Renal T1 and T2* mapping

T1 maps were generated using motion-correction and a 3-parameter T1 fit with Look-Locker correction while T2* maps were generated using a 2-parameter mono-exponential fit [35]. To ensure tissue homogeneity, the region of interest (ROI) was drawn one pixel in from the outer contour of the respective parenchymal area and for cortical ROIs the renal column was not delineated all the way down to the renal pelvis (Fig. 1). T1 values were acquired for renal cortex and medulla separately. Corticomedullary T1 differentiation, a marker of kidney dysfunction [36], was calculated as the ratio between cortical and medullary T1. T2* values were acquired for the renal cortex separately and for the entire renal parenchyma combined (cortex and medulla) as it was not possible to accurately distinguish between cortical columns and medulla in all echo images that were used for creating T2* maps (Fig. 1). Although acquired during breath-hold, minor motion made ROI transfer between echo images uncertain for T2* quantification.