The application of GEANT 4 simulation code to

The application of GEANT 4 simulation code to the verification of a brachytherapy calibration procedure F. Foppiano 1, S. Garelli 1, P. Moresco 1, G. Paoli 1, S. Agostinelli 2 1 Istituto Nazionale per la Ricerca sul Cancro di Genova, Italia 2 INFM and Dipartimento di Fisica di Genova, Italia With the collaboration of Maria Grazia Pia 3 and Matteo Tropeano 4 3 Istituto Nazionale di Fisica Nucleare di Genova, Italia 4 Dipartimento di Fisica di Genova, Italia

Brachytherapy facility installed at National Cancer Institute of Genova: Microselectron High Dose Rate (HDR) afterloading system 192 Ir source = 356 ke. V

Every new source is supplied by Mallinckrodt Medical B. V. Holland with a calibration certificate that specifies the air kerma rate measure at a distance of 1 m with uncertainty of ± 5 % For every new source • we perform calibration following the protocol for The Basic Dosimetry with Brachitherapy Sources of the Italian Association of Biomedical Physics (AIFB) using a 0. 6 cc Capintec chamber • we measure the air kerma rate using a well - type chamber PTW Freiburg

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( ) where is the longitudinal axial angle

Geant 4 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 medical physics studies. It is based on Object Oriented technology and has been developed using the C++ computer language. Our application • anisotropy correction factors of 192 Ir source • transverse axis energy deposition in water • verification of the calibration procedure of 192 Ir source

As a first test for Geant 4 application we perform the simulation of attenuation coefficient in different material of interest • 1. 000 photons generated • 120 sec on an Intel PC 300 MHz

Anisotropy cell dimension: 1 mm 3 number of photons generated: 10. 000 simulation time: 12 h on a Intel PC 300 MHz

Energy deposition in water cell dimension: 1 mm 3 number of photons generated: 10. 000 simulation time: 12 h on a Intel PC 300 MHz

Future developments Use of the new Geant 4 low energy model Simulation of air kerma rate Isodose distribution around shielded and unshielded applicators Conclusions We have developed a procedure to test Geant 4 toolkit, which provides a modern Montecarlo implementation and robust physics modelling. We have found a very interesting field of application for Geant 4 in brachytherapy.