X-ray fan beam coded aperture transmission and diffraction imaging for fast material analysis

Image degradation characteristics and restoration based on regularization for diffractive imaging

Synchrotron radiation x-ray imaging: A tool for crystal growth

X-ray diffraction (XRD) imaging yields spatially resolved, material-specific information, which can aid medical diagnosis and inform treatment. In this work we used simulations to analyze the utility of fan beam coded aperture XRD imaging for fast, high-resolution scatter imaging of biospecimens for tissue assessment. To evaluate the proposed system’s utility in a specific task, we employed a deterministic model to produce simulated data from biologically realistic breast tissue phantoms and model-based reconstruction to recover a spatial map of the XRD signatures throughout the phantoms. We found an XRD spatial resolution of ≈1 mm with a mean reconstructed spectral accuracy of 0.98 ± 0.01 for a simulated 1 × 150 mm2 fan beam operating at 160 kVp, 10 mA, and 4.5 s exposures. A classifier for cancer detection was developed utilizing cross-correlation of XRD spectra against a spectral library, with a receiver operating characteristic curve with an area under the curve value of 0.972. Our results indicated a potential diagnostic modality that could aid in tasks ranging from analysis of ex-vivo pathology biospecimens to intraoperative cancer margin assessment, motivating future work to develop an experimental system while enabling the development of improved algorithms for imaging and tissue analysis-based classification performance.

A detectable difference in X-ray diffraction data of healthy and diseased breast tissues has been observed. This information can be used to generate images with a higher contrast than that of conventional transmission mammography. A diffraction enhanced breast imaging (DEBI) system that simultaneously combines transmission and diffraction breast images is currently being developed. This paper presents the imaging system requirements for a clinical DEBI system. The DEBI imaging system employs a phosphor coated L3Vision CCD camera. The DEBI principle has been assessed at the SYRMEP synchrotron beamline (Elettra, Trieste) and with a purpose built mammographic X-ray imaging unit. Diffraction enhanced images have been obtained of realistic breast tissue phantoms, consisting of 4 cm thick slabs of excised breast tissue containing embedded carcinomas. The images were obtained at pre-determined momentum transfer values, allowing some tissue characterization to be achieved during imaging, as well as optimizing image contrast This paper presents the current state of the project. The spatial resolution of the diffraction images have been studied using test phantoms and suggestions are made for the collimation systems necessary for a clinical system. A correction procedure applied to the diffraction images is also presented.

Conventional x-ray transmission tomography provides the spatial distribution of the absorption coefficient inside a sample. Other tomographic techniques, based on the detection of photons coming from fluorescent emission, Compton and Rayleigh scattering, are used for obtaining information on the internal elemental composition of the sample. However, the reconstruction problem for these techniques is generally much more difficult than that of transmission tomography, mainly due to self-absorption effects in the sample. In this article an approach to the reconstruction problem is presented, which integrates the information from the three types of signals. This method provides the quantitative spatial distribution of all elements that emit detectable fluorescent lines (Z⩾15 in usual experimental conditions), even when the absorption effects are strong, and the spatial distribution of the global density of the lighter elements. The use of this technique is demonstrated on the reconstruction of a grain of the martian meteorite NWA817, mainly composed of low Z elements not measured in fluorescence and for which this method provides a unique insight. The measurement was done at the ID22 beamline of the European Synchrotron Radiation Facility.

The scattering properties of breast tissue have been suggested as a diagnostic tool in the early detection of breast cancer. To aid in the development of a clinical imaging system based upon these properties, a series of breast tissue samples have been subjected to diffraction microCT using the SYRMEP beamline at Elettra, Italy. Using 18 keV photons, both transmission and diffraction CT data sets were collected using a specially designed microCT system. This system was based around a finely collimated, X-ray sensitive L3Vision CCD camera and a simple rotary stage controlled using Lab View software. The images were reconstructed using routines developed in IDL. This paper presents both transmission and diffraction CT images of three samples. The samples were excised breast tissue sections known to contain either tumour, normal tissue adjacent to the tumour or a mixture of each. The results demonstrate that diffraction microCT can be used to evaluate the structure of breast tissue tumours. Registration of the transmission and diffraction CT images demonstrated that both techniques showed the same principle features in the sample and allowed the main components to be identified. However, the diffraction images demonstrated an average increase in image contrast over the transmission images. Further improvements in the collimator design used in the experiments will need to be made if detailed structure is to be seen.

In order to verify the technology of the membrane diffractive imaging system for Chinese next generation geo-stationary earth orbit (GEO) satellite, a series of ground experiments have been carried out using a membrane optical camera with 80 mm aperture (Φ80) lens. The inherent chromatic aberration due to diffractive imaging appears in the obtained data. To address the issue, an effective color restoration algorithm framework by matching, tailoring, and non-linearly stretching the image histograms is proposed in this letter. Experimental results show the proposed approach has good performances in color restoration of the diffractive optical images than previous methods. The effectiveness and robustness of the algorithm are also quantitatively assessed using various color deviation indexes. The results indicate that the chromatic aberration of diffractive images can be effectively removed by about 85%. Also, the proposed method presents reasonable computational efficiency.

X-ray diffraction imaging (XDI) is a novel modality in which the local x-ray diffraction (XRD) properties of inhomogenous objects are measured. Following a brief description of some of the areas in which x-ray diffraction is currently impacting on the detection of materials of interest in the security environment, the principles of energy-dispersive x-ray diffraction tomography employed in XDI are described. The Multi-Inverse Fan Beam (MIFB) topology for 3rd Generation XDI, in which the XRD properties of a spatial array of 2-D volume elements are investigated in parallel without mechanical scanning, is described. 3rd Generation XDI is being driven among other things by rapid technological developments taking place in the field of spectroscopic, room-temperature, semiconductor x-ray detectors. Detector requirements for Next-Generation MIFB XDI are summarized and the potential of 3rd Generation XDI for rapid, accurate and affordable screening in the Checkpoint and Hold Baggage environments is summarized.

Single‐fiber imaging technology offers unique insights for research and inspection in difficult‐to‐reach and narrow spaces. In particular, ultra‐compact multimode fiber (MMF) imaging, has received increasing interest over the past decade. However, MMF imaging will be seriously distorted when subjected to dynamic perturbations due to time‐varying mode coupling, and the imaging of space objects via Gaussian beam will be relatively degraded at the edge due to insufficient contrast. Here, a robust super‐resolution image transmission method based on a ring core fiber (RCF) with orbital angular momentum (OAM) is proposed and experimentally demonstrated. The OAM modes propagating in the RCF form a series of weakly coupled mode groups, making the imaging system robust to external perturbations. In addition, a spiral phase plate is used as a vortex filter to produce OAM for edge enhancement, thus improving the image resolution. Furthermore, a few‐shot U‐Transformer neural network is proposed to enhance the resilience of the developed RCF‐OAM imaging system against environmental perturbations. Finally, the developed RCF‐OAM imaging system achieves biological image transmission, demonstrating the practicality of the scheme. This pioneering RCF OAM image transmission system may have broad applications, potentially revolutionizing fields such as biological imaging and industrial non‐destructive testing.

Diffractive membrane imaging systems have been an important development trend for high-orbit satellite cameras owing to their advantages of large aperture, light weight, rapid manufacture, and low cost. However, caused by the cross-coupling effects of diffraction imaging, membrane properties, subaperture stitching, on-orbit disturbances, and other physical factors, lager-aperture space diffractive membrane imaging systems have specific and complex degradation characteristics: the modulation transfer function (MTF) and signal-to-noise ratio (SNR) have more prominent degradation and serious space-variant characteristics over fields of view, with obvious background radiation properties that seriously affect the application of imaging products. To address this problem, this study established a global information transmission model by characterizing the PSF and background radiation in a full field of view to represent the imaging law of an on-orbit system. Aiming at the inverse problem of the information transmission model, we also propose a novel image inversion restoration method for the special degradation characteristics. In particular, the effect of diffraction efficiency is introduced into the inversion restoration method to solve the background radiation problem. Moreover, we innovatively designed matrix regularization parameters to further improve the correction ability of spatial variation. When the diffraction efficiency was experimentally higher than 60% and the mean measured spatial variability was less than 0.2, the proposed method exhibited a satisfactory processing performance, and could improve multiobjective comprehensive processing, such as transfer function compensation, spatial variation correction, and background radiation removal.

The size of hydroxyapatite (HAP) crystals in calcified cartilage and cortical bone of the rat has been studied and compared with that of synthetic poorly crystalline hydroxyapatite (PCHA). Crystal size was determined by X-ray diffraction and selected-area dark field imaging, and their elemental compositions were determined by emission spectroscopy. The crystal size of cartilage, bone, and PCHA were found to be between 120 and 170 A in length by 50 A in width as determined by both X-ray diffraction and dark field imaging. Cartilage had a lower ash weight than bone but both have the same Ca/P ratio of 1.6. These findings, though in agreement with the X-ray diffraction literature, differ from observations made by conventional bright field electron microscopy. We conclude that mineral sites in cartilage and bone, which exist as platelike structures, are in fact aggregates of small 120-170 X 50 A HAP crystals. The consequences of these findings was discussed in view of crystal relationships with collagen and other macromolecules.

To evaluate the lattice misorientation at domain boundaries (DBs) in β‐Ga2O3, we performed X‐ray diffraction imaging (XRDI), X‐ray reticulography (XRR), and X‐ray topography (XRT) using a synchrotron radiation light source. Four reciprocal lattice vectors (g‐vectors) were applied, and the DBs showed different visibilities in the XRDI maps depending on the g‐vector. By analyzing possible characteristics of the misorientation, the XRDI results suggested that the DB being investigated was associated with a misorientation on the () plane and contained twist and tilt components. The apparent peak change in XRDI caused by the two components was calculated. We further succeeded in separating the tilt and twist components using XRR images in conjunction with simulation. Dislocation arrays at the DBs were observed using XRT, and the average distance between the dislocations in the array was consistent with the misorientation obtained using XRDI and XRR. The distribution of DBs across a wide area was acquired by a combination of XRR images recorded on a charge‐coupled device camera and X‐ray films. The fringe‐patterned XRR on X‐ray films provided a powerful and nondestructive tool to characterize DBs distributed across a large‐diameter wafer with an angular resolution on the order of several arc sec (low 10−5 rad).

Quantitative phase analysis of cementitious materials is crucial for understanding and predicting their performance. For anhydrous Portland cements, a variety of techniques based on microscopy, spectroscopy, and diffraction exist. Here, we employ two highly diverse techniques (X-ray Diffraction and Raman Imaging) to a common sample (ASTM Type I/II OPC). We find that, firstly, the two methods are highly complementary in the initial phase identification, given that certain clinker phases are difficult to detect in one as opposed to the other. Secondly, quantitative analysis can be influenced by parameters such as preferred orientation, order of phase addition, and the nature of the binarization algorithm. Specific signal-to-noise (SNT = 5) and epoxy-to-signal (EST = 10) thresholds resulted in the highest alignment between the two methods (R2 > 0.99, Δwt% < 2.5 %). Thirdly, Raman imaging area can be reliably reduced (25 mm2 to 9 mm2) to shorten scan time by 2.5× (8 h to 3 h).

After establishing the lattice parameters and orientation of the crystal on the diffractometer, the diffracted intensities can be measured in a controlled manner. Typically, a strategy to measure the required intensities is calculated with the user specifying parameters such as the maximum diffraction angle, redundancy, image width and measurement time per image. The fraction of the diffraction pattern to be measured depends on its point symmetry, which is commonly inferred from the metric features of the lattice but cannot be known conclusively until all of the diffracted intensities have been analysed. A sensible approach is to make the most conservative assumptions to ensure that sufficient data are measured. An alternative is simply to measure the complete diffraction pattern, if sufficient time is available. After data collection, the diffraction images are integrated, and a multi-scan correction is applied to minimise the effects of systematic errors such as anisotropic absorption or poor crystal centring. The final outcome of a single-crystal analysis is a statement of the unit cell and a list of intensities with hkl indices referring to that unit cell.

In various kinds of radiography, deficient transmission imaging may occur due to backlighting inside the detector itself arising from light or radiation scattering. The related intensity mismatches barely disturb the high resolution contrast, but its long range nature results in reduced attenuation levels which are often disregarded. Based on X-ray observations and an empirical formalism, a procedure is developed for a first order correction of detector backlighting. A backlighting factor is modeled as a function of the relative detector coverage by the sample projection. Different cases of sample transmission are regarded at different backlight factors and detector coverage. The additional intensity of backlighting may strongly affect the values of materials' attenuation up to a few 10%. The presented scenario provides a comfortable procedure for corrections of X-ray or neutron transmission imaging data.