This study aims to investigate the value of 68Ga-FAPI PET/CT in detecting recurrent and metastatic lesions in patients with thyroid cancer after surgery.

The investigators will number all participants, create a medical record file, and record their basic information (gender, age) as well as contact information and medical history information. All participants will undergo a 68Ga-FAPI PET/CT when recurrence or metastasis is suspected. The imaging response measurements will be compared with follow-up results or histopathological findings as the gold standard.

Inclusion Criteria:

1. Patients with thyroid cancer who have undergone surgery and are suspected of recurrence or metastasis during clinical evaluation.
2. Signed and dated informed consent form.
3. Commitment to comply with research procedures and co-operation in the implementation of the full research process.
4. Aged 18-80 years old.

Exclusion Criteria:

1. Patients with serious illnesses that researchers consider unsuitable for participation in this clinical study. Such as severe heart and lung failure, severe bone marrow suppression, severe liver and kidney dysfunction, etc.
2. Intestinal perforation, complete intestinal obstruction.
3. Pregnant women and women who may be pregnant, women who are breastfeeding.
4. Non-compliant person.

Inpatients and outpatients at Ruijin Hospital who meet the inclusion criteria.