A comparison of the sensitivity of monthly unenhanced and enhanced MRI techniques in detecting new multiple sclerosis lesions.

In this longitudinal study, the sensitivities of three magnetic resonance imaging techniques for detecting the appearance of new lesions in multiple sclerosis (MS) were evaluated and compared. Dual-echo conventional spin-echo (CSE), fast fluid-attenuated inversion recovery (fast-FLAIR) and post-contrast T1-weighted scans were obtained on four occasions, each separated by 28 days, from 18 patients with relapsing-remitting MS using a 1.5-T machine. New lesions seen using each sequence during the follow-up were counted by agreement by four observers in two stages (stage 1: random review of complete sets of scans from each technique; stage 2: side-by-side review with a 'retrospective' count of new lesions). At stage 1, 1.44 new lesions per patient per month were detected on CSE scans, 1.88 on fast-FLAIR (31\% more than CSE) and 2.07 on post-contrast T1-weighted scans (44\% more than CSE) (P = 0.03). Differences were, however, reduced after stage 2: fast-FLAIR detected 29\% and post-contrast T1-weighted scans detected 31\% more new lesions than CSE(P = 0.08). The combination of fast-FLAIR and post-contrast scans detected 144 new lesions, whilst the usual combination of CSE and post-contrast scans detected 133 new lesions. This study indicates that enhanced MRI remains the most sensitive method for detecting 'active' lesions in MS and that fast-FLAIR may be used when monitoring short-term disease activity in MS, either natural or modified by treatment.