TFRC and neoplasm: To exclude the possibility of non-TfR-specific accumulation of radiotracer in necrotic tumor tissue, we injected tumor-bearing mice with a non-specific anti-GFP VHHEnh-PEG-NOTA-64Cu conjugate (Figure 7B and D), which showed only weak passive accumulation in the lung metastases at 4 weeks post-tumor cell infusion.