Wide-Range T1 Mapping Using Two Variable Flip Angle Acquisitions

Introduction: Volumetric T1 mapping using two variable flip angle (VFA) acquisitions has become a popular clinical tool for T1 estimation due to short scan times and ease of implementation. The conventional approach to flip angle selection has been based on maximization of the signaldynamic range (S-DR) product for a single T1 value of interest (typically ≤ 1000 ms), with estimation accuracy and precision maintained only within a limited range of the chosen value [1,2]. However, no studies to date have investigated systematic bias in the S-DR product based on different choices of flip angle pairs (i.e. corresponding to different T1s of interest) and the potential implications for the range of effective T1 estimation. While alternative VFA approaches have been developed to allow T1 mapping over the whole biological range [3,4], the need for additional acquisitions may limit their utility when scan time is limited and/or signal averaging is required to achieve minimum SNR thresholds. Here we investigate the effect of flip angle selection on bias in the S-DR product with the aim of performing wide-range T1 mapping using only two VFA acquisitions.