X-ray phase contrast tomography by tracking near field speckle.

Hongchang Wang,Robert Atwood,Julia Herzen,David Laundy,Sebastien Berujon,Kawal Sawhney,Alexander Hipp

doi:10.1038/srep08762

Abstract

X-ray imaging techniques that capture variations in the x-ray phase can yield higher contrast images with lower x-ray dose than is possible with conventional absorption radiography. However, the extraction of phase information is often more difficult than the extraction of absorption information and requires a more sophisticated experimental arrangement. We here report a method for three-dimensional (3D) X-ray phase contrast computed tomography (CT) which gives quantitative volumetric information on the real part of the refractive index. The method is based on the recently developed X-ray speckle tracking technique in which the displacement of near field speckle is tracked using a digital image correlation algorithm. In addition to differential phase contrast projection images, the method allows the dark-field images to be simultaneously extracted. After reconstruction, compared to conventional absorption CT images, the 3D phase CT images show greatly enhanced contrast. This new imaging method has advantages compared to other X-ray imaging methods in simplicity of experimental arrangement, speed of measurement and relative insensitivity to beam movements. These features make the technique an attractive candidate for material imaging such as in-vivo imaging of biological systems containing soft tissue.

Highlights

We describe a new approach for X-ray phase contrast tomography based on the tracking of X-ray near-field speckle, a technique that was originally developed for two-dimensional (2D) X-ray wavefront sensing and imaging[22,23,24]
We demonstrate extension of the X-ray speckle tracking (XST) method from 2D projection to give 3D volumetric phase information using computed tomography (CT) reconstruction and we show how the approach can be extended to the simultaneous retrieval of dark-field images
With a simple experimental arrangement, the speckle based technique is implementable at a synchrotron radiation beamline since no perfect crystals analysers or precision gratings are required

Summary

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10 keV, for biological samples composed of light elements (carbon, oxygen, hydrogen etc.), d is typically three orders of magnitude larger than b and phase sensitive imaging can allow high contrast with lower radiation dose than conventional absorption radiography. We describe a new approach for X-ray phase contrast tomography based on the tracking of X-ray near-field speckle, a technique that was originally developed for two-dimensional (2D) X-ray wavefront sensing and imaging[22,23,24]. Since the higher orders shape functions account for deformations due to strong and rapid variations in the electronic density, they mirror the sample scattering This translates in a reduction in the correlation value between the reference and target subsets. The correlation coefficient is related to the scattering from the sample and can be used to generate a dark-field image

Results

Methods

Author contributions

Additional information