Portable ultra-low field MRI in neurocritical care and intensive care units: A systematic review of diagnostic performance and feasibility.

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Abstract

To synthesise evidence on the diagnostic performance, safety, feasibility and clinical impact of ultra-low-field portable magnetic resonance imaging (pMRI) in adult neurocritical care and intensive care unit (ICU) populations. PubMed, Scopus and Embase were searched from inception to 6 February 2026 and supplemented by grey literature and citation searching. We included original English-language studies of adult ICU, neurocritical care or emergency department patients undergoing pMRI at ≤ 0.1 T. Two reviewers independently screened studies and extracted data. Risk of bias in diagnostic comparisons was assessed with an adapted QUADAS-2 framework, and feasibility and safety outcomes were appraised narratively. Because of heterogeneity, findings were synthesised narratively. The review was prospectively registered with PROSPERO (CRD420261302014). Eleven studies published between 2020 and 2024 were included, comprising 694 patient participants and 715 patient examinations, plus 40 healthy controls. Cohorts overlapped substantially: six studies came wholly and one partly from a single institution, and one ECMO study was a subset of another. The number of unique patients is therefore estimated at 281 to 677. In the multicentre ECMO study, adverse events occurred in 3 of 50 patients (6%). One was serious: an intra-aortic balloon pump malfunction attributed to electrocardiographic artefact. No adverse events were reported in the other seven independent cohorts that reported safety outcomes, and two studies did not report safety outcomes. For ischaemic stroke, pMRI detected infarction in 45 of 50 patients (90%). By sequence, sensitivity was 100% for FLAIR, 98% for T2-weighted imaging and 86% for diffusion-weighted imaging. Visual DWI-FLAIR mismatch identified patients scanned within 4.5 h with 60% sensitivity, 82% specificity and a 93% negative predictive value. Sensitivity for intracerebral haemorrhage was 80.4% (specificity 96.6%) on initial blinded evaluation. It was 92.1% (specificity 99.3%) in a later cohort in which raters had clinical context and images used deep-learning reconstruction, with lower sensitivity for infratentorial haemorrhage (75.0%). Only one subdural haemorrhage and no extradural haemorrhages were reported. Midline-shift detection showed 93% sensitivity, 96% specificity and a kappa of 0.87. pMRI detected hypoxic-ischaemic brain injury in 12 of 12 affected post-cardiac-arrest patients. In ECMO patients, pMRI detected 8 of 8 ischaemic events, compared with 4 of 8 on head CT, but only 1 of 2 haemorrhages. Up to 28% of examinations were nondiagnostic, mainly because of motion. Ultra-low-field pMRI is a feasible bedside neuroimaging adjunct with a low but non-zero adverse-event rate. It is of particular value for ischaemic injury, midline shift and serial monitoring. Lower and variable sensitivity for haemorrhage, the nonspecificity of FLAIR hyperintensity, overlapping single-institution cohorts and small samples mean that larger multicentre validation studies are needed.

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