Computed tomographic reconstruction based on x-ray refraction contrast
TL;DR: In this article, the authors proposed a new mathematical algorithm and software for computed tomographic (CT) reconstruction based on refraction contrast, which provides information on the deflection of the x-ray beam when penetrating through the object.
Abstract: Computed tomographic (CT) reconstruction technique is widely used in many fields of research. Commonly the CT-reconstruction is based on the x-ray absorption contrast. However, recently, methods for generating other x-ray contrasts have been developed. One of them is the refraction contrast which provides information on the deflection of the x-ray beam when penetrating through the object. This contrast has certain advantages and allows us to observe details invisible in the absorption images. Thus, CT based on the refraction contrast must have the same advantages. However, it requires a new mathematical algorithm and software. This letter is dedicated to the solution of the problem including theoretical consideration on the mathematical model which is the basis for the computer modeling and experimental realization of the technique. Actual experimental results together with the reconstructed images are presented and described.
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TL;DR: An overview of the main theoretical and experimental developments and of the important steps performed towards the clinical implementation of phase-contrast x-ray imaging is given.
Abstract: Phase-contrast x-ray imaging (PCI) is an innovative method that is sensitive to the refraction of the x-rays in matter. PCI is particularly adapted to visualize weakly absorbing details like those often encountered in biology and medicine. In past years, PCI has become one of the most used imaging methods in laboratory and preclinical studies: its unique characteristics allow high contrast 3D visualization of thick and complex samples even at high spatial resolution. Applications have covered a wide range of pathologies and organs, and are more and more often performed in vivo. Several techniques are now available to exploit and visualize the phase-contrast: propagation- and analyzer-based, crystal and grating interferometry and non-interferometric methods like the coded aperture. In this review, covering the last five years, we will give an overview of the main theoretical and experimental developments and of the important steps performed towards the clinical implementation of PCI.
796 citations
Cites background from "Computed tomographic reconstruction..."
...When the ydirection is the rotation axis, the phase gradient dφ(x, y, z)/dy is the same at all rotation angles, but if the rotation is about the x-axis then a different CT algorithm is required (Maksimenko et al 2005)....
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TL;DR: The X-ray phase tomography of biological samples is reported in this paper, which is based on Xray Talbot interferometry, and imaging results obtained for a cancerous rabbit liver and a mouse tail with synchrotron radiation are presented.
Abstract: The X-ray phase tomography of biological samples is reported, which is based on X-ray Talbot interferometry. Its imaging principle is described in detail, and imaging results obtained for a cancerous rabbit liver and a mouse tail with synchrotron radiation are presented. Because an amplitude grating is needed to construct an X-ray Talbot interferometer, a high-aspect-ratio grating pattern was fabricated by X-ray lithography and gold electroplating. X-ray Talbot interferometry has an advantage that it functions with polychromatic cone-beam X-rays. Finally, the compatibility with a compact X-ray source is discussed.
327 citations
TL;DR: An evaluation of the recently developed X-ray grating interferometry technique, applied to obtain phase-contrast as well as absorption- Contrast synchrotron radiation-based microtomography of human cerebellum, and it is demonstrated that gratingInterferometry allows identifying besides the blood vessels, the stratum moleculare, thestratum granulosum and the white matter.
Abstract: Human brain tissue belongs to the most impressive and delicate three-dimensional structures in nature. Its outstanding functional importance in the organism implies a strong need for brain imaging modalities. Although magnetic resonance imaging provides deep insights, its spatial resolution is insufficient to study the structure on the level of individual cells. Therefore, our knowledge of brain microstructure currently relies on two-dimensional techniques, optical and electron microscopy, which generally require severe preparation procedures including sectioning and staining. X-ray absorption microtomography yields the necessary spatial resolution, but since the composition of the different types of brain tissue is similar, the images show only marginal contrast. An alternative to absorption could be X-ray phase contrast, which is known for much better discrimination of soft tissues but requires more intricate machinery. In the present communication, we report an evaluation of the recently developed X-ray grating interferometry technique, applied to obtain phase-contrast as well as absorption-contrast synchrotron radiation-based microtomography of human cerebellum. The results are quantitatively compared with synchrotron radiation-based microtomography in optimized absorption-contrast mode. It is demonstrated that grating interferometry allows identifying besides the blood vessels, the stratum moleculare, the stratum granulosum and the white matter. Along the periphery of the stratum granulosum, we have detected microstructures about 40 µm in diameter, which we associate with the Purkinje cells because of their location, size, shape and density. The detection of individual Purkinje cells without the application of any stain or contrast agent is unique in the field of computed tomography and sets new standards in non-destructive three-dimensional imaging.
134 citations
Cites background from "Computed tomographic reconstruction..."
...(2000), in which the tomographically reconstructed phase-related quantity is usually the gradient @d/@z, owing to the fact that both the tomography rotation axis and the diffraction plane are usually vertical, although occasional exceptions are reported (Maksimenko et al. 2005)....
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...…by Dilmanian et al. (2000), in which the tomographically reconstructed phase-related quantity is usually the gradient @d/@z, owing to the fact that both the tomography rotation axis and the diffraction plane are usually vertical, although occasional exceptions are reported (Maksimenko et al. 2005)....
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TL;DR: In this paper, the application of the conventional CT reconstruction algorithm is not always satisfactory for the new diffractionenhanced imaging (DEI-CT) imaging and a new mathematical framework for imaging reconstruction is presented.
Abstract: Recently taking advantage of the novel diffraction-enhanced imaging (DEI) method, one very effective and practical phase contrast imaging technique—a new x-ray computed tomography scheme based on DEI (DEI-CT) showed promising results, really superior to those of conventional CT imaging. In this letter, we show that the application of the conventional CT reconstruction algorithm is not always satisfactory for the new DEI-CT imaging and a new mathematical framework for imaging reconstruction is presented. Experimental data collected at the Beijing synchrotron radiation facility are also discussed using the new algorithm.
76 citations
TL;DR: In this article, a direct reconstruction algorithm for directional-derivative projections of computed tomography of diffraction enhanced imaging is proposed, which does not require any restoration processing compared with the current two-step methods.
Abstract: X-ray diffraction enhanced imaging based on synchrotron radiation has extremely high sensitivity of weakly absorbing low-Z samples in medical and biological fields. This letter is dedicated to a direct reconstruction algorithm for directional-derivative projections of computed tomography of diffraction enhanced imaging. It is a “one-step” algorithm and does not require any restoration processing compared with the current “two-step” methods. The actual values of the sample’s refractive index decrement can be estimated from its reconstruction images directly. The algorithm is proven by the actual experiment at the Beijing Synchrotron Radiation Facility and the reconstructed images are described finally.
76 citations
References
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Book•
01 Jan 1987TL;DR: Properties of Computerized Tomographic Imaging provides a tutorial overview of topics in tomographic imaging covering mathematical principles and theory and how to apply the theory to problems in medical imaging and other fields.
Abstract: Tomography refers to the cross-sectional imaging of an object from either transmission or reflection data collected by illuminating the object from many different directions. The impact of tomography in diagnostic medicine has been revolutionary, since it has enabled doctors to view internal organs with unprecedented precision and safety to the patient. There are also numerous nonmedical imaging applications which lend themselves to methods of computerized tomography, such as mapping of underground resources...cross-sectional imaging of for nondestructive testing...the determination of the brightness distribution over a celestial sphere...three-dimensional imaging with electron microscopy. Principles of Computerized Tomographic Imaging provides a tutorial overview of topics in tomographic imaging covering mathematical principles and theory...how to apply the theory to problems in medical imaging and other fields...several variations of tomography that are currently being researched.
5,620 citations
TL;DR: A technique in which X-ray transmission readings are taken through the head at a multitude of angles: from these data, absorption values of the material contained within the head are calculated on a computer and presented as a series of pictures of slices of the cranium.
Abstract: This article describes a technique in which X-ray transmission readings are taken through the head at a multitude of angles: from these data, absorption values of the material contained within the head are calculated on a computer and presented as a series of pictures of slices of the cranium. The system is approximately 100 times more sensitive than conventional X-ray systems to such an extent that variations in soft tissues of nearly similar density can be displayed.
3,420 citations
TL;DR: Diffraction enhanced imaging is a new x-ray radiographic imaging modality using monochromatic x-rays from a synchrotron which produces images of thick absorbing objects that are almost completely free of scatter.
Abstract: Diffraction enhanced imaging is a new x-ray radiographic imaging modality using monochromatic x-rays from a synchrotron which produces images of thick absorbing objects that are almost completely free of scatter. They show dramatically improved contrast over standard imaging applied to the same phantom. The contrast is based not only on attenuation but also the refraction and diffraction properties of the sample. This imaging method may improve image quality for medical applications, industrial radiography for non-destructive testing and x-ray computed tomography.
1,125 citations
TL;DR: In this article, a method for enhancing the contrast in hard X-ray images of weakly absorbing materials by resolving phase variations across the x-ray beam is described. But although X-rays penetrate deeply into carbon-based compounds, such as soft biological tissue, polymers and carbon-fibre composites, there is little absorption and therefore poor image contrast.
Abstract: IMAGING with hard X-rays is an important diagnostic tool in medicine, biology and materials science. Contact radiography and tomography using hard X-rays provide information on internal structures that cannot be obtained using other non-destructive methods. The image contrast results from variations in the X-ray absorption arising from density differences and variations in composition and thickness of the object. But although X-rays penetrate deeply into carbon-based compounds, such as soft biological tissue, polymers and carbon-fibre composites, there is little absorption and therefore poor image contrast. Here we describe a method for enhancing the contrast in hard X-ray images of weakly absorbing materials by resolving phase variations across the X-ray beam1–4. The phase gradients are detected using diffraction from perfect silicon crystals. The diffraction properties of the crystal determine the ultimate spatial resolution in the image; we can readily obtain a resolution of a fraction of a millimetre. Our method shows dramatic contrast enhancement for weakly absorbing biological and inorganic materials, compared with conventional radiography using the same X-ray energy. We present both bright-field and dark-field phase-contrast images, and show evidence of contrast reversal. The method should have the clinical advantage of good contrast for low absorbed X-ray dose.
951 citations