In vitro Gd‐DTPA relaxometry studies in oxygenated venous human blood and aqueous solution at 3 and 7 T

Abstract

In-vitro T1 and T2* relaxivities (r1 and r2*) of Gd-DTPA (GaD) in oxygenated human venous blood (OVB) and aqueous solution (AS) at 3T and 7T were calculated. GaD concentrations ([GaD]) in OVB and AS were prepared in the range 0–5 mM. All measurements were acquired at 37±2 °C. At both 3T and 7T, a linear relationship was observed between [GaD] and R1 in both AS and OVB. At 7T, r1 in AS decreased by 7.5% (p = 0.045) while there was a negligible change in OVB. With respect to R2*, a linear relationship with [GaD] was only observed in AS, while a more complex relationship was observed in OVB; quadratic below and linear above 2 mM at both field strengths. There was a significant increase of over four-fold in r2* with GaD in OVB at 7T (for [GaD] above 2mM, p ≪0.01) as compared to 3T. Furthermore, in comparison to r1, r2* in AS was less than two-fold higher at both field strengths while in OVB it was ~twenty-fold and ~ninety-fold higher at 3T and 7T, respectively. This observation emphasizes the importance of r2* knowledge at high magnetic fields, ≥3T. The comparison between r1 and r2* presented in this work is crucial in the design and optimization of high field MRI studies making use of paramagnetic contrast agents. This is especially true in multiple compartment systems such as blood where r2* dramatically increases while r1 remains relatively constant with increasing magnetic field strength.

Myocardial perfusion cardiovascular magnetic resonance: optimized dual sequence and reconstruction for quantification

“…Although the estimated concentration is dependent on the accuracy of these values, which may be slightly different in blood plasma, the quantified myocardial blood flow has been found through simulation to be quite insensitive since they affect the scale of both blood and myocardium. In-vivo values of blood T2* were significantly lower than for saline phantoms at a given [Gd] as previously reported [26]. The average blood T2* at 1.5 T was approximately 10 ms at 4 mmol/L peak [Gd], whereas the T2* was approximately 25 ms in saline at the same concentration.…”

“…The average blood T2* at 1.5 T was approximately 10 ms at 4 mmol/L peak [Gd], whereas the T2* was approximately 25 ms in saline at the same concentration. The T2* decreases with field strength [26] and values as low as 4 ms are likely to be encountered at 3 T using a dose of 0.05 mmol/kg leading to higher signal losses and greater importance for T2* correction. The conversion to [Gd] in the presence of error in FA due to unknown B1 was analyzed through simulation to cause small errors in [Gd] which in turn will result in an error in estimated flow of < 15% for ±20% variation in B1.…”

Analysis of pharmacokinetics of Gd-DTPA for dynamic contrast-enhanced magnetic resonance imaging

“…al . have observed a quadratic relationship between T1 relaxivity, r 1, and [Gd-DTPA] below the dose of 2mM and a linear relationship for concentration higher than 2mM [31]. Similar to their observation For [Gd-DTPA] below 1mM (we tested here in an aqueous phantom) we did not observe a linear relationship for the whole range.…”

Gd‐Encapsulated Carbonaceous Dots with Efficient Renal Clearance for Magnetic Resonance Imaging

“…Gd@C-dots showed an r 1 of 5.88 mM −1 s −1 on a Gd basis (Figure 2d,e), which is significantly higher than Gd-DTPA (3.10 mM −1 s −1 ). [14] The enhanced r 1 was mainly attributed to the increase in the rotational correlation time (τ R ) as a result of binding Gd to a nanoparticle [15] .…”