Portable ultralow-field MRI is feasible for bedside neuroimaging in critical care, new study suggests
Ultralow-field portable MRI may provide a useful bedside imaging option for critically ill patients who cannot easily be transported to conventional scanners.
These scanners may be especially beneficial for detecting ischemic brain injury and monitoring changes in intracranial structures, according to a systematic review of studies in adult intensive and neurocritical care populations. Authors involved in the analysis signaled support for the portable units in specific settings, as they could expedite treatment decisions in certain cases.
The review, which evaluated portable MRI systems operating at 0.1 tesla or lower, included 11 analyses published between 2020 and 2024. Together, the studies involved 694 patient participants and 715 examinations, along with 40 healthy controls.
For ischemic stroke, portable MRI detected infarction in 45 of 50 patients (90%). Sensitivity varied by imaging sequence, reaching 100% for fluid-attenuated inversion recovery (FLAIR), 98% for T2-weighted imaging and 86% for diffusion-weighted imaging. Visual assessment of diffusion-weighted imaging–FLAIR mismatch identified patients scanned within 4.5 hours with 60% sensitivity, 82% specificity and a 93% negative predictive value.
Performance for intracranial hemorrhage was more variable. Initial blinded evaluation found 80% sensitivity and 97% specificity. In a later cohort using deep-learning image reconstruction and providing readers with clinical context, sensitivity increased to 92%, with 99% specificity. However, sensitivity for infratentorial hemorrhage was lower, at 75%. Evidence for other extra-axial hemorrhages was limited, with only one subdural hemorrhage and no extradural hemorrhages reported.
The portable scanners also showed potential for identifying other neurologic complications. Midline-shift detection had 93% sensitivity and 96% specificity, with strong interrater agreement; hypoxic-ischemic brain injury in all 12 affected patients following cardiac arrest was detected as well. In patients receiving extracorporeal membrane oxygenation (ECMO), it identified all eight ischemic events, compared with four detected by head CT. However, it found only one of two hemorrhages.
Safety findings were generally favorable, but not completely free from adverse events. In a multicenter ECMO study, adverse events occurred in three of 50 patients (6%); this included one serious event involving an intra-aortic balloon pump malfunction attributed to electrocardiographic artifact. No adverse events were reported in seven other independent cohorts that assessed safety. However, it should be noted that around 28% of exams were nondiagnostic, largely due to patient motion.
“Ultralow-field pMRI is a feasible bedside neuroimaging adjunct with a low but nonzero adverse-event rate,” Cormac B. Mulhall, with the School of Surgery at the University of Western Australia, and colleagues noted. “It is of particular value for ischemic injury, midline shift and serial monitoring. Lower and variable sensitivity for hemorrhage, the nonspecificity of FLAIR hyperintensity, overlapping single-institution cohorts and small samples mean that larger multicenter validation studies are needed.”
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In addition to her background in journalism, Hannah also has patient-facing experience in clinical settings, having spent more than 12 years working as a registered rad tech. She began covering the medical imaging industry for Innovate Healthcare in 2021.