Practical Experience with the EMI Scanner
Until the advent of computer assisted x-ray tomography the fundamental techniques used in x-ray examination had not changed since their introduction by Roentgen nearly eighty years ago. Two inherent difficulties have limited the conventional radiograph. First, the resolution of structures is possible only when they differ quite markedly in their capacity to absorb x-rays (thus bone can be distinguished from soft tissue but individual soft tissue structures are difficult to define) and second, even with conventional tomography, all structures in the long axis of an x-ray beam are superimposed on the radiograph. A plain x-ray of the head will display the bones of the skull, but will not resolve the brain or the fluid filled chambers which lie within it. Information about the intracranial content can be obtained from conventional x-ray techniques only with the aid of artificial contrast media. Thus, the introduction of air or an iodine containing fluid into the cerebral ventricles or subarachnoid space allows these structures to be seen, and similarly, contrast media can be injected into the blood vessels of the brain to give an image of the vascular tree.
KeywordsIntracranial Aneurysm Cerebral Atrophy Obstructive Hydrocephalus Intracerebral Haematoma Intracranial Calcification
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