Enhancing the Visibility of Multiple Sclerosis Lesions using Fused Images of Fluid Attenuated Inversion Recovery (FLAIR) and white matter Attenuated Inversion Recovery (WAIR) MRI Sequences.

Introduction: Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system in which accurate lesion detection is essential for diagnosis and follow-up. Although the Fluid Attenuated Inversion Recovery (FLAIR) MRI sequence is routinely used, it may underestimate lesions in certain brain regions. This study evaluated whether fused images generated using minimum pixel value extraction (MinPE) from FLAIR and white matter-attenuated inversion recovery (WAIR) sequences improve lesion detection.

Materials and methods: This retrospective single-center study analyzed brain MRI examinations from 65 patients with suspected or confirmed MS. Imaging protocols included conventional FLAIR and MinPE FLAIR/WAIR images. Two experienced neuroradiologists, blinded to clinical data, independently identified and classified lesions. Lesion detection rates were compared using chi-square analysis, and interobserver agreement was assessed with Cohen's kappa.

Results: MinPE FLAIR/WAIR images showed improved lesion conspicuity and significantly higher detection rates compared with conventional FLAIR, particularly in the brainstem. Detection was markedly increased in the midbrain, pons, and medulla (p ≤ 0.0004), with additional improvement observed in the cerebellar hemispheres (p < 0.05).

Discussion: While advanced sequences such as Double Inversion Recovery (DIR) and Phase-Sensitive Inversion-Recovery (PSIR) enhance lesion detection, their longer acquisition times limit routine use. The MinPE FLAIR/WAIR technique improves lesion visibility in challenging regions with minimal impact on scan time, allowing a more accurate estimation of disease burden.

Conclusion: MinPE FLAIR/WAIR post-processing enhances MS lesion detection and may represent a practical addition to routine MRI protocols.