Background White matter hyperintensity (WMH) on magnetic resonance imaging (MRI) of the brain is associated with vascular cognitive impairment, cardiovascular disease, and stroke. We hypothesized ...that portable magnetic resonance imaging (pMRI) could successfully identify WMHs and facilitate doing so in an unconventional setting. Methods and Results In a retrospective cohort of patients with both a conventional 1.5 Tesla MRI and pMRI, we report Cohen's kappa (κ) to measure agreement for detection of moderate to severe WMH (Fazekas ≥2). In a subsequent prospective observational study, we enrolled adult patients with a vascular risk factor being evaluated in the emergency department for a nonstroke complaint and measured WMH using pMRI. In the retrospective cohort, we included 33 patients, identifying 16 (49.5%) with WMH on conventional MRI. Between 2 raters evaluating pMRI, the interrater agreement on WMH was strong (κ=0.81), and between 1 rater for conventional MRI and the 2 raters for pMRI, intermodality agreement was moderate (κ=0.66, 0.60). In the prospective cohort we enrolled 91 individuals (mean age, 62.6 years; 53.9% men; 73.6% with hypertension), of which 58.2% had WMHs on pMRI. Among 37 Black and Hispanic individuals, the Area Deprivation Index was higher (versus White, 51.8±12.9 versus 37.9±11.9;
<0.001). Among 81 individuals who did not have a standard-of-care MRI in the preceding year, we identified WMHs in 43 of 81 (53.1%). Conclusions Portable, low-field imaging could be useful for identifying moderate to severe WMHs. These preliminary results introduce a novel role for pMRI outside of acute care and the potential role for pMRI to reduce disparities in neuroimaging.
Radiological examination of the brain is a critical determinant of stroke care pathways. Accessible neuroimaging is essential to detect the presence of intracerebral hemorrhage (ICH). Conventional ...magnetic resonance imaging (MRI) operates at high magnetic field strength (1.5-3 T), which requires an access-controlled environment, rendering MRI often inaccessible. We demonstrate the use of a low-field MRI (0.064 T) for ICH evaluation. Patients were imaged using conventional neuroimaging (non-contrast computerized tomography (CT) or 1.5/3 T MRI) and portable MRI (pMRI) at Yale New Haven Hospital from July 2018 to November 2020. Two board-certified neuroradiologists evaluated a total of 144 pMRI examinations (56 ICH, 48 acute ischemic stroke, 40 healthy controls) and one ICH imaging core lab researcher reviewed the cases of disagreement. Raters correctly detected ICH in 45 of 56 cases (80.4% sensitivity, 95%CI: 0.68-0.90). Blood-negative cases were correctly identified in 85 of 88 cases (96.6% specificity, 95%CI: 0.90-0.99). Manually segmented hematoma volumes and ABC/2 estimated volumes on pMRI correlate with conventional imaging volumes (ICC = 0.955, p = 1.69e-30 and ICC = 0.875, p = 1.66e-8, respectively). Hematoma volumes measured on pMRI correlate with NIH stroke scale (NIHSS) and clinical outcome (mRS) at discharge for manual and ABC/2 volumes. Low-field pMRI may be useful in bringing advanced MRI technology to resource-limited settings.
Neuroimaging is a critical component of triage and treatment for patients who present with neuropathology. Magnetic resonance imaging and non-contrast computed tomography are the gold standard for ...diagnosis and prognostication of patients with acute brain injuries. However, these modalities require intra-hospital transport to strict, access-controlled environments, which puts critically ill patients at risk for complications and secondary injuries. A novel, portable MRI (pMRI) device that can be deployed at the patient's bedside provides a needed solution. In a dual-center investigation, Yale New Haven Hospital has obtained regular neuroimaging on patients using the pMRI as part of routine clinical care in the Emergency Department and Intensive Care Unit (ICU) since August of 2020. Massachusetts General Hospital has begun using pMRI in the Neuroscience Intensive Care Unit since January 2021. This technology has expanded the population of patients who can receive MRI imaging by increasing accessibility and timeliness for scan completion by eliminating the need for transport and increasing the potential for serial monitoring. Here we describe our methods for screening, coordinating, and executing pMRI exams and provide further detail on how to scan specific patient populations.
Brain imaging is essential to the clinical care of patients with stroke, a leading cause of disability and death worldwide. Whereas advanced neuroimaging techniques offer opportunities for aiding ...acute stroke management, several factors, including time delays, inter‐clinician variability, and lack of systemic conglomeration of clinical information, hinder their maximal utility. Recent advances in deep machine learning (DL) offer new strategies for harnessing computational medical image analysis to inform decision making in acute stroke. We examine the current state of the field for DL models in stroke triage. First, we provide a brief, clinical practice‐focused primer on DL. Next, we examine real‐world examples of DL applications in pixel‐wise labeling, volumetric lesion segmentation, stroke detection, and prediction of tissue fate postintervention. We evaluate recent deployments of deep neural networks and their ability to automatically select relevant clinical features for acute decision making, reduce inter‐rater variability, and boost reliability in rapid neuroimaging assessments, and integrate neuroimaging with electronic medical record (EMR) data in order to support clinicians in routine and triage stroke management. Ultimately, we aim to provide a framework for critically evaluating existing automated approaches, thus equipping clinicians with the ability to understand and potentially apply DL approaches in order to address challenges in clinical practice. ANN NEUROL 2022;92:574–587
Assessment of brain injury severity is critically important after survival from cardiac arrest (CA). Recent advances in low-field MRI technology have permitted the acquisition of clinically useful ...bedside brain imaging. Our objective was to deploy a novel approach for evaluating brain injury after CA in critically ill patients at high risk for adverse neurological outcome.
This retrospective, single center study involved review of all consecutive portable MRIs performed as part of clinical care for CA patients between September 2020 and January 2022. Portable MR images were retrospectively reviewed by a blinded board-certified neuroradiologist (S.P.). Fluid-inversion recovery (FLAIR) signal intensities were measured in select regions of interest.
We performed 22 low-field MRI examinations in 19 patients resuscitated from CA (68.4% male, mean standard deviation age, 51.8 13.1 years). Twelve patients (63.2%) had findings consistent with HIBI on conventional neuroimaging radiology report. Low-field MRI detected findings consistent with HIBI in all of these patients. Low-field MRI was acquired at a median (interquartile range) of 78 (40–136) hours post-arrest. Quantitatively, we measured FLAIR signal intensity in three regions of interest, which were higher amongst patients with confirmed HIBI. Low-field MRI was completed in all patients without disruption of intensive care unit equipment monitoring and no safety events occurred.
In a critically ill CA population in whom MR imaging is often not feasible, low-field MRI can be deployed at the bedside to identify HIBI. Low-field MRI provides an opportunity to evaluate the time-dependent nature of MRI findings in CA survivors.
In the 20th century, the advent of neuroimaging dramatically altered the field of neurologic care. However, despite iterative advances since the invention of CT and MRI, little progress has been made ...to bring MR neuroimaging to the point of care. Recently, the emergence of a low-field (<1 T) portable MRI (pMRI) is setting the stage to revolutionize the landscape of accessible neuroimaging. Users can transport the pMRI into a variety of locations, using a standard 110-220 V wall outlet. In this article, we discuss current applications for pMRI, including in the acute and critical care settings, the barriers to broad implementation, and future opportunities.
Brain imaging is essential to the clinical management of patients with ischemic stroke. Timely and accessible neuroimaging, however, can be limited in clinical stroke pathways. Here, portable ...magnetic resonance imaging (pMRI) acquired at very low magnetic field strength (0.064 T) is used to obtain actionable bedside neuroimaging for 50 confirmed patients with ischemic stroke. Low-field pMRI detected infarcts in 45 (90%) patients across cortical, subcortical, and cerebellar structures. Lesions as small as 4 mm were captured. Infarcts appeared as hyperintense regions on T2-weighted, fluid-attenuated inversion recovery and diffusion-weighted imaging sequences. Stroke volume measurements were consistent across pMRI sequences and between low-field pMRI and conventional high-field MRI studies. Low-field pMRI stroke volumes significantly correlated with stroke severity and functional outcome at discharge. These results validate the use of low-field pMRI to obtain clinically useful imaging of stroke, setting the stage for use in resource-limited environments.
Background Timely imaging is essential for patients undergoing mechanical thrombectomy (MT). Our objective was to evaluate the safety and feasibility of low‐field portable magnetic resonance imaging ...(pMRI) for bedside evaluation following MT. Methods Patients with suspected large‐vessel occlusion undergoing MT were screened for eligibility. All pMRI examinations were conducted in the standard ferromagnetic environment of the interventional radiology suite. Clinical characteristics, procedural details, and pMRI features were collected. Subsequent high‐field conventional MRI within 72±12 hours was analyzed. If a conventional MRI was not available for comparison, computed tomography within the same time frame was used for validation. Results Twenty‐four patients were included (63% women; median age, 76 years interquartile range, 69–84 years). MT was performed with a median access to revascularization time of 15 minutes (interquartile range, 8–19 minutes), and with a successful outcome as defined by a thrombolysis in cerebral infarction score of ≥2B in 90% of patients. The median time from the end of the procedure to pMRI was 22 minutes (interquartile range, 16–32 minutes). The median pMRI examination time was 30 minutes (interquartile range, 17–33 minutes). Of 23 patients with available subsequent imaging, 9 had infarct progression compared with immediate post‐MT pMRI and 14 patients did not have progression of their infarct volume. There was no adverse event related to the examination. Conclusion Low‐field pMRI is safe and feasible in a post‐MT environment and enables timely identification of ischemic changes in the interventional radiology suite. This approach can facilitate the assessment of baseline infarct burden and may help guide physiological interventions following MT.
Abstract only Introduction: Conventional MRI (cMRI) is not routinely available post-mechanical thrombectomy (MT), which can preclude accurate infarction assessment. Our objective was to evaluate the ...use of low-field portable MRI (pMRI) for bedside evaluation post-MT, including its use as a post-procedural baseline monitor. Methods: Low-field pMRI was used to obtain bedside imaging in post-MT patients between December 2021 to August 2022 at Yale-New Haven Hospital. All pMRI exams were conducted in the standard ferromagnetic environment of the IR suite. Volumetric analyses were performed by a neuroradiologist using 3D Slicer software. If cMRI was not available for comparison, a CT was used. Patients’ charts were reviewed for pre-revascularization MAP and occurrences of MAP dropping by 10% and 20% from individual baselines between the time of pMRI and delayed imaging. Results: A total of 25 patients (64% females, median age 77 years-old IQR 69.5-84.5) underwent bedside pMRIs in the IR suite post-MT. The median time from last known normal to access was 6 hours IQR 4-17. The median pMRI examination time was 30 minutes IQR 17-32. Of the 24 patients with available delayed imaging, 7 (29.2%) had infarct progression compared to immediate post-MT pMRI, while 15 patients (62.5%) had stable/decreased stroke volume. Two patients (8.3%) had parenchymal hemorrhage type 2 and were excluded from further analysis. There was no statistically significant difference between the proportions of favorable TICI scores (85.7% in the infarct progression group vs. 92.3% in the stable/decreased infarct group, p=1.00). Patients with infarct progression had comparable pre-revascularization MAP compared to those with stable/decreased delayed infarct volume (mean of 100.3±4.6 vs. 101.9±15.9 respectively, p=0.727) but had more occurrences of MAP dropping by 10% and 20% of their baseline between the time of pMRI and delayed imaging (mean of 35.0±23.3 vs. 14.7±11.3 occurrences, p=0.011; and mean of 21.7±16.5 vs. 8.5±9.5 occurrences, p=0.026, respectively). Conclusions: The use of low-field MRI in the post-MT setting can facilitate benchmark brain monitoring and serial examinations to evaluate the impact of potential physiological perturbations that may impact ongoing brain injury.
Abstract only Background and Aims: MRI is critical for diagnosing acute stroke and guiding candidate selection for potential reperfusion therapy. However, rapid stroke evaluation using MRI is often ...dissuaded by the time required for patients to travel to access-controlled, high-field (1.5-3T) systems. Advances in low-field MRI enable the acquisition of clinically valuable images at the bedside. We report neuroimaging in patients presenting to the Emergency Department (ED) with stroke symptoms using a low-field portable MRI (pMRI) device. Methods: A 64mT pMRI device was deployed in the Yale-New Haven Hospital ED from August 2020 to July 2021. Patients presenting as a “Stroke Code” or “Intracranial Hemorrhage Alert” with no MRI contraindications were scanned. Exams were performed at the bedside, in the vicinity of ED room equipment. Research staff acquired imaging via tablet, with images available immediately after acquisition. Sequences obtained and axial scan times (in minutes) included T1-weighted imaging (4:54), T2-weighted imaging (7:03), fluid-attenuated inversion recovery imaging (9:31), and diffusion-weighed imaging with apparent diffusion coefficient mapping (9:04). Patients’ demographic information, hours from the time of patients' last known normal (LKN) to time of scan, and discharge diagnoses (determined from final imaging interpretation) were assessed. Results: pMRI exams were obtained on 54 patients (28 females, 51.9%; median age 71 years, 20-98 years). Discharge diagnoses included ischemic stroke (42.6%) no intracranial abnormality (31.5%), intraparenchymal hemorrhage (7.4%), atherosclerosis (7.4%), tumor (5.6%), subdural hematoma (3.7%), and intraventricular hemorrhage (1.9%). Patient LKN times ranged from 2 to 144 hours (median of 12 hours; 3 patients with no LKN excluded). The pMRI did not interfere with ED equipment and no significant adverse events occurred. Conclusion: We report the use of a pMRI for bedside neuroimaging in the ED. This approach suggests that pMRI may be viable for supporting rapid diagnosis and treatment candidate selection in patients presenting with stroke symptoms to the ED.
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