Elimination of T1 Weighting in FLAIR by Optimized Double IR – Could this be the Only T2-Weighted Sequence Needed?

Introduction: Fluid-attenuated inversion recovery (FLAIR) is widely used for its improved conspicuity of long T2 lesions by suppressing cerebrospinal fluid (CSF). Concerns remain, however, that the IR imparts T1 weighting that can decrease detectability and lead to mischaracterization of some lesions. Frequently both T2 and FLAIR images are acquired in clinical protocols to guard against these concerns (1,2). Optimization of FLAIR to detect MS lesions, for example, has stressed the importance of very long repetition times (TR) to minimize T1 weighting (3). Recently, interest in double IR (DIR) preparations (4) to highlight certain types of brain lesions has intensified (5). Typically, DIR is optimized to null white matter (WM) and CSF, producing even stronger T1 contrast than FLAIR. We demonstrate that the two inversion times in a DIR can be optimized to simultaneously null CSF and eliminate T1 weighting, rather than null WM and CSF. Such optimization produces an image with pure T2 weighting over the range of T1’s typical of brain tissue.