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Propagation-based phase-contrast CT (PB-CT) is a novel imaging technique that visualises variations in both X-ray attenuation and refraction. This study aimed to compare the clinical image quality of breast PB-CT using synchrotron radiation with conventional absorption-based CT (AB-CT), at the same radiation dose. Seven breast mastectomy specimens were scanned and evaluated by a group of 14 radiologists and medical imaging experts who assessed the images based on seven radiological image quality criteria. Visual grading characteristics (VGC) were used to analyse the results and the area under the VGC curve was obtained to measure the differences between the two techniques. For six image quality criteria (overall quality, perceptible contrast, lesion sharpness, normal tissue interfaces, calcification visibility and image noise), PB-CT images were superior to AB-CT images of the same dose (AUCVGC: 0.704 to 0.914, P≤.05). For the seventh criteria (artefacts), PB-CT images were also rated better than AB-CT images (AUCVGC: 0.647) but the difference was not significant. The results of this study provide a solid basis for future experimental and clinical protocols of breast PB-CT.

The notions of spatial resolution and signal-to-noise are central to most forms of imaging. However, it appears that rigorous definitions of these quantities, which would be general enough to be useful in a broad range of imaging problems, while being also sufficiently specific to enable precise quantitative evaluation of the relevant properties of imaging systems, have been somewhat lacking. This is particularly true in respect to many modern forms of imaging that include digital processing of the acquired imaging data as an integral step leading to final images presented to the enduser. In the present paper, both the well-known historical definitions of spatial resolution and some more recent approaches suitable for many modern computational imaging techniques are discussed. An intrinsic duality of the spatial resolution and signal-to-noise exists in almost all types of imaging, with the related uncertainty relationship determining the inevitable trade-offs between the two quantities. Examples are presented with applications to some forms of X-ray imaging. Relations to Shannon and Fisher information capacity of imaging systems and super-resolution are also briefly discussed.

Phase-contrast imaging of the breast is expected to deliver significantly improved image quality and diagnostic value at a reduced radiation dose compared to present-day 2D X-ray mammography, digital breast tomosynthesis (DBT) and computed tomography (CT) and become a viable method for early diagnosis of breast cancer in women. This paper builds upon the evaluation of a novel protocol to evaluate 3D mammographic phase contrast imaging for the detection of breast cancer undertaken with a purpose designed phantom and selected breast cancer specimens. Following evaluation, propagation-based phase contrast imaging was demonstrated to have high contrast to noise ratio alongside an important reduction in radiation dose. The challenge now is to shift the focus of research to real clinic solutions, with the worldfirst demonstration of X-ray in-line full field phase-contrast mammographic tomography (PCT) with cancer patients through an international collaboration of a multi-disciplinary team.

X-ray computed tomography (XCT) is an important clinical diagnostic tool which is also used in a range of biological imaging applications in research. The increasing prevalence of metallic implants in medical and dental radiography and tomography has driven the demand for new approaches to solving the issue of metal artefacts in XCT. Metal artefacts occur when a highly absorbing material is imaged which is in boundary contact with one or more weakly absorbing components, such as soft-tissue. The resulting ‘streaking’ in the reconstructed images creates significant challenges for X-ray analysis due to the non-linear dependence on the absorption properties of the sample. In this paper we introduce a new approach to removing metal artefacts which exploits the capabilities of the recently available, photon-counting PiXirad detector. Our approach works for standard lab-based polychromatic X-ray tubes and does not rely on any postprocessing of the data. The method is demonstrated using both simulated data from a test phantom and experimental data collected from a cochlear implant. The results show that by combining the individual images, which are simultaneously generated for each different energy threshold, artefact -free segmentation of the implant from the surrounding biological tissue is achieved.

In this paper, we use optical coherence theory to define the limit for the spatial coherence length with respect to the degree of overlap between adjacent probe positions in ptychography. The influence of the degree of curvature of the probe in relation to partial coherence in the Fresnel geometry for a fixed overlap is also considered. This work has implications for the application of ptychographic coherent imaging using partially coherent sources. We validate these results through a simulation study of coherence versus overlap parameter and curvature.

Determining the specific spatial distributions of elements within compound samples is of critical importance to a range of applied research fields. The usual approaches to obtaining elemental contrast involve measurement of the characteristic peaks associated with x-ray fluorescence or measuring the x-ray transmission as a function of energy. In the laboratory these measurements are challenging due to the polychromaticity and lack of tunability of the source. Here we demonstrate how newly developed, high-resolution, energy-discriminating area detector technology can be exploited to enhance elemental contrast. The detector we employ here is the Pixirad area detector which can simultaneously have up to four separate colour channels. We also discuss the potential of this new technology in the context of tomographic imaging of soft tissue.

A software system has been developed for high-performance Computed Tomography (CT) reconstruction, simulation and other X-ray image processing tasks utilizing remote computer clusters optionally equipped with multiple Graphics Processing Units (GPUs). The system has a streamlined Graphical User Interface for interaction with the cluster. Apart from extensive functionality related to X-ray CT in plane-wave and cone-beam forms, the software includes multiple functions for X-ray phase retrieval and simulation of phase-contrast imaging (propagation-based, analyzer crystal based and Talbot interferometry). Other features include several methods for image deconvolution, simulation of various phase-contrast microscopy modes (Zernike, Schlieren, Nomarski, dark-field, interferometry, etc.) and a large number of conventional image processing operations (such as FFT, algebraic and geometrical transformations, pixel value manipulations, simulated image noise, various filters, etc.). The architectural design of the system is described, as well as the two-level parallelization of the most computationally-intensive modules utilizing both the multiple CPU cores and multiple GPUs available in a local PC or a remote computer cluster. Finally, some results about the current system performance are presented. This system can potentially serve as a basis for a flexible toolbox for X-ray image analysis and simulation, that can efficiently utilize modern multi-processor hardware for advanced scientific computations.

We discuss theoretical, experimental and numerical aspects of several new techniques for quantitative phase-contrast tomography using, for example, unfiltered radiation from a polychromatic X-ray microfocus source. The proposed algorithms allow one to reconstruct the three-dimensional distribution of complex refractive index in a sample consisting of one or more constituent materials, given one or more projection images per view angle. If the sample is weakly absorbing or consists predominantly of a single material, these reconstruction algorithms can be simplified and fewer projections may be required for an unambiguous quantitative reconstruction of the spatial distribution of the refractive index. In the case of weakly absorbing samples, the reconstruction algorithm is shown to be achromatic and stable with respect to high-spatial-frequency noise, in contrast to conventional tomography. A variation of the algorithm exploits the natural combination of binary tomography with a phase-retrieval method that makes explicit use of the single-material nature of the sample. Such consistent use of a priori knowledge dramatically reduces the number of required projections, implying significantly reduced dose and scanning time when compared to most alternative phase-contrast tomography methods. Experimental demonstrations are also given, using data from a point-projection X-ray microscope. The refractive index distribution, in test samples of both a polymer fibre scaffold and an adult mouse, is accurately reconstructed from polychromatic phase-contrast data. Applications of the new techniques to rapid non-destructive testing in materials science and biomedical imaging are considered.

X-ray phase-contrast tomographic microimaging is a powerful tool to reveal the internal structure of opaque soft-matter objects that are not easily seen in standard absorption contrast. In such low Z materials, the phase shift of X-rays transmitted can be important as compared to the absorption. An easy experimental set up that exploits refractive contrast formation can deliver images that are providing detailed structural information. Applications are abundant in fields including polymer science and engineering, biology, biomedical engineering, life sciences, zoology, water treatment and filtration, membrane science, and micro/nanomanufacturing. However, available software for absorptive contrast tomography cannot be simply used for structure retrieval as the contrast forming effect is different. In response, CSIRO has developed a reconstruction code for phase-contrast imaging. Here, we present a quantitative comparison of a micro phantom manufactured at SSLS with the object reconstructed by the code using X-ray images taken at SSLS. The phantom is a 500 μm thick 800 μm diameter cylindrical disk of SU-8 resist having various eccentric cylindrical bores with diameters ranging from 350 μm to 40 μm. Comparison of these parameters that are well known from design and post-manufacturing measurements with reconstructed ones gives encouraging results.

X-ray Microtomography bridges the 3D analysis gap between conventional x-ray tomography and TEM tomography. The use of a laboratory-based microfocus source opens up the opportunity to gain additional benefits from in-line phase contrast for enhancing the visibility of fine features, cracks, voids and boundaries in individual views. Coupled with phase retrieval methods, such images can be used as input to conventional reconstruction algorithms for three dimensional visualization. Working at high resolution brings challenges of physical stability of the system. Software approaches to overcoming these difficulties have enabled submicron resolution 3D reconstructions.

We report the results of quantitative hard X-ray phase- contrast microscopy and tomography using synchrotron radiation, in-line imaging geometry and a non-interferometric phase retrieval technique based on the Transport of Intensity equation. This quantitative imaging method is fast, simple, robust, does not require sophisticated X-ray optical elements and can potentially provide submicron spatial resolution over a field of view of the order of centimeters. In the present experiment a spatial resolution of approximately 0.8 micron has been achieved in images of a polystyrene sphere using 19.6 keV X-rays. We demonstrate that appropriate processing of phase-contrast images obtained in the in-line geometry can reveal important new information about the internal structure of weakly absorbing organic samples. We present some preliminary results of a phase-contrast tomographic reconstruction with and without phase retrieval in each X-ray projection. We believe that this method of quantitative X-ray phase-contrast imaging will find applications in biology and medicine, particularly for high-contrast imaging of soft tissues.

Conventional radiography is based on absorption contrast and geometrical (ray) optics. After an outline of the relevant theory, this article reports results displaying both phase- and absorption-contrast, collected with a technique which utilizes a micro-focus x-ray source to achieve a high degree of spatial coherence, and relatively large object-to-image distances to enable (wave) interference effects (Fresnel diffraction) to occur and manifest themselves as phase contrast in the image plane. Both soft tissue (chicken knee) and hard tissue (finger bone) samples are investigated for a range of source sizes and object-to-image distances, encompassing conditions somewhat analogous to conventional radiography. Variation in image contrast and resolution as a function of these variables is observed and discussed.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The quantitative imaging of phase object using 16 keV x-rays is reported. The theoretical basis of the techniques is presented along with its implementation using a synchrotron x-ray source. We find that our phase image is in quantitative agreement with independent measurements of the object.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.