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Publication Type
Journal Article
UWI Author(s)
Author, Analytic
Gilbert, David T.
Author Affiliation, Ana.
Department of Medicine
Article Title
Magnetic Resonance Imaging and Stroke
Medium Designator
n/a
Connective Phrase
n/a
Journal Title
West Indian Medical Journal
Translated Title
n/a
Reprint Status
Refereed
Date of Publication
2002
Volume ID
51
Issue ID
2
Page(s)
57-58
Language
n/a
Connective Phrase
n/a
Location/URL
n/a
ISSN
0043-3144
Notes
n/a
Abstract
Neuroimaging has revolutionised the diagnosis, investigation and management of neurological disease. The clinician in evaluating a patient with acute stroke, must answer several questions including: have non-stroke diagnoses been excluded (eg tumor, subdural)? What is the location and arterial territory represented by the stroke? Are the stroke mechanisms involved ischaemic or haemorrhagic? Are therapeutic interventions aimed at limiting or preventing recurrent brain injury feasible? Magentic resonance (MR) imaging techniques are playing an increasingly important role in providing answers to these questions. MR techniques are used not in identifying the location, size, number and mechanism of lesions in acute stroke but also in identifying appropriate patients for early intervention therapy and in influencing long-term management decisions (1,2). MR angiography is providing critical information on vascular anatomy in the evaluation of intra-and extracranial occlusive arterial disease and subarachnoid haemorrhage. MR imaging utilizes the principle that certain nuclei will emit a radio signal if they are placed in a strong magnetic field and then subjected to pulses of radiofrequency energy. Spinning atomic nuclei act as tiny 'bar magnets' which orient themselves along the axis of a strong magnetic field. Application, for a few milliseconds, of a radio wave pulse at the proper 'resonant' frequency will tilt the 'bar magnets' out of alignment with the field. When the radio wave pulse is turned off the atomic nuclei (hydrogen atoms in MR imaging) will reorient in alignment with the strong magnetic field, releasing energy in the form of radio waves that are used to generate the MR image. The hydrogen atoms reorient or 'relax' by two different mechanisms resulting in 'relaxation times' termed T1 and T2 relaxation times. Corresponding T1-weight images (T1WI) and T2-Weighted images (T2WI) and proton density-weighted images (PDWI) can then be generated. T1WI produce excellent anatomic detail while T2WI are sensitive to the presence of increased water and allow detection of oedema or tumor contrasting against normal brain.....
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