The sensitivity of thin-slice fast spin echo, fast FLAIR and gadolinium-enhanced T1-weighted MRI sequences in detecting new lesion activity in multiple sclerosis

Fast fluid-attenuated inversion-recovery (FLAIR) and proton density/T2-weig hted fast spin echo (FSE) brain images with 3-mm slices were acquired month ly for 7 months in 37 multiple sclerosis patients. New and enlarging lesion s were counted and compared according to the site of lesions seen with each sequence. In addition, the number of new enhancing lesions seen on gadolin ium-enhanced T1-weighted brain magnetic resonance imaging at the same time points was counted. All sequences used 3-mm contiguous axial slices. Overal l, 126 new or enlarging lesions were seen an FSE and 135 on fast FLAIR (P = 0.25, Wilcoxon signed ranks test). Regional comparisons revealed significa ntly more fast FLAIR lesions only in the cortical/sutbcortical areas. There was a total of 295 new enhancing lesions over the same period - a gain in the number of 'active lesions' of 234% seen with FSE and 218% with FLAIR. I t is concluded that serial thin slice fast FLAIR is only slightly superior to I;SE in detecting new and enlarging multiple sclerosis lesions but the d ifference is not sufficient to recommend that FLAIR should replace FSE in s hort-term, exploratory trials in MS using monthly scanning. Gadolinium-enha nced imaging is more then twice as sensitive as either FSE or East FLAIR to new multiple sclerosis lesion activity, and enhancing lesions should provi de the primary outcome measure in such studies.