PHASE-CONTRAST IMAGING

Researchers of the Paul Scherrer Institute (PSI) have developed a novel phase-contrast imaging technique, which makes use of the wave-optical properties of X-ray beams and offers significantly higher contrast than conventional X-ray radiography. Using a conventional X-ray tube source and a so-called Talbot grating interferometer, three images with different contrasts are simultaneously measured [1, 2]. Both the reseachers at the PSI as well as researchers at the Technical University of Munich (TUM) favor the use of photon-counting PILATUS detectors for this application.

Figure 1

Figure 1 shows the three images obtained from a chicken wing, which was studied as a test sample for biomedical X-ray imaging using a PILATUS 100K detector [3]. In comparision with the conventional attenuation image (a), enhanced contrast is found in the phase-contrast image (b) and the dark-field image (c), which provides information about the local X-ray scatter intensity. 


To obtain these images, a small intensity oscillation at each pixel (Figure 2) is recorded, while the grating interferometer is scanned. Here, the noise-free detection and the excellent point-spread function of the PILATUS detector lead to a very high image quality. Furthermore, the photon-counting of the PILATUS ensures that all photons are weighted equally, which in comparison to charge-summing detectors, enhances the contribution of the low-energetic X-ray photons that typically provide higher image contrast.