Gadolinium-based contrast agents (GBCAs) are widely used in magnetic resonance imaging (MRI) to improve detection and characterization of pathological lesions [1–3]. The presence of current commercial GBCAs in tissues and body fluids most prominently changes images acquired with T1-weighted (T1w) contrast, due to a Gd-induced shortening of corresponding tissue- and fluid-water T1 times [4,5]. The agent-specific parameter that quantitatively captures this effect is the longitudinal molar relaxivi…