Radiotracer I: Standard Tracer

Abstract

Molecular imaging combines non-invasive imaging methods with tools of molecular and cellular biology. Traditional imaging approaches in nuclear medicine were solely based on the detection of anatomical and structural features. Complementary to these conventional methods, advances in biology made it possible to visualize cellular and biochemical processes. Until the event of PET imaging, the spectrum of nuclides used for tracers was largely restricted to iodine isotopes and 99 m-technetium. Today, several PET nuclides have largely extended the possibilities of tracer design. The uptake of several archetypical diagnostic radiopharmaceuticals is illustrated in Figs. 18.1–18.3. Yet most of the commonly used tracers are derivatives of natural products. At present, the main effort in the field of radiotracer development is the identification of specific probes for targeting cellular structures, e g. tumour-associated receptors. These new ligands can be used for diagnosis as well as for treatment, a concept known as theranostics. Further, non-invasive imaging paradigms studied in small animals are currently being translated into the clinics. In the future, molecular imaging will provide new ways in the diagnosis of cancer and monitoring treatment response in oncology. For instance, studies using PET-based imaging of reporter genes have already been described in gene therapy approaches.