Accurate and Efficient Mapping of Flip Angle and T1 using Simultaneous Actual Flip Angle - Variable Flip Angle Imaging (AFI-T1)

Introduction: The knowledge of flip angle values is essential for accurate modeling in many quantitative MRI techniques. Recently, Actual Flip Angle Imaging (AFI) was proposed to account for multiple sources of flip angle variations such as transmit field inhomogeneity, B0 variations, slab profile, and excitation pulse effects [1]. AFI was successfully applied to yield system-independent T1 relaxivity maps from variable flip angle (VFA) SPGR measurements [1-4]. AFI assumes the repetition time is much less than T1. When this assumption is violated, significant errors in flip angle and in subsequent T1 estimates may arise.