The EMI scanner. A brief review of the first 650 patients

The results obtained from the EMI scans of the first 650 patients are reviewed. Disease processes are seen as changes in the capacity of tissues to absorb X-ray photons, often with a demonstration of the distorted anatomy. The method operates most accurately where there is a large difference between the absorption values of diseased tissue and those of normal brain. This large difference in absorption values is best seen in lesions arising from trauma and cerebro-vascular accidents. The distinction between all types of haematoma which have high absorption values and cerebral oedema which has a low absorption value is relatively simple. In cerebro-vascular accidents a distinction between haemorrhage and infarction may be made. Infarction may show as a region of low absorption values as early as eight hours. Tumours produce visible change in a high percentage of cases but identification of tumour type is not often possible. Infarction, infection, coagulative necrosis, oedema and unclotted blood may produce similar appearances and have similar average values. The anatomical changes in hydrocephalus of all types are well seen but it is not usually possible to accurately describe the type of obstruction. The description of changes seen in cases of cerebral atrophy is similar to those demonstrated by cerebral pneumography.