ABSTRACT
In addition to the previously discussed methods for using positron emission tomography (PET) imaging techniques to measure induced positron annihilation gamma emission in the patient, researchers have also studied imaging prompt gamma (PG) emission from the patient, as a means of verifying proton and ion beam treatment delivery. During proton or heavy ion therapy, primary particles from the treatment beam interact with elemental nuclei in the tissue, which can leave behind an intact nucleus in an excited state. This excited state quickly (<10−9 s) decays by emitting a characteristic PG. Since the PG emission only occurs in regions in which the treatment beam interacts in the tissue, the distribution of PG creation in the patient is correlated to the distribution of dose delivery to the patient. Also, since the excited nuclear states are quantized, each element emits a unique and characteristic PG spectrum. Thus, spectral analysis of PG emitted from tissue may provide useful information about the elemental concentration, composition, and type of the tissues irradiated during treatment.
