Transition from Computer Tomography to Nuclear Magnetic Resonance Scanning
Since it became commercially available in 1973, X-ray computer (axial) tomography (CT) scanning has revolutionized the practice of neurology and neurosurgery because it has allowed direct visualization of brain tissue structures without the introduction of any significantly toxic contrast media. A CT scan is actually a map of specific gravity, the local tissue density. Bone appears white because it is significantly more dense than brain tissue. Brain tissue in turn is slightly more dense than the cerebrospinal fluid which fills the ventricles and the subarachnoid space. Within the hemispheres, white matter appears darker since it is slightly less dense than the surrounding gray matter.
KeywordsNuclear Magnetic Resonance Main Field Radio Frequency Signal Nuclear Magnetic Resonance Imaging Magnetic Gradient
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