In nude mice, the A375-hPD-L1 tumor-to-muscle ratio in the 0.3–10 μg/animal dose group was approximately 2.5–3.5 times greater than that in the 100 μg/animal group, indicating that 68Ga-NOTA-Nb109 has a better target-to-background ratio at low doses. The gene discussed is CD274; the disease is neoplasm.