**4. Conclusions**

Improvements in effective nuclear imaging are not only dependent on progression in imaging equipment and technology, but is also strongly dependent on the availability of powerful probes with optimal pharmacokinetic and imaging characteristics. The diversity of methods for syntheses of peptides and proteins and the variety of possibilities for modification, stabilization, labeling (radiolabeling and labeling for other modalities), and construction of more complex multivalent and multimodal constructs, make radiolabeled peptides and proteins a flexible class of tracers and meaningful molecules for nuclear imaging of several diseases such as cancer, thrombosis, infection, and inflammation in pre-clinical and clinical research.

Radiotracers enable early diagnosis and thus early treatment of disease and they enable better stratification of patients with disease-stage-adapted therapy instead of escalating to the most aggressive and costly therapy. Moreover, radiolabeled compounds are used to monitor the therapeutic effect of drugs and are used as therapeutic radiopharmaceuticals when labeled with either β<sup>−</sup> - or α-emitting radionuclides such as 90Y, 186Re, 188Re, 131I, 177Lu and 211At and 213Bi, respectively.

The growth of the world population and the overall rise in life expectancy in the last decades will increase the demand for radiopharmaceuticals, including basic research into and the development of new radiopharmaceuticals.
