Imaging features of collimators

The decisive signification of collimator-data for the image quality is shown and the necessity of standardization in the collimator-region is clarified. As long as there are no standing standards, the manufacturers are expected to unconditionally submit data, which makes the choice of a suitable collimator possible. An explanation to these data is given by the principal structure of scanner- and various camera-collimators. In order to show the basic resolution attitude of these collimators, the spatial resolution (FWHM) is compared, depending on the distance between collimator and object. System resolution curves supplementary show an influence of the intrinsic resolution of the scintillation-camera-systems. The parameter spatial resolution, sensitivity and energy range are direct attributes for the choice of a collimator. The meaning of the maximum permissible quantum energy and the resulting partition of collimators from various energy regions are shown. The collimators of most manufacturers regarding resolution and sensitivity, are generally divided into three groups, namely high resolution, general purpose and high sensitivity. An analysis of manufacturers' data for resolution and sensitivity shows, that there are grave differences within the groups mentioned and that these general collimator designations cannot act as an attribute to selection. For this reason and for comparing collimators, exact stipulations of energy margins, plane-sensitivity and spatial-resolution attitude in depth are necessary. (orig.)