Quantitative X-ray dark-field and phase tomography using single directional speckle scanning technique

Abstract

X-ray dark-field contrast tomography can provide important supplementary information inside a sample to the conventional absorption tomography. Recently, the X-ray speckle based technique has been proposed to provide qualitative two-dimensional dark-field imaging with a simple experimental arrangement. In this letter, we deduce a relationship between the second moment of scattering angle distribution and cross-correlation degradation of speckle and establish a quantitative basis of X-ray dark-field tomography using single directional speckle scanning technique. In addition, the phase contrast images can be simultaneously retrieved permitting tomographic reconstruction, which yields enhanced contrast in weakly absorbing materials. Such complementary tomography technique can allow systematic investigation of complex samples containing both soft and hard materials.

State of the Art of X-ray Speckle-Based Phase-Contrast and Dark-Field Imaging

“…Furthermore, quantitative phase and dark-field tomographies of a phantom sample were successfully demonstrated using the 1D XSS method (see Section 3.2.2) [129]. However, it should be noted that an object with features oriented mainly along the axis orthogonal to the scanning direction was chosen, and only the refraction signal in the scanning direction was considered in the tomography reconstruction.…”

“…The correlation coefficient was also used in a dark-field approach proposed for 1D XSS dark-field tomography [87,129,136]. The sample speckle pattern is modelled as the convolution of the reference speckle pattern and the optical transfer function of the specimen.…”

“…As the speckles have an irregular, random shape and a distribution of sizes, only an average speckle size can be estimated. This is done for example by determining the spatial frequency at the maximum of the power spectrum [86,87,123,129] or from a 2D auto-correlation of the speckle pattern [88,128,[130][131][132][133][134]. Generally, well-defined, small speckles that can be resolved easily and cover a few pixels in the detector plane are desired.…”

Near-field speckle-scanning-based x-ray tomography

“…Besides, the reconstructions displayed here necessitated five images per projection while, in contrast, 40 images were used in the 1D XSS scheme of Ref. [21]. In addition, the method presented here offers the advantage over 1DXSS of a better sensitivity for the second beam transverse direction and results in a more accurate phase recovery.…”

“…Yet, the main current drawback of the XSS method lies in the large number of exposures to the x-ray beam necessary for each projection to recover the phase gradient induced by the sample presence. Using a twodimensional (2D) approach, more than 100 images are usually required in each projection scan while a one dimensional (1D) approach providing a high sensitivity in only one direction requires about 40 exposures per projection [20,21].…”