PARACEST Contrast Agents
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PARACEST Contrast Agents book
This chapter discusses the concept of using chemical exchange saturation transfer (CEST) methods to produce contrast in magnetic resonance (MR) images. Since MR image intensity is largely determined by the water content of tissues and the relaxation characteristics of that water, any molecule that is in chemical exchange with water can potentially be used to transfer saturated spins into the pool of a water protons, and hence used to initiate CEST contrast. The magnitude of the shifts induced by lanthanide ions in the proton resonances of a molecule can be quite large, even several hundred ppm, and this is especially true of protons that are part of the lanthanide complex itself. The observation of a resonance arising from the coordinated water molecule in the NMR spectrum of these complexes has opened an entirely new avenue for a generating image contrast.