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Gregor Jost, Gunnar Schuetz, Hubertus Pietsch

ISMRM Annual Meeting 2018, 16-21 June 2018,Paris, France

Abstract

Gadoxetate has been clinically approved for detection and characterization of focal liver lesions by MRI. It exhibits moderate protein binding and is excreted from the body partially through the kidneys and partially by a hepatobiliary pathway. Hepatocytes take up gadoxetate mainly via OAPT and NTCP transporters and excrete it into the bile mainly utilizing Mrp2. By means of dynamic acquisition of gadoxetate signal intensity during liver uptake and excretion followed by application of a suitable kinetic model, the activity of the aforementioned liver transporters can be estimated. For kinetic modelling the gadoxetate concentration for each time point is needed which can be calculated from the signal intensity if r1 in tissue is known. In 1992 Schuhmann-Giampieri et al. reported r1 of gadoxetate to be significantly higher in liver tissue compared to blood at 0.47T. This effect has been attributed to gadoxetate’s protein binding which leads to an increased rotational correlation time. Gadoxetate relaxivities at 1.5T, 3T and 4.7T have since then been reported for water and plasma, but not for hepatocytes. We here present relaxivities for gadoxetate in hepatocytes at 1.5T and 3T to complement the original Schuhmann-Giampieri data. Measurements at 7T are in progress. Interestingly, r1 of gadoxetate after uptake into hepatocytes is about 2x higher compared to plasma and does not decrease with increasing field strength as has been shown for high relaxivity Gd based contrast agents exhibiting high protein binding e.g. gadofosveset. Gadoxetate’s higher r1 in hepatocytes has to be taken into account for pharmacokinetic modelling of dynamic gadoxetate MRI at clinical field strength, which has not been done so far.