Analyzer-based Phase Contrast Imaging Research Articles

X-ray analyzer-based phase-contrast computed laminography.

X-ray analyzer-based phase-contrast imaging is combined with computed laminography for imaging regions of interest in laterally extended flat specimens of weak absorption contrast. The optics discussed here consist of an asymmetrically cut collimator crystal and a symmetrically cut analyzer crystal arranged in a nondispersive (+, -) diffraction geometry. A generalized algorithm is given for calculating multi-contrast (absorption, refraction and phase contrast) images of a sample. Basic formulae are also presented for laminographic reconstruction. The feasibility of the method discussed was verified at the vertical wiggler beamline BL-14B of the Photon Factory. At a wavelength of 0.0733 nm, phase-contrast sectional images of plastic beads were successfully obtained. Owing to strong circular artifacts caused by a sample holder, the field of view was limited to about 6 mm in diameter.

Design, development and first experiments on the X-ray imaging beamline at Indus-2 synchrotron source RRCAT, India.

A full-field hard X-ray imaging beamline (BL-4) was designed, developed, installed and commissioned recently at the Indus-2 synchrotron radiation source at RRCAT, Indore, India. The bending-magnet beamline is operated in monochromatic and white beam mode. A variety of imaging techniques are implemented such as high-resolution radiography, propagation- and analyzer-based phase contrast imaging, real-time imaging, absorption and phase contrast tomography etc. First experiments on propagation-based phase contrast imaging and micro-tomography are reported.

Laboratory-based multi-modal X-ray microscopy and micro-CT with Bragg magnifiers.

We report on the successful demonstration of X-ray phase contrast microscopy and micro computed tomography (CT) with a Bragg magnifier microscope (BMM) in a laboratory setup. The Bragg magnifiers, constituted by two channel-cut crystals in asymmetric diffraction, produced a 15X magnification of the X-ray beam, thus enabling high resolution imaging to be attained. The angular sensitivity of the crystals was used to implement analyzer-based phase contrast imaging: acquiring images at different angular positions and the three parametric images (apparent absorption, differential phase and scattering) have been obtained. Micro-CT, with resolution of about 5 μm is demonstrated with the same system. The main limitations, as well as the ways to mitigate them, are discussed with the aid of the experimental data. The technique demonstrated herein extends high-resolution, multi-modal, x-ray imaging and micro-CT to compact laboratory setups, with the potential of broadening the reach of these techniques outside the community of synchrotron users.

A single-image method for x-ray refractive index CT

X-ray refraction-based computer tomography imaging is a well-established method for nondestructive investigations of various objects. In order to perform the 3D reconstruction of the index of refraction, two or more raw computed tomography phase-contrast images are usually acquired and combined to retrieve the refraction map (i.e. differential phase) signal within the sample. We suggest an approximate method to extract the refraction signal, which uses a single raw phase-contrast image. This method, here applied to analyzer-based phase-contrast imaging, is employed to retrieve the index of refraction map of a biological sample. The achieved accuracy in distinguishing the different tissues is comparable with the non-approximated approach. The suggested procedure can be used for precise refraction computer tomography with the advantage of a reduction of at least a factor of two of both the acquisition time and the dose delivered to the sample with respect to any of the other algorithms in the literature.

Analyzer-based phase-contrast imaging system using a micro focus X-ray source.

Here we describe a new in-laboratory analyzer based phase contrast-imaging (ABI) instrument using a conventional X-ray tube source (CXS) aimed at bio-medical imaging applications. Phase contrast-imaging allows visualization of soft tissue details usually obscured in conventional X-ray imaging. The ABI system design and major features are described in detail. The key advantage of the presented system, over the few existing CXS ABI systems, is that it does not require high precision components, i.e., CXS, X-ray detector, and electro-mechanical components. To overcome a main problem introduced by these components, identified as temperature stability, the system components are kept at a constant temperature inside of three enclosures, thus minimizing the electrical and mechanical thermal drifts. This is achieved by using thermoelectric (Peltier) cooling/heating modules that are easy to control precisely. For CXS we utilized a microfocus X-ray source with tungsten (W) anode material. In addition the proposed system eliminates tungsten's multiple spectral lines by selecting monochromator crystal size appropriately therefore eliminating need for the costly mismatched, two-crystal monochromator. The system imaging was fine-tuned for tungsten Kα1 line with the energy of 59.3 keV since it has been shown to be of great clinical significance by a number of researchers at synchrotron facilities. In this way a laboratory system that can be used for evaluating and quantifying tissue properties, initially explored at synchrotron facilities, would be of great interest to a larger research community. To demonstrate the imaging capability of our instrument we use a chicken thigh tissue sample.

Analyzer-based phase contrast imaging and phase retrieval using a rotating anode x-ray source

We have performed an analyzer crystal based phase contrast imaging (ABI) experiment using a rotating anode x-ray source. The use of such an incoherent source demonstrates the potential of ABI as a quantitative characterization tool for the laboratory environment. A phase contrast image of a plastic phantom was recorded on high resolution x-ray film and the projected thickness was retrieved from a single image. The projected thickness recovered from the phase contrast image was shown to quantitatively agree with a reference optical microscope measurement.