A Simplified Nonlinear Fitting Strategy for Estimating T1 from Variable Flip Angle Sequences

Joshua Trzasko¹, Petrice M. Mostardi¹, Stephen J. Riederer, Armando Manduca¹

Variable flip angle SPGR imaging, despite challenges due to transmit field inhomogeneities, remains a widely used strategy for T1 mapping. Nonetheless, there has been little work on numerical strategies for computing T1 values from such image series, and most estimations are performed using either a two-parameter nonlinear least squares fitting, which is accurate but computationally intensive, or a linear regression approximation, which is significantly faster but prone to error. In this work, we describe a simple numerical optimization strategy which can accelerate NLLS computation by over an order of magnitude without compromising its accuracy.