Computed Tomography and Magnetic Resonance Imaging

Their Uses in the Diagnosis of Brain Disorders

The use of computed tomography (CT) and magnetic resonance imaging (MRI) present both advantages and disadvantages relative to imaging for the diagnosis of brain disorders. While the MRI typically yields superior visibility of the suspected brain tumor mass, CT is superior to the use of radionuclide scans to set primary intracranial lesions. Further, while MRI does not "see" (image) bone, thus making it superior to CT for suspected intracranial brain tumor, its viability in scanning for vascular disease is as of yet unproved. In addition to these, contrast-enhanced CT appears to be superior to MRI flow measurements in the investigation of plaque morphology (Troupin, 1985).

Kim and Haynie (1987, p. 71) note that single-photon emission computed tomography (SPECT) is similar conceptually to x-ray computed tomography. Frackowiak (Terry, 1988, p. 89) reports that computed tomography (CT) also includes single-photon counting systems (SPC) and magnetic resonance imaging (MRI). Kim and Haynie (1987) indicate that all of these computed tomography reconstruction techniques prove invaluable to diagnostic imaging.

There are several points of comparison between SPECT and x-ray CT, including the generation of focal points, detail, generation of cross-sectional images, and contrast resolution (Powers & James, 1984, p. 185).

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In three of the cases, the NMR technique was unable to identify the foci of calcification within the tumors. Thus, nuclear magnetic imaging is more sensitive than the CT technique in the imaging of pathologic change in normal tissue constituents, and it more thoroughly depicts the extent of the tumor(s). The foci of abnormal enhancement on CT may be mistaken for vascular structures; however, they are readily distinguished using NMR imaging. In that NMR sometimes does not demonstrate calcifications, it may be difficult to distinguish malignant brain tissue from an edematous periphery. Here, MRI contrast studies prove useful. Brant-Zawadzki, Norman, and Newton (Vogler, Helms, & Callen, 1986, p. 576) found in a diagnostic study of glioma that tumor calcification was not visible using the MRI technique. The patient had a "butterfly" glioma that was situated at the level of the genu of the corpus callosum. There were thin crescentic arcs of calcification that were clearly visible using CT. Using the MRI technique, however, the calcification was not appreciable because the small crescents of signal void that they produce were "drowned out" by means of confluent zones of increased signal due to relative T2 prolongation of both t
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Some common words found in the essay are:
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Approximate Word count = 2778
Approximate Pages = 11 (250 words per page)

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