A 0A liquid Xe PET camera for neuro-science research 15 mn

Johann Collot ISN Grenoble, France

Liquid Xe has been considered as a good active medium candidate for positron emission tomography for more than 10 years . Recently , in collaboration with two departments of the Grenoble Michalon Hospital , a project to develop a liquid Xe PET camera dedicated to the study of the human brain has started . The execution of this project is organized along two phases : in the first place , a R&D investigation which includes the construction of a small prototype to confirm the viability of the project , then the development and the construction of a full device. We will present the operation principles of this device , its simulated performance and the first results obtained in the ongoing R&D phase.

Status of the art and future perspectives for small animal PET machines 25 mn

Stefaan Tavernier Vrije Universiteit Brussel, Belgium

There is a growing demand for small animal Positron Emission Tomograph scanners. Such machines require a better resolution than what is needed in clinical PET scanners for human patients. For this reason, and because of their modest size, small animal PET scanners are en ideal testing ground for new ideas and concepts in PET. I will review the different developments in this field.

First applications of the YAPPET small animal scanner 15 mn

Guido Zavattini University of Ferrara, Italy

At Ferrara University we have built a dedicated 3-D PET scanner (YAPPET) with a very high spatial resolution and sensitivity as necessary for radiopharmaceutical studies on rats and mice. In collaboration with the Institute H.S. Raffaele in Milano we have performed both distribution and dynamical uptake studies of various radioactive tracers in rats. We have acquired tomographic images of live rats after having injected them with 18F-FESP, Flumazenil labeled with 11C, and with 18F-. In the case of 18F-FESP tracing, used for studying dopamine receptors in the brain, an image was also taken of an extracted brain. The 18F- was injected for imaging the rat skeleton. In addition, we studied the uptake and washout curve of 11C-Flumazenil in the rat brain from tomographic images. These images and the scanner's characteristics will be presented.

HIGH RESOLUTION GAMMA CAMERAS 15 mn

Franco Garibaldi Istituto Superiore di Sanita', Rome, Italy

? The role of scintillator and PSPMT pixellation in the performances of compact gamma-cameras F. Garibaldi, E. Cisbani, F. Cusanno, G.M. Urciuoli Istituto Superiore di Sanita' - Laboratorio di Fisica , Rome - Italy R. Pani, A. Soluri, R. Pellegrini, R. Scafe', L. Indovina, M.N. Cinti, G. Trotta Department of Experimental Medicine, University of Rome La Sapienza - Rome - Italy Abstract Recently there has been a growing interest for compact discrete gammacameras, mostly for early breast cancer detection. These gammacameras offer advantages over traditional larger cameras in terms of spatial resolution, sensitivity, size and weight. The proposed devices use continuous or pixellated scintillators and pixellated photodetectors, like PSPMT's, silicon photodiodes or CZT detectors. It is well known that the total spatial resolution of a gammacamera is dominated by collimator, so, once the collimator has been chosen one has to optimize the scintillator pixellation, that genarates the light spread and the PSPMT anode pixellation that generates the charge spread which determines the intrinsic spatial resolution. We will show the results of simulations performed to optimize the gammacamera performances in terms of position resolution and image reconstruction as well as the results of measurements on different "geometries" for scintillator "geometries" coupled to different PSPMT's with different anode pixellation. We have used NaI and CsI(Tl) continuous and CsI(Tl) pixellated scintillators and Hamamatsu R5900-C8, R5900-M16 and R5900-M64 PSPMT's. Measurements have been done of pulse linearity, position response, interchannel gain variation and anodes cross talk by using a light source coupled to a 1mm diameter optical fiber for the three PSPSMT's. The PSPMT were successively coupled to Na(Tl) and CsI(Tl) continuous scintillators as well as to a 5 CsI(Tl) scintillator arrays with pixel sizes ranging between 1.5 X 1.5 mm2 and 4 X 4 mm2. The results of these measuremets will be reported as well as the comparison with the simulation.

Evaluation of a Combined Array-Planar Crystal for Gamma-ray Scintillation Imagers 15 mn

Roberto Pani University of Rome "La Sapienza", Italy

R.Pani 1, R.Scafè 2, R.Pellegrini 1, A.Soluri 3, N.Burgio 2, C.Ciavola2, M.N.Cinti 1, L.Indovina 1, G.De Vincentis 1, F.Garibaldi 4, F.Cusanno 4, G.M.Urciuoli 4 , E.Cisbani 4 1 Dept of Experimental Medicine, University of Rome "La Sapienza", Rome, Italy 2 ENEA, C.R. Casaccia, Rome, Italy 3 Institute of Biomedical Technologies, CNR, Rome, Italy 4 Laboratory of Physics, ISS, Rome, Italy Abstract Over the last few years our interest was dedicated to the development of small field of view imagers for nuclear medicine applications, particularly in oncology. Some years ago, the authors have described an original scintillation gamma camera based on a matrix of 2x2 R5900-C8 Hamamatsu Position Sensitive PhotoMultiplier Tube (PSPMT) coupled to a scintillating array. The intrinsic spatial resolution obtained was adequate for high resolution imaging applications. On the contrary, the prototype was affected by reduced performances at the borders between PSPMT. The subsequent introduction by Hamamatsu of the R7600 flange-less PSPMT family reduced the dead areas at the borders, and the C12 model, with lower anode pitch, improved the charge sampling. This permits a better choice of scintillation light distributions in order to improve the spatial resolution and to optimize the spatial response. A good compromise was obtained designing a Combined Array-Planar Crystal (CAPC) geometry. It consists of a planar crystal segmented in the top in a 15x15 array, 3 mm square pixel, 1 mm thick, 0.25 mm gap. Two CsI assemblies, Na and Tl doped, respectively, were manufactured for this study by Hilger. An experimental evaluation of CAPC performances in the 2x2 PSPMT scintillation camera is presented. A Monte Carlo simulation study was also carried out to compare the detection efficiency at 140 keV of the CAPC with respect to array and planar, 3 mm thick, CsI crystals, respectively.

The application of GEANT4 simulation code for brachytherapy treatment 10 mn

Franca Foppiano Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy

F. Foppiano1, S. Agostinelli2, S. Garelli1, G. Paoli1, M.G. Pia3 1 Istituto Nazionale per la Ricerca sul Cancro di Genova, Italy 2 INFM, Dipartimento di Fisica di Genova, Italy 3 INFN, Dipartimento di Fisica di Genova, Italy Abstract At the National Cancer Institute of Genova Ir-192 brachytherapy treatments are performed by a High Dose Rate (HDR) Microselectron afterloading unit. The system uses high activity (10 Ci) 192Ir source, which can be programmed to move along the catheter path in customisable steps. The source is a 0.6 mm diameter cylinder of 3.5 mm length packed in a stainless steel capsule of 1.1. mm of diameter and 5.0 mm length. We use Geant4 Toolkit to simulate our source obtaining different new information usable for clinical application. Geant4 is a new toolkit for the simulation of the passage of particles through matter. Its application areas include high-energy physics and nuclear experiments, medical, accelerator and space physics studies. It is based on Object Oriented technology and has been developed using the C++ computer language. In particular we focused our attention on the dose rate distribution around the high-intensity 192Ir source. The Microselectron HDR Treatment Planning System (PLATO), in order to account for the internal absorption and source encapsulation uses a list of anisotropy correction factors Fi(f) where f is the longitudinal axial angle. We simulate dose distribution around our source in water medium at difference distance from the source itself and we compare them with measured data.

SIMULATION -Effect of air-cavities on Monte Carlo dose calculations for typical clinical photons and electron beams

Grisel Mora Paula CFNUL, Lisbon University, Portugal

The 3-D information of the anatomical structures given by the CT (computer tomography) image data is used as input to Monte Carlo dose calculation for radiotherapy treatment planning. The material and density information of the patient simulation geometry is derived from the patient CT data. An ideal conversion scheme would be using the same resolution as that of the CT data (about 1 mm resolution). Although it is more practically to use large dose calculation voxels to reduce the CPU time required for calculation. The resolution loosing causes the change in the material and density distribution in the converted patient simulation geometry and therefore affect the dose distributions. In this work, we have investigated the effect of dose-resolution on the dose distributions calculated by Monte Carlo for clinical photon and electron beams from linear accelerators. We have observed significant dose resolution effect on the dose distributions calculated in the air cavity regions .