FLAIR(2) post-processing: improving MS lesion detection in standard MS imaging protocols

BACKGROUND: Technical improvements in magnetic resonance imaging (MRI) acquisition, such as higher field strength and optimized sequences, lead to better multiple sclerosis (MS) lesion detection and characterization. Multiplication of 3D-FLAIR with 3D-T2 sequences (FLAIR(2)) results in isovoxel images with increased contrast-to-noise ratio, increased white–gray-matter contrast, and improved MS lesion visualization without increasing MRI acquisition time. The current study aims to assess the potential of 3D-FLAIR(2) in detecting cortical/leucocortical (LC), juxtacortical (JC), and white matter (WM) lesions. OBJECTIVE: To compare lesion detection of 3D-FLAIR(2) with state-of-the-art 3D-T2-FLAIR and 3D-T2-weighted images. METHODS: We retrospectively analyzed MRI scans of thirteen MS patients, showing previously noted high cortical lesion load. Scans were acquired using a 3 T MRI scanner. WM, JC, and LC lesions were manually labeled and manually counted after randomization of 3D-T2, 3D-FLAIR, and 3D-FLAIR(2) scans using the ITK-SNAP tool. RESULTS: LC lesion visibility was significantly improved by 3D-FLAIR(2) in comparison to 3D-FLAIR (4 vs 1; p = 0.018) and 3D-T2 (4 vs 1; p = 0.007). Comparing LC lesion detection in 3D-FLAIR(2) vs. 3D-FLAIR, 3D-FLAIR(2) detected on average 3.2 more cortical lesions (95% CI − 9.1 to 2.8). Comparing against 3D-T2, 3D-FLAIR(2) detected on average 3.7 more LC lesions (95% CI 3.3–10.7). CONCLUSIONS: 3D-FLAIR(2) is an easily applicable time-sparing MR post-processing method to improve cortical lesion detection. Larger sampled studies are warranted to validate the sensitivity and specificity of 3D-FLAIR(2). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00415-021-10833-x.