Showing papers by "Martin Bech published in 2008"

Hard-X-ray dark-field imaging using a grating interferometer

Abstract: Imaging with visible light today uses numerous contrast mechanisms, including bright- and dark-field contrast, phase-contrast schemes and confocal and fluorescence-based methods. X-ray imaging, on the other hand, has only recently seen the development of an analogous variety of contrast modalities. Although X-ray phase-contrast imaging could successfully be implemented at a relatively early stage with several techniques, dark-field imaging, or more generally scattering-based imaging, with hard X-rays and good signal-to-noise ratio, in practice still remains a challenging task even at highly brilliant synchrotron sources. In this letter, we report a new approach on the basis of a grating interferometer that can efficiently yield dark-field scatter images of high quality, even with conventional X-ray tube sources. Because the image contrast is formed through the mechanism of small-angle scattering, it provides complementary and otherwise inaccessible structural information about the specimen at the micrometre and submicrometre length scale. Our approach is fully compatible with conventional transmission radiography and a recently developed hard-X-ray phase-contrast imaging scheme. Applications to X-ray medical imaging, industrial non-destructive testing and security screening are discussed.

Region-of-interest tomography for grating-based x-ray differential phase-contrast imaging

Abstract: We report numerical and experimental results demonstrating accurate region-of-interest computed tomography (CT) reconstruction based on differential phase-contrast projection (DPC) images The approach removes the constraint of covering the entire sample within the field of view of the image detector Particularly for biomedical applications, the presented DPC-CT region-of-interest approach will allow for the visualization of previously inaccessible details deep inside an entire animal or organ We envisage that this development will also be of interest for potential future clinical applications, because grating-based DPC-CT can be implemented with standard x-ray tube sources

Advances in the visualization of unstained brain tumors using grating-based x-ray phase-contrast tomography

Abstract: We report advances and complementary results concerning a recently developed method for high-sensitivity grating-based hard x-ray phase tomography. We demonstrate how the soft tissue sensitivity of the technique can be used to obtain in-vitro tomographic images of a tumor bearing rat brain specimen, without use of contrast agents. In particular, we demonstrate that brain tumors and the white and gray brain matter structure in a rat's cerebellum can be resolved by this approach. The findings are potentially interesting from a clinical point of view, since a similar approach using three transmission gratings can be implemented with more readily available x-ray sources, such as standard x-ray tubes. Moreover, open the results the way to in-vivo experiments in the near future.