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Stroke and Transient Ischemic Attacks of the Brain and Eye
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Gradient echo T2-weighted susceptibility images have high sensitivity, equivalent to CT, for diagnosing acute hemorrhage (Figures 12.32–12.35), and greater sensitivity than CT for previous hemorrhage (Figures 12.36, 12.37). Susceptibility-weighted imaging (SWI) also enables detection of cerebral microbleeds (CMBs), which might indicate underlying cerebral amyloid angiopathy (CAA), and might be associated with an increased risk of intracranial hemorrhage after IV thrombolysis.
Biomedical Imaging Magnetic Resonance Imaging
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
Susceptibility-weighted imaging (SWI) is a GRE-based technique with several enhancements to increase its sensitivity to tissue susceptibilities (Haacke et al. 2004). It can distinguish paramagnetic (e.g., hemorrhage/iron) from diamagnetic (e.g., calcification) lesions. It can also produce venograms based on the susceptibility differences. In quantitative susceptibility mapping (QSM), the phase information in GRE images is further analyzed to quantify susceptibility values using various mathematical methods (Wang and Liu 2015).
Subarachnoid hemorrhage
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Essentials of Anesthesia for Neurotrauma, 2018
Emily G.Y. Koo, Mandy H.M. Chu, Patricia K.Y. Kan, Eunice Y.L. Dai, Matthew T.V. Chan
Susceptibility weighted imaging (SWI) uses flow compensated, long echo, and GRE sequences to acquire images.22 SWI is extremely sensitive to blood (Figure 9.4). Images from the filtered phase that were acquired from SWI show differentiation of blood from calcification, which will appear as opposite signal intensities.
High signal-intensity abnormalities in susceptibility-weighted imaging for primary intracerebral hemorrhage
Published in International Journal of Neuroscience, 2019
Jing-Jing Liang, Lu Lei, Yan-Ping Zeng, Zhe-Man Xiao
Susceptibility-weighted imaging (SWI) is an MRI technique that enhances image contrast by using susceptibility differences between the adjacent brain parenchyma [7–10]. SWI is considered to be more sensitive than other multimodal MRI techniques, including conventional MRI and gradient-recalled echo pulse sequences, as it detects the paramagnetic effects of blood products, such as deoxyhemoglobin, methemoglobin, hemosiderin, and ferritin, which are present in a hematoma at different stages [7]. According to this principle, SWI has been applied to image various pathologies, including ICH, microbleeds, calcification, vascular malformation, traumatic brain injury, stroke, neoplasm, and multiple sclerosis [5,11,12], and can help better evaluate the underlying pathophysiology and etiology of ICH. SWI has gradually been adopted into routine clinical imaging within the past decade.
Quantifying changes on susceptibility weighted images in amyotrophic lateral sclerosis using MRI texture analysis
Published in Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2019
Scott L.M. Johns, Abdullah Ishaque, Muhammad Khan, Yee-Hong Yang, Alan H. Wilman, Sanjay Kalra
Susceptibility weighted imaging (SWI) combines standard T2*-weighted magnitude with thresholded phase images to create image contrast dependent on magnetic susceptibility—the degree to which a material is magnetized within a magnetic field (5). SWI is sensitive to both heme and non-heme iron and calcium (6). SWI has identified white matter damage (7) and iron accumulation in ALS (8) but is limited to qualitative gross visual comparison of signal intensity over large regions. A recent study by Endo et al. demonstrates automated comparison of signal intensity in SWI has potential to objectively identify upper motor neuron impairment (9). Recent studies examining quantitative susceptibility mapping identify motor cortex and whole-brain susceptibility changes in ALS which SWI may detect (10,11). A method that is quantitative, automated, and unbiased is preferred to provide more accurate and objective results.
A systematic review of neuroimaging findings in children and adolescents with sports-related concussion
Published in Brain Injury, 2018
Emilie Chamard, Jonathan D. Lichtenstein
Interestingly, some studies have used multiple imaging techniques to investigate the impact of SRC in adolescents (33,34). Bartnik-Olsen and colleagues (34) used conjointly MRS and DTI, as well as PWI, and found a spectrum of injury including impaired axonal function, neuronal metabolism, and perfusion. The authors associated these injuries with the involvement of the ‘neurovascular unit’ (defined by the authors by the physiological relationship between neuronal networks, blood vessels, and glia) in the presence of persistent symptoms in pediatric patients with SRC (34). Another study used these two techniques in addition to susceptibility weighted imaging (SWI), a technique that exploits the magnetic susceptibility differences of various tissues, such as blood, iron, and calcification, as a new source of contrast enhancement (96). While no differences were found with MRS and DTI, differences in Cerebral Blood Flow (CBF) values persisted after resolution of symptoms in athletes with concussion; the authors suggested that a single pediatric SRC produces a state of physiologic disruption rather than a structural or metabolic injury (33). Studies using multiple neuroimaging techniques are particularly interesting as they offer complementary information regarding the pathophysiology of a concussion. However, it remains unclear if the changes observed with different methods correlate together and or if they follow the same course of recovery.