Non-responsiveness to therapy often occurs during treatment of RA. To avoid prolonging ineffective treatments, it is important to ensure effectiveness early upon treatment initiation. With a SPECT scan using anti-FAP antibodies as a tracer, we were able to detect minimal affected joints. After treatment with liposomal prednisolone, a new therapeutic approach for RA, uptake in inflamed joint was lower compared to joints in untreated mice. This indicates that the anti-FAP SPECT scan can be used to monitor the therapeutic efficacy of new drugs. The last part of this thesis shows that the therapeutic effect of anti-IL-22 as a new treatment could be monitored using radiolabelled anti-FAP imaging as well.