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

In vitro T1 and T2* relaxivities (r1 and r2*) of Gd‐DTPA (GaD) in oxygenated human venous blood (OVB) and aqueous solution (AS) at 3 and 7 T 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 3 and 7 T, a linear relationship was observed between [GaD] and R1 in both AS and OVB. At 7 T, 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 4‐fold in r2* with GaD in OVB at 7 T (for [GaD] above 2 mM, p <<0.01) as compared with 3 T. Furthermore, in comparison to r1, r2* in AS was less than 2‐fold higher at both field strengths while in OVB it was ~20‐fold and ~90‐fold higher at 3 and 7 T, respectively. This observation emphasizes the importance of r2* knowledge at high magnetic fields, ≥3 T. 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. Copyright © 2014 John Wiley &...

Source: Contrast Media and Molecular Imaging - February 12, 2014 Category: Radiology Authors: Chaitanya Kalavagunta, Shalom Michaeli, Gregory J. Metzger Tags: Full Paper Source Type: research