Cancer spreads to the everywhere in whole body along with time, which makes it difficult to fundamental treatment. Therefore, the early detection, diagnosis and treatment of cancer are strongly demanded. Abnormally high proliferative activity is a prominent feature of tumor cells, therefore, its non-invasive measurements using several thymidine analogs labeled with positron-emitting nuclei, such as ¹¹C and ¹⁸F by positron emission tomography (PET) are thought to be useful for the early detection of cancer in human.

We have tried to evaluate whether that ¹¹C-labeled AZT and d4T, which are known as thymidine analogs and anti-HIV drugs, are useful for PET tumor imaging and we found that the [¹¹C]AZT were remarkably accumulated in tumor. Interestingly, we also observed that [¹¹C]AZT showed low accumulation in the normal proliferative tissues, such as bone and intestine. Since most of thymidine analog PET probes are known to accumulate in normal proliferative tissue, [¹¹C]AZT could be useful to detect not only the bone tumor but also bone metastasis. We look forward to the clinical application of [¹¹C]AZT.