Modulating the relaxivity of hyperpolarized substrates with gadolinium contrast agents.

Gadolinium contrast agents are known to affect the outer-sphere relaxivities of nuclei other than protons. We have investigated the heteronuclear relaxivities of four commercial gadolinium contrast agents (Magnevist, Omniscan, Dotarem and Gadovist) on the relaxation of (13)C in glycine, (13)C in pyruvate and (15)N in choline with long relaxation times. Marked differences in the relaxivities were found between different contrast agents and are attributed to electrostatic effects. This methodology may find applications in the field of hyperpolarized magnetic resonance and by way of example we show that injection of a bolus of contrast agent into an aqueous solution containing hyperpolarized (15)N labeled tetramethylammonium or (13)C labeled pyruvate leads to a predictable shortening of the lifetime of the hyperpolarized signal. Copyright (c) 2009 John Wiley & Sons, Ltd.