PCSV team of the LPC laboratory in Clermont-Ferrand is involved in the deployment of biomedical applications on the grid architecture. One of these applications deals with the deployment of GATE (Geant4 Application for Tomographic Emission) for medical physics application. The aim of the developments actually performed is to enable an application of the GATE platform in clinical routine. However, this perspective is only possible if the computing time and user time are highly reduced. The new grid architecture, developed within the framework of the European project Enabling Grid for E-sciencE (EGEE) is there to answer this requirement. The use of the grid resources must be transparent easy and rapid for the medical physicists. For this perpose, we adapted the GENIUS web portal in order to facilitate the GATE simulations planning on the grid. We will present a demonstration of the GENIUS portal which integrates all the functionalities of EGEE: to create, to submit and manage GATE jobs on the grid architecture. Our GATE activities for dosimetry application entered in to direct phase of evaluation by the cancer treatment center of Clermont Ferrand (Centre Jean perrin).A work station is currently available in this center to test the use of GATE application on the grid through GENIUS. This portal will allow in a long term to use GATE application in brachytherapy and radiotherapy treatment planning using medical data (medical images, DICOM, binary data dose calculation in the heterogeneous mediums) and to analyze the results obtained in visual form. Other functionalities are under development and will make possible to register medical data on grid storages elements and to manage them. However, these data must be anonymised before their recording on the grid. Their access via the GENIUS portal must be made safe and fast (compared simulation computing time). In order to be sure that the medical data are accessible for calculations, their replication on various storage element (SE) should be possible. The grid services give the possibility of managing this information in a free way and transparently. Operations of data handling and catalogues on the grid are ensured by the Replica Manager system which integrates all tools making it possible to manage data on the grid. The computing grid give promising results and meet a definite need: reach acceptable computing time for a future use of Monte Carlo simulations for treatment planning in brachytherapy and radiotherapy.