Monte Carlo simulation of a clinical beam line: Geant4 and GRID technology approach

A preliminary study on the possible use of the GEANT4 (GEometry ANd Tracking) toolkit and Grid technology, for the Monte Carlo simulation of a clinical beam line for proton therapy, has been investigated. We realized a GEANT4 application giving the possibility to simulate a typical proton therapy beam line (including all its elements and two dosimetric systems: an ionisation chamber and a radiochromic film). The application realized was tested simulating the proton therapy beam line operating at the Laboratori Nazionali del Sud of the Instituto Nazionale di Fisica Nucleare in Catania, Italy. Actually the main disadvantage of a Monte Carlo simulation are the long computation times. In order to overcome this problem and to obtain resonable computation times we decided to exploit the power of the Grid. We based our work on the local Grid installed at the Physics Department of the Catania University consisting of 20 machine, each one with two INTEL-Xeon at 2.8 GHz processors. The Grid approach, consisting in the distribution of a single big job in many CPUs, permitted us to decrease, in the actual configuration, of a factor 20 the time necessary for a complete simulation. Obtained results permit us to adfirm that GEANT4 toolkit, coupled with the Grid, can represent an answer for the routinary use of the Monte Carlo method for designing and simulating a clinical proton beam line. Moreover this can represent a first step for the use of Monte Carlo in proton treatment planning software development.