Diffusion-Weighted Imaging Fluid-Attenuated Inversion Recovery Mismatch on Portable, Low-Field Magnetic Resonance...

Area of Science:

• Neurology
• Radiology
• Medical Imaging

Background:

• Diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) are crucial for identifying DWI-FLAIR mismatch in acute ischemic stroke patients with unknown onset times, guiding thrombolytic therapy.
• Limited access to MRI for hyperacute stroke hinders timely intervention.

Purpose of the Study:

• To evaluate the capability of a portable, low-field (LF)-MRI scanner in identifying DWI-FLAIR mismatch in acute ischemic stroke.
• To assess the diagnostic performance of LF-MRI in detecting stroke lesions and guiding treatment decisions.

Main Methods:

• Acquisition of LF-MRI (0.064-T) in 71 acute ischemic stroke patients within 24 hours of last known well.
• Qualitative assessment of lesion visibility on LF-FLAIR by two trained assessors.
• Quantitative analysis using an image coregistration pipeline to derive LF-FLAIR signal intensity ratio (SIR).

Main Results:

• High interobserver agreement (κ=0.85) for identifying visible FLAIR hyperintensities.
• Visual DWI-FLAIR mismatch demonstrated 60% sensitivity and 82% specificity for stroke onset <4.5 hours.
• LF-FLAIR SIR thresholds were established, with an optimal cut-point of 1.15 (85% sensitivity, 70% specificity) for identifying mismatch and a cut-point of 6.6 hours for FLAIR SIR <1.15.

Conclusions:

• A 0.064-T portable LF-MRI scanner can successfully identify DWI-FLAIR mismatch in acute ischemic stroke patients.
• Further prospective validation of thresholds and evaluation of LF-MRI's role in guiding thrombolysis for stroke patients with uncertain onset are warranted.