Novel positron emission tomography tracers for imaging of rheumatoid arthritis.

Positron emission tomography (PET) is a nuclear imaging modality that relies on visualization of molecular targets in tissues, which is nowadays combined with a structural imaging modality such as computed tomography (CT) or Magnetic Resonance Imaging (MRI) and referred to as hybrid PET imaging. This technique allows to image specific immunological targets in rheumatoid arthritis (RA). Moreover, quantification of the PET signal enables highly sensitive monitoring of therapeutic effects on the molecular target. PET may also aid in stratification of the immuno-phenotype at baseline in order to develop personalized therapy. In this systematic review we will provide an overview of novel PET tracers, investigated in the context of RA, either pre-clinically, or clinically, that specifically visualize immune cells or stromal cells, as well as other factors and processes that contribute to pathology. The potential of these tracers in RA diagnosis, disease monitoring, and prediction of treatment outcome will be discussed. In addition, novel PET tracers established within the field of oncology that may be of use in RA will also be reviewed in order to expand the future opportunities of PET imaging in RA.