New Method for Colour Scanning

In the original colour-scanning system reported by the authors, a ratemeter which had a seven-coloured fan-shaped filter on its pointer was inserted in a dark box between a 35-mm colour film and a lamp lit synchronously with the counting impulses. This system needed to be improved since a long scanning time was required, to get a good colour scintigram, whilst the 35 -mm colour film was too small for diagnostic purposes. To improve these defects of the original method, a new colour-scanning method has been developed with the support of the Japanese Ministry of Education. This new method, referred to as the ''fixed-time counter method'', uses no ratemeter but an electronic gating circuit. Ten gates intercept the signals from the detector and at any one time only one of these is opened, depending on the number of counts recorded at a fixed time. Each gate actuates a chosen colour filter which filters the light from a xenon discharge tube. The filtered light is then used to form a photographic picture. Colour- printing papers are used instead of 35 -mm colour films to get scintigrams of the natural size of organs and also to save the time needed for developing film. Using this method, the one-way scanning that was adopted to get a good quality scan in original system type is no longer necessary, because the movement of the colour filter rapidly follows changes in the counting rate. Image distortion is thus avoided and scanning time is reduced. Clinical results with the new system are presented. (author)