DWI uses the principle of brownian motion to evaluate dynamic microstructural tissue properties in an effort to help characterize vascular pathology. DWI is useful in the diagnosis of hyperacute stroke because it can reflect the immediate changes that begin upon failure of cellular mechanisms to regulate intra- and extracellular fluid volumes and result in subtle biochemical changes not readily apparent on other MRI sequences. This in turn can facilitate more rapid treatment decisions with greater certainty in the setting of acute stroke. The information obtained from DWI and ADC sequences can also help predict various other vascular pathologies, such as watershed and lacunar infarcts, cerebral hyperperfusion, and venous infarction, with increased accuracy and precision. DWI and ADC must be used in the context of the clinical picture and other available imaging; however, vascular mimics, such as infection, tumor,

Acute demyelinating lesions mimicking acute vascular pathology

Fig. 6.19 Acute demyelinating lesions mimicking acute vascular pathology. (a) Axial fluid-attenuated inversion recovery (FLAIR) image shows classical multiple periventricular and deep white matter demyelinating plaques (arrowheads). (b) Diffusion weighted imaging and (c) apparent diffusion coefficient map show area of restricted diffusion in an active plaque (arrow). This lesion may be confused for a lacunar infarct. The classical distribution of lesions on FLAIR/T2- weighted images, CSF examination, and follow-up imaging can help in clinching the diagnosis.

demyelinating lesions, and metabolic abnormalities, can be confused for vascular infarcts if appropriate context is not taken into account. The addition of DWI and ADC provides a valuable tool in the expeditious diagnosis of cerebral vascular infarcts and helps complement previous technology in the management of various cerebral pathologies.

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