PARTIALLY SATURATED FLUID ATTENUATED INVERSION-RECOVERY (FLAIR) SEQUENCES IN MULTIPLE-SCLEROSIS - COMPARISON WITH FULLY RELAXED FLAIR AND CONVENTIONAL SPIN-ECHO

Fluid attenuated inversion recovery (FLAIR) sequences produce selectiv e cerebrospinal fluid (CSF) suppression by employing a very long inver sion time (TI). We used the FLAIR sequence to study patients with mult iple sclerosis (MS) at 0.6 T. So far, a very long TR (and long acquisi tion time) has been used in a fully relaxed (FR-FLAIR) system. To spee d up the FLAIR sequences, we used a shorter TR, and demonstrated that complete CSF suppression can be maintained with partial saturation (PS -FLAIR) by reducing TI at the same time. The introduction of partial s aturation, however, reduced the contrast between lesions and normal ap pearing white matter (NAWM). Suboptimal CSF suppression therefore had to be accepted to maintain sufficient lesion to NAWM contrast. Using a TE of 60 ms, the PS-FLAIR and PR-FLAIR performed equally well in the detection of MS-lesions, although the former provided poorer CSF suppr ession. Both FLAIR sequences, however, provided poorer contrast betwee n lesions and NAWM compared to conventional spin-echo sequences. Altho ugh the long acquisition time of the FLAIR sequence can be reduced by using partial saturation, complete CSF suppression and good lesion to NAWM contrast are incompatible at short TRs. Using a TE of 60 ms, conv entional spin-echo sequences detect more lesions and provide better co ntrast between lesions and NAWM than FLAIR sequences in MS patients.