Monte Carlo simulation
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- 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
When a patient is examined by positron emission tomography (PET), radiotracer dose amount (activity) has to be determined. However, the rules for activity correction according to patients' weight used nowadays do not correspond with practical experience. Very high image quality is achieved for slim patients, whereas noisy images are produced for obese patients. There is opportunity to modify the correction rule with the aim to equalize image quality within the broad spectrum of patients and to diminish radiation risk to slim patients, with special importance for children. We have built a model of a particular PET scanner and approximated human trunk, which is our region of interest, by a cylindrical model with segments of liver, outer adipose tissue, and the rest. We have performed Monte Carlo simulations of PET imaging using the GATE simulation package. Under reasonably simplifying assumptions and for special parameters, we have developed curves that recommend amount of injected activity based on body parameters to give PET images of constant quality, the quality being expressed in terms of noise equivalent counts. The dependence qualitatively differs from the rules used in clinical practice nowadays, and the results indicate potential for improvement.
- MeSH
- biologické modely MeSH
- dávka záření * MeSH
- fantomy radiodiagnostické MeSH
- index tělesné hmotnosti MeSH
- lidé MeSH
- metoda Monte Carlo * MeSH
- počítačová rentgenová tomografie MeSH
- počítačová simulace MeSH
- počítačové zpracování obrazu MeSH
- pozitronová emisní tomografie metody MeSH
- radioaktivní indikátory MeSH
- trup fyziologie radiografie MeSH
- velikost těla fyziologie MeSH
- výpočet dávky léku * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
BACKGROUND: In-vivo monitoring methods of carbon ion radiotherapy (CIRT) includes explorations of nuclear reaction products generated by carbon-ion beams interacting with patient tissues. Our research group focuses on in-vivo monitoring of CIRT using silicon pixel detectors. Currently, we are conducting a prospective clinical trial as part of the In-Vivo Monitoring project (InViMo) at the Heidelberg Ion Beam Therapy Center (HIT) in Germany. We are using an innovative, in-house developed, non-contact fragment tracking system with seven mini-trackers based on the Timepix3 technology developed at CERN. PURPOSE: This article focuses on the implementation of the mini-tracker in Monte Carlo (MC) based on FLUKA simulations to monitor secondary charged nuclear fragments in CIRT. The main objective is to systematically evaluate the simulation accuracy for the InViMo project. METHODS: The implementation involved integrating the mini-tracker geometry and the scoring mechanism into the FLUKA MC simulation, utilizing the finely tuned HIT beam line. The systematic investigation included varying mini-tracker angles (from 15∘$15^\circ$ to 45∘$45^\circ$ in 5∘$5^\circ$ steps) during the irradiation of a head-sized phantom with therapeutic carbon-ion pencil beams. To evaluate our implemented FLUKA framework, a comparison was made between the experimental data and data obtained from MC simulations. To ensure the fidelity of our comparison, experiments were performed at the HIT using the parameters and setup established in the simulations. RESULTS: Our research demonstrates high accuracy in reproducing characteristic behaviors and dependencies of the monitoring method in terms of fragment distributions in the mini-tracker, track angles, emission profiles, and fragment numbers. Discrepancies in the number of detected fragments between the experimental data and the data obtained from MC simulations are less than 4% for the angles of interest in the InViMo detection system. CONCLUSIONS: Our study confirms the potential of our simulation framework to investigate the performance of monitoring inter-fractional anatomical changes in patients undergoing CIRT using secondary nuclear charged fragments escaping from the irradiated patient.
- MeSH
- fantomy radiodiagnostické MeSH
- lidé MeSH
- metoda Monte Carlo * MeSH
- radioterapie těžkými ionty * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- validační studie MeSH
Understanding the fundamental mechanisms involved in the induction of biological damage by ionizing radiation remains a major challenge of today's radiobiology research. The Monte Carlo simulation of physical, physicochemical and chemical processes involved may provide a powerful tool for the simulation of early damage induction. The Geant4-DNA extension of the general purpose Monte Carlo Geant4 simulation toolkit aims to provide the scientific community with an open source access platform for the mechanistic simulation of such early damage. This paper presents the most recent review of the Geant4-DNA extension, as available to Geant4 users since June 2015 (release 10.2 Beta). In particular, the review includes the description of new physical models for the description of electron elastic and inelastic interactions in liquid water, as well as new examples dedicated to the simulation of physicochemical and chemical stages of water radiolysis. Several implementations of geometrical models of biological targets are presented as well, and the list of Geant4-DNA examples is described.
- MeSH
- chemické jevy MeSH
- DNA chemie MeSH
- lidé MeSH
- metoda Monte Carlo * MeSH
- molekulární modely * MeSH
- voda chemie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy 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
The main limitation in the high-sensitive HPGe gamma-ray spectrometry has been the detector background, even for detectors placed deep underground. Environmental radionuclides such as 40K and decay products in the 238U and 232Th chains have been identified as the most important radioactive contaminants of construction parts of HPGe gamma-ray spectrometers. Monte Carlo simulations have shown that the massive inner and outer lead shields have been the main contributors to the HPGe-detector background, followed by aluminum cryostat, copper cold finger, detector holder and the lead ring with FET. The Monte Carlo simulated cosmic-ray background gamma-ray spectrum has been by about three orders of magnitude lower than the experimental spectrum measured in the Modane underground laboratory (4800 m w.e.), underlying the importance of using radiopure materials for the construction of ultra-low-level HPGe gamma-ray spectrometers.
- MeSH
- laboratoře MeSH
- metoda Monte Carlo MeSH
- monitorování radiace * MeSH
- počítačová simulace MeSH
- radioaktivní znečišťující látky analýza MeSH
- radionuklidy MeSH
- spektrometrie gama * MeSH
- thorium analýza MeSH
- uran analýza MeSH
- záření gama MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Francie MeSH
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.
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.
PURPOSE: The aim of this study was to determine fluence corrections necessary to convert absorbed dose to graphite, measured by graphite calorimetry, to absorbed dose to water. Fluence corrections were obtained from experiments and Monte Carlo simulations in low- and high-energy proton beams. METHODS: Fluence corrections were calculated to account for the difference in fluence between water and graphite at equivalent depths. Measurements were performed with narrow proton beams. Plane-parallel-plate ionization chambers with a large collecting area compared to the beam diameter were used to intercept the whole beam. High- and low-energy proton beams were provided by a scanning and double scattering delivery system, respectively. A mathematical formalism was established to relate fluence corrections derived from Monte Carlo simulations, using the fluka code [A. Ferrari et al., "fluka: A multi-particle transport code," in CERN 2005-10, INFN/TC 05/11, SLAC-R-773 (2005) and T. T. Böhlen et al., "The fluka Code: Developments and challenges for high energy and medical applications," Nucl. Data Sheets 120, 211-214 (2014)], to partial fluence corrections measured experimentally. RESULTS: A good agreement was found between the partial fluence corrections derived by Monte Carlo simulations and those determined experimentally. For a high-energy beam of 180 MeV, the fluence corrections from Monte Carlo simulations were found to increase from 0.99 to 1.04 with depth. In the case of a low-energy beam of 60 MeV, the magnitude of fluence corrections was approximately 0.99 at all depths when calculated in the sensitive area of the chamber used in the experiments. Fluence correction calculations were also performed for a larger area and found to increase from 0.99 at the surface to 1.01 at greater depths. CONCLUSIONS: Fluence corrections obtained experimentally are partial fluence corrections because they account for differences in the primary and part of the secondary particle fluence. A correction factor, F(d), has been established to relate fluence corrections defined theoretically to partial fluence corrections derived experimentally. The findings presented here are also relevant to water and tissue-equivalent-plastic materials given their carbon content.
- MeSH
- algoritmy MeSH
- cyklotrony MeSH
- dávka záření MeSH
- grafit MeSH
- kalorimetrie přístrojové vybavení metody MeSH
- metoda Monte Carlo MeSH
- nejistota MeSH
- počítačová simulace MeSH
- protonová terapie přístrojové vybavení metody MeSH
- protony MeSH
- teplota MeSH
- tlak MeSH
- voda MeSH
- Publikační typ
- časopisecké články MeSH
