The xray dose for a given image quality depends on the sensitivity of the setup, i. Pdf recent developments on xray phase contrast imaging. Here we present, to our knowledge, the first phasecontrast tomography acquired at a compact light source, a recently developed compact synchrotron based on inverse compton scattering. The material properties are inferred from the differences in the number of photons detected. Propagationbased xray phase contrast imaging using an. Xray gratingbased phase contrast imaging has raised interest regarding a variety of potential clinical applications, whereas the method is feasible using a medical xray tube. High resolution laboratory gratingbased xray phasecontrast ct. Phasecontrast xray imaging virtually all xrays imaging in a medical or biological context is performed by measuring differences in the attenuation of xrays by the tissues. Phasecontrast imaging using xray sources with high spatial coherence is an emerging tool in biology and material science. We will limit this discussion to few highlights like micro and nanotomography applications,,,, lung imaging,, and breast tissue imaging, including invivo.
Fast xray differential phase contrast imaging with one exposure. Phasecontrast xray imaging of breast article pdf available in acta radiologica 518. This means, to obtain high quality phasecontrast and darkfield images a high visibility is mandatory. Several parameters influence the visibility of such a system, like for example the xray spectrum, the intergrating distances or the parameters of the three gratings. Phasecontrast imaging highlights edges and internal boundaries of a sample and is thus complementary to. The performance of a talbotlau interferometer depends to a great extent on its visibility. Current noninvasive medical imaging methods lack the combination of resolution and contrast required to characterize atherosclerotic plaque.
Phasecontrast xray imaging pci is an innovative method that is sensitive to the refraction of the xrays in matter. Current xray detectors only measure the intensity of an xray beam, which can be in the form of the integrated energy of the incident beam or the number of photons. Laboratorybased xray phase contrast ct technology for. Review of xray phase contrast imaging techniques and. Recent developments on xray phase contrast imaging technology at csem. An xray interferometer was used to obtain xray phase contrast. Biomedical xray phasecontrast imaging and tomography. Phase contrast imaging techniques are being applied to a number of challenging clinical situations including mammography, bonecartilage. Xray phasecontrast imaging adds the dimensions of bulk refractive index and wave scattering.
We assume that the absorption and phase components are correlated and solve the transport of intensity equation tie. Xray phasecontrast imaging xpci holds great promise for medical xray imaging with high softtissue contrast. Recently, a new mode of medical imaging known as xray phase contrast imaging xpci has been shown to produce exceptional contrast in soft tissues, and has the potential to noninvasively characterize. Pci is particularly adapted to visualize weakly absorbing details like those often encountered in biology and medicine. Taking xray phase contrast imaging into mainstream. Xpci could revolutionise all applications of xray imaging. Xray phasecontrast imaging techniques either directly or indirectly sense wave refraction through. The cone beam projects the selfimages of g 1 onto the plane of g 2 with a slightly magnified period p 1 14, resulting approximately in a combined phase oscillation of the form. Phased contrast xray imaging, which uses silicon gratings to detect distortions in the xray wave front, may be applicable to mail or luggage scanning for explosives. While traditional xray imaging yields an image that maps a samples absorptive properties by measuring xray photon flux from an xray source after it traverses a sample, xray phase. Phasecontrast imaging with synchrotron xrays for detecting cancer.
Phasecontrast xray ct is an emerging imaging technique that makes use of xray phaseshift in. Absorptionbased xray tomography suffers from low contrast for soft tissue. The paper concludes with application areas and upcoming developments. The small xray source size of sr is inherently suited to dynamic small area imaging applications, such as absorption microangiography and phasecontrast imaging. We demonstrate a quantitative xray phase contrast imaging xpci technique derived from propagation dependent phase change. The use of edge illumination makes possible working with large focus, polychromatic xray sources reducing acquisition times of tomography scans down to values compatible with clinical use, while maintaining phase sensitivity in a compact device. The phasecontrast xray imaging system consisted of a silicon asymmetrical cut crystal to make a 2d beam, a monolithic xray interferometer, a phase shifter, an object cell, and an xraysensing pickup tube. The proposed technology uses xray differential phasecontrast pc which is a method that involves using the phase change of the xray beam to create images.
This book fills an important gap in the existing literature by providing a comprehensive discussion of xray phase contrast imaging xpci and its various uses and implementations. Xray phasecontrast tomography with a compact laser. This is the only generally applicable technique that has the necessary spatial and temporal resolutions, penetrating power, and sensitivity to soft tissue that is required to visualize the internal. Abstractthe electron density resolution is times higher for synchrotronradiation phasecontrast ct. To overcome the limited soft tissue contrast in conventional absorptionbased imaging, several new xray phasecontrast imaging methods. Phasecontrast imaging depicts not only the absorption contrast but also the refraction contrast of the transmitted xray beam. Vessel imaging by interferometric phasecontrast xray. Hertz biomedical and xray physics, royal institute of technology, albanova university center, se10691stockholm, sweden anna. Theoretical foundation and design considerations of a clinical feasible x. Xray phase contrast imaing xpci became a research focus about some decades ago with the awareness of its high spatial resolution and contrast on imaging soft tissues 11, 12. Phase retrieval in xray phasecontrast imaging suitable. Different from the analysis of imaging phase object with weak absorption in literature, we proposed a new formalism for in.
Highresolution phasecontrast imaging of biological specimens. A conventional inline phase imaging geometry was employed. Fig 4 shows exemplary colorcoded images of healthy and degraded cartilage for each imaging technique. These ideas are applied to twodimensional and threedimensional propagationbased phasecontrast imaging using. Exploring xray phase tomography with synchrotron radiation. Since roentgens discovery well over a century ago, xray imaging has been based on attenuation. This method allows to strongly enhance the visibility of soft tissues such as cartilage, tendons, blood. Choosing sensitivity to reduce xray dose in medical phase.
To overcome the limited soft tissue contrast in conventional absorptionbased imaging, several new xray phase contrast imaging methods have been developed 1. It is capable for detecting the direction deviation when xrays travel through one object. Inline phasecontrast xray imaging and tomography for. Phasecontrast xray imaging pci or phasesensitive xray imaging is a general term for. Compressed xray phasecontrast imaging using a coded. Xray phase contrast imaging and tomography make use of the refraction of x rays by the sample in image formation. The design of an xray phase contrast tomography system for intraoperative specimen imaging based on edge illumination is presented. Before explaining phase contrast technology, the outline of xrays will be described.
While this is an effective and reliable approach, it is known to have limitations whenever objects with similar attenuation characteristics have to be distinguished, as this leads to poor image contrast. This provides considerable additional information in the image compared to conventional xray imaging methods, which rely solely on xray absorption by the sample. A fundamental step for a significant contrast enhancement in xray imaging has been achieved by the transfer of the phasecontrast imaging principle from visible light to. There are four main techniques for xray phasecontrast imaging, which use different principles to convert phase variations in the xrays emerging from the object into intensity variations at an xray detector.
Phase diversity was achieved by acquiring phase contrast images at two distinct energies9 and kev. Designing the phase grating for talbotlau phasecontrast. The xray absorption difference absorption contrast of the body structure such as bones and muscles are recorded to films as image information by setting a cassette that works as x. To overcome the limited soft tissue contrast in conventional absorptionbased imaging, several new xray phasecontrast imaging methods have been developed 1. We consider the transportofintensity equation, as one particular method for xray phase contrast imaging among many, before passing on to the inverse problem of phase retrieval. Obviating optical elements in the imaging chain, propagationbased xpci pbxpci has definite advantages over other xpci techniques in terms of cost, alignment and scalability. Phasecontrast xray imaging pci or phasesensitive xray imaging is a general term for different technical methods that use information concerning changes in the phase of an xray beam that passes through an object in order to create its images. Standard xray imaging techniques like radiography or computed tomography ct rely on a decrease of the xray beams intensity attenuation when. Early data suggest that this new modality may overcome some of the diagnostic limitations associated with current clinically available mammography systems and that it has potential for improving breast cancer detection. Multiple implementations of phase contrast imaging have been developed over time for different microscope architectures. Technology xray phasecontrast scanning radiography. Contrast enhancement of propagation based xray phase. Xray phasecontrast early detection of cancer and angiography applications are just two examples that can directly benefit from an imaging modality with excellent softtissue contrast.
These tutorials introduce some basics of imaging with coherent xrays, focusing on phase contrast. Phase retrieval and differential phasecontrast imaging with lowbrilliance xray sources. The recent advances are going beyond microradiology and. Development toward highresolution xray phase imaging. Srbased xray phasecontrast tomography xpct has, in principle, approximately a thousand times more sensitivity in detecting light elements than conventional xray absorption.
Owing to the strong contrast, the radiation dose can be greatly reduced, so that a highresolution phasecontrast xray tomography of the breast is possible with. Propagationbased phase contrast uses freespace propagation to get edge enhancement, talbot and polychromatic farfield interferometry uses a set of diffraction gratings to measure the. Xray grating interferometry is promising to achieve this while keeping radiation dose and examination costs low. Xray phasecontrast imaging is an important method for visualizing cellular and histological structures for a wide range of biological and medical studies. Xray phasecontrast imaging and tomography make use of the refraction of xrays by the sample in image formation. Phase retrieval in xray phasecontrast imaging suitable for tomography anna burvall. Measurement ranges of existing phase contrast setups are either too high or too low for perfectly imaging a human finger in air. Realistic waveoptics simulation of xray phasecontrast. Applications of freespace propagation xray phasecontrast imaging are vast and definitely too many to be covered here.
In the last decade xray imaging based on phase contrast greatly advanced thanks to the use of unmonochromatic synchrotron hard x rays. Xray imaging is of paramount importance for clinical and preclinical imaging but it is fundamentally restricted by the attenuationbased contrast mechanism, which has remained essentially the same since roentgens discovery a century ago. Phasecontrast xray imaging could identify tumors earlier. Xradia ultra uses the zernike principle to achieve phase contrast see. Propagationbased xray phasecontrast imaging pbi is a powerful nondestructive. Xray phase tomography is an imaging technique that uses penetrating xrays to create volumetric views through slices or sections of soft biological tissues, such as tumors, and it offers. The ability of phasecontrast xray imaging to depict blood vessels without contrast agents was tested by observing livers of a mouse and a rat with synchrotron x rays. Us6804324b2 xray phase contrast imaging using a fabry.
Multiple implementations of phase contrast imaging have been. For both energies, a point source with a vertical and horizontal fwhm of 0. Pdf in the last decade xray imaging based on phase contrast greatly advanced thanks to the use of unmonochromatic synchrotron. The pioneer method is the gratingbasedinterferometry which has no special requirements to the xray source and object size. Over the last few years, it has been shown that gratingbased phasecontrast xray tomography can overcome this limitation. While traditional xray imaging yields an image that maps a samples absorptive properties by measuring xray photon. Xray phasecontrast imaging with nanoradian angular resolution pdf. Several types of phasecontrast techniques have been reported in the xray region,18,19, and many of them have advanced from phasecontrast imaging to phase imaging. High resolution laboratory gratingbased xray phase. We obtained image contrast in pathologic specimens without the use of contrast material by using phasecontrast imaging with synchrotron xrays.
Synchrotron xray phase contrast imaging shows great promise as a powerful new tool for internal visualization in biological and medical research. Phase contrast xray imaging was first tested by snigirev et al. Livers were excised by tying arteries and veins to prevent blood from flowing out of the liver. In medical xray imaging, phase contrast imaging is to measure refraction angles caused by the patient.