The precision of TI hypointense lesion volume quantification in multiple sclerosis treatment trials: a multicenter study

The volume of hypointense lesions on TI weighted brain MRI represents on in creasingly used MR endpoint in phose III MS treatment trials. In this study we evaluated the reproducibility of hypointense TI lesion volume quantific ation in a cohort of Multiple Sclerosis (MS) patients. The gadolinium enhan ced TI weighted brain MR images of 33 MS patients from three European cente rs were used in this study. These images were acquired as Port of a phose I II trial of interferon beta-1b in secondary progressive MS. The MRI machine manufacturers and imaging parameters varied according to the MRI acquisiti on center. Three experienced observers used a semi-automated local threshol ding technique to quantify the hypointense TI lesion volume on Two occasion s, separated by a delay. The intra and inter observer coefficients of varia tion were 3.7% and 4.9% respectively with similar values derived for images obtained at oil three sites. There was a generally high level of agreement between the lesion volumes obtained by the three raters. However, a modest but significant measurement drift was identified between the first and sec ond sessions for one of the three raters, highlighting the very reel possib ility of measurement drift even for experienced observers. Our results supp ort the increasing role for TI hypointense lesion volume as on outcome meas ure in multicenter phose III MS treatment trials.