Das reale Strahlenrelief bei einer Röntgenaufnahme des Thorax

Abstract

At present digital detectors for diagnostic X-ray imaging become more and more important. The image quality provided by these detector systems does not only depend on the properties of the systems but also on the X-ray intensity pattern in the detector plane. This pattern for a radiograph of the thorax was measured with high spatial resolution. This was done by exposing a specially prepared phantom of the lung to X-rays applying the standard examination conditions for thoracic imaging. The X-ray images were stored on industrial X-ray film generally used for non-destructive testing. These images were digitised with a high-resolution drum film scanner. The scanner and the film were able to reproduce the information in the pattern in the range of spatial frequencies up to 15 mm–1 and there were no problems with aliasing due to the scanning process. Using the characteristic curves of the film and the scanner the X-ray intensity pattern was calculated. A new method to evaluate the information content of the X-ray intensity pattern in the frequency domain was developed. The results of this evaluation were used to propose a requirement for digital detector systems to have a sampling Intervall less than 100 μm.