Very-Low-Field MRI for the Diagnosis of Acute Stroke

The goal of this clinical trial is to learn if a very-low-field MRI scanner (0.064 Tesla), combined with artificial intelligence (AI) image enhancement, can accurately diagnose acute ischemic stroke in adults with suspected stroke. Healthy adult volunteers are also included to optimize image quality. The main questions it aims to answer are: How accurately does AI-enhanced very-low-field MRI detect ischemic stroke (sensitivity and specificity) compared with standard high-field MRI (3 Tesla)? Does AI enhancement improve diagnostic performance compared with very-low-field MRI images without AI? Researchers will compare very-low-field MRI images, with and without AI enhancement, to the 3 Tesla MRI performed as part of routine care. Two neuroradiologists will read the images independently, without knowing the results of the other scan. This study has three parts: Part 1: healthy volunteers (30 participants). Participants will undergo one 3 Tesla MRI and one very-low-field MRI on the same day (45 minutes maximum). Part 2: patients with recent stroke, 1 to 7 days after onset (40 participants). Participants will undergo one very-low-field MRI within 6 hours of their routine 3 Tesla MRI. Part 3: patients with suspected stroke within the last 24 hours (160 participants). Participants will undergo one very-low-field MRI (about 30 minutes) within 4 hours of their routine 3 Tesla MRI, after any emergency treatment. About half will have a second very-low-field MRI around 24 hours later.

Inclusion Criteria: All participants: * Age 18 years or older * Affiliated with or beneficiary of a social security scheme Part 1 (healthy volunteers): * No known neurological disease * Written informed consent * Registered in the national file of healthy volunteers (VRB) Part 2 (subacute stroke): * Confirmed acute ischemic stroke on 3T MRI * Symptom onset 1 to 7 days before inclusion * Very-low-field MRI feasible within 6 hours of 3T MRI * Written informed consent Part 3 (suspected hyperacute stroke): * Clinical suspicion of acute stroke with symptom onset within 24 hours * 3T MRI performed as part of routine care * Very-low-field MRI feasible within 4 hours of 3T MRI, during working hours (8 a.m.-6 p.m.) * Informed consent from the patient, or, if the patient is unable to consent, from a relative, the trusted person or an independent physician (emergency procedure, Article L.1122-1-3 of the French Public Health Code), followed by the patient's consent to continue as soon as possible Exclusion Criteria: * Contraindication to MRI (e.g., non-MRI-compatible pacemaker or implanted device, metallic foreign body) * Pregnancy or breastfeeding * Clinical instability incompatible with an additional MRI examination * Inability to remain still for the duration of the examination * Adults under legal protection (guardianship or curatorship), unless allowed by the protocol * Participation in another interventional study that may interfere with this study