Can the Theoretical Fitting of the Proton-Nuclear-Magnetic-Relaxation-Dispersion (Proton NMRD) Curves of Paramagnetic Complexes Be Improved by Independent Measurement of Their Self-Diffusion Coefficients?
✍ Scribed by Luce Vander Elst; Audrey Sessoye; Sophie Laurent; Robert N. Muller
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- German
- Weight
- 245 KB
- Volume
- 88
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
The self‐diffusion (D~c~) coefficients of various lanthanum(III) diamagnetic analogues of open‐chain and macrocyclic complexes of gadolinium used as MRI contrast agents were determined in dilute aqueous solutions (3–31 mM) by pulsed‐field‐gradient (PFG) high‐resolution ^1^H‐NMR spectroscopy. The self‐diffusion coefficient of H~2~O (D~w~) was obtained for the same samples to derive the relative diffusion constant, a parameter involved in the outersphere paramagnetic‐relaxation mechanism. The results agree with an averaged relative diffusion constant of 2.5 (±0.1)×10^−9^ and of 3.3 (±0.1)×10^−9^ m^2^ s^−1^ at 25 and 37°, respectively, for 'small' contrast agents (M~r~ 500–750 g/mol), and with the value of bulk H~2~O (2.2×10^−9^ and 2.9×10^−9^ m^2^ s^−1^ at 25° and at 37°, respectively) for larger complexes. The use of the measured values of D~c~ for the theoretical fitting of proton NMRD curves of gadolinium complexes shows that the rotational correlation times (τ~R~) are very close to those already reported. However, differences in the electronic relaxation time (τ~SO~) at very low field and in the correlation time (τ~V~) related to electronic relaxation were found.