MRI imaging

FIGURE 2 An MRI image of a human brain. The patient must lie within the strong magnetic field. The detectors can be rotated around the patient s head, thereby allowing many different views to be recorded. 

Fig. 3.7.6 DDIF spectra and SPRITE MRI images of Berea obtained in different saturation states. (A) The DDIF spectra during cocurrent imbibition at different water saturation (Sw) levels. Note the similar shape of DDIF spectra at different Sw. (B) The DDIF spectra during counter-current imbibition acquired at different water saturation levels. Note the change in the DDIF spectral shape for the different saturation levels. (C, D) A pair of images show 2D longitudinal slices from 3D...

A more quantitative method is the so-called phase method, the phase being one of two parameters that an MRI image yields, the other being signal amplitude. We show below (Section 4.8.2.6) that the phase is correlated with the velocity of the sample, so a spatially resolved image of the signal phase can yield a velocity image. 

Signal-intensity analysis yields further insight into cellular pathology. Tl- and T2-weighted MRI imaging... 

Table 7.3 Properties of Some Gadolinium(III) MRI Imaging Agents... 

Figure 7.19 Several ligands and gadolinium(III) complexes used in MRI imaging. (A) DTPA ligand (B) [Gd(DTPA)(H20)]2, Magnevist (C) MS-264-L, ethylene-bridge-substituted DTPA (D) BOPTA, acetate-substituted DTPA (E) [Gd(B0PTA)(H20)]2, MultiHance (F) AngioMARK . (Adapted with permission from Chart 1 of Caravan, P. Ellison, J. J. McMurry, T. J. Lauffer, R. B. Chem. Rev., 1999, 99(9), 2293-2352. Copyright 1999, American Chemical Society.)...

Figure 7.21 indicates the several neutral complexes used as MRI imaging agents. Neutrality is accomplished through bisamide substituents on DTPA [Gd(DTPA-BMA)(H20)], Omniscan (Figure 7.21A,B) or via the cyclic ligand HP-D03A [Gd(HP-D03A)(H20)], ProHance (Figure 7.21C.D).

In addition to X-ray crystallographic studies, two-dimensional NMR solution experiments (i.e., COSY, 1D-NOE, and NOESY, discussed in Sections 3.5.9 and 3.5.10) have been carried out on many lanthanide(III), Ln(ffl), chelate complexes to confirm that the structure of the MRI imaging agent, used in aqueous solution, will correspond to the solid-state X-ray crystallographic structure. Two-dimensional exchange spectroscopy (2D-EXSY) has been applied to lanthanide chelates to study the dynamics of conformational equilibria (how acetate arms chelate and how... 

Table 6.25 Relative Repetition and Echo Times for Different MRI Image Contrasts...

MRI contrast agents that are currently used clinically are all non specific extracellular agents. Their ability to enhance the contrast of MRI images stems essentially from their preferential blood distribution and their small size. Furthermore, the relatively low sensitivity of the magnetic resonance technique requires the injection of large amounts of contrast agent. 

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