Optimized double inversion recovery for reduction of T1 weighting in fluid-attenuated inversion recovery

Abstract

Fluid-attenuated inversion recovery (FLAIR) is a routinely used technique in clinical practice to detect long T2 lesions by suppressing the cerebrospinal fluid. Concerns remain, however, that the inversion pulse in FLAIR imparts T1 weighting that can decrease the detectability and mischaracterize some lesions. Hence, FLAIR is usually acquired in conjunction with a standard T2 to guard against these concerns. Recently, double inversion recovery (DIR) preparations have highlighted certain types of lesions by suppressing both cerebrospinal fluid and white matter but produce even stronger T1 contrast than FLAIR. This work shows that the inversion times in a DIR sequence can be optimized to minimize unwanted T1 weighting, enabling the acquisition of cerebrospinal fluid-suppressed images with pure T2 weighting. This technique is referred to as T 1-nulled DIR. The theory to determine the optimized inversion times is discussed and the results are shown by simulations, normal volunteer studies, and multiple sclerosis patient studies. T1-nulled DIR provides equivalent or superior contrast between gray and white matters as well as white matter and multiple sclerosis lesion at the same repetition time. Multiple sclerosis lesions appeared sharper on T1-nulled DIR compared to FLAIR. T1-nulled DIR has the potential to replace the combination of standard T2 and FLAIR acquisitions in many clinical protocols. Copyright © 2011 Wiley-Liss, Inc.