Biomedical subjects

A F Chatziioannou

Publications and source records attributed to A F Chatziioannou.

3 recordsLinked to original sources

PubMed2004

GATE: a simulation toolkit for PET and SPECT.

Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the description of time-dependent phenomena such as source or detector movement, and source decay kinetics. This feature makes it possible to simulate time curves under realistic acquisition conditions and to test dynamic reconstruction algorithms. This paper gives a detailed description of the design and development of GATE by the OpenGATE collaboration, whose continuing objective is to improve, document and validate GATE by simulating commercially available imaging systems for PET and SPECT. Large effort is also invested in the ability and the flexibility to model novel detection systems or systems still under design. A public release of GATE licensed under the GNU Lesser General Public License can be downloaded at http:/www-lphe.epfl.ch/GATE/. Two benchmarks developed for PET and SPECT to test the installation of GATE and to serve as a tutorial for the users are presented. Extensive validation of the GATE simulation platform has been started, comparing simulations and measurements on commercially available acquisition systems. References to those results are listed. The future prospects towards the gridification of GATE and its extension to other domains such as dosimetry are also discussed.

Computer Simulation↗

PubMed2000

Quantitative assessment of longitudinal metabolic changes in vivo after traumatic brain injury in the adult rat using FDG-microPET.

With the advent and emerging importance of neurobiology and its relation to behavior, scientists desire the capability to apply noninvasive, quantitative imaging of neuronal activity to small rodents. To this end, the authors' laboratory has developed microPET, a high-resolution positron emission tomography (PET) scanner that is capable of performing in vivo molecular imaging at a resolution sufficient to resolve major structures in the rat brain. The authors report in this article that, in conjunction with 2-[18F]fluoro-2-deoxyglucose (FDG), microPET provides accurate rates of cerebral glucose metabolism (59.7 to 108.5 micromol/100 g x min) in conscious adult rats as validated by within-subject autoradiographic measurements (59.5 to 136.2 micromol/100 g x min; r = 0.88; F[1,46] = 168.0; P < 0.001). By conducting repeated quantitative scanning, the authors demonstrate the sensitivity and accuracy of FDG-microPET to detect within-subject metabolic changes induced by traumatic brain injury. In addition, the authors report that longitudinal recovery from traumatic brain injury-induced metabolic depression, as measured by quantitative FDG-microPET, is significantly correlated (r = 0.65; P < 0.05) to recovery of behavioral dysfunction, as assessed by the Morris Water Maze performance of the same rats, after injury. This is the first study to demonstrate that FDG-microPET is quantitative, reproducible, and sensitive to metabolic changes, introducing a new approach to the longitudinal study of small animal models in neuroscience research.

Animals↗

PubMed1999

Performance evaluation of microPET: a high-resolution lutetium oxyorthosilicate PET scanner for animal imaging.

UNLABELLED: A new dedicated PET scanner, microPET, was designed and developed at the University of California, Los Angeles, for imaging small laboratory animals. The goal was to provide a compact system with superior spatial resolution at a fraction of the cost of a clinical PET scanner. METHODS: The system uses fiberoptic readout of individually cut lutetium oxyorthosilicate (LSO) crystals to achieve high spatial resolution. Each microPET detector consists of an 8 x 8 array of 2 x 2 x 10-mm LSO scintillation crystals that are coupled to a 64-channel photomultiplier tube by optical fibers. The tomograph consists of 30 detectors in a continuous ring with a 17.2-cm diameter and fields of view (FOVs) of 11.25 cm in the transaxial direction and 1.8 cm in the axial direction. The system has eight crystal rings and no interplane septa. It operates exclusively in the three-dimensional mode and has an electronically controlled bed that is capable of wobbling with a radius of 300 microm. We describe the performance of the tomograph in terms of its spatial, energy and timing resolution, as well as its sensitivity and counting-rate performance. We also illustrate its overall imaging performance with phantom and animal studies that demonstrate the potential applications of this device to biomedical research. RESULTS: Images reconstructed with three-dimensional filtered backprojection show a spatial resolution of 1.8 mm at the center of the FOV (CFOV), which remains <2.5 mm for the central 5 cm of the transaxial FOV. The resulting volumetric resolution of the system is <8 microL. The absolute system sensitivity measured with a 0.74 MBq (20 microCi) 68Ge point source at the CFOV is 5.62 Hz/kBq. The maximum noise equivalent counting rate obtained with a 6.4-cm diameter cylinder spanning the central 56% of the FOV is 10 kcps, whereas the scatter fraction is 37% at the CFOV for an energy window of 250-650 keV and the same diameter cylinder. CONCLUSION: This is the first PET scanner to use the new scintillator LSO and uses a novel detector design to achieve high volumetric spatial resolution. The combination of imaging characteristics of this prototype system (resolution, sensitivity, counting-rate performance and scatter fraction) opens up new possibilities in the study of animal models with PET.

Animals↗