The use of an off-line static display system with a computerized transverse axial tomographic unit

Computer-assisted transverse axial tomography employing the EMI scanner (E.M.I. Ltd., Hayes, Middlesex) is a non-invasive radiological investigation potentially capable of analysing the physical properties of sections of normal brain and many pathological processes which may affect the brain. Details of the technique and equipment are well documented together with evaluations of early clinical series (Hounsfield, 1973; Ambrose, 1973). The method has been employed in Manchester for a year, during which time 1,500 examinations have been undertaken in a wide variety of neurological disorders. Clinical and radiological management of neurological and neurosurgical patients has been significantly affected by the new procedure. The large quantity of information produced for each reconstructed section of brain presents problems of storage, display and analysis. No photographic medium can record reliably the available range of data. Analysis employing the machine's own display and controls can be performed on site but not whilst the machine is scanning. A video-display processor (VDP) has been developed by Elscint Limited (Elscint Ltd., Haifa, Israel) primarily for display and analysis of radioisotope images. In its present form the display unit has recirculating shift registers which can store two images each consisting of up to 128 × 96 eight-bit data words. The images can be viewed separately as “flicker free” pictures displayed on a colour television in which eight colours are used quantitatively to display an adjustable band of the available data. As an alternative, the picture may be presented in eight shades of grey.