(PARACEST) The alteration of the proton density or total water signal changes contrast and can be detected by the MRI scanner. Paramagnetic chemical exchange saturation transfer contrast agents are based upon the magnetization transfer mechanism.
Lanthanide ion complexes formed with tetra-amide based ligands display unusually slow water exchange kinetics and this feature may be used to alter image contrast by applying a selective presaturation pulse in an imaging sequence. This results in chemical exchange saturation transfer (CEST) from the lanthanide-bound water to bulk water thereby altering image contrast.
Chemical Exchange Saturation Transfer (CEST) agents are a class of contrast agents that could potentially revolutionize the MRI field because of their improved sensitivity and can have a great impact on functional magnetic resonance imaging.