Last update:
21-Jul-2006

Molecular imaging techniques provide the opportunity of studying the cell biochemistry in vivo. Radioisotopic techniques (positron emission tomography, PET), due to their inherent high sensitivity, comprise the preferred approach, although magnetic resonance imaging-based methods (MRI) appear to be gaining momentum. Due to impressive advances in molecular biology and the feasibility of gene therapy, a non-invasive method of assessment has become imperative. Imaging of gene transfer and expression and the time frame of this expression are currently being studied by various groups, using mainly PET-based methods. This review provides an overview of the various methodologies in use (direct and indirect imaging methods) and the various radiopharmaceuticals employed. The concept of the reporter gene is discussed in the context of indirect imaging methods, the various modifications of which are briefly discussed, with emphasis on the bicistronic and the artificial receptor approaches. The most frequently used reporter genes, such as the thymidine kinase (TK) and the post-synaptic dopaminergic receptor 2 (D₂R) genes are described. The principles of the artificial receptor approach are discussed.

Key words: Artificial receptors, Bicistronic approach, Direct imaging, Indirect imaging, Molecular imaging, Transgene expression.