This study proposes to evaluate 99mTc-CTR-FAPI SPECT imaging as a cost-effective, low-radiation, and widely accessible alternative to 68Ga-FAPI PET/CT for assessing synovial lesions in RA patients, aiming to validate its diagnostic consistency with both PET/CT and physical examinations while correlating imaging findings with clinical disease activity metrics to establish a practical tool for long-term RA monitoring.

This study will enroll 20 rheumatoid arthritis patients meeting the 2010 ACR/EULAR classification criteria with moderate-to-high disease activity, with all participants undergoing both 99mTc-CTR-FAPI SPECT and 68Ga-FAPI PET/CT imaging for head-to-head comparison.The imaging results of both 99mTc-CTR-FAPI SPECT and 68Ga-FAPI PET/CT were independently interpreted by two nuclear medicine physicians with ≥10 years of diagnostic experience. A joint-by-joint comparison was performed between: (1) FAPI-positive joints identified by 99mTc-CTR-FAPI SPECT versus 68Ga-FAPI PET/CT, and (2) imaging-detected joints versus tender/swollen joints confirmed by physical examination.

Inclusion Criteria:

1. Age: 18-75 years old;
2. Meet the classification criteria for rheumatoid arthritis of the American College of Rheumatology/European Union for Rheumatology in 2010;
3. The highest disease activity in clinical practice (CDAI or SDAI score

Exclusion Criteria:

1. Patients with other autoimmune diseases;
2. Patients with concurrent tumors;
3. Women who are pregnant or planning to become pregnant, women in the preconception period, pregnant and lactating women, and women with child-rearing plans during the study period; Subjects of childbearing age need to take effective contraceptive measures during the research process;
4. Active infection
5. Suffering from claustrophobia or other mental disorders, with poor compliance resulting in inability to cooperate with this researcher; (6) Situations where other researchers consider it inappropriate to participate in this clinical trial.

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