CXCR4 and neoplasm: Consistently with the PET findings, high uptake of the tracer was observed in the A549/CXCR4 tumors, and the uptake can be significantly reduced via blocking with an excess of NOTA-QHY-04, which indicated again that the tumor accumulation of [18F]AlF-NOTA-QHY-04 was CXCR4 specific.