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Dernière mise à jour : lundi 29 août 2011, par
Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT)  are highly sensitive imaging techniques (fM-pM) and offer the potential for whole body scanning. However, they have the disadvantage of poor spatial and temporal resolution. Both modalities are based on the use of a radiopharmaceutical and the emission of a γ radiation.
In TEP, a positron-emitting radionucleide (β+) is used (18F, 11C, 64Cu,...). The annihilation of a positron with an electron releases two γ rays which are emitted 180° apart. In SPECT, β emitters are used (99mTc, 111In, 67Ga,...).
In both cases, the emitted γ rays are detected by a γ camera to produce tridimensional images of the radiotracer’s location within the organism.
To date, 18F labelled DFG (DeoxyFluoroGlucose)  is the only clinically approved PET radiotracer but its application is limited by the short lifetime of 18F (t1/2 = 109.7 min). However, 64Cu has a significantly longer half-life (t1/2 = 12.7 h) and has the potential for use in PET , (β+, 17.8%, 653 KeV) as well as for radiotherapy, due to the additional high-energy β- particle (38.4%, 579 KeV).
Several families of ligands have been studied in order to optimise the in vivo stability of the 64Cu-radiolabeled complexes and their efficiency as radiopharmaceuticals. Four requirements have been identified : (i) high kinetic and thermodynamic stabilities, (ii) high selectivity for Cu(II) in comparison to other endogenous cations, (iii) a low reduction potential and (iv) a fast kinetic of complexation.  
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