Grating-based X-ray phase-contrast imaging (XPCI), have shown great potential for biological and medical imaging applications. However, the fabrication of the absorption grating, an indispensable element in conventional Talbot-Lau interferometer (TLI), making it a great challenge to this technology into practical use. In this paper, we implemented a cascade TLI (CTLI) for XPCI composed by a TLI and an inverse TLI, the self-image of TLI being used as the source of the inverse TLI, with the purpose to avoid the fabrication of small-period high aspect-ratio absorption gratings. Experiments validated the method and demonstrated the versatility and tunability of the system. The angular sensitivity as a function of the sample position was measured and discussed. Results show that the highest sensitivity is obtained, when the investigated object is close to any of two phase gratings. Furthermore, a CTLI with interference fringes being magnified to be directly detected by a common large-area detector would be established using this method. This will be useful for designing an XPCI system for applications of biomedical imaging in large field of view.
X-ray phase contrast imaging technique that can be used as a practical diagnostic tool for
medical purposes requires the image detector of higher resolution and sensitivity, and of larger
format as well. The above mentioned parameters cannot be come to their best on one detector at
present, so there is some kind of compromise among these parameters, for example, improving
one parameter may be at the cost of impairing another one. This paper designed an x-ray image
detector composed of a structured scintillation screen, optic taper and CCD camera etc.
Photo-assisted electrochemical etching method was used to make an array of deep holes in the
crystal silicon. The scintillator (CsI:Tl) was molten into the deep holes after the silicon wafer had
been heat-oxidized. When the screen was coupled with CCD camera by optic taper, the detector
fabrication was finished. We use the detector and an x-ray tube of 1mm focal spot to image a test
pattern, the spatial resolution better than 20lp/mm was obtained under the x-ray tube voltage of
45kVp and current of 2mA. The total image pixel of this detector is 2048 x 2048, with the 13.5
micrometer pixel size of the camera. The ratio of the input face size of optic taper to output size
was 2:1. High sensitivity was implemented by the course of x-rays in the scintillator, the longer
the course, the more the x-ray was absorbed, and the higher the sensitivity. In our detector
scintillation screen, the depth of the holes was great than 150 micrometers, with the 1.5
micrometers side length of the square section of a hole.