IMPROVED DETECTION OF ENHANCING AND NONENHANCING LESIONS OF MULTIPLE-SCLEROSIS WITH MAGNETIZATION-TRANSFER

PURPOSE: To determine whether magnetization transfer imaging can impro ve visibility of contrast enhancement of multiple sclerosis plaques. M ETHODS: Fifty-nine enhancing and 63 nonenhancing lesions in 10 patient s with multiple sclerosis were evaluated to calculate contrast-to-nois e ratios on conventional T1-weighted and T1-weighted magnetization tra nsfer images. The signal intensity of the lesion and the background (w hite matter) were measured on precontrast T1-weighted and T1-weighted magnetization transfer images (800/20/1 [repetition time/echo time/exc itations]) and on postcontrast Tl-weighted and T1-weighted magnetizati on transfer images. Mean contrast to-noise ratios was calculated for a ll lesions. RESULTS: The contrast-to-noise ratio was significantly hig her for enhancing and nonenhancing lesions on T1-weighted magnetizatio n transfer images than on conventional T1-weighted images. For enhanci ng lesions, the contrast-to-noise ratio was significantly higher on po stcontrast T1-weighted magnetization transfer images, 32 +/- 2 compare d with 21 +/- 2 on conventional T1-weighted images. Fifty of the 59 en hancing lesions were seen on both the T1-weighted and the T1-weighted magnetization transfer images. Nine enhancing lesions were seen only o n the postcontrast T1-weighted magnetization transfer images. In addit ion, of 63 nonenhancing lesions seen on proton-density, T2-weighted, a nd T1-weighted magnetization transfer images, 16 were not seen on the conventional T1-weighted images. Seven of the 63 nonenhancing lesions and 7 of the 59 enhancing lesions had high signal intensity on the pre contrast T1-weighted magnetization transfer images suggestive of lipid signal, a finding not seen on the conventional precontrast T1-weighte d images. CONCLUSION: Magnetization transfer improves the visibility o f enhancing multiple sclerosis lesions, because they have a higher con trast-to-noise ratio than conventional postcontrast T1-weighted images . High signal intensity on both nonenhancing and enhancing lesions not ed only on precontrast T1-weighted magnetization transfer suggests a l ipid signal was unmasked. If magnetization transfer is used in multipl e sclerosis patients, a precontrast magnetization transfer image is ne cessary.