In-line Phase Contrast Research Articles

Coded source neutron imaging with a MURA mask

Abstract In coded source neutron imaging the single aperture commonly used in neutron radiography is replaced with a coded mask. Using a coded source can improve the neutron flux at the sample plane when a very high L / D ratio is needed. The coded source imaging is a possible way to reduce the exposure time to get a neutron image with very high L / D ratio. A 17×17 modified uniformly redundant array coded source was tested in this work. There are 144 holes of 0.8 mm diameter on the coded source. The neutron flux from the coded source is as high as from a single 9.6 mm aperture, while its effective L / D is the same as in the case of a 0.8 mm aperture. The Richardson–Lucy maximum likelihood algorithm was used for image reconstruction. Compared to an in-line phase contrast neutron image taken with a 1 mm aperture, it takes much less time for the coded source to get an image of similar quality.

Non-Invasive Microstructure and Morphology Investigation of the Mouse Lung: Qualitative Description and Quantitative Measurement

BackgroundEarly detection of lung cancer is known to improve the chances of successful treatment. However, lungs are soft tissues with complex three-dimensional configuration. Conventional X-ray imaging is based purely on absorption resulting in very low contrast when imaging soft tissues without contrast agents. It is difficult to obtain adequate information of lung lesions from conventional X-ray imaging.MethodsIn this study, a recently emerged imaging technique, in-line X-ray phase contrast imaging (IL-XPCI) was used. This powerful technique enabled high-resolution investigations of soft tissues without contrast agents. We applied IL-XPCI to observe the lungs in an intact mouse for the purpose of defining quantitatively the micro-structures in lung.FindingsThe three-dimensional model of the lung was successfully established, which provided an excellent view of lung airways. We highlighted the use of IL-XPCI in the visualization and assessment of alveoli which had rarely been studied in three dimensions (3D). The precise view of individual alveolus was achieved. The morphological parameters, such as diameter and alveolar surface area were measured. These parameters were of great importance in the diagnosis of diseases related to alveolus and alveolar scar.ConclusionOur results indicated that IL-XPCI had the ability to represent complex anatomical structures in lung. This offered a new perspective on the diagnosis of respiratory disease and may guide future work in the study of respiratory mechanism on the alveoli level.

Optimization of image recording distances for quantitative X-ray in-line phase contrast imaging

Compared to phase retrieval from single sample-to-detector distance (SDD) image, phase retrieval with multiple SDD images could improve the precision in quantitative X-ray in-line phase contrast imaging (QXIPCI). Among all the related phase retrieval approaches, the two-SDD-image-based one is the simplest and well compromises between precision and dose. However, how to optimize the recording distances for the two images to achieve highest precision, remains unsolved. In this paper, the problem was investigated systematically based on digital simulation and related experiments. Spectral correlation degree (SCD) is introduced to evaluate the pertinence between the two SDD images. The simulation results show that the highest retrieving precision could be obtained while the SDD of the second image is three times that of the first image. The best retrieval could be achieved when SDD of the first image is selected properly, meanwhile the SCD occurs with a typical damping oscillation. Experiments, carried out at the X-ray imaging beamline of SSRF, demonstrated the simulation results.

空间相干与入射光子能量对临床类同轴X射线相衬成像影响

X-ray source is usually considered as a monochromatic point source,regardless of whose size effect.However,in clinical practical applications,an X-ray tube is a polychromatic source with a finite focal spot.The incident X-ray source was supposed as the average intensity distribution of a qusi-monochromatic light circular source in the beginning,and then it was extended to the polychromatic case.Based on Fresnel-Kirchhoff diffraction theory,taking the spatial coherence into account,the new in-line X-ray Phase-contrast imaging formula was derived by Fourier transform.The absorption contrast transmission function γre and phase contrast transmission function γre2πλR2u2/M were obtained from the new formula,which represented absorption effect and phase effect,respectively.The curves of the above functions for different radiuses were given by software Matlab and the optimal positions for different source radiuses were also calculated.The theoretical analysis results are as follows: 1) the spatial coherence effect should be considered when source radius is bigger enough,and decreasing the source radius would increase phase effect;2) there is the definitive relationship between the radius and the optimal imaging position,which has been presented in a special case;3) the effect of source size on phase effect is not infinite,which could be ignored when the size is equal to a suitable value.The suitable radius is given in a special case;4) decreasing incident X-ray photon energies would strengthen PE obviously,and the variation of photon energies has no effect on the optimal imaging position;as a result,the new formula could be extended to the polychromatic case.In order to verify the theoretical results,the micro-focus X-ray phase-contrast imaging experiments for the breakage surface of optical glass detection were carried out.Some experimental results are in good agreement with theoretical analysis,while some do not meet our expectations.The related explanations were also presented.

Quantitative studies on inner interfaces in conical metal joints using hard x-ray inline phase contrast radiography

Quantitative investigation of micrometer and submicrometer gaps between joining metal surfaces is applied to conical plug-socket connections in dental titanium implants. Microgaps of widths well beyond the resolving power of industrial x-ray systems are imaged by synchrotron phase contrast radiography. Furthermore, by using an analytical model for the relatively simple sample geometry and applying it to numerical forward simulations of the optical Fresnel propagation, we show that quantitative measurements of the microgap width down to 0.1 μm are possible. Image data recorded at the BAMline (BESSY-II light source, Germany) are presented, with the resolving power of the imaging system being 4 μm in absorption mode and ∼14 μm in phase contrast mode (z(2)=0.74 m). Thus, phase contrast radiography, combined with numerical forward simulations, is capable of measuring the widths of gaps that are two orders of magnitude thinner than the conventional detection limit.

Quantitative evaluation of single-shot inline phase contrast imaging using an inverse compton x-ray source

Inverse compton scattering (ICS) x-ray sources are of current interest in biomedical imaging. We present an experimental demonstration of inline phase contrast imaging using a single picosecond pulse of the ICS source located at the BNL Accelerator Test Facility. The phase contrast effect is clearly observed. Its qualities are shown to be in agreement with the predictions of theoretical models through comparison of experimental and simulated images of a set of plastic wires of differing composition and size. Finally, we display an application of the technique to a biological sample, confirming the possibility of time-resolved imaging on the picosecond scale.

Design of the experimental stage for coherent diffraction imaging

The I13 beamline of Diamond Light Source encompasses two fully independent branches devoted for coherent imaging experiments (coherent X-ray diffraction and ptychography) and X-ray imaging and tomography (full-field microscopy and in-line phase contrast imaging). This contributed paper outlines the main features of the coherence beamline and a preliminary design of the experimental station for coherent X-ray diffraction imaging.

Quasi-monochromatic hard X-ray source via laser Compton scattering and its application

We have developed a quasi-monochromatic hard X-ray source via laser Compton scattering (LCS) based on an S-band compact electron linac at AIST. The number of total photons and the maximum X-ray energy was 10 7 photons/sec and about 40 keV, respectively, in 15-degree crossing angle between a 42 MeV electron beam and a 800 nm Ti:Sa laser. The biological observation of the human bone with fractures has been successfully demonstrated using the LCS X-ray of 26.4 keV with the in-line phase contrast scheme. Good contrast enhancement is clearly observed between the absorption and the phase contrast images.

Numerical Simulations and Preliminary Experiments of the Principle of X-Ray In-Line Phase-Contrast Imaging

主要对微焦点源X射线同轴相衬成像系统的系统参数进行了设计与讨论,并对结果进行了实验验证.根据实际选取X射线能量以及物体的折射率改变量和吸收因子来确定物体传输函数,从物体到探测面的距离、物体边缘渐变宽度等因素对图像可见度的影响进行分析,提出了改进分辨率方法并通过数值模拟得到验证.最后,在实验中对普通三角板进行相衬成像,并与其吸收衬度成像进行对比.实验结果表明,利用数值模拟的方法可以指导微焦点源相衬成像参数设计,同时验证了该实验仪器的相衬能力.

X射线同轴相衬成像的参数优化系统

X射线同轴相衬成像的参数优化系统

X-ray phase imaging of a packaged IC chip using X-ray array source

We have developed a novel configuration of an X-ray grating interferometer for the phase imaging of a packaged IC chip. A square source grating is used, and a beam splitter and an analyzer grating are positioned downstream of the investigated sample. In the proposed method, the period of source grating is smaller than the last of two gratings, the configuration of which could be implemented for phase imaging. Phase images retrieved using the principle of in-line phase contrast imaging and phase detection are the phase stepping method used in the X-ray grating interferometer. The wrapped phase images of the packaged IC chip are obtained from nine Moire fringe patterns, using an exposure time of 34ms for each scan.

Transmission hard X-ray microscope with increased view field using planar refractive objectives and condensers made of SU-8 polymer

Planar X-ray refractive lenses in crossed geometry providing 2D focusing are fabricated from SU-8 polymer using tilted deep X-ray lithography. The profiles of the objective lens elements are parabolic. The lens elements for the condensers were designed with a power of the surface function of 1.5, 1.7 and 2 to vary the field of views for a transmission X-ray microscope (TXM). With these lenses a TXM was set up at the ESRF beamline BM-5 for a photon energy of 15 keV. Different test nanostructures were imaged with this TXM using inline phase-contrast, with X-ray magnification factors of 29, demonstrated spatial detail resolution of 100 nm (half-period of lines and spaces) and exposure times around 10 s. Further improvement of a TXM based on the SU-8 lenses using refractive condensers with large apertures is considered with the aim to reduce exposure times.

Imaging of cochlear tissue with a grating interferometer and hard X‐rays

This article addresses an important current development in medical and biological imaging: the possibility of imaging soft tissue at resolutions in the micron range using hard X-rays. Challenging environments, including the cochlea, require the imaging of soft tissue structure surrounded by bone. We demonstrate that cochlear soft tissue structures can be imaged with hard X-ray phase contrast. Furthermore, we show that only a thin slice of the tissue is required to introduce a large phase shift. It is likely that the phase contrast image of the soft tissue structures is sufficient to image the structures even if surrounded by bone. For the present set of experiments, structures with low-absorption contrast have been visualized using in-line phase contrast imaging and a grating interferometer. The experiments have been performed at the Advanced Photon Source at Argonne National Laboratories, a third generation source of synchrotron radiation. The source provides highly coherent X-ray radiation with high-photon flux (>10(12) photons/s) at high-photon energies (5-70 keV). Radiographic and light microscopy images of the gerbil cochlear slice samples were compared. It has been determined that a 20-mum thick tissue slice induces a phase shift between 1/3pi and 2/3pi.

Visibility of tumor-like details in inline phase contrast mammography using quasimonochromatic X-ray sources

A new generation of quasimonochromatic high-flux X-ray sources, based on the X-ray radiation produced through Compton scattering between an electron beam and a laser beam, is under development. One of the possible applications of this source is inline phase contrast mammography, based on the observation of the edge-enhancement effect that can be observed at the border of structures inside the breast in images produced using a partially or totally coherent X-ray beam. In this work we present the results of a set of simulations of inline phase contrast mammography using typical inverse Compton scattering sources parameters. The simulated sample was a tumour-like mass having spherical shape, diameter between 200 μm and 5 mm, placed inside a breast-like matrix, 4 cm thick, and a standard composition of 50% glandular tissue and 50% adipose tissue. We discuss the minimum requirements for mammography using inverse Compton scattering sources and we discuss how the working parameters of the experimental setup (focal spot size, source–object distance, object–detector distance, detector point spread function, mean energy, energy bandwidth) affect the image quality, and specifically the edge-enhancement visibility. In particular, we show that the energy bandwidth does not significantly affect the visibility up to several keV. On the other hand, the edge-enhancement visibility depends substantially on other parameters such as source–object distance and detector point spread function.

X-ray elastography: Modification of x-ray phase contrast images using ultrasonic radiation pressure

The high resolution characteristic of in-line x-ray phase contrast imaging can be used in conjunction with directed ultrasound to detect small displacements in soft tissue generated by differential acoustic radiation pressure. The imaging method is based on subtraction of two x-ray images, the first image taken with, and the second taken without the presence of ultrasound. The subtraction enhances phase contrast features and, to a large extent, removes absorption contrast so that differential movement of tissues with different acoustic impedances or relative ultrasonic absorption is highlighted in the image. Interfacial features of objects with differing densities are delineated in the image as a result of both the displacement introduced by the ultrasound and the inherent sensitivity of x-ray phase contrast imaging to density variations. Experiments with ex vivo murine tumors and human tumor phantoms point out a diagnostic capability of the method for identifying tumors.

High-resolution investigations of edge effects in neutron imaging

Edge enhancement is the main effect measured by the so-called inline or propagation-based neutron phase contrast imaging method. The effect has originally been explained by diffraction, and high spatial coherence has been claimed to be a necessary precondition. However, edge enhancement has also been found in conventional imaging with high resolution. In such cases the effects can produce artefacts and hinder quantification. In this letter the edge effects at cylindrical shaped samples and long straight edges have been studied in detail. The enhancement can be explained by refraction and total reflection. Using high-resolution imaging, where spatial resolutions better than 50 μm could be achieved, refraction and total reflection peaks – similar to diffraction patterns – could be separated and distinguished.

Phase-contrast and holographic computed laminography

In-line phase contrast is combined with laminography to image in three dimensions regions of interest in laterally extended flat specimens of weak absorption contrast. The principle of the method and a theoretical description of the imaging process are outlined. The present instrumental implementation enables reconstructing nondestructively the internal structure at different lateral specimen positions with micron resolution. The feasibility and application potential are demonstrated for both phase-contrast and holographic (i.e., using phase retrieval) laminography by the three-dimensional imaging of fuel-cell diffusion layers.

Preliminary Feasibility Study of an In-line Phase Contrast X-Ray Imaging Prototype

In this study, a series of imaging experiments on biological specimens, including human breast core biopsies, lumpectomy, and chicken tissues, as well as standard phantoms, were performed in an effort to investigate the feasibility of an in-line phase contrast X-ray imaging prototype. The prototype system employed in the study consists of a microfocus X-ray source with tungsten target and a digital flat panel detector, and it can be operated in both conventional attenuation-based imaging mode and in-line phase contrast imaging mode. Biological specimens were imaged in the conventional mode and phase contrast mode with the same source-to-image-detector distance (SID), and phase contrast images exhibited both improved image quality compared with conventional images, and the overshooting patterns along the boundaries in the specimens, which revealed the occurrence of the edge enhancement effect provided by the phase contrast technique. In addition, the performance of the phase contrast mode and conventional mode was compared based on the American College of Radiology (ACR) phantom imaging and contrast detail mammography (CDMAM) phantom-based contrast detail analysis with two experimental settings: one with the same SID and the other with the same object entrance exposure. In both pairs of comparison under our experimental conditions, the phase contrast imaging mode exhibited improved image quality as compared to the conventional mode, which further supported the feasibility of the prototype.

Cochlear Soft Tissue Imaging Using In-Line Phase Contrast

Problem Most contemporary imaging methods require invasive specimen preparation and/or are time consuming, or lack sufficient spatial resolution. Methods Experiments were made at the Advanced Photon Source (APS), Argonne National Laboratory. The APS is a synchrotron radiation source of the third generation, for which the particular characteristic is the highly coherent X-ray radiation. X-rays are generated with an undulator, inserted in a straight section of the storage ring. Images taken with hard X-rays and the grating interferometer were compared with images from the same specimen acquired with light microscopy. Results The results show that imaging of cochlear soft tissue structures is possible with hard X-rays and a grating interferometer. Conclusion Imaging of cochlear soft tissue structures is possible with hard X-rays and a grating interferometer. Significance It is important to examine cochlear morphology from many points of view, including comparative anatomy, cochlear developmental changes, malformation caused by genetic defects, changes related to diseases, sensory physiology, and cochlear modeling. Best imaging results were obtained from in situ experiments in the absence of tissue distortion. However, most contemporary imaging methods require invasive specimen preparation and/or are time consuming, or lack sufficient spatial resolution. A method that potentially overcomes these shortcomings is presented in this paper and it uses hard X-rays and a grating interferometer. Furthermore, hard X-rays would allow imaging cochlear soft tissue structures without opening the cochlea itself. Support The UNICAT facility at the Advanced Photon Source is supported by the U.S. DOE under Award No. DEFG02-91ER45439, through the Frederick Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign, the ORNL (U.S. DOE contract DE-AC.

Quantitative Evaluation Methods of In-Line X-Ray PhaseContrast Techniques

By revealing the relationship between edge visibility and imagingparameters in in-line phase contrast imaging (PCI), we propose a methodto quantitatively measure the contribution of absorption and phaseshift from acquired images. We also prove that edge visibility willgrow with the increasing source-object distance and object-detectordistance. The result is validated by relative phase factor and byexperiments conducted on a microfocus x-ray source. This methodprovides a new approach to evaluate in-line PCI images and is helpfulfor deciding imaging parameters.