Yuqi Ren

Effect of Suture Properties on Stability of Middle Cerebral Artery Occlusion Evaluated by Synchrotron Radiation Angiography

Background and Purpose— The intraluminal suture technique for producing middle cerebral artery occlusion in rodents is the most commonly used method for modeling focal cerebral ischemia associated with clinical ischemic stroke. Synchrotron radiation angiography may provide a novel solution to directly monitor the success of middle cerebral artery occlusion. Methods— Twenty adult Sprague-Dawley rats for middle cerebral artery occlusion models were prepared randomly with different suture head silicone coating. In vivo imaging was performed at beam line BL13W1, Shanghai Synchrotron Radiation Facility, Shanghai, China. Results— Silicone-coated suture was superior to uncoated suture for producing consistent brain infarction. Additionally, silicone coating length was an important variable controlling the extent of the ischemic lesion: infarcts affected predominantly the caudate–putamen with large variability (<2 mm), both the cortex and caudate–putamen (2–3.3 mm), and most of the hemisphere, including the hypothalamus (>3.3 mm). Conclusions— Synchrotron radiation angiography provides a useful tool to observe hemodynamic changes after middle cerebral artery occlusion, and the physical properties of suture are critical to the success of the middle cerebral artery occlusion model.

Phase retrieval for hard X-ray computed tomography of samples with hybrid compositions

X-ray tomography of samples containing both weakly and strongly absorbing materials are necessary in material and biomedical imaging. Extending the validity of the phase-attenuation duality (PAD) method, the propagation-based phase-contrast computed tomography (PPCT) of a sample with hybrid compositions of both the light and dense components with 60 keV of synchrotron radiation is investigated. The experimental results show that the PAD-based PPCT is effective in imaging both the weakly and strongly absorbing components simultaneously. Compared with the direct PPCT technique, the PAD-based PPCT technique demonstrates its excellent capability in material discrimination and characterization. In addition, the PAD-based PPCT exhibits a striking performance on the image contrast enhancement and noise suppression. Therefore, this technique is useful for material and biomedical imaging applications, especially when the radiation dose involved imposes a serious constraint.

X-ray biomedical imaging beamline at SSRF

Since May 6, 2009, the X-ray biomedical imaging beamline at Shanghai Synchrotron Radiation Facility (SSRF) has been formally opened to users. The beamline is composed of a wiggler source with the intensity of magnetic field of 2.0 Tesla, a double crystal monochromator (DCM) cooled with liquid nitrogen, a 6-axis filter for high heat load reducing on the downstream optics such as Be window and DCM. The photon energy range for the monochromatic beam is 8-72.5keV. Three sets of digital X-ray detectors are provided to users with the pixel size range being 0.37-13 mu m. Several imaging methods such as micro-CT, in-line phase contrast imaging could be applied in biomedicine, material science and paleontology studies. The spatial resolution of 0.8 mu m and the temporal resolution of 1 ms could be realized. By the end of 2012, the beamline has provided more than 13900 hours beamtime for users, while over half of the research proposals come from biomedicine field. Nearly 2000 person-times have come and done their experiments at the beamline. More than 470 user proposals have been perfomed and more than 110 papers from users have been published. Some typical experimental results on biomedical applications will be introduced.

X-ray propagation-based equally sloped tomography for mouse brain

BACKGROUND The outstanding functional importance of the brain implies a strong need for brain imaging modalities. However, the current imaging approaches that target the brain in rodents remain suboptimal. OBJECTIVE AND METHODS In this paper, X-ray propagation-based phase contrast imaging combined with equally sloped tomography (PPCI-EST) was employed to nondestructively investigate the mouse brain. RESULTS The grey and white matters, which have extremely small differences in electron density, were clearly discriminated. The fine structures, including the corpus callosum (cc), the optic chiasma (ox) and the caudate putamen (CPu), were revealed. Compared to the filtered back projection reconstruction, the PPCI-EST significantly reduce projection number while maintaining sufficient image quality. CONCLUSIONS It could be a potential tool for fast and low-dose phase-contrast imaging to biomedical specimens.

Quantitative multi-scale analysis of mineral distributions and fractal pore structures for a heterogeneous Junger Basin shale

Three dimensional (3D) characterization of shales has recently attracted wide attentions in relation to the growing importance of shale oil and gas. Obtaining a complete 3D compositional distribution of shale has proven to be challenging due to its multi-scale characteristics. A combined multi-energy X-ray micro-CT technique and data-constrained modelling (DCM) approach has been used to quantitatively investigate the multi-scale mineral and porosity distributions of a heterogeneous shale from the Junger Basin, northwestern China by sub-sampling. The 3D sub-resolution structures of minerals and pores in the samples are quantitatively obtained as the partial volume fraction distributions, with colours representing compositions. The shale sub-samples from two areas have different physical structures for minerals and pores, with the dominant minerals being feldspar and dolomite, respectively. Significant heterogeneities have been observed in the analysis. The sub-voxel sized pores form large interconnected clusters with fractal structures. The fractal dimensions of the largest clusters for both sub-samples were quantitatively calculated and found to be 2.34 and 2.86, respectively. The results are relevant in quantitative modelling of gas transport in shale reservoirs.

X-ray microtomography at Shanghai Synchrotron Radiation facility

BL13W, an X-ray imaging beamline has been built and opened to users since May 6, 2009. More than 70 user proposals per year are granted and implemented at the beamline, with about 500 user visits/year. Up to now, X-ray microtomography (XMCT) is the dominated method for BL13W user operation, more than 70% user experiments were carried out with XMCT, covering the research fields in material science, biomedicine, physics, environmental science, archaeology and paleontology. To meet the user requirements, micro-CT imaging methods based on a variety of contrast mechanisms, including absorption, phase contrast, X-ray fluorescence, have been developed. Algorithms and related software have been developed achieve the low dose and fast data collection. Quantitative analysis to the three dimensional CT images is highly emphasized and related software for 3D information extraction with high precision and high efficiency, has been developed. Three-dimensional structure evolution has been attracting more and more attention in many scientific research fields. Two-Hertz dynamic phase contrast CT based on monochromatic SR beam was established at SSRF. The limitation of fluorescence X-ray CT from practical applications is the data-collection efficiency. The ordered-subsets expectation maximization algorithm was inducted to improve practicability of X-ray fluorescence computed tomography (XFCT), greatly. A scheme for full field XFCT was also proposed.

Full field X-ray nano-imaging at SSRF

Full field X-ray nano-imaging focusing on material science is under developing at SSRF. A dedicated full field X-ray nano-imaging beamline based on bending magnet will be built in the SSRF phase-II project. The beamline aims at the 3D imaging of the nano-scale inner structures. The photon energy range is of 5-14keV. The design goals with the field of view (FOV) of 20μm and a spatial resolution of 20nm are proposed at 8 keV, taking a Fresnel zone plate (FZP) with outermost zone width of 25 nm. Futhermore, an X-ray nano-imaging microscope is under developing at the SSRF BL13W beamline, in which a larger FOV will be emphasized. This microscope is based on a beam shaper and a zone plate using both absorption contrast and Zernike phase contrast, with the optimized energy set to 10keV. The detailed design and the progress of the project will be introduced.