ROLE OF PORTAL IMAGING IN CLINICAL RADIOTHERAPY - FLORENCE EXPERIENCE

A portal imaging device developed at the Netherland's Cancer Institute (NKI) in Amsterdam was provided to the Radiotherapy Section of the Un iversity of Florence as a partner of a cooperative study on quality as surance (QUIRT) granted by the EC (AIM Project). The device was used f or portal imaging in 30 patients treated for tumors of different sites (5 rectum, 6 prostate, 5 Hodgkin's lymphomas, 5 head and neck tumors, 9 other sites). Portal images were obtained three times per week over the whole treatment period. An off-line quantitative analysis of disc repancies with respect to the simulation image was performed for the 5 rectum cases; a similar analysis was also done on the portal images o f 4 rectal cases treated at the NKI in Amsterdam. The analysis proved capable of demonstrating the existence of some systematic errors in bo th centres and the different level of global accuracy between them. Th e on-line use of the device was also able to demonstrate some major er rors of patient setup during the first session, which were immediately corrected.