Abstract #2107

Moraal B, Pouwels P, Vrenken H, Guttmann C, van Schijndel R, Barkhof F, Meier D, Poppe P

MRI indices are used as a secondary outcome measure in phase III clinical multiple sclerosis (MS) trails. Serial analysis to detect and quantitate disease activity is difficult, inaccurate and time consuming due to repositioning errors and a background of unaltered non-active lesions. Registration and subsequent subtraction circumvent these difficulties. Using data from a multicentre clinical trial, we evaluated the changes in MS lesions on registered and subtracted images, as well as on the original baseline and follow-up images. On the subtracted images, 77% more active lesions (positive activity) were detected. Interobserver agreement has not yet been analysed but is expected to be better for subtracted images.