X-Ray Microtomography (μCT) Using Phase Contrast for the Investigation of Organic Matter

Beckmann, Felix; Bonse, U.; Busch, Felix; Günnewig, Olaf

doi:10.1097/00004728-199707000-00006

Cited by 167 publications

(74 citation statements)

References 17 publications

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“…To have a signal (i.e., change in attenuation) that adequately exceeds the photon noise (the statistical noise due to the quantum nature of the X-ray photons Ӎ ͌N, where N is the number of photons per resolution unit), at least 10 4 -10 5 photons have to be exposed to the region of interest per resolution unit (27). A methodology that shows some promise toward practical use is X-ray imaging, which is based on the consequences of refraction of X-rays (resulting from the slightly different velocity of X-ray photons through different materials, essentially the same as the refraction of light) within the tissues (28,29). This has been shown to increase the density resolution of soft tissues tenfold or more over current attenuation-based imaging, but it also has the potential for reduced radiation exposure because the signal is the phase shift or refraction of individual photons rather than the reduction in numbers of photons.…”

Section: Discussionmentioning

confidence: 99%

Micro-Computed Tomography of the Lungs and Pulmonary-Vascular System

Ritman¹

2005

Proceedings of the American Thoracic Society

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Three-dimensional imaging of the intact lung and its vasculature is essential if the hierarchical and volumetric aspects of its structures and functions are to be quantitated. Although this is possible with clinical multislice helical CT scanners, the spatial resolution does not scale down adequately for small rodents for which cubic voxel dimensions of 50-100 m are required. Micro-computed tomography (micro-CT) provides the necessary spatial resolution of 3D images of the intact thoracic contents. Micro-CT can provide higher resolution so that basic micro-architectural structures, such as alveoli, can be individually visualized and quantitated. Dynamic events, such as the respiratory and cardiac cycles, can be imaged at multiple time points throughout a representative cycle by coordinating the scan sequence (i.e., gating) to the cycle phase of a sequence of cycles. Fusion of the micro-CT image data with other image data, such as micro-SPECT or histology, can enhance the information content beyond the mainly structural information provided by micro-CT. Conventional attenuation-based X-ray imaging can involve significant X-ray exposures at high spatial resolutions, and this could affect the phenotype (e.g., via interstitial fibrosis) and genotype (e.g., via mutation), so its use in longitudinal studies using micro-CT may be limited in some cases. However, because of recent developments in which the phase shift or refraction of X-rays rather than attenuation is used, the X-ray exposure may be significantly reduced.Keywords: microarchitecture; pulmonary hypertension; alveoli; airways Micro-computed tomography (micro-CT) is a rapidly developing imaging capability that has been described in detail elsewhere (1). This development is driven in large measure by the fact that because mice are rapidly becoming the experimental animals of choice for many research endeavors, there is motivation to scale clinical imaging capabilities down to the mouse level. There are several aspects to the scaling of the spatial and temporal resolution and volume scanned (2). One is to scale so as to generate a transaxial tomographic image equivalent to a clinical scan. Thus, with clinical multislice helical scanning, CT of the thorax generates 3D images that are approximately 300 to 400 mm in transverse diameter and are made up of voxels (a 3D picture-element or pixel) ‫ف‬ 1 mm 3 in volume. A "mini" CT scanner that is scaled to a proportional voxel resolution in a mouse (with a 20 mm thoracic diameter) would involve voxels ‫ف‬ 75 m in diameter. The mouse's lungs have a combined volume of about 1.3 cm 3 ; therefore, in the mouse a 3D volume of at least 2 cm 3 must be imaged to capture the entire lung. How- ever, the mouse heart and respiratory rate are much higher than in humans, so cardio-respiratory dynamic processes are much more difficult to image in mice than in humans (3) because the micro-CT scan durations are generally limited by the rate of X-ray production. If microscopic structures are to be imaged with micro-CT, image resolution...

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Section: Discussionmentioning

confidence: 99%

Micro-Computed Tomography of the Lungs and Pulmonary-Vascular System

Ritman¹

2005

Proceedings of the American Thoracic Society

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“…If the object is of unknown structure, we may determine its structure by imaging it by means of our hard X-ray microscope and by reconstructing the three-dimensional distribution n xY yY z in equation (58) via a tomographic approach. Techniques have been developed for how this may be performed (Gilboy, 1995;Grodzins, 1983;Raven et al, 1996Raven et al, , 1997Spanne et al, 1999;Momose, 1995;Beckmann et al, 1997). Here, we would like to consider the transversal and longitudinal resolving power of our microscope.…”

Section: Theory Of Imagingmentioning

confidence: 99%

Imaging by parabolic refractive lenses in the hard X-ray range

et al. 1999

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The manufacture and properties of compound refractive lenses (CRLs) for hard X-rays with parabolic pro®le are described. These novel lenses can be used up to $60 keV. A typical focal length is 1 m. They have a geometrical aperture of 1 mm and are best adapted to undulator beams at synchrotron radiation sources. The transmission ranges from a few % in aluminium CRLs up to about 30% expected in beryllium CRLs. The gain (ratio of the intensity in the focal spot relative to the intensity behind a pinhole of equal size) is larger than 100 for aluminium and larger than 1000 for beryllium CRLs. Due to their parabolic pro®le they are free of spherical aberration and are genuine imaging devices. The theory for imaging an X-ray source and an object illuminated by it has been developed, including the effects of attenuation (photoabsorption and Compton scattering) and of the roughness at the lens surface. Excellent agreement between theory and experiment has been found. With aluminium CRLs a lateral resolution in imaging of 0.3 mm has been achieved and a resolution below 0.1 mm can be expected for beryllium CRLs. The main ®elds of application of the refractive X-ray lenses are (i) microanalysis with a beam in the micrometre range for diffraction,¯uorescence, absorption, scattering; (ii) imaging in absorption and phase contrast of opaque objects which cannot tolerate sample preparation; (iii) coherent X-ray scattering.

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“…In a conventional X-ray CT image, the absorption differences among cancer, fibrosis, necrosis, and normal tissues are difficult to detect because the differences in the linear attenuation coefficients of these tissues are very small. As mentioned earlier, XII enables visualization of the inner structures of human cancer specimens (Takeda et al, 2000) and animal cancer specimens (Momose et al, 1996;Takeda et al, 2004d), the brain (Beckmann et al, 1997), and the kidney (Wu et al, 2009) without contrast agents composed of heavy atomic elements. Here, we describe the images of cancer specimens obtained using XII at 35-keV X-ray energy.…”

Section: Formalin-fixed Colon Cancer Specimens From Nude Micementioning

confidence: 99%