FLAIR2 post-processing: improving MS lesion detection in standard MS imaging protocols

Tobias Zrzavy,Thomas Berger,Karl Heinz Nenning,Alice Wielandner,Alexander Rauscher,Fritz Leutmezer,Sophie Bartsch,Paulus Rommer,Lukas Haider,Gregor Kasprian

doi:10.1007/s00415-021-10833-x

Abstract

BackgroundTechnical 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 (FLAIR2) 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-FLAIR2 in detecting cortical/leucocortical (LC), juxtacortical (JC), and white matter (WM) lesions.ObjectiveTo compare lesion detection of 3D-FLAIR2 with state-of-the-art 3D-T2-FLAIR and 3D-T2-weighted images.MethodsWe 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-FLAIR2 scans using the ITK-SNAP tool.ResultsLC lesion visibility was significantly improved by 3D-FLAIR2 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-FLAIR2 vs. 3D-FLAIR, 3D-FLAIR2 detected on average 3.2 more cortical lesions (95% CI − 9.1 to 2.8). Comparing against 3D-T2, 3D-FLAIR2 detected on average 3.7 more LC lesions (95% CI 3.3–10.7).Conclusions3D-FLAIR2 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-FLAIR2.

Highlights

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS) in which magnetic resonance imaging (MRI) is an invaluableWhile white matter (WM) lesions have long been the main focus of research in multiple sclerosis (MS), cortical lesions (CL) are more and more recognized as playing an important role [12]
A total of 1067 3D-FLAIR2, 809 3D-FLAIR, and 577 3D-T2-weighted lesions were detected in these 13 patients
WM lesions were more common on 3D-FLAIR2 sequences compared to 3D-FLAIR and 3D-T2-weighted scans (Figs. 1, 2)

Summary

Introduction

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS) in which magnetic resonance imaging (MRI) is an invaluableWhile white matter (WM) lesions have long been the main focus of research in MS, cortical lesions (CL) are more and more recognized as playing an important role [12]. In contrast to WM lesions, which are identified using standard MRI techniques [8], less than 25% of histopathologically confirmed CL are detectable by conventional (FLAIR and T2) clinical MR imaging [4] Both white and gray matter lesions have been associated with disability accumulation and potential outcome parameters in clinical trials [7, 10]. It was recently shown that the combination of 3D-T2 weighted images with 3D-FLAIR, referred to as 3D-FLAIR2, leads to a better contrast-to-noise ratio and white–gray-matter contrast, while still suppressing CSF signals and thereby to improved lesion visualization without the need for additional scan time [27]. Larger sampled studies are warranted to validate the sensitivity and specificity of 3D-FLAIR2

Objectives

Methods

Results

Conclusion