Source location and dose verification for X-ray intra-operative radiotherapy (IORT)

A recent development in radiotherapy has been the introduction of the PRS Intrabeam system (Karl Zeiss LtD) for the treatment of both brain and breast tumours. This is essentially a miniaturized, electron-driven photon generator that allows high intensity, soft-energy x-rays to be delivered directly to the tumour site in a single fraction. The isotropical distribution of these photons about the tip of a magnetically shielded needle can be viewed as a point source buried in the body. This work has looked into ways of localizing the source in the body in an Emission Computerized Tomography (ECT) procedure. Various detection systems have been considered as possible candidates for this work. The accuracy with which the source can be localized has been investigated. Furthermore, Monte Carlo studies have been employed in order to extract information on the dosimetric aspect of the resulting image. The final goal of this work is to formulate a direct mathematical relation (Transform Map) between the image created by the escaping photons and the dose map as predicted by the theoretical model. This could allow for a real-time monitoring system of the radiation delivery during the treatment and provide dose verification maps for patient records