Objectives. Diffusion-weighted MRI is widely used in CNS imaging, especially in diagnosing acute ischemic stroke in an early phase, white matter structural abnormalities in various conditions -from trauma to schizophrenia or dyslexia, and in the differential diagnosis of infectious lesions and neoplasms.
Review. Due to the growing role of DWI in MR diagnostics this technique is presently available not only on high-tesla 1,5-3 T units, but also on low-tesla magnetic resonance systems 0,2-0,3 T. DWI together with the ADC map is very sensitive (>95%) and specific in diagnosing early stages of the acute ischemic stroke. Only the acute stroke shows hyperintensive signal on DWI, while chronic post-stroke lesions show hypointensive signal. Neoplasms, mostly gliomas and metastases with the accompanying edema, show attenuated signal on DWI, and a slightly elevated or normal signal on the ADC map. Epidermoid and arachnoid cysts look alike in conventional MRI scans, but DWI differentiates these pathologies: the epidermoid cyst has a hyperintensive signal, while the arachnoid cyst-hypointensive. The ADC map is very useful in differentiating between vasogenic and cytotoxic edema, as the former is associated with an unchanged or slightly elevated signal, while the latter - with hypointensive one. Infectious inflammatory diseases appear hyperintensive on DWI and hypointensive on the ADC map. DWI is helpful also in differentiation between acute and chronic demyelinisation lesions in multiple sclerosis. D WI allows detecting pathologicalfeatures in the brain tissue earlier than do any other neuroimaging techniques. Moreover, DWI can reveal abnormalities invisible in routine CT and MR studies.