Magnetic resonance imaging relaxivity

The commercial development of Gd(dota) as a magnetic resonance imaging relaxation agent, as well as the demonstrated ability of lanthanide complexes to catalytically cleave RNA, have stimulated research into the synthesis of complexes derived from macrocyclic ligands with pendant arms. NMR studies have been carried out on many of the paramagnetic complexes derived from this class of ligands, which are reviewed in the following sections. 

The classical description of magnetic resonance suffices for understanding the most important concepts of magnetic resonance imaging. The description is based upon the Bloch equation, which, in the absence of relaxation, may be written as... 

Human skin is the largest organ in the human body. It is fundamentally important to health as the semi-permeable barrier - the first line of defence - between the body and the external world. However, it remains relatively inaccessible to conventional magnetic resonance imaging, firstly because it is thin and therefore requires high spatial resolution, and secondly because it is characterized by relatively short T2 relaxation times, particularly in the outermost stratum comeum. Conventional studies have not usually achieved a resolution better than 70-150 pm, with an echo time of the order of a millisecond or so. As a planar sample, skin has proved amenable to GARField study where it has been possible to use both a shorter echo time and achieve a better spatial resolution, albeit in one direction only. Such studies have attracted the interest of the pharmaceutical and cosmetic industries that are interested in skin hydration and the transport of creams and lotions across the skin. 

The use of magnetic resonance imaging (MRI) to study flow patterns in reactors as well as to perform spatially resolved spectroscopy is reviewed by Lynn Gladden, Michael Mantle, and Andrew Sederman (University of Cambridge). This method allows even unsteady-state processes to be studied because of the rapid data acquisition pulse sequence methods that can now be used. In addition, MRI can be used to study systems with short nuclear spin relaxation times—e.g., to study coke distribution in catalytic reactors. 

Keywords Metallofullerene, endohedral, gadolinium, magnetic resonance imaging, contrast agent, relaxivity, cellular imaging, molecular imaging... 

Toth E, Helm L, Merbach AE (2001) Relaxivity of Gadolinium(III) Complexes theory and mechanism. In Toth , Merbach AE (eds.) The chemistry of contrast agents in medical magnetic resonance imaging. Wiley, Chichester, pp. 45-119. 

Chamuleau RA, Creyghton JH, De Nie I, et al. 1988. Is the magnetic resonance imaging proton spin-lattice relaxation time a reliable noninvasive parameter of developing liver fibrosis. Hepatology 8 217-221. 

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