Interscanner variation in brain MR lesion load measurements in multiple sclerosis using conventional spin-echo, rapid relaxation-enhanced, and fast-FLAIR sequences.

BACKGROUND AND PURPOSE

Different MR pulse sequences have been proposed for measuring multiple sclerosis (MS)-related abnormalities. The reproducibility of measured brain MS lesion volumes was compared for MR images performed using different scanners and different pulse sequences.

METHODS

Nine patients with relapsing-remitting MS were each imaged on two scanners and, on each occasion, dual-echo conventional spin-echo, dual-echo rapid-acquisition relaxation-enhanced (RARE), and fast fluid-attenuated inversion recovery (fast-FLAIR) images were obtained. The lesion volume present on each image was evaluated three times by a single observer in random order, using a local thresholding technique.

RESULTS

The mean lesion volumes present on fast-FLAIR images were significantly higher than those measured on dual-echo conventional spin-echo and RARE images. The mean intraobserver coefficients of variation for the different sequences and scanners ranged from 3.0% to 4.2% (no statistically significant difference). For each of the sequences, the use of different scanners introduced a variability that was higher than the intraobserver variability: the interscanner coefficient of variation was 7.4% for conventional spin-echo, 9.5% for RARE, and 18.5% for fast-FLAIR images.

CONCLUSION

Our study confirms that the use of different scanners significantly influences lesion loads measured from MR images of patients with MS and establishes that newer sequences are more susceptible to measurement variability. It also indicates that, if newer sequences are to be used in clinical trials, careful standardization is needed.