QUANTIFICATION OF MRI LESION LOAD IN MULTIPLE-SCLEROSIS - A COMPARISON OF 3 COMPUTER-ASSISTED TECHNIQUES

Several computer-assisted techniques for measuring multiple sclerosis lesion load on MR images have been developed to provide a quantitative and sensitive means for monitoring disease activity, particularly in the context of treatment trials. We have evaluated three techniques: m anual outlining (similar to that of the North American interferon beta -lb trial), semiautomated lesion contouring (local lesion based thresh old), and intensity-based thresholding for the whole brain. Contiguous , 5 mm-thick, axial, T-2-weighted images of the brain were obtained on a 1.5T MR imager in eight patients with clinically definite multiple sclerosis. Analyses of the scans were performed twice, independently b y three operators, using the three different techniques. The coefficie nt of variation of the measurement techniques was: (a) intrarater prec ision, 9.0 +/- 5.2 (mean +/- SD) (range 0.4-18.5) for the manual outli ning, 2.5 +/- 2.1 (0.1-7.7) for the contour technique, and 7.5 +/- 6.9 (0.2-22.0) for the global threshold technique; (b) interrater precisi on, 11.0 +/- 5.8 (4.9-21.7) for the manual outlining, 4.5 +/- 1.6 (1.8 -6.6) for the contour technique, and 11.4 +/- 4.9 (2.8-19.2) for the g lobal threshold technique (0.0 = perfect precision). The absolute lesi on loads measured were very similar using the manual outlining and the contour techniques but were significantly smaller using the global th reshold technique. We conclude that the contour technique is a promisi ng tool for use in treatment trials. Further studies are needed to ass ess sensitivity to changes in lesion load over time.