Clinical Use of Bedside Portable Ultra-Low-Field Brain Magnetic Resonance Imaging in Patients on Extracorporeal Membrane Oxygenation: Results From the Multicenter SAFE MRI ECMO Study

Abstract

Background: Early detection of acute brain injury (ABI) at the bedside is critical in improving survival for patients with extracorporeal membrane oxygenation (ECMO) support. We aimed to examine the safety of ultra-low-field (ULF; 0.064-T) portable magnetic resonance imaging (pMRI) in patients undergoing ECMO and to investigate the ABI frequency and types with ULF-pMRI.

Methods: This was a multicenter prospective observational study (SAFE MRI ECMO study [Assessing the Safety and Feasibility of Bedside Portable Low-Field Brain Magnetic Resonance Imaging in Patients on ECMO]; NCT05469139) from 2 tertiary centers (Johns Hopkins, Baltimore, MD and University of Texas-Houston) with specially trained intensive care units. Primary outcomes were safety of ULF-pMRI during ECMO support, defined as completion of ULF-pMRI without significant adverse events.

Results: Of 53 eligible patients, 3 were not scanned because of a large head size that did not fit within the head coil. ULF-pMRI was performed in 50 patients (median age, 58 years; 52% male), with 34 patients (68%) on venoarterial ECMO and 16 patients (32%) on venovenous ECMO. Of 34 patients on venoarterial ECMO, 11 (22%) were centrally cannulated and 23 (46%) were peripherally cannulated. In venovenous ECMO, 9 (18%) had single-lumen cannulation and 7 (14%) had double-lumen cannulation. Of 50 patients, adverse events occurred in 3 patients (6%), with 2 minor adverse events (ECMO suction event; transient low ECMO flow) and one serious adverse event (intra-aortic balloon pump malfunction attributable to electrocardiographic artifacts). All images demonstrated discernible intracranial pathologies with good quality. ABI was observed in 22 patients (44%). Ischemic stroke (36%) was the most common type of ABI, followed by intracranial hemorrhage (6%) and hypoxic-ischemic brain injury (4%). Of 18 patients (36%) with both ULF-pMRI and head computed tomography within 24 hours, ABI was observed in 9 patients with a total of 10 events (8 ischemic, 2 hemorrhagic events). Of the 8 ischemic events, pMRI observed all 8, and head computed tomography observed only 4 events. For intracranial hemorrhage, pMRI observed only 1 of them, and head computed tomography observed both (2 events).

Conclusions: Our study demonstrates that ULF-pMRI can be performed in patients on ECMO across different ECMO cannulation strategies in specially trained intensive care units. The incidence of ABI was high, seen in 44% of ULF-pMRI studies. ULF-pMRI imaging appears to be more sensitive to ABI, particularly ischemic stroke, compared with head computed tomography.

Keywords: brain injuries; critical care; extracorporeal membrane oxygenation; magnetic resonance imaging.

Figure 1.

ULF-p MRI in the intensive care unit. Positioning of a patient with extracorporeal membrane oxygenation (ECMO) support within the Swoop scanner. A, A patient on ECMO receiving ultra–low-field portable magnetic resonance imaging (ULF-pMRI) with the location of equipment and patient relative to the scanner. ECMO was kept outside the scanner 5-gauss line (extended yellow ring over the patient). Standard medical devices such as the ventilator and intravenous pump on the right side of the patient are safe and fully functional outside the 5-gauss line. B, Position of the patient inside the head coil of ULF-pMRI relative to mechanical ventilation. C, How ULF-pMRI moves through an intensive care unit hallway. D, Schematic of the 5-gauss line and strength of the magnetic field.

Figure 2.

Comparison of images between ULF-pMRI and HCT. Axial noncontrast and magnetic resonance imaging (MRI) of the brain at the level of the centrum semiovale (top) and at the level of the basal ganglia (bottom). On computed tomography (CT) scan images, there was no evidence of acute infarcts. However, on subsequent ultra–low-field portable MRI (ULF-pMRI), there was evidence of multiple acute watershed vs embolic infarcts in bilateral cerebral hemispheres and the head of the right caudate nucleus (arrows), which show restriction on diffusion-weighted imaging (DWI), with corresponding low signal attenuation on apparent diffusion coefficient (ADC) and hyperintense signal on fluid-attenuated inversion recovery (FLAIR). The entire series of MRI sequences and images for these patients are available as the link to Digital Imaging and Communications in Medicine (DICOM) in the Hyperfine Cloud. HCT indicates head computed tomography.

Figure 3.

Different examples of acute brain injury in ULF-pMRI. Ultra–low-field portable magnetic resonance imaging (ULF-pMRI) and head computed tomography images in patients with extracorporeal membrane oxygenation support. A, E, and I, Diffusion-weighted magnetic resonance imaging (MRI). B, F, and J, Apparent diffusion coefficient MRI. C, G, and K, Fluid-attenuated inversion recovery MRI. D, H, and L, T2-weighted MRI scan. Patient 1 (A–D) demonstrated a small ischemic stroke in the left cerebellum denoted by red arrows. Patient 2 (E–H) demonstrated moderate ischemic stroke in the left occipital lobe. Patient 3 (I–L) had an intracranial hemorrhage in the right superior frontal sulcus (red arrow). The entire series of MRI sequences and images for these patients are available as the link to Digital Imaging and Communications in Medicine (DICOM) in the Hyperfine, Inc Imaging Viewer.