Among the X-ray phase contrast imaging (XPCI) techniques, both propagation-based and grating-based micro-tomography recently dominate the non-destructive three-dimensional inner-structure measurement in biomedical research, especially for visualizing tiny density variations in soft tissues and organs. In order to quantitatively evaluate the advantages and disadvantages of both techniques for comprehensive application through carrying out a comparison study of high energy propagation-based micro-tomography with generalized phase-and-attenuation duality (PAD) phase retrieval and Talbot grating interferometer-based micro-tomography, implemented with two biomedical specimens, mouse fetus and rat brain, on the basis of synchrotron radiation facility. We find that the grating-based micro-tomography is superior in the contrast-to-noise ratio (CNR) or the mass density resolution, and inferior in the spatial resolution (SR), compared with that of propagation-based micro-tomography. We found that for achieving a given CNR, the grating-based micro-tomography applies about 1.5 times radiation dose involved as compared to the propagation-based micro-tomography with PAD phase retrieval. Additionally, the complex coherent degrees of light source related to the both techniques were duly taken into account in the analysis of their SR comparison. Finally, the mass density distribution of soft biomedical specimens can be estimated using our presented method preliminarily. Our work gives indications for applications and developments of phase sensitive micro-tomography for soft biomedical specimens and low-Z materials.
A noniterative method for dynamic X-ray phase imaging from the recorded far-field diffraction intensity distribution of the object wavefront, sampled by a sampling plate, is proposed. The sampling plate consists of a two-dimensional (2D) aperture array and a central reference aperture. In this method, the complex amplitude of the object wavefront, especially the phase that carries the inner refraction information, can be retrieved from the inverse Fourier transform of the diffraction intensity distribution by directly filtering with a same aperture array. As this method requires only a single measurement of the diffraction intensity pattern and does not need any iterative algorithm, in principle, it provides a practical approach for dynamic phase imaging in a wide range of wavelengths. The experimental results demonstrated that the proposed method is practicable. The proposed may have potential application in high-efficiency phase retrieval for coherent diffraction imaging and phase contrast imaging.
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 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.
In this paper, the design of the infrared beamline BL01B at Shanghai Synchrotron Radiation Facility (SSRF) has been preformed. The present status of this beamline will be described. This beamline is under construction. It utilizes both edge radiation and bending magnet radiation by using a unique extraction optics system. The expected performances of the beamline have been discussed. Moreover, the endstations and main research fields have been described.
The optical and dielectric properties of NaCl and alkali halide are studied by Terahertz time-domain spectroscopy (THz-TDS) technique from 0.3 THz to 1.4 THz. The absorption spectral features of measured samples are discussed based on their characteristic and common features. Further, the measured complex refractive index and dielectric functions of NaCl are well fitted by a standard Lorentz model. Theoretical calculations indicate that characteristic phonon resonance of NaCl is dominated by the transverse optical phonon mode at 5.10 THz.
A long trace profiler (LTP) is specially designed for the metrology of long aspheric optical surfaces and has been widely used in the fields of synchrotron radiation and astronomy. An LTP with an innovative design has been successfully developed at SSRF. An f-θ system based on phase plate diffraction collimation is employed for the first time. Effect of source instability and ambient factors on the precision is greatly reduced, compared to other LTPs now available. The scanning range is 350mm, precision better than 0.5μrad, static repeatability 0.1μrad. The profiler has been calibrated by a standard mirror from Chinese National Institute of Metrology.
A ne method to record x-ray in-line holograms with quasi- equal-path is proposed in this paper, the key is using a micro zone plate. This method has several advantages over the traditional x-ray in-line holography. First, the requirement of the temporal coherence for the x-ray beam is very low. Second, it reduces the requirement of the resolution of recording media, and last it weakens the disturbance of the twin image. The method can also be used to measure the spatial coherence of x-ray with a single exposure.
In this paper, aberrations in reconstruction are analyzed, and aberration elimination method are discussed, and the feasibility of direct reconstruction of lensless Fourier transform x-ray hologram with visible light is investigated.
The requirements for the temporal coherence in x-ray holography are theoretically analyzed. The conclusion is that the temporal coherence length required is a quadratic function of the resolution in x-ray holography.
Aberrations in in-line and lensless Fourier transform x-ray hologram are analyzed quantitatively based on two typical experiments. Some conclusions are also given correspondingly.
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