Signal sensitivity to T1 effects, as a function of tissue T2*, for a range of pulse sequence combinations (a: TR = 1.5s, FA = 30, 60, and 90º; b: FA = 60º, TR = 1, 1.5, and 2 s). Multi-echo TE = 0 (black) and single-echo protocols (red and blue) vary with TR and FA. Single-echo protocols must balance T1 and T2* sensitivity, whereas multi-echo protocols separate these effects. For multi-echo protocols, the TE combination and tissue T2* do not impact the relative T1 sensitivity.