Enhanced Detection of Acute Ischemic Stroke With Low-Field MRI

Area of Science:

• Medical Imaging
• Neurology
• Biomedical Engineering

Background:

• Portable, low-field magnetic resonance imaging (MRI) offers expanded neuroimaging access.
• Low-field diffusion-weighted imaging (DWI) faces challenges in signal-to-noise ratio and gradient strength for acute ischemic stroke evaluation.
• Optimized pulse sequences and hardware are explored to enhance lesion detection in low-field MRI.

Purpose of the Study:

• To evaluate novel pulse sequences and low-field MRI hardware for enhanced lesion detection in acute ischemic stroke.
• To assess the diagnostic accuracy and lesion detection limits of single-direction (SD) and multi-direction (MD) DWI sequences on different low-field MRI systems.
• To compare low-field MRI performance against conventional high-field MRI as the ground truth.

Main Methods:

• Prospective enrollment of 95 patients with suspected acute ischemic stroke across 3 centers.
• Acquisition of DWI using SD or custom MD sequences on two 0.064 T MRI systems (Swoop v1 and v2).
• Calculation of diagnostic accuracy, positive predictive value, and lesion detection limits, comparing results to 1.5-3 T MRI.

Main Results:

• Multi-direction (MD) DWI demonstrated higher inter-rater agreement (κ=0.84) and positive predictive value (95%) compared to single-direction (SD) DWI (κ=0.72, 78.2%).
• MD imaging enabled detection of smaller lesions (0.4 mL cut-off, sensitivity 86%) than SD imaging (0.6 mL cut-off, sensitivity 89%).
• Next-generation v2 system with MD imaging improved uniformity, reduced scan time by ~30%, and detected lesions as small as 0.15 mL.

Conclusions:

• Optimized diffusion-weighted imaging strategies on low-field MRI significantly improve the detection of very small acute ischemic strokes.
• The enhanced detection capabilities are achieved within a clinically feasible timeframe.
• This advancement holds promise for expanding access to critical stroke diagnostics.