Time, possess potential application as negative contrast agentsĪt high magnetic fields due to their efficient transverse Generally, dysprosium complexes where the water molecules have a long residence Large magnetic susceptibility which induces local field gradients Residence time in order to optimise the r 2 relaxivity. They display slow water exchange, due to the need to lengthen the Result, the interest in dysprosium-based complexes is increasing as Gd(III) based contrast agents exhibit poor water relaxivity. MRI, being classed as a negative contrast agent. Use of other Lanthanide (III) ions as MRI contrast agentsĭysprosium(III) is another lanthanide ion that has been used in Consequently paramagnetic Ln(III) other than Gd (III) are less efficient T 1 relaxation agents. It has been observed that the Curie spin relaxation effect affects the transverse relaxation more than the longitudinal relaxation. (The Curie-spin relxation effect is significant at lower temperatures and higher magnetic fields and for ions with a large magnetic moment). Other Ln (III) ions tend to undergo Curie relaxation enhancement arising from the interaction of the nuclear spin with the thermal average of the electron spin. This in turn results in a strong magneticĪnisotropy and fast electronic relaxation states with very short T 1, Relaxation rate that is six orders of magnitude slower than the Symmetric seven electron ground state results in an electronic The Gadolinium ion is also unique among other Ln(III) because its Other Ln(III) ions with large magnetic moments are less efficient in shortening T 1. It has the ability to shorten both the longitudinal and transverse relaxation times of water protons approximately to the same extent by relaxing all nearby protons. Gadolinium (III) ion is unique in a number of respects: Gadolinium(III) chelate complexes are routinely used as contrast agents in magnetic resonance imaging (MRI) 1 the usual explanation is that paramagnetic species contain unpaired electrons, which cause relaxation of nearby $\ce$s at the magnetic field strengths used in MRI
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