Value of Independent Flip Angle Mapping for Transverse Relaxometry with Stimulated Echo Compensation

INTRODUCTION: Stimulated echo compensation [1] enables standard multi-echo spin echo sequences to be used for accurate single component T2 quantification by accounting for slice profile and both stimulated and spin echo pathways. This method produces both a T2 map and a relative flip angle map. However, for a given T2 decay, two solutions exist with refocusing angles above and below 180 ̊, with potentially different T2 values. Therefore, the flip angle (FA) solution is typically constrained to refocusing angles of 180 ̊ or less. Including prior knowledge from an independent FA map eliminates one fitting parameter, and the need to constrain FA solutions. However an independent FA determination is not always available, takes additional time, and typically has different slice profiles than those used in multi-echo spin echo relaxometry. The purpose of this work is to evaluate the flip angle constraint on stimulated echo compensation and determine the value of an independently measured FA map for transverse relaxometry using a multi-echo spin echo acquisition.