Cerebral edema can develop as a complication of different types of acute brain injuries, including large-territory infarction, spontaneous intracranial hemorrhage, and traumatic brain injury1,2,3. Progressive, space-occupying edema can exert mass effect and displace midline structures4,5. Midline shift (MLS) of the brain is a widely recognized marker of mass effect that is associated with poor outcome5,6,7,8,9,10,11,12, altered consciousness11, and neurological deterioration5,11,13,14,15. The degree of MLS can be used to guide clinical decision-making5,14. For example, the presence of MLS greater than 5 mm can serve as a benchmark for emergency surgical evacuation of intracranial hemorrhage16,17,18. Although MLS is often considered the gold standard marker of mass effect11,12,19, it is a gross radiologic measure that is less sensitive to smaller morphological changes induced by brain swelling19. Other relevant markers of mass effect include the compression of thesal cistern, effacement of the ventricles, and displacement of the brainstem20. Additionally, net water uptake21 and diffusion-weighted imaging lesion volumes22 are important quantitative imaging biomarkers predictive of malignant edema.
Mass Effect [portable]
Capitalizing on advances in MRI technology, we recently developed and deployed a portable MRI (pMRI) scanner operating at low magnetic field (0.064 T) for the bedside assessment of brain injury in intensive care patients28. In another report, we systematically assessed the use of low-field pMRI in obtaining clinically significant imaging of intracerebral hemorrhage29. In contrast to high-field MRI systems, low-field pMRI exams can be performed in environments that contain ferromagnetic material, including ventilators, vital signs monitors, and infusion pumps. Despite operation at low-field, this pMRI system can acquire imaging sequences akin to conventional MRI systems, including diffusion-weighted, T2-weighted, T1-weighted, and fluid-attenuated inversion recovery (FLAIR) imaging.
Our recent reports demonstrate the safety and feasibility of pMRI in an intensive care setting28 and in the evaluation of intracerebral hemorrhage29. However, the utility and applications of pMRI in the assessment of neuropathology remain relatively unexplored. In this study, we evaluated the use of low-field pMRI as a bedside neuroimaging solution for assessing MLS in intensive care patients. We hypothesized that pMRI could be used to identify and quantify MLS as a surrogate of mass effect. Our secondary hypothesis was that pMRI-based midline measurements could predict the neurological outcome of stroke patients.
0.064 T Portable MRI scanner in an intensive care unit room. Low-field portable MRI exams were performed in the presence of operational intensive care equipment. The portable MRI operator and bedside nurse were able to remain in the room during scanning. All portable MRI images were available for real-time viewing on an iPad as each sequence was acquired and processed.
Example midline shift measurements on portable MRI (pMRI) and standard-of-care (SOC) imaging exams. (a) 81-year-old male with right intracerebral hemorrhage. Midline shift was measured to be 9.0 mm and 8.4 mm on the pMRI T2-weighted (T2W) and standard-of-care (SOC) MRI fluid-attenuated inversion recovery (FLAIR) images, respectively. (b) 43-year-old male with right intracerebral hemorrhage. No midline shift was measured on either pMRI T2W or SOC MRI T2W exams. (c) 71-year-old male with right M1 occlusion. Midline shift was measured to be 5.1 mm and 6.2 mm on the pMRI T2W and SOC CT images, respectively. (d) 44-year-old female with left M2 occlusion. No midline shift was measured on either pMRI T2W or SOC MRI T2W exams. Figure created using: Microsoft PowerPoint, Version 16.52, -us/microsoft-365/powerpoint.
To assess the relationship between MLS and discharge functional outcome, we performed a χ2 test to see if there was an association between the presence of MLS and discharge mRS scores. We then assessed the relationship between dichotomous and continuous MLS assessments and clinical outcomes using unadjusted and adjusted binary logistic regression models. We expressed the effect of MLS on functional outcome as unadjusted and adjusted common odds ratios (cOR and acOR, respectively). In stratified analyses, we evaluated ischemic stroke (IS) and intracranial hemorrhage (ICH) patients separately. To adjust forseline prognostic variables, our adjusted models included sex, race, age, stroke severity (NIH Stroke Scale score at admission), history of diabetes mellitus, atrial fibrillation, and prior stroke. All statistical analyses were performed using RStudio version 1.2.5033.
To account for confounding effects due to evolving improvements of the pMRI system, the abovementioned analyses were performed in three groups of patients: patients scanned using pMRI software versions RC3 and RC4, patients scanned using pMRI software versions RC5 and RC6, and patients scanned using pMRI software versions RC7 and RC8.
Evolving image quality and continuous development of the portable MRI (pMRI) device. (a) 71-year-old male with leftsal ganglia intracerebral hemorrhage; software RC3. (b) 71-year-old female with left frontal intracerebral hemorrhage; software RC4. (c) 58-year-old male with left cerebellar infarct; software RC5. The pMRI fluid-attenuated inversion recovery (FLAIR) did not capture the lesion. (d) 50-year-old male with right middle cerebral artery infarct; software RC6. (e) 68-year-old male with rightsal ganglia intracerebral hemorrhage; software RC7. (f) 81-year-old male with right frontoparietal intracerebral hemorrhage; software RC8. All SOC MRI exams shown are FLAIR images. T2W indicates T2-weighted; SOC indicates standard-of-care imaging. Figure created using: Microsoft PowerPoint, Version 16.52, -us/microsoft-365/powerpoint.
We report the use of low-field pMRI for bedside assessment of MLS in patients with IS and ICH. This approach enabled the acquisition of bedside neuroimaging exams that visualized MLS, a well-known marker of mass effect and cerebral edema5,10,11,37. We show that MLS measurements on pMRI images are consistent with measurements obtained on conventional MRI and CT studies. We also demonstrate that MLS on pMRI neuroimaging is associated with worse discharge functional outcome, recapitulating a well-established clinical relationship5,6,7,8,9,10,11.
Neuroimaging studies are integral to the initial assessment and neurological monitoring of patients with acute brain injuries. In conventional imaging pathways, patients must be transported to a dedicated imaging suite. However, intrahospital transport of patients is associated with numerous cardiovascular and respiratory risks23,24,25,26,27, which may render the acquisition of conventional CT or MRI imaging unfeasible for clinically unstable patients38. MRI scanners operating at low-field magnetic strength enable scanning outside of traditional imaging suites, as they are compatible with nearby ferromagnetic material. While previous approaches in low-field MRI, such as pre-polarized MRI, have been explored39, there has not been a low-field MRI device for head imaging that is entirely portable and has been successfully deployed in a clinical environment.
We previously reported the first use of a highly mobile low-field pMRI device to obtain head imaging at the bedside of intensive care patients28 and to evaluate intracerebral hemorrhage29. The current study extends our understanding of the unique applications of pMRI in evaluating neuropathology at the bedside. In brain-injured patients, attribution of a change in the level of arousal often requires neuroimaging to diagnose MLS, a well-known marker of mass effect and brain-swelling5,10,11,37. MLS is one of multiple important biomarkers for acute brain injuries, and the detection of significant MLS can serve as a radiologic indicator for treatment with hyperosmolar agents or neurosurgical interventions, such as decompressive craniectomy and hematoma evacuation. Monitoring changes in MLS is also important when evaluating the efficacy of such treatments, as unresolved MLS predicts worse clinical outcome40,41,42 while reversal of MLS is associated with improved consciousness and survival43,44,45. Our data show that pMRI can identify and quantify MLS with clinically significant accuracy, demonstrating the unique utility of low-field pMRI as a bedside tool for monitoring MLS. Further study is required to assess the ability of pMRI to detect smaller morphological markers of mass effect, includingsal cistern compression, ventricle effacement, and brainstem displacement.
Many fans are quick to point out that the fact the Legendary Edition will not be available on Nintendo Switch right away is already being met with a negative reaction from fans who feel that the series would be perfect for Nintendo Switch as well as those that say the ability to play Mass Effect on a portable console is honestly the only way that they can see themselves replaying through the series again.
Methods: In this single-blind, parallel group randomized controlled trial in Ulaanbaatar Mongolia, we randomly assigned 540 pregnant women to receive 1-2 portable high efficiency particulate air (HEPA) filter air cleaners or no air cleaners. We measured height and weight when children were a mean age of 23.8 months. Our primary outcome was age- and sex-specific BMI z-score based on the World Health Organization 2007 Growth Charts. Secondary outcomes included age- and sex-specific weight z score, overweight/obesity (defined as BMI z-score > 2.00), and catch-up growth (defined using various cut-offs to identify children with relatively low birth weight for sex and gestational age and relatively high age- and sex-specific weight in childhood). We imputed missing outcome data using multiple imputation with chained equations and our primary analysis was by intention to treat (ITT). We estimated intervention effects on continuous and binary outcomes using linear and logistic regression, respectively. 2ff7e9595c
Comments