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Several promising tau imaging probes have been developed by Tohoku University ([18F]THK series), National Institute of Radiological Sciences([11C]PBB3), Eli Lilly ([18F]T807), and Hoffman-La Roche ([18F]R06958948). In this paper we discussed some of the criteria required for the tau imaging probe in Alzheimer's disease. It will be certain that tau imaging plays an important role in an accurate diagnosis and as companion diagnostics.

Progressive accumulation of amyloid plaques in the brain is a characteristic pathological change in Alzheimer's disease (AD) and precedes the presentation of cognitive impairment. In vivo detection of amyloid deposits using molecular imaging technique would thus prove useful for early diagnosis of AD and tracking disease progression. Several imaging agents have been developed that can noninvasively detect amyloid plaques in the brain and successfully differentiated AD patients from healthy normal individuals using positron emission tomography. Although validation remains required as to whether retention of these agents in the neocortex truly reflects the level of amyloid deposition, such findings suggest the potential usefulness of amyloid imaging technique for early diagnosis of AD.

A novel [18F]FRP-170 injection for imaging hypoxia by PET was developed for clinical use. The preparation was based on the simple on-column basic-hydrolysis and the whole procedure was automated by detecting He flow change for transferring and evaporating liquids. [18F]FRP-170 was prepared in around 15-20% decay-corrected radiochemical yield within 60 min and stable in saline for more than 6 hr. Radiochemical purity was over 99% and specific activity at EOS was 40-60 GBq/micromol. The radiation-absorbed dose to the whole body was estimated to be 1.0 mSv/185 MBq. The [18F]FRP-170 injection proved to be suitable for clinical use without acute toxicity or mutagenicity.