Augmenting Soft Tissue Contrast Using Edge-Enhancing Phase-Imaging Techniques in X-Ray Microtomography

Conventional X-ray imaging is based on the attenuation of X-rays and the technique provides sufficient contrast when the difference between attenuation coefficients of neighboring structures is sufficient. A promising imaging possibility on a µCT is the use of phase information of an X-ray beam to generate an image of the sample. This is known as phase-contrast imaging. Propagation-based phase imaging sets the least amount of requirements on the imaging setup - lateral coherence for the X-ray source and a movable detector and source. The Zeiss Xradia MicroXCT-400 at our laboratory provides this possibility. Therefore, the phase-contrast imaging protocol, which provides an edge-enhancement effect, on the µCT device was optimized using thin polylactic acid fibers in order to enhance the visibility of low density samples. The optimization consisted of source and detector distance variation measurements. To demonstrate the contrast enhancement results, the optimization was applied to two types of collagen samples embedded in air, ethanol, and water.The results showed enhanced contrast for the edge-enhanced phase-contrast images compared to absorption images. Most importantly, the results indicated that the source does not need to placed at the negative limit to obtain useful phase information. Additionally, the visibility increases with increasing sample-to-detector distance. Finally, significantly enhanced contrast was obtained for the collagen sample embedded in water using phase-imaging techniques. The technique is limited due to the focal spot size and voltage of the X-ray source. The phase-imaging technique has the possibility to enhance contrast of low density samples and to reveal structures that cannot be seen using other imaging techniques.