(a) Single-echo AIF (red) and VOF (blue), both calculated from the GEEPI time course acquired at TE2 = 34.1ms. The presence of T1-shortening effects caused an underestimation of contrast agent concentration in the VOF, visible at the onset of the first bolus passage and during the post-bolus period. The AIF was also affected by T1-effects, but to a lesser extent. (b) Comparison of single-echo AIF (red) with multi-echo AIF (purple). The multi-echo AIF was corrected for T1-shortening effects, with the result of elevated post-bolus contrast agent concentrations, reflecting residual Gd in the blood stream. (c) Single-echo VOF (blue) vs. multi-echo VOF (cyan). The multi-echo fitted VOF was corrected for T1-induced negative contrast agent concentrations. However, during the first passage of the bolus, the multi-echo VOF experienced signal saturation, resulting in incorrect R2* estimations. Therefore, for quantitative DSC-PWI, AIF scaling was based on the post-bolus levels of the multi-echo fitted AIF (purple area under the concentration curve) and the multi-echo fitted VOF (cyan).