68Ga- and 18F-CAIX PET Imaging Study

This exploratory clinical imaging study will evaluate the safety, tolerability, biodistribution, lesion detection, and tumor uptake characteristics of 68Ga- and 18F-labeled carbonic anhydrase IX (CAIX)-targeted positron emission tomography/computed tomography (PET/CT) in patients with renal tumors or suspected renal cell carcinoma. Participants will be randomly assigned to receive either 68Ga-CAIX or 18F-CAIX PET/CT. All participants will also undergo 18F-FDG PET/CT for comparison. The study will further explore the association between CAIX-targeted PET findings and CAIX expression assessed by immunohistochemistry, as well as the diagnostic performance of CAIX-targeted PET/CT for lesion detection.

Inclusion Criteria: \- 1. Adults aged 18 years or older. 2. Voluntarily provide written informed consent before participation. 3. Patients with an indeterminate renal mass, suspected renal cell carcinoma, previously diagnosed clear cell renal cell carcinoma, or suspected recurrent renal cell carcinoma based on clinical or imaging findings. 4\. Estimated life expectancy of at least 6 months. 5. Participants of childbearing potential must use appropriate and highly effective contraception for at least 35 days after administration of the study tracer. Exclusion Criteria: * 1\. Renal tumor known to represent metastasis from another primary malignancy. 2. Other active malignancies requiring treatment. 3. Chemotherapy, radiotherapy, or immunotherapy within 4 weeks before study enrollment. 4\. Renal dysfunction with an estimated glomerular filtration rate (eGFR) ≤60 mL/min/1.73 m². 5\. Uncontrolled psychiatric disorders that may interfere with study participation. 6\. Pregnancy or breastfeeding. 7. Severe nonmalignant diseases, including infectious, autoimmune, or metabolic diseases, that in the investigator's opinion may interfere with the study objectives, participant safety, or study compliance. 8\. Individuals belonging to vulnerable populations.