Improved in vivo detection of cortical lesions in multiple sclerosis using double inversion recovery MR imaging at 3 Tesla

Abstract

Objective: To investigate the impact of a higher magnetic field strength of 3 Tesla (T) on the detection rate of cortical lesions in multiple sclerosis (MS) patients, in particular using a dedicated double inversion recovery (DIR) pulse sequence.

Methods: Thirty-four patients with clinically isolated syndromes or definite MS were included. All patients underwent magnetic resonance imaging (MRI) at 1.5 T and 3 T, including T2-weighted turbo spin echo (TSE), fluid-attenuated inversion recovery (FLAIR) and DIR sequences. All images were analysed for focal lesions categorised according to their anatomical location.

Results: The total number of detected lesions was higher at 3 T across all pulse sequences. We observed significantly higher numbers of lesions involving the cortex at 3 T using a DIR sequence. DIR at 3 T showed 192% more pure intracortical (p < 0.001) and 30% more mixed grey matter-white matter lesions (p = 0.008). No significant increase in cortical lesions could be detected on the FLAIR and T2-weighted images. Using the T2-weighted and FLAIR sequences, significantly more lesions could be detected at 3 T in the infratentorial, periventricular and juxtacortical white matter.

Conclusion: DIR brain MR imaging at 3 T substantially improves the sensitivity of the detection of cortical lesions compared with the standard magnetic field strength of 1.5 T.

Fig. 1

Transverse sections of the infratentorial brain at 3 T (top row) and 1.5 T (bottom row) obtained from a 50-year-old woman with relapsing-remitting MS. The DIR sequence (left column) is able to detect more infratentorial lesions at 3 T compared with 1.5 T and other pulse sequences such as FLAIR (middle column) and T2 TSE (right column). Those lesions can also affect the cortex (closed arrowhead). Please note the higher propensity of DIR to vessel and CSF pulsation artefacts particularly in the posterior fossa (open arrowhead)

Fig. 2

Transverse sections of the supratentorial brain of a 31-year-old man with relapsing-remitting MS. Upper row images were obtained at 3 T, bottom row images were obtained at 1.5 T. Left column DIR images, middle column FLAIR images, right column T2 TSE images. The 3-T images offer better image quality allowing better delineation of focal inflammatory lesions, regardless of the specific anatomical location. At both field strengths, the DIR sequence allows a better classification of lesions close to the cortex or in the cortex itself as juxtacortical lesions (closed-head arrows) or cortical lesions and mixed white matter-grey matter lesions (open-head arrows), respectively. In particular, the DIR at 3 T shows more lesions purely located in the grey matter and lesions partially located in the grey and white matter

Fig. 3

Transversal sections of a DIR sequence at 1.5 T (left) and 3 T (right) from a 44-year-old woman with relapsing-remitting MS. Please note the higher conspicuity and improved detection of a lesion purely located in the cortex (closed-head arrow). Please note also the diffuse high signal changes in the parasagittal cingulate cortex which can also be frequently observed in healthy control subjects and have to be considered artefacts (open-head arrow)

Fig. 4

Two consecutive DIR sections of the supratentorial brain of a 31-year-old man with relapsing-remitting MS obtained at 1.5 T (top row) and 3 T (bottom row). The DIR sequence benefits from the higher signal at 3 T leading to better delineation of the cortex and inflammatory lesions affecting the cortex (close-headed arrows). Please note also diffuse symmetric high signal changes in the occipital cortex (open-head arrows) which do not represent real cortical abnormalities and have to be considered artefacts