Physics of ionizing radiation

Nuclear Medicine and Molecular Imaging make use of radiation that in virtue of its interaction with matter can be used for therapy and/or diagnostics. In particular radiation that interacts with the human body with high intensity and releases its energy locally is a good candidate for therapy, in that this energy release can be used to avoid cells reproduction. On the other side radiation that penetrates the human body and that can be intercepted further away by a detector is a good candidate for diagnostics. This chapter will describe the interactions with matter and the generation of the radiation of interest for Nuclear Medicine and Molecular Imaging. Since the effects of interest are generated by a physics process called “ionization” of either the radiation itself or its products, the term “ionizing radiation” is typically used for it. We firstly introduce the interactions of the ionizing radiation with matter, then we discuss its impact on living tissues and finally we describe the nuclear decays that generate it.