INTRAOBSERVER AND INTEROBSERVER VARIABILITY IN SCHEMES FOR ESTIMATINGVOLUME OF BRAIN-LESIONS ON MR-IMAGES IN MULTIPLE-SCLEROSIS

PURPOSE: Our goal was to evaluate the intraobserver and interobserver reproducibility of measurements of brain lesion load in multiple scler osis (MS) by using two proposed acquisition schemes, METHODS: Three-mi llimeter-thick conventional spin-echo (CSE) and fast fluid-attenuated inversion-recovery (FLAIR) sequences were obtained and the lesions seg mented using a semiautomated technique based on local thresholdling to calculate intraobserver and interobserver reproducibility, These were compared with images obtained from two separate MR units in which 5-m m CSE sequences were obtained and segmented by using the local thresho lding technique and also by manual outlining, RESULTS: The intraobserv er coefficient of variation was 4.0% (95% confidence interval [CI], 3. 0% to 4.5%) for the 5-mm CSE sequence measured with manual outlining, 3.1% (95% CI, 2.5% to 3.2%) and 5.1% (95% CI, 4.1% to 5.6%) for the tw o sets of 5-mm CSF sequences measured using the local thresholding tec hnique, 5.7% (95% CI, 3.9% to 6.6%) for the 3-mm CSF sequence, and 2.6 % (95% CI, 2.1% to 2.7%) for the fast FLAIR sequence, The interobserve r coefficient of variation was 7.1% (95% CI, 4.9% to 8.7%) and 8.3% (9 5% CI, 6.4% to 9.6%) for the two sets of 5-mm CSE sequences, 7.3% (95% CI, 4.7% to 9.1%) for the 3-mm CSE sequence, and 2.9% (95% CI, 2.3% t o 3.3%) for the fast FLAIR sequence, The intraobserver and interobserv er reproducibility of measurements obtained with the fast FLAIR techni que was significantly better than those obtained with the other techni ques, CONCLUSIONS: Our data indicate that the intraobserver and intero bserver variability in quantifying MS lesions can be reduced significa ntly with the use of fast FLAIR sequences, while no significant improv ement is gained by reducing the section thickness from 5 mm to 3 mm.