Used in molecular imaging, particularly in positron emission tomography (PET), as a radiolabeled compound for tracking cellular processes such as proliferation and DNA synthesis. It serves as a substrate for thymidine kinase 1 (TK1), an enzyme upregulated in rapidly dividing cells, making it useful in cancer diagnostics and monitoring treatment response. Its ability to mimic natural nucleosides allows incorporation into DNA, enabling visualization of tumor metabolism and viral activity in vivo.