or to that conducted with CT (Troupin, 1985, p. 182). For example, when MRI was used to perform a scan for a suspected brain tumor, this technique did not "see" bone, as did the CT. The results of such a scan taken with the CT technique produced distorted density measurements, which had to be averaged. This is because a pixel (volume) includes both the bone and some brain edge in the computations. With the MRI, which has multiplanar capability, the sagittal imaging revealed malignant growth, with excellent visibility of the mass and cervical cord. As well, with the distinct negative signal from the flowing blood, large intracranial aneurysms and arteriovenous malformations were readily imaged by the MRI.
In addition to the above-noted benefits of SPECT, increased anatomic-definition and the production of quantitative information are superior to planar images (Powers & James, 1984, p. 185). As evidence of this, note that the measurements of regional cerebral blood flow can be obtained with the use of SPECT when such radiopharmaceuticals as N-isopropyl-(123I)-iodoamphetamine are used. This agent has the ability to cross the blood-brain barrier and proportionally distribute to the regional blood flow. As such, it can remain in the brain sufficiently long for the SPECT to be performed. With arteriovenous malformations, there is a dangerous impact on the surrounding brain by means of local pressure, seizure foci, sudden hemorrhage, or the chronic "steal" of flow from adjacent brain tissue. Troupin (1985, pp. 183-184) notes that, for arteriovenous malformations in general, CT, MRI, or radionuclide flow studies can be performed. The imaging technique of choice must be supplemented, however, with an arteriography to provide definitive information. Further, there has been excellent palliative treatment of nonresectable lesions with the use of interventional neuroradiology using selective catheterization and occlusion techniques.<...