• Journal of the Korean Society of Visualization
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• v.4 no.2
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• pp.69-75
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• 2006

The microbubbles were used in various fields, such as turbulent control, drag reduction, material science and life science. The X-ray PTV using X-ray micro-imaging technique was employed to mea-sure the size and velocity of micro-bubbles moving in an opaque tube simultaneously. Micro-bubbles of $10{\sim}60{\mu}m$ diameter moving upward in an opaque tube (${\phi}$=2.7mm) were tested. Due to the different refractive indices of water and air, phase contrast X-ray images clearly show the exact size and shape of over-lapped microbubbles. In all of the working fluids tested (deionized water, tap water, 0.01 and 0.10M NaCl solutions), the measured terminal velocity of the microbubbles rising through the solution was proportional to the square of the bubble diameter. The rising velocity was increased with increasing mole concentration. The microbubble can be useful as contrast agent or tracer in life science and biology. The X-ray PTV technique should be able to extract useful information on the behavior of various bio/microscale fluid flows that are not amenable to analysis using conventional methods.

• Korean Journal of Digital Imaging in Medicine
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• v.8 no.1
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• pp.51-55
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• 2006

The effects of Asaddition in amorphous selenium(a-Se) films for digital X-ray conversion material have been studied using the moving photocarrier grating(MPG) technique. This method utilizes the moving interference pattern generated by the superposition of the two frequency shifted laser beams for the illumination of the sample. This moving intensity grating induces a short circuit current, j$_{sc}$ in a-Se:As film. The transport parameters of the sample are extracted from the grating-velocity dependent short circuit current induced in the sample along the modulation direction. The electron and hole mobility, and recombination lifetime of a-Se films with arsenic(As) additions have been obtained. We have found an Increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with X-ray sensitivity for a-Se:As device. The fabricated a-Se(0.3% As) device film exhibited the highest X-ray sensitivity out of 5 samples.

• Progress in Medical Physics
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• v.28 no.3
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• pp.83-91
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• 2017

In this work, we investigated the recently proposed phase-contrast x-ray imaging (PCXI) technique, the so-called single grid-based PCXI, which has great simplicity and minimal requirements on the setup alignment. It allows for imaging of smaller features and variations in the examined sample than conventional attenuation-based x-ray imaging with lower x-ray dose. We performed a systematic simulation using a simulation platform developed by us to investigate the image characteristics. We also performed a preliminary PCXI experiment using an established a table-top setup to demonstrate the performance of the simulation platform. The system consists of an x-ray tube ($50kV_p$, 5 mAs), a focused-linear grid (200-lines/inch), and a flat-panel detector ($48-{\mu}m$ pixel size). According to our results, the simulated contrast of phase images was much enhanced, compared to that of the absorption images. The scattering length scale estimated for a given simulation condition was about 117 nm. It was very similar, at least qualitatively, to the experimental contrast, which demonstrates the performance of the simulation platform. We also found that the level of the phase gradient of oriented structures strongly depended on the orientation of the structure relative to that of linear grids.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.1
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• pp.21-27
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• 2002

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. A number of visual or optical technologies have been successfully applied to measure three-dimensional surfaces. However, those conventional visual or optical methods have inherent shortcomings such as occlusion and variant surface reflection. X-ray vision system can be a good solution to these conventional problems, since we can extract the volume information including both the surface geometry and the inner structure of any objects. In the x-ray system, the surface condition of an object, whether it is lambertian or specular, does not affect the inherent characteristics of its x-ray images. In this paper, we propose a three-dimensional x-ray imaging method to reconstruct a three dimensional structure of an object out of two dimensional x-ray image sets. To achieve this by the proposed method, two or more x-ray images projected from different views are needed. Once these images are acquired, the simultaneous algebraic reconstruction technique(SART) is usually utilized. Since the existing SART algorithms have several shortcomings such as low performance in convergence and different convergence within the reconstruction volume of interest, an advanced SART algorithm named as USART(uniform SART) is proposed to avoid such shortcomings and improve the reconstruction performance. Because, each voxel within the volume is equally weighted to update instantaneous value of its internal density, it can achieve uniform convergence property of the reconstructed volume. The algorithm is simulated on various shapes of objects such as a pyramid, a hemisphere and a BGA model. Based on simulation results the performance of the proposed method is compared with that of the conventional SART method.

• 순환기질환의공학회:학술대회논문집
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• 2001.11a
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• pp.22-23
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• 2001

• 순환기질환의공학회:학술대회논문집
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• 2003.11a
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• pp.14-15
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• 2003

• Journal of the Korean Society of Radiology
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• v.6 no.6
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• pp.477-481
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• 2012

An X-ray diffractometer which has various X-ray optics can give qualitative and quantitative information for a sample using a nondestructive analysis method. A parallel beam optic passes the parallel beam and removes divergent beam generated from an X-ray tube. The parallel beam optic used in the X-ray diffractometer was fabricated by wire cut and grading of stainless steel plates and was evaluated its performance using an X-ray imaging system. The measured parallelization of 6.6 mrad for the fabricated the parallel beam optic was a very close to the expected value of 6 mrad. An X-ray imaging technique for evaluating the parallel beam optics can estimate parallelization for each plate and can be used to other X-ray optics.

• Journal of International Society for Simulation Surgery
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• v.3 no.1
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• pp.16-21
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• 2016

Computed tomography (CT) can completely digitize the interior and the exterior of nearly any object without any destruction. Generally, the resolution for industrial CT is below a few microns. The industrial CT scanning, however, has a limitation because it requires long measuring and processing time. Whereas, 2D X-ray imaging is fast. In this paper, we propose a novel concept of 3D non-destructive inspection technique using the advantages of both micro-CT and dual X-ray images. After registering the master object’s CT data and the sample objects’ dual X-ray images, 3D non-destructive inspection is possible by analyzing the matching results. Calculation for the registration is accelerated by parallel computing using graphics processing unit (GPU).

• Transactions on Electrical and Electronic Materials
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• v.4 no.3
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• pp.10-14
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• 2003

In this paper, we have introduced the x-ray detector built with a CsI:Na scintillation layer deposited on amorphous selenium. To determine the thickness of the CsI:Na layer, we have estimated the transmission spectra and the absorption of continuous x-rays in diagnostic range by using computer simulation (MCNP 4C). A x-ray detector with 65 ${\mu}m$-CsI:Na/30 ${\mu}m$-Se layer has been fabricated by a thermal evaporation technique. SEM and PL measurements have been performed. The dark current and x-ray sensitivity of the fabricated detector has been compared with that of the conventional a-Se detector with 100 ${\mu}m$ thickness. Experimental results show that both detectors exhibit a similar dark current, which was of a low value below $400 pA/cm^2$ at 10 V/${\mu}m$. However, the CsI:Na-Se detector indicates high x-ray sensitivity, roughly 1.3 times that of a conventional a-Se detector. Furthermore, a CsI:Na-Se detector with an aluminium reflective layer shows a 1.8 times higher x-ray sensitivity than an a-Se detector. The hybrid type detector proposed in this work exhibits a low dark current and high x-ray sensitivity, and, in particular, excellent linearity to the x-ray exposure dose.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.1
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• pp.46-53
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• 2010

A Compton X-ray backscatter technique has been developed to quantitatively assess impact damage in quasi-isotropic laminated composites made by a drop-weight tester. X-ray backscatter imaging system with a slit-type camera is constructed to obtain a cross-sectional profile of impact-damaged laminated composites from the electron-density variation of the cross section. A nonlinear scattering model based on Boltsman equation is introduced to compute Compton X-ray backscattering field for the defect assessment. An adaptive filter is also used to reduce noises from many sources including quantum noise and irregular distributions of fibers and matrix in composites. Delaminations masked or distorted by the first delamination are detected and characterized effectively by the Compton X-ray backscatter technique, both in width and location, by application of error minimization algorithm.