribution in the bone material, or (2) inadequate shape/size for simulating an adult skull. Good agreement was found between Monte Carlo results and measurements, which supports Monte Carlo calibration of body counters as an alternative method when appropriate physical phantoms are not available and the detector and source are well known.
- MeSH
- algoritmy MeSH
- americium analýza MeSH
- dospělí MeSH
- fantomy radiodiagnostické * MeSH
- lebka účinky záření MeSH
- lidé MeSH
- metoda Monte Carlo * MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
- Geografické názvy
- Evropa MeSH
- Severní Amerika MeSH
NASA has encouraged studies on 226Ra deposition in the human brain to investigate the effects of exposure to alpha particles with high linear energy transfer, which could mimic some of the exposure astronauts face during space travel. However, this approach was criticized, noting that radium is a bone-seeker and accumulates in the skull, which means that the radiation dose from alpha particles emitted by 226Ra would be heavily concentrated in areas close to cranial bones rather than uniformly distributed throughout the brain. In the high background radiation areas of Ramsar, Iran, extremely high levels of 226Ra in soil contribute to a large proportion of the inhabitants' radiation exposure. A prospective study on Ramsar residents with a calcium-rich diet was conducted to improve the dose uniformity due to 226Ra throughout the cerebral and cerebellar parenchyma. The study found that exposure of the human brain to alpha particles did not significantly affect working memory but was significantly associated with increased reaction times. This finding is crucial because astronauts on deep space missions may face similar cognitive impairments due to exposure to high charge and energy particles. The current study was aimed to evaluate the validity of the terrestrial model using the Geant4 Monte Carlo toolkit to simulate the interactions of alpha particles and representative cosmic ray particles, acknowledging that these radiation types are only a subset of the complete space radiation environment.
- MeSH
- DNA MeSH
- lidé MeSH
- lineární přenos energie MeSH
- metoda Monte Carlo MeSH
- mozek MeSH
- prospektivní studie MeSH
- radium * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
By optimization of so-called correlation weights of attributes of simplified molecular input-line entry system (SMILES) quantitative structure - activity relationships (QSAR) for toxicity towards Pimephales promelas are established. A new SMILES attribute has been utilized in this work. This attribute is a molecular descriptor, which reflects (i) presence of different kinds of bonds (double, triple, and stereo chemical bonds); (ii) presence of nitrogen, oxygen, sulphur, and phosphorus atoms; and (iii) presence of fluorine, chlorine, bromine, and iodine atoms. The statistical characteristics of the best model are the following: n=226, r(2)=0.7630, RMSE=0.654 (training set); n=114, r(2)=0.7024, RMSE=0.766 (calibration set); n=226, r(2)=0.6292, RMSE=0.870 (validation set). A new criterion to select a preferable split into the training and validation sets are suggested and discussed.
PURPOSE: The Geant4 Monte Carlo simulation toolkit was used to reproduce radiobiological parameters measured by irradiating three different cancerous cell lines with monochromatic and clinical proton beams. METHODS: The experimental set-up adopted for irradiations was fully simulated with a dedicated open-source Geant4 application. Cells survival fractions was calculated coupling the Geant4 simulations with two analytical radiobiological models: one based on the LEM (Local Effect Model) approach and the other on a semi-empirical parameterisation. Results was evaluated and compared with experimental data. RESULTS AND CONCLUSIONS: The results demonstrated the Geant4 ability to reproduce radiobiological quantities for different cell lines.
In this paper, three Monte Carlo codes were tested for electron transport in various materials. MCNPX (version 2.4.0), Penelope (version 2003) and EGSnrc codes were used for modeling simple problems. These problems were focused on bremsstrahlung, energy deposition in matter, electron ranges and production of secondary electrons by gamma radiation. The electrons were primary particles, except in the last exercise, where photons were used. Various materials, e.g., water, lead and tungsten were used. The energy of the primary particles was within the energy range from 20 to 450 keV. The simulation results were compared with each other.
