Basics of radiobiology

Abstract

Nuclear medicine uses radionuclides for the diagnosis (imaging radionuclides) and for treating cancer (therapeutic radionuclides). As the number of radionuclides used for diagnosis or therapy is increasing, how radiation acts in the specific field of nuclear medicine must be precisely understood. The cytotoxic effects of ionizing particles emitted by radionuclides are exploited for cancer treatment, but they should be avoided in diagnosis. The nature of the particles emitted by radionuclides and the dose delivered to tissues, which is roughly correlated with the injected activity, allow discriminating between diagnostic and therapeutic applications. The aim of this book chapter is to describe the basic principles of radiobiology with a special focus on nuclear medicine. First, it will describe the steps of physical interaction of particles with biological matter and the chemical events resulting from free radical species production. Then, the notions of particle tracks, linear energy transfer and multiple damage sites will be discussed in function of the cellular targets (i.e., nuclear DNA, but also lipids and proteins). After a presentation of radiation early and late effects at the tissue scale, the mechanisms involved in cell death and the consequences at the tissue levels will be presented. Lastly, new radiobiology paradigms, such as extranuclear targets and non-targeted effects, will be discussed.