It has been reported that positron emission tomography (PET) or single photon emission computed tomography (SPECT) study targeted TSPO probes, including 11C-(R)-PK11195, 11C-DPA-713, 18F-DPA-714 or 99mTc-DTPA-CB86, can visualize RA (Gent et al., 2014a; Gent et al., 2014b; Liu et al., 2020). Here, TSPO is linked to rheumatoid arthritis.