Imaging of Acute Ischemic Stroke
Section snippets
Physiopathology: the concept of penumbra
When a cerebral artery is occluded, a core of brain tissue dies rapidly. Surrounding this infarct core is an area of brain that is hypoperfused, but still viable because of collateral blood flow. This area of at-risk, but potentially salvageable, tissue is called the ischemic penumbra.6, 7, 8
Studies in primates and positron emission tomography studies in humans9, 10, 11, 12 have shown that brain parenchyma can compensate for hypoperfusion through an increase in oxygen extraction down to a
Why image a patient with acute stroke?
The central premise of acute stroke treatment is to rescue the ischemic penumbra. The current guidelines14 neglect the fact that the portion of potentially salvageable ischemic tissue is not only dependent on the time window, but also on the individual patient’s collateral blood flow. The presence and extent of the ischemic penumbra are time-dependent, but are especially patient-dependent. From patient to patient, survival of the penumbra can vary from less than 3 hours to well beyond 48 hours.
Multimodal MR Imaging Stroke Protocol
A typical stroke MR imaging protocol consists of T2/fluid attenuated inversion recovery (FLAIR), T2*, diffusion-weighted (DW) and perfusion-weighted (PW) images (Table 1) and MR angiography (MRA).22 This protocol can be performed in less than 30 minutes. It achieves reliable information about the site of vessel occlusion, the extent of potentially salvageable brain tissue, and the exclusion of differential diagnoses of ischemic stroke.
T2 and FLAIR imaging
On T2-weighted and FLAIR images, ischemic infarction appears
Multimodal CT Stroke Protocol
Modern CT imaging, including NCT, PCT (Table 2), and CT angiography (CTA), fulfills all the requirements for hyperacute stroke imaging.52 NCT can exclude hemorrhage; PCT can differentiate between penumbra and irreversibly damaged brain tissue52; and CTA identifies intracranial thrombus and vascular narrowing. Multimodal CT offers rapid data acquisition and can be performed with conventional CT equipment.
Noncontrast CT
With its widespread availability, short scan time, noninvasiveness and safety, NCT has been
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Automated multimodal segmentation of acute ischemic stroke lesions on clinical MR images
2022, Magnetic Resonance ImagingComputed Tomography, Computed Tomography Angiography, and Perfusion Computed Tomography Evaluation of Acute Ischemic Stroke
2018, Neuroimaging Clinics of North AmericaCitation Excerpt :Brain regions with significantly decreased CBV or CBF correspond to the infarct core, and areas with prolonged MTT represent the overall area of low perfusion pressure. Mismatch between both regions can help delineate the ischemic penumbra, ischemic parenchyma at risk of infarction that can be potentially saved from infarction if early successful vessel recanalization and tissue reperfusion.3 Selection of acute ischemic stroke patients for revascularization based on physiologic information may potentially shift the treatment paradigm from a rigid time-based paradigm to a more flexible and individualized, tissue-based approach, which may optimize patient selection, and, it is hoped, increase the proportion of patients amenable to treatment.
An audit of clinical practice, referral patterns, and appropriateness of clinical indications for brain MRI examinations: A single-centre study in Ghana
2018, RadiographyCitation Excerpt :Microbleeds (small hemosiderin deposits) not apparent on CT, can be detected by T2*-weighted images.39 Fat-saturated axial T1 (T1-FS)-weighted through the neck should be considered if cervical artery dissection is suspected.35,40 MRI is the imaging modality of choice in the investigation of patients with epilepsy.41,42
Classification of Posterior Fossa CT Brain Slices using Artificial Neural Network
2018, Procedia Computer ScienceMR imaging in hyperacute ischemic stroke
2017, European Journal of Radiology
The authors have nothing to disclose.