Application of Positron Emission Tomography for Radiotherapy Monitoring

Positron emission tomography (PET) is used for independent monitoring of dose delivery in ion therapy. An in-beam PET scanner registers the annihilation γ-rays following the decay of minor amounts of β+ radioactive nuclei, which are produced via nuclear reactions between the ions of the therapeutic beam and the atomic nuclei of the irradiated tissue. From a comparison of the reconstructed activity distributions with those predicted from the treatment plan, deviations between the prescribed and the applied dose distributions can be detected. In-beam PET, therefore, allows to verify the physical beam model used in the treatment planning, to detect patient dislocations and density changes in the irradiated tissue. Treatment of more than 400 patients has been monitored by means of in-beam PET at Gesellschaft für Schwerionenforschung (GSI), Darmstadt, Germany. The in-beam PET method demonstrated a positive clinical impact as in vivo, in situ, non-invasive technique for independent monitoring of dose application.