Diagnostic Accuracy of Portable Low- and Ultra-Low-Field MRI for Acute Ischemic Stroke: A Systematic Review and Meta-Analysis.
BACKGROUND Portable low-field and ultra-low-field MRI enables bedside imaging, but its diagnostic performance for acute ischemic stroke (AIS) detection remains uncertain. PURPOSE To evaluate the diagnostic performance of portable MRI for AIS detection. DATA SOURCES Four databases were searched on February 2, 2026. STUDY SELECTION Eligible studies enrolled adults with suspected or confirmed AIS undergoing portable MRI. Nine studies comprising 474 patients with AIS were included. DATA ANALYSIS In studies with an appropriate reference standard, pooled sensitivity and specificity were synthesized using a bivariate random-effects model, and a hierarchical summary receiver operating characteristic curve was generated. Across all eligible AIS cohorts, the pooled lesion detection rate was estimated using a generalized linear mixed-effects model with random effects. DATA SYNTHESIS In six comparative studies, the pooled sensitivity for AIS detection was 73.3% (95% CI, 65.4-80.0), corresponding to approximately one in four confirmed infarcts being missed, with missed lesions generally small or sub-centimetric. Pooled specificity was 79.3% (95% CI, 69.1-86.8), and the area under the curve was 0.818. The pooled AIS lesion detection rate was 87.65% (95% CI, 75.7-94.2). LIMITATIONS There was substantial between-study heterogeneity (I2 = 74.2%). This estimate was interpreted as secondary and descriptive because it included case-only confirmed AIS cohorts. CONCLUSIONS Portable low/ultra-low-field MRI showed moderate diagnostic performance for AIS detection in comparative studies and may serve as a bedside adjunct where conventional MRI is constrained. However, given the false-negative risk, portable MRI should not be relied upon as a stand-alone rule-out test for AIS when clinical suspicion persists.