The success of molecular imaging with positron‐emission tomography (PET) depends on the availability of selective molecular probes labeled with positron‐emitters, such asfluorine‐18 (t1/2 = 109.7 min). No‐carrier‐added (NCA) [18F]fluoride ion (18F–) is the primary reagent for the preparation of 18F‐labeled tracers in high specific activity. In this microreview, we survey current and advancing radiochemical methods and technologies for the use of NCA [18F]fluoride ion in the preparation of 18F‐labeled radiotracers for applications with PET. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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Two of the main pathological hallmarks of Alzheimer's disease (AD) are neuritic plaques and neurofibrillary tangles. Significant evidence supports a critical and probable causative role of amyloid (A ) plaque formation. Since neuroprotective treatments are typically most effective at early stages of injury, the detection and measurement of A load in living brain should be performed at early and perhaps even presymptomatic stages of AD. Two primary targets of molecular imaging research with positron emission tomography (PET) are to develop surrogate markers (radioligands) for assessing disease progression and for monitoring the efficacy of developmental therapeutics. Here, we review the current status of radioligand development for PET imaging of A aggregates. General structure-activity relationships have emerged, including the identification of at least three different ligand binding sites in various A aggregates and recognition of the general structural requirements for ligand binding at each site. Also a few radioligands applicable to imaging A plaques in living human brain with positron emission tomography (PET) have emerged, including [ 11 C]PIB, [ 11 C]SB-13 and [ 18 F]FDDNP.