Consecutive patients accessing the emergency department with suspected stroke dispatch will be recruited at 3 study units: 1) ASL Abruzzo 1, hospitals of L'Aquila and Avezzano; 2) ASL Abruzzo 2, hospital of Chieti; 3) IRCCS Humanitas Research Hospital of Milan. Anonymized clinical and low-field (LF) MRI data as well as conventional neuroimaging data will be independently assessed by external units (Università Politecnica delle Marche and Policlinico di Messina, respectively). Both units will independently adjudicate the best treatment option, while the latter will also provide historical MRI data of stroke patients to develop artificial intelligence algorithms facilitating LF-MRI images interpretation (Libera Università di Bolzano). Agreement with conventional neuroimaging will be evaluated at different time points (hyperacute, acute -24 h, subacute -72 h, discharge, chronic -4 weeks). Further investigations will include feasibility study to develop an ambulance (mobile stroke unit) equipped with LF-MRI and cost-effectiveness analysis of LF-MRI. This trial will provide necessary data to validate the use of LF-MRI in the acute stroke care.

POCS study is a multicentric, prospective clinical trial involving adult patients with suspected stroke. Recruitment of patients will be performed at 3 study units: 1) ASL1 Abruzzo 1 Avezzano-Sulmona-L'Aquila, hospitals of L'Aquila and Avezzano (ASLAQ); 2) ASL2 Abruzzo Lanciano-Vasto-Chieti, hospital of Chieti (ASLCH); 3) IRCCS Humanitas Research Hospital - Milano (HUM). Additional units contributing to the study will include: 1) Università dell'Aquila (UNIVAQ): will be in charge of study coordination, data analysis and management, optimization of low-field (LF) MRI protocol, and pharmacoeconomic assessment; 2) Università Politecnica delle Marche (UNIPM): will perform independent assessment and adjudication of anonymized clinical and LF-MRI data in a blinded fashion; it will also identify the best possible treatment option for patients with suspected ischemic stroke (intravenous thrombolysis, endovascular treatment, combined revascularization treatment, no revascularization); 3) Policlinico di Messina (POLIME): will perform blinded and independent assessment and adjudication of anonymized clinical and conventional neuroimaging data. POLIME will also identify the best possible treatment option for patients with suspected ischemic stroke (intravenous thrombolysis -IVT, endovascular thrombectomy - EVT, combined revascularization treatment, no revascularization) and provide historical MRI data of patients with stroke to develop AI algorithms for LF-MRI images interpretation; 4) Libera Università di Bolzano (UNIBZ): will develop AI algorithms to facilitate LF-MRI interpretation starting from anonymized conventional MRI and LF-MRI data provided by ASLAQ, ASLCH, HUM, and POLIME; 5) Università di Cassino e del Lazio Meridionale (UNICAS): will perform a feasibility study to develop an ambulance equipped with a LF-MRI scan. This unit will not deal with patient data.

Patients with suspected acute stroke will undergo diagnostic procedures and management according to usual clinical care. LF-MRI will be performed at the admission, 24 h, 72 h, at hospital discharge and 4 weeks after the event. LF-MRI findings will not be used to make clinical decisions on patients management. Every time a stroke dispatch will be activated, the dedicated research staff will be alerted by the local neurologist on duty. The research staff will check eligibility criteria, obtain informed consent and perform study procedures independently of the personnel in charge of managing the acute stroke case. All included patients with suspected stroke will be managed and treated per usual care by the hospital staff not involved in study procedures. Conventional stroke imaging will be performed as needed according to current clinical practice (non-contrast CT + CT angiography and/or high-field MR + MR angiography in selected cases, with/without CT or MR perfusion study).

For the aim of the study, all included patients will be investigated with LF-MRI at predefined time points (24 h, 72 h, hospital discharge, 4 weeks). The acquisition of LF-MRI will be performed by a dedicated study staff who will be distinct from the clinical staff involved in the care of the acute stroke patient, thus not subtracting time or resources to usual care. Information obtained by LF-MRI will not be used to take clinical decisions regarding further investigations or treatment.

The following clinical variables will be collected at the specified time point: (1) Hyperacute (ED): demographical data, time from symptom onset (precise onset, unwitnessed, wake-up stroke), onset-to-door-time, door-to-imaging-time, clinical severity (National Institute of Health Stroke Scale - NIHSS), type of neuroimaging, duration of LF-MRI scanning, conventional neuroimaging and LF-MRI findings (detection of ischemic or hemorrhagic lesion(s), lesion(s) number, location and volume, detection and characteristics of possible LVO, collateral flow assessment, Alberta Stroke Program early CT score - ASPECTS and/or DWI/FLAIR mismatch for MR, pre-EVT grade of perfusion according to the thrombolysis in cerebral infarction - TICI - scale), treatment decision (IVT, EVT, IVT+EVT, none), time (door-to-needle for IVT and door-to-groin for EVT), clinical outcome (NIHSS score immediately after IVT/EVT - if performed), and reperfusion outcome (TICI score immediately after EVT - if performed). (2) Acute (24 h) and subacute (72 h): clinical severity (NIHSS), conventional neuroimaging type and findings, LF-MRI findings (lesion volume and characteristics, evolution - e.g. presence and entity of hemorrhagic transformation). (3) Hospital discharge: days of hospital stay, functional outcome at discharge (modified Rankin scale - mRS), final adjudication of the event (ischemic stroke, ICH, SAH, or mimic), assessment of etiology according to the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) classification - for ischemic stroke. (4) Chronic (4 weeks): conventional neuroimaging type and findings, LF-MRI findings (lesion volume, characteristics, and evolution), assessment of stroke etiology (TOAST) also considering findings from post-discharge clinical investigations.

LF-MRI diagnostic accuracy will be assessed as sensitivity and specificity, which in turn will be calculated basing on the proportion of true/false positives and true/false negatives in respect to the gold standard (i.e. the final adjudication of the event, based upon clinical and radiological examinations). Positive and negative predictive values will be also calculated. Agreement between LF-MRI and conventional neuroimaging will be evaluated using the Cohen Kappa coefficient.

Inclusion Criteria:

1. symptoms suggestive of acute stroke (acute onset of a focal neurological deficit which can be referred to the involvement of a specific CNS region);
2. stroke onset <24 h since when the patient was last known healthy;
3. written informed consent provided by the patient himself or by proxy (for unconscious patients, cognitively impaired or aphasic).

Exclusion Criteria:

1. symptoms not indicative of acute stroke (e.g. syncope, tonic or clonic activity, dizziness or wooziness alone, confusion and amnesia alone, subacute or chronic development of a focal neurological deficit);
2. inability to undergo LF-MRI due to critically impaired vital functions (e.g. hemodynamically unstable patients, need of immediate life-saving maneuvers);
3. implanted ferromagnetic devices potentially interfering with LF-MRI (e.g. cochlear implants);
4. impossibility to achieve written informed consent.

The study will include consecutive patients admitted to the Emergency Department (ED) of recruiting centers with a dispatch of suspected stroke. Dispatches will be provided by Emergency Medical Services or ED physicians according to local acute stroke management protocols and current clinical practice.

This study does not provide IPD