Conventional magnetic resonance imaging of acute stroke

Abstract

I T HAS BEEN 2 decades since conventional magnetic resonance imaging (MRI) technique successfully showed experimental cerebral ischemia of less than 2 hours of duration in animals. The ability to detect acute ischemic injury with MRI has expanded to humans. In the past 10 years, there has been a tremendous amount of research and progress that has changed our understanding of different neurologic disorders. Advances in cerebral vascular disease by far have been the most beneficial. Conventional MRI provides excellent structural information and is the base of new complementary techniques focused on cerebral physiology and pathophysiology. Acute cerebral ischemia is definitely the most interesting and focused phase of stroke conventional MRI; it depends on the following biophysical factors for the diagnosis: (1) absent or diminished intravascular flow voids, (2) gray matter shows development of edema, (3) decreased diffusion of water, (4) increased signal intensity on T2-weighted images and proton density (PD), and (5) changes in metabolites. MRI sequences were of limited use until 1995 when the National Institute for Neurological Disease and Stroke published results on the recombinant tissue plasminogen activator (rt-PA) trial, which showed efficacy for treatment of acute cerebral ischemia. ~ The potential advantages of this technique with patients in acute cerebral ischemia are based on detection of viable cerebral tissue and vessel patency. A recent publication has also shown the usefulness of T2-weighted images in the detection of microbleeds or microhematomas as a predicting risk factor for hemorrhagic transformation after inrtra-artrterial trombolytic treatment. 2 Small cortical infarcts and infarcts of the posterior fossa are better detected on MRI than in computed tomography (CT)? The limitations of CT in the posterior fossa are because of beam