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Abstract:
Molecular imaging is a rather new biomedical research field investigating non-invasive visualization and characterization of biological processes at the molecular and cellular level in living systems.
During the last decade since the dawn of molecular imaging a multitude of targeting strategies has been developed and different classes of targeting modalities exist, although with certain overlap among them: 1) Specific molecules on the surface of cells can be imaged (e.g. receptors). 2) Molecules specific for a certain cell type or tissue can be visualized (e.g. enzymes, mRNA). 3) The expression of certain genes can be imaged. Whereas several targeting approaches are already in clinical use with highly sensitive methods such as positron emission tomography (PET), the application for magnetic resonance imaging (MRI) is still restricted because of its low sensitivity and hence the much higher probe concentrations required for imaging.
But, in combination with an ever increasing number of agents capable of generating contrast in MRI, an almost limitless number of targeted MRI probes can be envisioned. Yet, MRI contrast agents (CAs) can be basically classified into positive (appearing bright in images, e.g. paramagnetic Gadolinium chelates) and negative CAs (appearing mostly dark in images, e.g. superparamagnetic ion oxide nanoparticles).
Some examples of targeted MRI CAs developed by our group will be described in detail.
