Karen A. Tong

Clinical applications of neuroimaging with susceptibility-weighted imaging

Susceptibility‐weighted imaging (SWI) consists of using both magnitude and phase images from a high‐resolution, three‐dimensional, fully velocity compensated gradient‐echo sequence. Postprocessing is applied to the magnitude image by means of a phase mask to increase the conspicuity of the veins and other sources of susceptibility effects. This article gives a background of the SWI technique and describes its role in clinical neuroimaging. SWI is currently being tested in a number of centers worldwide as an emerging technique to improve the diagnosis of neurological trauma, brain neoplasms, and neurovascular diseases because of its ability to reveal vascular abnormalities and microbleeds. J. Magn. Reson. Imaging 2005.

Guidelines for the acute medical management of severe traumatic brain injury in infants, children, and adolescents--second edition.

Author Affiliations Patrick M. Kochanek, MD, FCCM, Professor and Vice Chair, Department of Critical Care Medicine, University of Pittsburgh School of Medicine Nancy Carney, PhD, Associate Professor, Department of Medical Informatics and Clinical Epidemiology, Oregon Health & Science University P. David Adelson, MD, FACS, FAAP, Director, Barrow Neurological Institute at Phoenix Children’s Hospital, Chief, Pediatric Neurosurgery/ Children’s Neurosciences Stephen Ashwal, MD, Distinguished Professor of Pediatrics and Neurology, Chief of the Division of Child Neurology, Department of Pediatrics, Loma Linda University School of Medicine Michael J. Bell, MD, Associate Professor of Critical Care Medicine, University of Pittsburgh School of Medicine Susan Bratton, MD, MPH, FAAP, Professor of Pediatric Critical Care Medicine, University of Utah School of Medicine Susan Carson, MPH, Senior Research Associate, Department of Medical Informatics and Clinical Epidemiology, Oregon Health & Science University Randall M. Chesnut, MD, FCCM, FACS, Professor of Neurological Surgery, Orthopedics and Sports Medicine, University of Washington School of Medicine Jamshid Ghajar, MD, PhD, FACS, Clinical Professor of Neurological Surgery, Weill Cornell Medical College, President of the Brain Trauma Foundation Brahm Goldstein, MD, FAAP, FCCM, Senior Medical Director, Clinical Research, Ikaria, Inc., Professor of Pediatrics, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School Gerald A. Grant, MD, Associate Professor of Surgery and Pediatrics, Duke University School of Medicine Niranjan Kissoon, MD, FAAP, FCCM, Professor of Paediatrics and Emergency Medicine, British Columbia’s Children’s Hospital, University of British Columbia Kimberly Peterson, BSc, Research Associate, Department of Medical Informatics and Clinical Epidemiology, Oregon Health & Science University Nathan R. Selden, MD, PhD, FACS, FAAP, Campagna Professor and Vice Chair of Neurological Surgery, Oregon Health & Science University Robert C. Tasker, MBBS, MD, FRCP, Chair and Director, Neurocritical Care, Children’s Hospital Boston, Professor of Neurology and Anesthesia, Harvard Medical School Karen A. Tong, MD, Associate Professor of Radiology, Loma Linda University Monica S. Vavilala, MD, Professor of Anesthesiology and Pediatrics, University of Washington School of Medicine Mark S. Wainwright, MD, PhD, Director, Pediatric Neurocritical Care, Associate Professor of Pediatrics, Northwestern University Feinberg School of Medicine Craig R. Warden, MD, MPH, MS, Professor of Emergency Medicine and Pediatrics, Chief, Pediatric Emergency Services, Oregon Health & Science University/Doernbecher Children’s Hospital

Susceptibility-Weighted MR Imaging: A Review of Clinical Applications in Children

SUMMARY: Susceptibility-weighted imaging (SWI) is a high-spatial-resolution 3D gradient-echo MR imaging technique with phase postprocessing that accentuates the paramagnetic properties of blood products such as deoxyhemoglobin, intracellular methemoglobin, and hemosiderin. It is particularly useful for detecting intravascular venous deoxygenated blood as well as extravascular blood products. It is also quite sensitive to the presence of other substances such as iron, some forms of calcification, and air. We have used this technique in the past several years to study a wide variety of pediatric neurologic disorders. We present a review with selected case histories to demonstrate its clinical usefulness in the improvement of the following: 1) detection of hemorrhagic lesions seen in various conditions, including traumatic brain injury and coagulopathic or other hemorrhagic disorders; 2) detection of vascular malformations such as cavernous angiomas, telangiectasias, or pial angiomas associated with Sturge-Weber syndrome; 3) demonstration of venous thrombosis and/or increased oxygen extraction in the setting of infarction, hypoxic/anoxic injury, or brain death; 4) delineation of neoplasms with hemorrhage, calcification, or increased vascularity; and 5) depiction of calcium or iron deposition in neurodegenerative disorders. SWI has provided new understanding of some of these disease processes. It is hoped that as SWI becomes more widely available, it will provide additional diagnostic and prognostic information that will improve the care and outcome of affected children.

Diffuse axonal injury in children: Clinical correlation with hemorrhagic lesions

An inception cohort of 40 children and adolescents with traumatic brain injury and suspected diffuse axonal injury were studied using a new high‐resolution magnetic resonance imaging susceptibility‐weighted technique that is very sensitive for hemorrhage. A blinded comparison was performed between the extent of parenchymal hemorrhage and initial clinical variables as well as outcomes measured at 6 to 12 months after injury. Children with lower Glasgow Coma Scale scores (≤8, n = 30) or prolonged coma (>4 days, n = 20) had a greater average number (p = 0.007) and volume (p = 0.008) of hemorrhagic lesions. Children with normal outcomes or mild disability (n = 30) at 6 to 12 months had, on average, fewer hemorrhagic lesions (p = 0.003) and lower volume (p = 0.003) of lesions than those who were moderately or severely disabled or in a vegetative state. Significant differences also were observed when comparing regional injury to clinical variables. Because susceptibility‐weighted imaging is much more sensitive than conventional T2*‐weighted gradient‐echo sequences in detecting hemorrhagic diffuse axonal injury, more accurate and objective assessment of injury can be obtained early after insult, and may provide better prognostic information regarding duration of coma as well as long‐term outcome. Ann Neurol 2004;56:36–50

Susceptibility-Weighted Imaging and Quantitative Susceptibility Mapping in the Brain

Susceptibility‐weighted imaging (SWI) is a magnetic resonance imaging (MRI) technique that enhances image contrast by using the susceptibility differences between tissues. It is created by combining both magnitude and phase in the gradient echo data. SWI is sensitive to both paramagnetic and diamagnetic substances which generate different phase shift in MRI data. SWI images can be displayed as a minimum intensity projection that provides high resolution delineation of the cerebral venous architecture, a feature that is not available in other MRI techniques. As such, SWI has been widely applied to diagnose various venous abnormalities. SWI is especially sensitive to deoxygenated blood and intracranial mineral deposition and, for that reason, has been applied to image various pathologies including intracranial hemorrhage, traumatic brain injury, stroke, neoplasm, and multiple sclerosis. SWI, however, does not provide quantitative measures of magnetic susceptibility. This limitation is currently being addressed with the development of quantitative susceptibility mapping (QSM) and susceptibility tensor imaging (STI). While QSM treats susceptibility as isotropic, STI treats susceptibility as generally anisotropic characterized by a tensor quantity. This article reviews the basic principles of SWI, its clinical and research applications, the mechanisms governing brain susceptibility properties, and its practical implementation, with a focus on brain imaging. J. Magn. Reson. Imaging 2015;42:23–41.

Emerging Imaging Tools for Use with Traumatic Brain Injury Research

This article identifies emerging neuroimaging measures considered by the inter-agency Pediatric Traumatic Brain Injury (TBI) Neuroimaging Workgroup. This article attempts to address some of the potential uses of more advanced forms of imaging in TBI as well as highlight some of the current considerations and unresolved challenges of using them. We summarize emerging elements likely to gain more widespread use in the coming years, because of 1) their utility in diagnosis, prognosis, and understanding the natural course of degeneration or recovery following TBI, and potential for evaluating treatment strategies; 2) the ability of many centers to acquire these data with scanners and equipment that are readily available in existing clinical and research settings; and 3) advances in software that provide more automated, readily available, and cost-effective analysis methods for large scale data image analysis. These include multi-slice CT, volumetric MRI analysis, susceptibility-weighted imaging (SWI), diffusion tensor imaging (DTI), magnetization transfer imaging (MTI), arterial spin tag labeling (ASL), functional MRI (fMRI), including resting state and connectivity MRI, MR spectroscopy (MRS), and hyperpolarization scanning. However, we also include brief introductions to other specialized forms of advanced imaging that currently do require specialized equipment, for example, single photon emission computed tomography (SPECT), positron emission tomography (PET), encephalography (EEG), and magnetoencephalography (MEG)/magnetic source imaging (MSI). Finally, we identify some of the challenges that users of the emerging imaging CDEs may wish to consider, including quality control, performing multi-site and longitudinal imaging studies, and MR scanning in infants and children.

The role of advanced MR imaging findings as biomarkers of traumatic brain injury.

Treatment of traumatic brain injury (TBI) requires proper classification of the pathophysiology. Clinical classifiers and conventional neuroimaging are limited in TBI detection, outcome prediction, and treatment guidance. Advanced magnetic resonance imaging (MRI) techniques such as susceptibility weighted imaging, diffusion tensor imaging, and magnetic resonance spectroscopic imaging are sensitive to microhemorrhages, white matter injury, and abnormal metabolic activities, respectively, in brain injury. In this article, we reviewed these 3 advanced MRI methods and their applications in TBI and report some new findings from our research. These MRI techniques have already demonstrated their potential to improve TBI detection and outcome prediction. As such, they have demonstrated the capacity of serving as a set of biomarkers to reveal the heterogeneous and complex nature of brain injury in a regional and temporal manner. Further longitudinal studies using advanced MRI in a synergistic approach are expected to provide insight in understanding TBI and imaging implications for treatment.

Predicting outcomes of traumatic brain injury by imaging modality and injury distribution.

Early prediction of outcomes after traumatic brain injury (TBI) is often difficult. To improve prognostic accuracy soon after trauma, we compared different radiological modalities and anatomical injury distribution in a group of adult TBI patients. The four methods studied were computed tomography (CT), magnetic resonance imaging (MRI) with T2-weighted imaging (T2WI), fluid-attenuated inversion recovery (FLAIR) imaging, and susceptibility weighted imaging (SWI). The objective of this study was to identify which modality and anatomic model best predict outcome. The patient population consisted of 38 adults admitted between February 2001 and May 2003. Early CT, T2WI, FLAIR, and SWI were obtained for each patient as well as a Glasgow Outcome Score (GOS) between 0.1 and 22 months (mean 9.2 months) after injury. Using a semi-automated computer method, intraparenchymal lesions were traced, measured, and converted to lesion volumes based on slice thickness and pixel size. Lesions were assigned to zones and regions. Outcomes were dichotomized into good (GOS 4-5) and poor (GOS 1-3) outcome groups. Brain injury detected by imaging was analyzed by median total lesion volume, median volume per lesion, and median number of lesions per outcome group. T2WI and FLAIR imaging most consistently discriminated between good and poor outcomes by median total lesion volume, median volume per lesion, and median number of lesions. In addition, T2WI and FLAIR imaging most consistently discriminated between good and poor outcomes by zonal distribution. While SWI rarely discriminated by outcome, it was very sensitive to intraparenchymal injury and its optimal use in evaluating TBI is unclear. SWI and other new imaging modalities should be further studied to fully evaluate their prognostic utility in TBI evaluation.

Prospective Longitudinal Proton Magnetic Resonance Spectroscopic Imaging in Adult Traumatic Brain Injury

To investigate whether longitudinal magnetic resonance proton spectroscopic imaging (MRSI) demonstrates regional metabolite abnormalities after traumatic brain injury (TBI) that predict long‐term neurologic outcome.

Diffusion-weighted imaging improves outcome prediction in pediatric traumatic brain injury.

Diffusion-weighted imaging (DWI) and consequent apparent diffusion coefficient (ADC) maps have been used for lesion detection and as a predictor of outcome in adults with traumatic brain injury (TBI), but few studies have been reported in children. We evaluated the role of DWI and ADC for outcome prediction after pediatric TBI (n=37 TBI; n=10 controls). Fifteen regions of interest (ROIs) were manually drawn on ADC maps that were grouped for analysis into peripheral gray matter, peripheral white matter, deep gray and white matter, and posterior fossa. All ROIs excluded areas that appeared abnormal on T2-weighted images (T2WI). Acute injury severity was measured using the Glasgow Coma Scale (GCS) score, and 6-12-month outcomes were assessed using the Pediatric Cerebral Performance Category Scale (PCPCS) score. Patients were categorized into five groups: (1) controls; (2) all TBI patients; (3) mild/moderate TBI with good outcomes; (4) severe TBI with good outcomes; and (5) severe TBI with poor outcomes. ADC values in the peripheral white matter were significantly reduced in children with severe TBI with poor outcomes (72.8+/-14.4x10(-3) mm2/sec) compared to those with severe TBI and good outcomes (82.5+/-3.8x10(-3) mm2/sec; p<0.05). We also found that the average total brain ADC value alone had the greatest ability to predict outcome and could correctly predict outcome in 84% of cases. Assessment of DWI and ADC values in pediatric TBI is useful in evaluating injury, particularly in brain regions that appear normal on conventional imaging. Early identification of children at high risk for poor outcome may assist in aggressive clinical management of pediatric TBI patients.