Background <p>Rheumatoid arthritis (RA) is a common chronic, inflammatory autoimmune disease, and early clinical diagnosis is crucial for its treatment. CXCR4 expression was characterized in arthritic mouse models and joints of RA patients, and [¹⁸&#xa0;F]AIF-NOTA-QHA-04 specificity was assessed in non-malignant cells with elevated CXCR4 expression. This study explored the application of CXCR4-targeted PET probe [¹⁸&#xa0;F]AIF-NOTA-QHA-04 in monitoring disease activity and therapeutic efficacy in RA. To this aim, the metabolic characteristics of [¹⁸&#xa0;F]AIF-NOTA-QHA-04 and correlation of [¹⁸&#xa0;F]AIF-NOTA-QHA-04 uptake with arthritis severity were evaluated by PET imaging in arthritic mice. [¹⁸&#xa0;F]AIF-NOTA-QHA-04 potential in evaluating therapeutic efficacy was further investigated in arthritic mice following methotrexate (MTX) and etanercept (ETC) treatment.</p> Results <p>CXCR4 expression was significantly increased in the inflamed joints of collagen-induced arthritis (CIA) and collagen-antibody induced arthritic (CAIA) mice, and in synovial tissues of RA patients. [¹⁸&#xa0;F]AIF-NOTA-QHA-04 showed high specificity for CXCR4, with increased probe uptake in arthritic joints that was strongly correlated with arthritis severity scores. PET imaging revealed that increased uptake of [¹⁸&#xa0;F]AIF-NOTA-QHA-04 in arthritic joints paralleled disease activity, with uptake decreasing upon remission. Furthermore, [¹⁸&#xa0;F]AIF-NOTA-QHA-04 PET imaging provided earlier and more sensitive assessments of the efficacy of MTX and ETC compared to traditional methods.</p> Conclusion <p>The CXCR4-targeted PET probe [¹⁸&#xa0;F]AIF-NOTA-QHA-04 is a promising tool for RA diagnosis and monitoring, with high specificity and sensitivity. The potential of this probe as a biomarker for disease activity and therapeutic response underscores its value in personalized medication strategies for the management of RA.</p>