# Diagnostic Accuracy of Isotropic FLAIR-T2* Fusion Imaging for Central Vein Sign Detection in Multiple Sclerosis: a Comparative Study at 1.5 T and 3 T

## TL;DR

This study compares the accuracy of a new imaging technique for detecting a key sign of multiple sclerosis at two different MRI scanner strengths.

## Contribution

The study introduces and evaluates the diagnostic performance of isotropic FLAIR-T2* fusion imaging for central vein sign detection at 1.5 T and 3 T.

## Key findings

- 1.5 T FLAIR-T2* fusion achieved 90% sensitivity and 95% specificity for MS diagnosis.
- 3 T FLAIR-T2* fusion showed higher accuracy with 100% sensitivity and 95% specificity.
- The select-6* method reduced misclassification at both field strengths.

## Abstract

The central vein sign (CVS) is a promising imaging biomarker for multiple sclerosis (MS) diagnosis. While isotropic T2* at 3 T and 7 T has demonstrated high diagnostic performance, its utility at 1.5 T remains unclear. This study evaluates the performance of unenhanced FLAIR-T2* fusion at 1.5 T compared to 3 T in MS participants.

This prospective observational study included 20 MS patients and 20 control subjects. Each participant underwent unenhanced isotropic Epi-T2* and isotropic FLAIR (0.8 mm voxel size) at both 1.5 T and 3 T. Subsequently, the derived isotropic T2* and FLAIR were combined to create the final FLAIR-T2* fusion in both magnetic field strengths. Two independent raters assessed the CVS status of white matter (WM) lesions using NAIMS criteria. WM lesions were classified as CVS+ or CVS-, and two methods—select-n* and CVS+ proportion—were applied. Sensitivity and specificity were computed, and CVS performance was compared across WM lesion locations.

Among eligible WM lesions (MS: 258; controls: 255), the mean CVS+ lesion proportion per participant was 66.9 ± 15.4% for 1.5 T FLAIR-T2* and 77.0 ± 13.6% for 3 T FLAIR-T2* (p < 0.01). At a 40% threshold, 1.5 T FLAIR-T2* achieved 90% sensitivity and 95% specificity, while 3 T FLAIR-T2* achieved 100% sensitivity and 95% specificity. The Select-6* method resulted in only one MS patient being misclassified at both field strengths. 3 T FLAIR-T2* detected more CVS+ lesions in deep WM (87.5% vs. 57.1%, p = 0.05).

1.5 T FLAIR-T2* fusion demonstrates high performance in CVS assessment, although slightly outperformed by 3 T FLAIR-T2*. The select-6* method may enhance 1.5 T performance, supporting its feasibility for CVS evaluation.

The online version of this article (10.1007/s00062-025-01531-6) contains supplementary material, which is available to authorized users.