Evaluation Scheme for a Positron Emission Tomography System Used in Monitoring of Radiation Therapy

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 β-radioactive nuclei produced via nuclear reactions between the ions of the therapeutic beam and 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 can be detected. In-beam PET, therefore, allows to verify the physical beam model of the treatment planning, to detect patient dislocations and density changes in the irradiated tissue. Issues related to the image quality and evaluation of a whole PET imaging system are discussed in this paper.