X-ray imaging is an essential tool for non-invasive assessment of various samples, both for biomedical diagnosis and non-destructive testing applications. Many technical approaches have been proposed to enhance the level of information recorded in the X-ray images. When absorption properties are very similar between two components of a sample, it makes it difficult to separate them using X-ray absorption imaging. X-Ray Phase Contrast Imaging (X-PCI) shows great capability to differentiate elements with similar absorption (Bravin, 2013).
We propose a novel, single-exposure X-ray quantitative phase imaging system based on a Hartmann Wavefront sensor (HWS). The system provides high spatial sampling (20µm without magnification) and high sensitivity (~100 nrad) over a 5 to 25 keV energy range. The system can be used to perform tomographic experiments.
Here we present the imaging system (Fig. 1a) installed at the Syrmep beamline at Elettra as well as first images obtained on reference samples. This test sample was composed of four different micro-spheres: Si (480µm in diameter), Al2O3 (500µm), quartz (350µm) and soda lime glass (700µm). Each hole in the Hartmann mask generates a bright spot on the camera and the lateral shift of the spot compared to the image without sample is proportional to the deflection generated by the sample. From two acquisitions (with and without sample), both absorption and deflections in the two transverse directions are obtained simultaneously. Since the Hartmann technology is achromatic, it also allows hyperspectral imaging. The figure illustrates the absorption in (1b) and deflections in the X and Y directions (1c and 1d respectively) generated by the samples and measured by the HWS. Our approach provides an alternative to already proposed X-PCI methods. A HWS can be used to discriminate transparent objects. Furthermore, the knowledge of object shapes, when combined to quantitative phase measurements can lead to local density measurements of complex objects, with multiple possible applications in biomedical imaging or material science.
Bravin, A., Coan P. and Suortti, P., X-ray phase-contrast imaging: from pre-clinical applications towards clinics”, Phys. Med. Biol. 58, (2013), R1-R35
This research was funded by the 3DXlight project (European Union’s Horizon 2020 research and innovation program) under grant agreement nº 851956, by the XPulse project (Région Nouvelle-Aquitaine and the European Union FEDER, FEDER/FSE Aquitaine 2014–2020), grant agreement n°3334910, LASERLAB-Europe Joint Research Activity grant agreement n°871124 and the support of Prematuration 2019 project from IP Paris. MI gratefully acknowledge the support of the Accelerator and Detector Research Program, part of the Scientific User Facility Division of the Basic Energy Science Office of the U.S. Department of Energy, under the project “Wavefront Preserving Mirrors.” This work has received funding from the European Union’s Horizon 2020 research. The FISR Project ‘Tecnopolo di nanotecnologia e fotonica per la medicina di precisione’ (funded by MIUR/CNR, CUP B83B17000010001) and the TECNOMED project (funded by Regione Puglia, CUP B84I18000540002) are also acknowledged. We acknowledge all the team at the SYRMEP beamline of Elettra for giving us access to the beamline and for their technical support.