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G Santin

Publications and source records attributed to G Santin.

5 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↗
PubMed2004

Validation of the GATE Monte Carlo simulation platform for modelling a CsI(Tl) scintillation camera dedicated to small-animal imaging.

Monte Carlo simulations are increasingly used in scintigraphic imaging to model imaging systems and to develop and assess tomographic reconstruction algorithms and correction methods for improved image quantitation. GATE (GEANT4 application for tomographic emission) is a new Monte Carlo simulation platform based on GEANT4 dedicated to nuclear imaging applications. This paper describes the GATE simulation of a prototype of scintillation camera dedicated to small-animal imaging and consisting of a CsI(Tl) crystal array coupled to a position-sensitive photomultiplier tube. The relevance of GATE to model the camera prototype was assessed by comparing simulated 99mTc point spread functions, energy spectra, sensitivities, scatter fractions and image of a capillary phantom with the corresponding experimental measurements. Results showed an excellent agreement between simulated and experimental data: experimental spatial resolutions were predicted with an error less than 100 microns. The difference between experimental and simulated system sensitivities for different source-to-collimator distances was within 2%. Simulated and experimental scatter fractions in a [98-182 keV] energy window differed by less than 2% for sources located in water. Simulated and experimental energy spectra agreed very well between 40 and 180 keV. These results demonstrate the ability and flexibility of GATE for simulating original detector designs. The main weakness of GATE concerns the long computation time it requires: this issue is currently under investigation by the GEANT4 and the GATE collaborations.

Animals↗
PubMed1992

[Respiratory inductive plethysmography in the functional evaluation of patients undergoing coronary by-pass surgery].

The functional respiratory changes following coronary by-pass surgery were previously evaluated with the traditional spirometric method. Aim of this work is to introduce the respiratory inductive plethismography (RIP), a well known non-invasive technique, into the study of those volumetric and ventilatory modifications. Eight cardioischemic patients were selected: all but one were free from pulmonary disorders. The tidal volume, the respiratory rate, the minute ventilation, the vital capacity and the relation between the abdominal and the thoracic part of the ventilatory act, were measured in the pre-intervention session and in the 1st, 3rd and 7th day after the operation of coronary by-pass. In the same sessions, except the 1st day after surgery, the maximal respiratory pressures were evaluated with traditional manometers. The functional changes of the examined parameters, statistically studied with the variance analysis, closely resemble the spirometric modifications registered by other authors. Furthermore the relative contributions of the thoracic and abdominal compartments of the pulmonary ventilation were evaluated, thanks to the non-invasive plethysmographic method. Rip makes it possible to measure the ventilatory pattern and some pulmonary volumes in the very early phases after thoracic surgery, without any trouble for the patient and in a non-collaborative state of consciousness, too.

Aged↗
PubMedDate not supplied

Peribulbar and retrobulbar combined anesthesia for vitreoretinal surgery using ropivacaine.

PURPOSE: To evaluate the efficacy and clinical effects of local retrobulbar anesthesia using ropivacaine in vitreoretinal surgery. METHODS: Prospective study. A total of 919 vitreoretinal operations were followed. The operations were divided into three groups, depending on the degree of anesthesia needed. Group A: Vitrectomies with episcleral procedures (208 vitrectomies for detached retina or perforating trauma). Group B: Episcleral procedures only (410 operations for detached retina without vitrectomy). Group C: Vitrectomies without episcleral surgery (301 operations for macular pucker or hole, proliferative diabetic retinopathy, or silicone oil removal). Anesthesia was administered using a 23-gauge Atkinson-type retrobulbar needle, after topical anesthesia. Six mL of the solution containing 7.5 mg ropivacaine/mL were injected into the peribulbar space, and the other 4 mL deeper, into the retrobulbar space. The degree of infiltration of the palpebral region, the motor block in the extrinsic ocular muscles, and pain felt were checked and rated. RESULTS: Swelling of lids was seen in 885 patients (96%); in 21 (2%) swelling was partial. In 13 patients (1%) there were no signs of infiltration. The motor block was total in 801 (87%) eyes, while 118 (12%) had reduced ocular movements. The degree of anesthesia was as follows, considering the three groups together: no pain = 855 (93%) patients; moderate pain = 44 (4%) patients; very strong pain = 20 (2%) patients. No adverse events or side effects were observed. CONCLUSIONS: Ropivacaine used for retrobulbar-peribulbar combined anesthesia in vitreoretinal surgery showed excellent clinical efficacy as regards analgesia and muscle akinesia.

Adult↗