Method for Adjusting the Anger Camera

The uniformity of the Anger camera is a basic condition for the interpretation of scintiphotos and its importance increases with the accuracy of the evaluation method used for the interpretation of the scintiphotos. This is especially true for the use of three-dimensional multichannel-analysers with quantitative data output. With the standard method, used until now, all photo multipliers are tuned to give the same coun t-ra te when the crystal close to the centre of each photomultiplier is irradiatedby a collimated source. If there after the crystal is irradiated by a uniform flux of gamma rays, the density of the dots increases from the centre of the scintiphoto towards the outer edge. This means that uniformity has not been achieved. In clinical use hot spots would be simulated for those parts of an organ that are visualized at the outer part of the crystal. By using the magnetic core memory of a multichannel analyser for quantitative evaluation of the scintiphotos, we developed a method by which the photomultipliers are tuned with respect to their geometrical position. Thus, it is possible to achieve a uniformity within a few per cent over the whole crystal. The method and its theory are discussed. Data for the resolution of the Anger camera after this tuning process are given. (author)