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The differential phase computed tomography (DP-CT) imaging is a kind of X-ray-phase-based CT methods, which is widely used in various X-ray imaging laboratories. At present, a collection of projections with the horizontal direction (perpendicular to the sample rotation axis) DP information is often acquired in DP-CT. In an ideal experiment, if the background is zero, then we can accurately reconstruct the information of each direction of the sample with horizontal data only. Actually, background information will produce streaking artifacts to affect the resolution in directions other than the horizontal direction. To mitigate the streaking artifacts in the conventionally reconstructed DP-CT images. This study develops a novel analytical DP-CT reconstruction framework by jointly using the bilateral DP information obtained along two perpendicular directions. In addition, a new data acquisition scheme is also proposed to quickly acquire the bilateral DP signal without the need of changing the direction of refraction signal acquisition. Experimental results demonstrate that this new algorithm is able to greatly reduce the streaking artifacts on DP-CT images.

The analysis of organic residues in pottery can provide abundant information on the lives of ancient people, including the natural resources consumed, the techniques applied, the functions of pottery, and so on. In this paper, a variety of methods, including FT-IR (Fourier transform infrared spectroscopy), GC–MS (gas chromatography-mass spectrometry), SEM (scanning electron microscopy) and SR-μCT (synchrotron radiation micro-computed tomography), have been employed to characterize the carbonized residues from an amphora, unearthed from the Changning site, Qinghai Province, Northwest China. The pottery residues were identified as birch bark tar, so ancient people in China could have used the particular local plant resources, birch bark, to produce tar as early as the Qijia cultural period (c. 4,000–3,500 bp). The birch bark tar could have been used to make composite tools discovered at the Changning site, and the amphora has probably been used for tar production. This, to our knowledge so far, is the earliest evidence for the use of birch bark tar in China. Due to the special geographical location of the Gansu-Qinghai Region, and the transition of subsistence strategy during the Qijia cultural period, the production and utilization of birch bark tar could not rule out the possibility of western influence, which needs further evidence.

Impressive developments in X-ray imaging are associated with X-ray phase contrast computed tomography based on grating interferometry, a technique that provides increased contrast compared with conventional absorption-based imaging. A new "single-step" method capable of separating phase information from other contributions has been recently proposed. This approach not only simplifies data-acquisition procedures, but, compared with the existing phase step approach, significantly reduces the dose delivered to a sample. However, the image reconstruction procedure is more demanding than for traditional methods and new algorithms have to be developed to take advantage of the "single-step" method. In the work discussed in this paper, a fast iterative image reconstruction method named OSEM (ordered subsets expectation maximization) was applied to experimental data to evaluate its performance and range of applicability. The OSEM algorithm with different subsets was also characterized by comparison of reconstruction image quality and convergence speed. Computer simulations and experimental results confirm the reliability of this new algorithm for phase-contrast computed tomography applications. Compared with the traditional filtered back projection algorithm, in particular in the presence of a noisy acquisition, it furnishes better images at a higher spatial resolution and with lower noise. We emphasize that the method is highly compatible with future X-ray phase contrast imaging clinical applications.

The investigation of the internal morphology of insects is usually performed using classical microtomy yielding optical micrographs of stained thin sections. The achievement of high-quality cross sections for microtomy is time-consuming and the risk of damaging sections is unavoidable. Moreover, the approach is impractical, in particular when quick acquisition of 3D structural information is required. Recently, X-ray computed microtomography (micro-CT) with a high spatial resolution was considered as a potential tool for the morphological classification of insects. We used micro-CT to investigate Quedius beesoni Cameron at the cellular length scale. This method provides a new powerful and nondestructive approach to obtain 3D structural information on the biological organization of insects. The preliminary images presented in this contribution clearly reveal the endoskeleton and the muscles of the head and the thorax with a full 3D structure. We also reconstructed the 3D structure of the brain of Quedius beesoni Cameron, and this is the first reconstruction in Staphylinidae, which will be a great advancement for morphological and phylogenic research. We claim that both the spatial resolution and the contrast characteristic of micro-CT imaging may fulfill the requirements necessary for zoological insect morphology and phylogeny, in particular, when a classification of a rare and unique insect specimen is required.

A simple framework that allows a new general diffraction enhanced imaging (DEI) equation to be derived is presented. This latter equation may explain all open problems associated with the equation introduced by Chapman and those not explained by the first DEI equation, such as the noise background due to the small-angle scattering reflected by the analyzer. Combing the DEI equation with computed tomography (CT) theory, we propose a new DEI-CT formula that explains qualitatively the contour contrast caused by extinction of the refraction. Two formulae with a new method to extract the refraction angle are also introduced. Within this new theoretical framework the three components of the gradient of the refractive index can be reconstructed.

Differential phase-contrast (DPC) X-ray imaging has been performed in the Talbot-Lau configuration, in which the X-ray source was a combination of an absorption grating and a laboratory X-ray generator. We report here quantitative analysis of partial coherence effects on the X-ray Talbot-Lau interferometer. Based on the visibility of the self-image, the well-known geometry condition is reproduced. It is shown that effects of partial coherence are determined by the opening ratio of the source grating, and that the effects are independent of the Talbot order and the type of the phase grating, a condition quite different from those in a Talbot interferometer. A possible explanation is discussed from the point of view of the effective spatial coherence length. Taking into account the available X-ray flux and experimental fluctuations, we present the optimum opening ratio. Furthermore, we mention that our results can also be successfully used to discuss the properties of a multiline X-ray source.