Nuclear Medicine

Nuclear medicine covers the area of a medical practice based on the resources of physics, its tools and products nuclear meaning related to the nucleus of the atom in order to be applied both for diagnosis and therapeutics. In both cases, a substance containing a radioactive isotope or radionuclide (one speaks about a labelled substance) is administered to a patient. It goes straight towards a biological tissue or organ after having selectively searched for it. The concentration of this radionuclide in the targeted tissue or organ is favoured by the design of the organic or biological substrate or vector on which it is grafted. The emitted radioactivity will then be used either to locate the radionuclide (diagnosis) or to initiate the deterioration of surrounding cells (therapy).

The term radiotracer refers to the notion of minute (trace) amounts of the substances in use, and also to the advantageous ability to "trace" the dissemination of the molecule in the body. The selection of the radionuclide, based on the nature of the emitted radiation, its physical properties, i.e. energy and half-life, and its chemical properties, will define the final purpose of this molecule, called a radiopharmaceutical. The diagnosis imaging technology, also called scintigraphy, is obtained with substances labelled with ?-emitter isotopes.

The use of radionuclides as an external source of radioactivity, of temporary radioactive implants for therapy purposes or of particle beam generators (neutrontherapy and protontherapy, which are both external therapies) is controlled by radiotherapists. Hence, it does little or not concern nuclear physicians. The same applies to brachytherapy, or curietherapy as it is known in some countries, a technology that is devoted to the use of permanent or temporary radioactive implants. These areas will however be described in this work. Finally, analogue sources (mainly X-rays) are used in radiology to obtain organ image data from different angles around the body.

After about fifty years of practice and experience, nuclear medicine reached a turning point. The new imaging modalities that appeared on the market at the dawn of the new millennium, as well as the new molecules and therapeutic technologies associated to radioactivity open new and promising perspectives that fascinate experts from other medical disciplines, and more particularly oncologists, haematologists and neurologists.

This work does not intend to put forward new therapies and original answers to pathologies that seem hopeless. Physicians do have all the competencies required to prescribe the most appropriate treatments for specific patients and diseases. This book simply aims to provide detailed information, using a vocabulary that is as accessible as possible, to a public that is usually not even aware that this discipline does exist and that it brings a new breath of life to diagnosis and therapy, especially in oncology.

For a long time, therapy by means of nuclear medicine was restricted to very difficult cases and last chance treatments. Physicians usually think of using metabolic radiotherapy only after chemotherapy and external radiotherapy protocols repeatedly failed.

In this introductory chapter, we will see how patients can benefit from the knowledge acquired in nuclear medicine during the past half century, and learn about the revolutionary aspect of these new techniques and medicinal products; then, we will take a look at all the opportunities brought by this technology when it is associated to other innovative medical modalities. All these aspects will be developed in detail further in this book.