MRI Data Processing

Until recently, the most common way of generating MRI contrast was by using heavy metal based contrast agents. Examples of these substances are the commercial Gadolinium(III) based Magnevist and the Iron Oxide based Resovist. A very obvious downside of using heavy metals is the toxicity of the agents in the human body. Fortunately, a new type of MRI has been developed, which allows for the use of organic compounds as contrast agent .

The Principle

This new type of MRI goes by the name Chemical Exchange Saturation Transfer MRI or CEST MRI. The principle behind this technique is based on compounds that contain pools of exchangeable protons that can be selectively saturated using radiofrequency irradiation. Upon proton exchange with bulk water, these compounds can be indirectly visualized by measuring the bulk water. The amino acids lysine, arginine, threonine and serine contain those exchangeable protons and polypeptides containing those amino acids in abundance are therefore potential contrast agents. An other advantage of CEST MRI is that different kind of protons (e.g. amide and hydroxide protons) can be distinguished, which allows for 'multi-color' imaging using multiple contrast agents simultanously.

References