Imaging of active multiple sclerosis plaques: efficiency of contrast-enhanced magnetization transfer subtraction technique

Abstract

Purpose: T1-weighted (T1W) magnetic resonance images with magnetization transfer (MT) are widely used in the evaluation of multiple sclerosis (MS) plaques. We aimed to evaluate the contribution of the subtraction technique with MT in the detection of acute MS plaques.

Materials and methods: Sixty-four patients during an MS attack were enrolled in the study. Axial T1W spin echo (SE) with MT, axial-sagittal T2W fast SE, axial FLAIR and postcontrast axial T1W SE magnetic resonance imaging sequence with MT were acquired from all patients. The subtraction (postcontrast-precontrast) images were obtained on the workstation. FLAIR and T2W images were used as reference for plaque imaging. Contrast material enhanced plaques were considered as acute plaques. Qualitatively, both subtracted and contrast-enhanced with MT images were evaluated visually. Quantitatively, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated.

Results: A total of 464 plaques were detected on T2W and FLAIR images. Thirty-five acute plaques were detected on both postcontrast MT and subtracted images. Additionally, 66 acute plaques were only detected on subtracted images visually. CNR and SNR values of acute MS plaques were significantly higher on subtracted MT images than on postcontrast MT images (P < 0.001).

Conclusion: The subtraction technique seems to facilitate the detection of acute MS plaques by intensifying the visibility of poorly enhanced plaques without use of high dose contrast medium. We suggest the use of subtraction technique in routine imaging work-up of MS patients with acute attacks.