Calibrating variable flip angle (VFA)-based T1 maps: when and why a simple scaling factor is justified

Variable Flip Angle (VFA)-based T1 maps are known to be prone to errors deriving from B1 errors (inaccurate knowledge of flip angles) and poor signal spoiling. In general, in vivo T1_VFA values tend to overestimate T1 values obtained using a gold standard inversion recovery method :T1_IR. Calibrating T1_VFA with T1_IR has been proposed but it requires knowledge of the exact relationship between these. This work models the contribution of B1 errors and poor spoiling to T1_VFA errors and via simulations, the conditions for T1_VFA/T1_IR= constant (i.e. simple scaling) are derived. Experiments on phantoms and in vivo are used for validation.