Assessment of a simulation software for scintillation detector

Aim: A Monte Carlo code based on GEANT 3.21 and Linux platform has been developed and adaptated to simulate gamma detectors dedicated to specific scintigraphic applications. Materials and methods: GEANT 3.21 is freely available at the CERN program library. It has been written for simulating the interactions of particles with energy greater than 10keV. The energy of the gamma rays used in scintigraphic imaging never exceeds 511keV. Interaction cross- sections for energies between 10keV and 10MeV and three media of interest obtained with this program have been compared with data available on the NIST web site. A gamma peroperative hand-held probe has then been simulated. Sensitivity and spatial resolution were evaluated. Results: The high standard deviation for total attenuation coefficient is 4.7% with an uncertainty around 4% given by NIST. The good results obtained have allowed us to go farther in computer programming. In the hope of integrating all the detection lines new routines have been introduced for the simulation of scintillation photons and optical effects. First simulated optical spots have a diameter of 2.5mm (FWHM) for a 6mm NaI(Tl) thickness and gamma rays of 140keV. Conclusion: The code was recently improved with the implementation of a photomultiplier tube and the algorithm for the image reconstruction. In this way, the computed image can be compared with optical image obtained just before the photocathode to improve algorithm. Soon, simulation results will be tested with a mini gamma- camera prototype.