X-ray phase tomography

Figure 6.14. Reconstructed image of PS/PMMA blend by x-ray phase tomography (A) phase tomogram and (B) volume-rendering view of reconstructed three dimensional data, where PS region has been made transparent. (From Momose et al. [297] reproduced with permission.)...

Alternatively, the X-ray phase shift induced by polymers is significantly large. X-ray phase tomography measures such X-ray phase shift and reconstmcts a tomogram that maps the refractive index difference, which is roughly proportional to the mass density of polymers. Although X-ray phase tomography has been available only in synchrotron radiation facilities, recent developments have made it possible to perform X-ray... 

I>(x, z) corresponds to g(x, z 0) in Section 2.22.2, and <5(x, y, z) corresponds to /(x, y, z) apart from the coefficient -InjX. Therefore, (x, y, z) can be reconstmcted by measuring the phase shift in plural projection directions using the X-ray CT procedtue. This technique is called X-ray phase tomography. The high sensitivity of X-ray phase imaging is also expected in X-ray phase tomography. 

The three crystal lamellae function as X-ray half mirrors via Bra diffraction, and Mach-Zehnder-type interfering beams are formed, as shown in Figure 9(b). When a sample is placed in one of the beams, interference fringes corresponding to the phase shift contours are generated. X-ray phase tomography was invented and first demonstrated with this device. ... 

Figure 9 X-ray crystal interferometer (a) and setup for X-ray phase tomography (b).

The operation arg[ ] implies the calculation of the argument. Note that A(x, z) can be determined without the object in the same manner. By repeating this procedure at every angular position of the sample rotation. X-ray phase tomography is performed. 

Figure 10 shows a phase tomogram obtained for a PS/ PMMA blend with SR. In this case, no modification was done by heavy elements, but the phase separation structure could be revealed, showing the excellent sensitivity of X-ray phase tomography. The sample was observed in water, and the tomogram maps the refractive index difference from that of water. The noise level in the tomogram was 8.7 x 10 °, which corresponds to a density resolution of 1.2 mgcm" (see Section 2.22.5.1). 

Figure 11 shows the histogram of the reconstmcted voxel values, where the two peaks correspond to PS-rich and PMMA-rich regions. The arrows show the values of pure PS and PMMA. Thus, the peaks appeared slightly inside the arrows, indicating that the PS-rich phase contained a small amount of PMMA and vice versa. This result quantitatively demonstrates that X-ray phase tomography can be used not only to depict stmctures but also to measure the composition of each phase. 

X-ray computed tomography (CT) (Kneafsey et at., 2005) Hydrate, water, gas phase distribution Yes P, T, hydrate, water vs. time (min) Typically up to 1000 psi microns Density profile of hydrate plug contained in cell. Phase fractions, thermal conductivity with ITOUGH2 modehng... 

Detailed description of a porous microstructure is an essential prerequisite for unveiling the influence of pore morphology on the underlying two-phase behavior. This can be achieved either by 3-D volume imaging or by constructing a digital microstructure based on stochastic reconstruction models. Non-invasive techniques, such as X-ray micro-tomography, are the popular methods for 3-D... 

Harvel, G.D., Hori, K., Kawanishi, K., and Chang, J.S. (1999), Cross-sectional void fraction distribution measurements in a vertical annulus two-phase flow by high speed X-ray computed tomography and real-time neutron radiography techniques, Flow Measurement and Instrumentation, 10(4) 259-266. 

Burvall A, Lundstrom U, Takman Pac et al (2011) Phase retrieval in X-ray phase-contrast imaging suitable for tomography. Opt Express 19 10359-10376... 

Figure 1 shows the spatial resolution of various types of microscopy and scattering methods, including 3D microscopy techniques such as laser scanning confocal microscopy (LSCM), X-ray computerized tomography (X-ray CT), and TEMT. LSCM has been extensively used to investigate the phase-separated bicontinuous structures of polymer blends. It should be noted that X-ray CT is particularly useful for opaque specimens with micrometer-sized stmctures, while transparent specimens are necessary for LSCM. X-ray CT has been also extensively used in medical sdence. In the early 1990s, the spatial resolution of X-ray CT was limited to ca. 100 im. Recently, the resolution has substantially improved and is now comparable with ( 1 pm) or even superior to that of optical microscopy. 

It is shown how phase contrast X-ray microtomography can be realised with a (commercial) polychromatic X-ray microfocus tomograph provided the source size and the resolution of the detector are sufficiently small and the distance between source and detector is sufficiently large. The technique opens perspectives for high resolution tomography of light objects... 

Computed tomography (CT) techniques share a common mechanism for spatial encoding. A two dimensional projection of the object (similar to a standard x-ray or a single read out in MRI without phase encoding) at multiple angles can be reconstructed into two or three dimensional images. Data... 

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