Stability and Toxicity of Contrast Agents

Abstract

Magnetic Resonance Imaging (MRI) derives directly from the phenomenon of Nuclear Magnetic Resonance (NMR [1][2][3][4]), which is widely used by chemists to determine molecular structure. The word "nuclear" was dropped in the switch to imaging to avoid alarming patients as NMR has nothing to do with radioactivity. This book is intended mainly for chemists, who are generally familiar with the NMR spectra. After a brief overview of the technique explaining the notion of relaxation time and saturation transfer used in MRI, we will describe localization techniques, which are less well-known in chemistry. The purpose of this short chapter is not to provide a complete theory of MRI [5][6][7][8], but to understand the rest of the book concerning the action of contrast agents. We will not go into the theoretical background of the phenomena, and while it is important to have some understanding of quantum mechanics, it is not our purpose to develop this aspect. This is a "nuts and bolts" description of MRI. Whenever possible, we refer to chemists' knowledge of NMR (for example, "2D NMR"). Theoretical basis of NMR Short description of NMRIn most cases, MRI focuses on one type of atomic nucleus, that of hydrogen in H 2 O. We will therefore only use this nucleus, termed the " 1 H proton."The physical phenomenon of NMR lies at the boundary between "conventional" and "quantum" treatment due to the small transition energies involved. Traditionally, the 1 H proton can be considered as a charged

H4octapa: Highly Stable Complexation of Lanthanide(III) Ions and Copper(II)

“…26 + species formed at low concentration may also be observed when using the Cu 2+ ion as a ligand scavenger at pH ≥ 4.6. By taking into account the dissociation pathways mentioned above, the overall map of dissociation can be illustrated by the general scheme shown in Scheme 2.…”

“…As often observed for complexes with nonmacrocyclic chelators, 26 dissociation under physiological conditions occurs mainly through metal-assisted (Cu 2+ ) pathways, both due to a direct attack of the exchanging metal ion with the formation of a dinuclear intermediate and the catalytic role of the Cu(OH) + species. However, these dissociation pathways are expected to play a limited role in biological media due to the very low concentration of uncomplexed Cu 2+ .…”

Approaching the Kinetic Inertness of Macrocyclic Gadolinium(III)‐Based MRI Contrast Agents with Highly Rigid Open‐Chain Derivatives

“…[18] Moreover, the stability of [Gd(cddadpa)] -is comparable to or slightly lower than those of the Gd 3+ complexes formed with macrocyclic do3a 3-and its derivatives used as commercial contrast agents (hp-do3a 3-and do3a-butrol 3-). [19] Given the considerably lower basicity of cddadpa 4-, the conditional stability constant of [Gd(cddadpa)] -will be higher near physiological conditions, despite the comparable stability constants of the complexes. This is demonstrated by comparing the pGd values calculated as proposed by K. N. Raymond and co-workers (Table 1).…”

Development of the application of speciation in chemistry

“…The majority of clinical Gd(III)-based agents, which represent around 90% of all clinical contrast agent injections, have low molecular weight, an extracellular space localization, and they are non- [189,190] (Fig. 9).…”