FLAIR2: A Combination of FLAIR and T2 for Improved MS Lesion Detection

Area of Science:

• Radiology
• Neuroimaging
• Medical Physics

Background:

• Fluid-attenuated inversion recovery (FLAIR) and double inversion recovery (DIR) are crucial MRI sequences for multiple sclerosis (MS) lesion detection.
• These sequences suppress signals from cerebrospinal fluid (CSF) and white matter (WM), enhancing contrast between lesions, WM, and gray matter (GM).
• However, DIR acquisition is debated, and both methods can reduce signal-to-noise ratio (SNR).

Purpose of the Study:

• To present a novel approach for generating contrast-enhanced MRI images with improved lesion conspicuity in MS.
• To achieve better differentiation between lesions, WM, and GM without significantly compromising SNR.
• To determine if additional MRI acquisition is necessary for optimal contrast in MS imaging.

Main Methods:

• A retrospective analysis was performed on 3D T2-weighted and 3D FLAIR MRI data from healthy volunteers and MS patients.
• A technique termed FLAIR(2) was developed by coregistering and multiplying FLAIR and T2-weighted images.
• Signal-to-noise ratio (SNR) and contrast-to-noise (CNR) were measured for lesions, GM, and WM.

Main Results:

• FLAIR(2) demonstrated a 133% higher GM-WM CNR compared to standard FLAIR.
• Lesion-to-WM contrast was significantly improved with FLAIR(2) compared to T2, DIR, and FLAIR (31%–158% improvement).
• FLAIR(2) enhanced the conspicuity of cortical, juxtacortical, callosal, and infratentorial lesions, leveraging its 3D nature.

Conclusions:

• A simple, retrospective method (FLAIR(2)) provides CSF suppression and superior contrast-to-noise ratio compared to conventional FLAIR and DIR.
• This approach avoids the need for additional MRI acquisition time.
• FLAIR(2) images can be computed retrospectively from existing T2 and FLAIR scans, offering a practical enhancement for MS assessment.