Enhancing magnetic resonance imaging with contrast agents for ultra-high field strengths

Abstract

Contrast agents are diagnostic tools that often complement magnetic resonance imaging. At ultra-high field strengths (≥7 T), magnetic resonance imaging is capable of generating desirable high signal-to-noise ratios, but clinically available contrast agents are less effective at ultra-high field strengths relative to lower fields. This gap in effectiveness demands the development of contrast agents for ultra-high field strengths. In this minireview, we summarize contrast agents reported during the last three years that focused on ultra-high field strengths.

<strong>A heteronuclear ZnGd complex as a potential contrast agent for magnetic resonance imaging</strong>

“…Thus, longitudinal R 1 and transversal R 2 relaxivities were measured. The R 1 value of 4.90 mM -1 s -1 is comparable with those found for other commercial agents, 6 and, therefore, it could be said that 1·6H 2 O should be a good T 1 contrast agent. Nevertheless, the R 2 value is 38.63 mM -1 s -1 , and, therefore, the T 1 /T 2 (R 2 /R 1 ) ratio is 7.9, value that strongly differs from 1.…”

Filling Tricompartmental Ligands with GdIII and ZnII Ions: Some Structural and MRI Studies

“…For ZnGd, the r 1 value of 4.90 mM −1 s −1 (Table 1) extracted from methanol solutions is comparable with those found for other commercial agents [56], so it may be considered as a potential T 1 contrast agent. Nevertheless, the r 2 value is 38.63 mM −1 s −1 ( Figure 5) and, therefore, the T 1 /T 2 (r 2 /r 1 ) ratio is 7.9, a value that strongly differs from 1.…”

“…This result appear to suggest that an increasing Gd:Zn molar ratio in the complex could improve its relaxometric properties. The r 1 relaxivity value found of Zn 2 Gd (7.14 mM −1 s −1 ) is even higher than those values reported for some classical commercial T 1 CAs [56]. However, as occurred before, calculated r 2 value is even higher (84.83 mM −1 s −1 ), while the T 1 /T 2 ratio of 11.88 clearly shows that instead of a T 1 contrast, Zn 2 Gd could be proposed as a potential candidate for T 2 CA.…”

Overcoming the concentration-dependence of responsive probes for magnetic resonance imaging

“…48 The use of Eu 2+ -containing cryptates is potentially advantageous because r 1 increases at ultra-high magnetic field strengths (≥7 T), 88 whereas the r 1 of Gd 3+ -containing complexes decrease. 89 Furthermore, higher magnetic field strengths can lead to greater spatial and temporal resolutions that are desirable for diagnostic scans. However, a limitation with Eu 2+ is its propensity to oxidize to Eu 3+ .…”