A new class of contrast agents for magnetic resonance imaging based on selective reduction of water-T2 by chemical exchange.

Compounds containing mobile protons can act as contrast agents by increasing the value of the term (1/12 - 1/11). The efficiency of this method is markedly pH- and field-dependent. There are many such compounds allowing a choice to be made based on the characteristics of the tissue or organ, magnetic field strength, and solution pH levels. The properties of some of these chemicals have been investigated at different magnetic field strength and solution pH levels. The authors report herein the properties of iopamidol a well-known x-ray contrast agent, and stress its potential effect as an MRI contrast agent. The influence on the T2 decrease of the chemical shift separation delta omega (in frequency units) between water and exchangeable proton of the contrast agent may be increased by adding suitable shift reagents which interact with basic sites close to the protons involved in the chemical exchange.