Showing papers by "Giovanni Santin published in 2003"

Geant4—a simulation toolkit

Abstract: G eant 4 is a toolkit for simulating the passage of particles through matter. It includes a complete range of functionality including tracking, geometry, physics models and hits. The physics processes offered cover a comprehensive range, including electromagnetic, hadronic and optical processes, a large set of long-lived particles, materials and elements, over a wide energy range starting, in some cases, from 250 eV and extending in others to the TeV energy range. It has been designed and constructed to expose the physics models utilised, to handle complex geometries, and to enable its easy adaptation for optimal use in different sets of applications. The toolkit is the result of a worldwide collaboration of physicists and software engineers. It has been created exploiting software engineering and object-oriented technology and implemented in the C++ programming language. It has been used in applications in particle physics, nuclear physics, accelerator design, space engineering and medical physics.

Search for neutrino oscillations on a long base-line at the CHOOZ nuclear power station

Abstract: This final article about the CHOOZ experiment presents a complete description of the $\bar{ u}_e$ source and detector, the calibration methods and stability checks, the event reconstruction procedures and the Monte Carlo simulation. The data analysis, systematic effects and the methods used to reach our conclusions are fully discussed. Some new remarks are presented on the deduction of the confidence limits and on the correct treatment of systematic errors.

GATE: a Geant4-based simulation platform for PET and SPECT integrating movement and time management

Abstract: GATE, the Geant4 application for tomographic emission, is a simulation platform developed for PET and SPECT. It combines a powerful simulation core, the Geant4 toolkit, with newly developed software components dedicated to nuclear medicine. In particular, it models the passing of time during real acquisitions, allowing it to handle dynamic systems such as decaying source distributions or moving detectors. We present several series of results that illustrate the possibilities of this new platform. The simulation of decaying sources is illustrated on a dual-isotope acquisition with multiple time-frames. Count rate curves taking into account random coincidences and dead-time are shown for a dual-crystal setup and for a small-animal PET scanner configuration. Simulated resolution curves and reconstructed images are shown for rotating PET scanners. Lastly, we present first comparisons of simulated point-spread functions and spectra with experimental results obtained from a small-animal gamma camera prototype.

GATE (geant4 application for tomographic emission): a PET/SPECT general-purpose simulation platform

Abstract: We present the development of GATE, the Geant4 Application for Tomographic Emission, as a new general purpose simulation platform for PET and SPECT applications. Built on top of the Geant4 simulation toolkit, it provides multiple new features with the objective to ease the use of Geant4 in the field of nuclear medicine. The handling of time, with the description of time-dependent phenomena such as movement of geometry elements or source decay kinetics, is a key and original feature of the platform. Scripting via a command language substitutes to C++ coding. This allows to set up simulations, from the description of the geometry to the modelling of the electronics. The high modularity of the design of GATE has allowed a fast and efficient development of its various components.

Monte Carlo simulations of a scintillation camera using GATE: validation and application modelling

Abstract: Geant4 application for tomographic emission (GATE) is a recently developed simulation platform based on Geant4, specifically designed for PET and SPECT studies. In this paper we present validation results of GATE based on the comparison of simulations against experimental data, acquired with a standard SPECT camera. The most important components of the scintillation camera were modelled. The photoelectric effect, Compton and Rayleigh scatter are included in the gamma transport process. Special attention was paid to the processes involved in the collimator: scatter, penetration and lead fluorescence. A LEHR and a MEGP collimator were modelled as closely as possible to their shape and dimensions. In the validation study, we compared the simulated and measured energy spectra of different isotopes: 99mTc, 22Na, 57Co and 67Ga. The sensitivity was evaluated by using sources at varying distances from the detector surface. Scatter component analysis was performed in different energy windows at different distances from the detector and for different attenuation geometries. Spatial resolution was evaluated using a 99mTc source at various distances. Overall results showed very good agreement between the acquisitions and the simulations. The clinical usefulness of GATE depends on its ability to use voxelized datasets. Therefore, a clinical extension was written so that digital patient data can be read in by the simulator as a source distribution or as an attenuating geometry. Following this validation we modelled two additional camera designs: the Beacon transmission device for attenuation correction and the Solstice scanner prototype with a rotating collimator. For the first setup a scatter analysis was performed and for the latter design, the simulated sensitivity results were compared against theoretical predictions. Both case studies demonstrated the flexibility and accuracy of GATE and exemplified its potential benefits in protocol optimization and in system design.

Monte Carlo simulation for the ECAT EXACT HR+ system using GATE

Abstract: GATE (Geant4 Application for Tomographic Emission) is a Monte Carlo simulation platform for nuclear medicine imaging, based on the Geant4 toolkit package. This tool was used to construct a full and realistic simulator for the ECAT EXACT HR+ scanner, with the objective of optimising data acquisition protocols, image quantification and reconstruction techniques. In this study, we will compare the performances of the simulator against experimental data obtained with the HR+ scanner in order to validate its use for PET imaging systems simulations. Simulated and measured data were found to be in good agreement. An example of a coupling PET and MRI system is also simulated with GATE and we give some results about the image resolution for this multimodality device.

Search for neutrino oscillations on a long base-line at the CHOOZ nuclear power station

Abstract: This final article about the CHOOZ experiment presents a complete description of the electron antineutrino source and detector, the calibration methods and stability checks, the event reconstruction procedures and the Monte Carlo simulation. The data analysis, systematic effects and the methods used to reach our conclusions are fully discussed. Some new remarks are presented on the deduction of the confidence limits and on the correct treatment of systematic errors.

Status of the DESIRE project: Geant4 physics validation studies and first results from Columbus/ISS radiation Simulations

Abstract: The DESIRE (Dose Estimation by Simulation of the ISS Radiation Environment) project aims to accurately calculate radiation fluxes and doses to astronauts inside the European Columbus module of the International Space Station using Geant4. Firstly physics benchmark studies have been performed and comparisons made to experimental data and other particle transport programs. This will be followed by a detailed evaluation of the incident radiation fields on the ISS and culminate with the geometry modeling and full-scale flux and dose simulations for the Columbus. Geant4 validation studies are presented here. These concern the angle and energy distribution of particles leaving irradiated targets and of energy depositions in the targets. Comparisons are made between simulations using different Geant4 physics models, experimental data and other particle transport programs. Geant4 using the "Binary Cascade" model for inelastic nucleon reactions performs very well in these comparisons but some issues with other models remain to be resolved if these models are to be used for space radiation shielding applications. Results of Geant4 simulations of the transport of relevant radiation field components through the hull of the Columbus/ISS are also presented.

Geant4 for space: mission simulations and engineering tools

Abstract: Radiation shielding analysis is a crucial process in the spacecraft and space instrument development cycle. A number of dedicated tools have been developed in the last decades Cor the study of the effects of radiation on materials and instruments in space. We present here a set of detailed analyses based on Monte Carlo radiation transport simulations, and dew tools for space applications, both based on the Geant4 simulation toolkit, devetoped as part of the European Space Agency activities in the Geant4 collaboration. I N recent years the use of Monte Carlo (MC) simulations has rapidly increased in the space domain, with applications ranging from instrument and detector response verification to radiation shielding optimisation, component effects, support of scientific studies, and analysis of biological effects. The advance in computer technology and the advent of new simulation toolkits for particle transport such as Geant4 have allowed MC studies to be not anymore reserved for research scientists but to become standard engineering tools. Radiation shielding analysis is a crucial process in the spacecraft and space instrument development cycle. A number of dedicated tools have been developed in the last decades for the study of the effects of radiation on materials and instruments in space. We present here a set of applications and new tools for space based on the Geant4 simulation toolkit, developed as part of the European Space Agency (ESA) activities in the Geant4 collaboration. 11. THE ROLE OF GEANT4 IN THE SPACE DOMAIN