Estimation of visibility of phase contrast with extraction voltages for field emission gun electron microscopes

Energy Technology Data Exchange (ETDEWEB)

Meng, Xing, E-mail: xmeng101@gmail.com

2017-02-15

Estimation was made for visibility of phase contrast with varying extraction voltages. The resulting decay rates of visibility show that images with low image contrast from cryo EM will be seriously impacted with high extraction voltages. - Highlights: • Cryo EM • Phase contrast • Extraction votage.

New generation quantitative x-ray microscopy encompassing phase-contrast

International Nuclear Information System (INIS)

Wilkins, S.W.; Mayo, S.C.; Gureyev, T.E.; Miller, P.R.; Pogany, A.; Stevenson, A.W.; Gao, D.; Davis, T.J.; Parry, D.J.; Paganin, D.

2000-01-01

Full text: We briefly outline a new approach to X-ray ultramicroscopy using projection imaging in a scanning electron microscope (SEM). Compared to earlier approaches, the new approach offers spatial resolution of ≤0.1 micron and includes novel features such as: i) phase contrast to give additional sample information over a wide energy range, rapid phase/amplitude extraction algorithms to enable new real-time modes of microscopic imaging widespread applications are envisaged to fields such as materials science, biomedical research, and microelectronics device inspection. Some illustrative examples are presented. The quantitative methods described here are also very relevant to X-ray projection microscopy using synchrotron sources

Enhanced renal image contrast by ethanol fixation in phase-contrast X-ray computed tomography.

Science.gov (United States)

Shirai, Ryota; Kunii, Takuya; Yoneyama, Akio; Ooizumi, Takahito; Maruyama, Hiroko; Lwin, Thet Thet; Hyodo, Kazuyuki; Takeda, Tohoru

2014-07-01

Phase-contrast X-ray imaging using a crystal X-ray interferometer can depict the fine structures of biological objects without the use of a contrast agent. To obtain higher image contrast, fixation techniques have been examined with 100% ethanol and the commonly used 10% formalin, since ethanol causes increased density differences against background due to its physical properties and greater dehydration of soft tissue. Histological comparison was also performed. A phase-contrast X-ray system was used, fitted with a two-crystal X-ray interferometer at 35 keV X-ray energy. Fine structures, including cortex, tubules in the medulla, and the vessels of ethanol-fixed kidney could be visualized more clearly than that of formalin-fixed tissues. In the optical microscopic images, shrinkage of soft tissue and decreased luminal space were observed in ethanol-fixed kidney; and this change was significantly shown in the cortex and outer stripe of the outer medulla. The ethanol fixation technique enhances image contrast by approximately 2.7-3.2 times in the cortex and the outer stripe of the outer medulla; the effect of shrinkage and the physical effect of ethanol cause an increment of approximately 78% and 22%, respectively. Thus, the ethanol-fixation technique enables the image contrast to be enhanced in phase-contrast X-ray imaging.

Generalized phase contrast:

DEFF Research Database (Denmark)

Glückstad, Jesper; Palima, Darwin

Generalized Phase Contrast elevates the phase contrast technique not only to improve phase imaging but also to cross over and interface with diverse and seemingly disparate fields of contemporary optics and photonics. This book presents a comprehensive introduction to the Generalized Phase Contrast...

Characterisation of phase evolution under load by means of phase contrast imaging using synchrotron radiation

International Nuclear Information System (INIS)

Besseghini, S.; Stortiero, F.; Carcano, G.; Villa, E.; Mancini, L.; Tromba, G.; Zanini, F.; Montanari, F.; Airoldi, G.

2003-01-01

Phase contrast radiography (PCR) is a quite novel technique that is collecting increasing attention due to the possibility to obtain image information in presence of very small differences in the densities of the materials under analysis. Phase contrast imaging (PCI) has some specific advantage when compared with common microscopic techniques: (a) no special preparation of the sample is needed (b) the simultaneously investigated area is very large and (c) it allows the setting up of complex experimental apparatus. The results here presented are a good evidence of these three advantages. In this paper, we report on the application of phase contrast imaging in the study of the phase evolution during pseudoelastic transformation in the NiTiCu shape memory alloys (SMAs). The investigation was undertaken with the aim to identify some modification of the structure taking place at the end of the transformation plateau in the pseudoelastic behaviour of the alloy

Quantitative phase imaging and differential interference contrast imaging for biological TEM

International Nuclear Information System (INIS)

Allman, B.E.; McMahon, P.J.; Barone-Nugent, E.D.; Nugent, E.D.

2002-01-01

Full text: Phase microscopy is a central technique in science. An experienced microscopist uses this effect to visualise (edge) structure within transparent samples by slightly defocusing the microscope. Although widespread in optical microscopy, phase contrast transmission electron microscopy (TEM) has not been widely adopted. TEM for biological specimens has largely relied on staining techniques to yield sufficient contrast. We show here a simple method for quantitative TEM phase microscopy that quantifies this phase contrast effect. Starting with conventional, digital, bright field images of the sample, our algorithm provides quantitative phase information independent of the sample's bright field intensity image. We present TEM phase images of a range of stained and unstained, biological and material science specimens. This independent phase and intensity information is then used to emulate a range of phase visualisation images familiar to optical microscopy, e.g. differential interference contrast. The phase images contain features not visible with the other imaging modalities. Further, if the TEM samples have been prepared on a microtome to a uniform thickness, the phase information can be converted into refractive index structure of the specimen. Copyright (2002) Australian Society for Electron Microscopy Inc

Advantages of intermediate X-ray energies in Zernike phase contrast X-ray microscopy.

Science.gov (United States)

Wang, Zhili; Gao, Kun; Chen, Jian; Hong, Youli; Ge, Xin; Wang, Dajiang; Pan, Zhiyun; Zhu, Peiping; Yun, Wenbing; Jacobsen, Chris; Wu, Ziyu

2013-01-01

Understanding the hierarchical organizations of molecules and organelles within the interior of large eukaryotic cells is a challenge of fundamental interest in cell biology. Light microscopy is a powerful tool for observations of the dynamics of live cells, its resolution attainable is limited and insufficient. While electron microscopy can produce images with astonishing resolution and clarity of ultra-thin (3D images of cryo-preserved cells. The relatively low X-ray energy (3D imaging (e.g., ~1 μm DoF for 20 nm resolution). An X-ray microscope operating at intermediate energy around 2.5 keV using Zernike phase contrast can overcome the above limitations and reduces radiation dose to the specimen. Using a hydrated model cell with an average chemical composition reported in literature, we calculated the image contrast and the radiation dose for absorption and Zernike phase contrast, respectively. The results show that an X-ray microscope operating at ~2.5 keV using Zernike phase contrast offers substantial advantages in terms of specimen size, radiation dose and depth-of-focus. Copyright © 2012 Elsevier Inc. All rights reserved.

Zernike phase-contrast electron cryotomography applied to marine cyanobacteria infected with cyanophages.

Science.gov (United States)

Dai, Wei; Fu, Caroline; Khant, Htet A; Ludtke, Steven J; Schmid, Michael F; Chiu, Wah

2014-11-01

Advances in electron cryotomography have provided new opportunities to visualize the internal 3D structures of a bacterium. An electron microscope equipped with Zernike phase-contrast optics produces images with markedly increased contrast compared with images obtained by conventional electron microscopy. Here we describe a protocol to apply Zernike phase plate technology for acquiring electron tomographic tilt series of cyanophage-infected cyanobacterial cells embedded in ice, without staining or chemical fixation. We detail the procedures for aligning and assessing phase plates for data collection, and methods for obtaining 3D structures of cyanophage assembly intermediates in the host by subtomogram alignment, classification and averaging. Acquiring three or four tomographic tilt series takes ∼12 h on a JEM2200FS electron microscope. We expect this time requirement to decrease substantially as the technique matures. The time required for annotation and subtomogram averaging varies widely depending on the project goals and data volume.

Multiscale differential phase contrast analysis with a unitary detector

KAUST Repository

Lopatin, Sergei; Ivanov, Yurii P.; Kosel, Jü rgen; Chuvilin, Andrey

2015-01-01

A new approach to generate differential phase contrast (DPC) images for the visualization and quantification of local magnetic fields in a wide range of modern nano materials is reported. In contrast to conventional DPC methods our technique utilizes the idea of a unitary detector under bright field conditions, making it immediately usable by a majority of modern transmission electron microscopes. The approach is put on test to characterize the local magnetization of cylindrical nanowires and their 3D ordered arrays, revealing high sensitivity of our method in a combination with nanometer-scale spatial resolution.

Multiscale differential phase contrast analysis with a unitary detector

KAUST Repository

Lopatin, Sergei

2015-12-30

A new approach to generate differential phase contrast (DPC) images for the visualization and quantification of local magnetic fields in a wide range of modern nano materials is reported. In contrast to conventional DPC methods our technique utilizes the idea of a unitary detector under bright field conditions, making it immediately usable by a majority of modern transmission electron microscopes. The approach is put on test to characterize the local magnetization of cylindrical nanowires and their 3D ordered arrays, revealing high sensitivity of our method in a combination with nanometer-scale spatial resolution.

Generalized Phase Contrast

CERN Document Server

Glückstad, Jesper

2009-01-01

Generalized Phase Contrast elevates the phase contrast technique not only to improve phase imaging but also to cross over and interface with diverse and seemingly disparate fields of contemporary optics and photonics. This book presents a comprehensive introduction to the Generalized Phase Contrast (GPC) method including an overview of the range of current and potential applications of GPC in wavefront sensing and phase imaging, structured laser illumination and image projection, optical trapping and manipulation, and optical encryption and decryption. The GPC method goes further than the restrictive assumptions of conventional Zernike phase contrast analysis and achieves an expanded range of validity beyond weak phase perturbations. The generalized analysis yields design criteria for tuning experimental parameters to achieve optimal performance in terms of accuracy, fidelity and light efficiency. Optimization can address practical issues, such as finding an optimal spatial filter for the chosen application, ...

Wide-Field Vibrational Phase Contrast Imaging Based on Coherent Anti-Stokes Raman Scattering Holography

International Nuclear Information System (INIS)

Lv Yong-Gang; Ji Zi-Heng; Dong Da-Shan; Gong Qi-Huang; Shi Ke-Bin

2015-01-01

We propose and implement a wide-field vibrational phase contrast detection to obtain imaging of imaginary components of third-order nonlinear susceptibility in a coherent anti-Stokes Raman scattering (CARS) microscope with full suppression of the non-resonant background. This technique is based on the unique ability of recovering the phase of the generated CARS signal based on holographic recording. By capturing the phase distributions of the generated CARS field from the sample and from the environment under resonant illumination, we demonstrate the retrieval of imaginary components in the CARS microscope and achieve background free coherent Raman imaging. (paper)

Zernike Phase Contrast Electron Cryo-Tomography Applied to Marine Cyanobacteria Infected with Cyanophages

Science.gov (United States)

Dai, Wei; Fu, Caroline; Khant, Htet A.; Ludtke, Steven J.; Schmid, Michael F.; Chiu, Wah

2015-01-01

Advances in electron cryo-tomography have provided a new opportunity to visualize the internal 3D structures of a bacterium. An electron microscope equipped with Zernike phase contrast optics produces images with dramatically increased contrast compared to images obtained by conventional electron microscopy. Here we describe a protocol to apply Zernike phase plate technology for acquiring electron tomographic tilt series of cyanophage-infected cyanobacterial cells embedded in ice, without staining or chemical fixation. We detail the procedures for aligning and assessing phase plates for data collection, and methods to obtain 3D structures of cyanophage assembly intermediates in the host, by subtomogram alignment, classification and averaging. Acquiring three to four tomographic tilt series takes approximately 12 h on a JEM2200FS electron microscope. We expect this time requirement to decrease substantially as the technique matures. Time required for annotation and subtomogram averaging varies widely depending on the project goals and data volume. PMID:25321408

Development of full-field x-ray phase-tomographic microscope based on laboratory x-ray source

Science.gov (United States)

Takano, H.; Wu, Y.; Momose, A.

2017-09-01

An X-ray phase tomographic microscope that can quantitatively measure the refractive index of a sample in three dimensions with a high spatial resolution was developed by installing a Lau interferometer consisting of an absorption grating and a π/2 phase grating into the optics of an X-ray microscope. The optics comprises a Cu rotating anode X-ray source, capillary condenser optics, and a Fresnel zone plate for the objective. The microscope has two optical modes: a large-field-of-view mode (field of view: 65 μm x 65 μm) and a high-resolution mode (spatial resolution: 50 nm). Optimizing the parameters of the interferometer yields a self-image of the phase grating with 60% visibility. Through the normal fringe-scanning measurement, a twin phase image, which has an overlap of two phase image of opposite contrast with a shear distance much larger than system resolution, is generated. Although artifacts remain to some extent currently when a phase image is calculated from the twin phase image, this system can obtain high-spatial-resolution images resolving 50-nm structures. Phase tomography with this system has also been demonstrated using a phase object.

Re-evaluation of differential phase contrast (DPC) in a scanning laser microscope using a split detector as an alternative to differential interference contrast (DIC) optics.

Science.gov (United States)

Amos, W B; Reichelt, S; Cattermole, D M; Laufer, J

2003-05-01

In this paper, differential phase imaging (DPC) with transmitted light is implemented by adding a suitable detection system to a standard commercially available scanning confocal microscope. DPC, a long-established method in scanning optical microscopy, depends on detecting the intensity difference between opposite halves or quadrants of a split photodiode detector placed in an aperture plane. Here, DPC is compared with scanned differential interference contrast (DIC) using a variety of biological specimens and objective lenses of high numerical aperture. While DPC and DIC images are generally similar, DPC seems to have a greater depth of field. DPC has several advantages over DIC. These include low cost (no polarizing or strain-free optics are required), absence of a double scanning spot, electronically variable direction of shading and the ability to image specimens in plastic dishes where birefringence prevents the use of DIC. DPC is also here found to need 20 times less laser power at the specimen than DIC.

Using the phase-space imager to analyze partially coherent imaging systems: bright-field, phase contrast, differential interference contrast, differential phase contrast, and spiral phase contrast

Science.gov (United States)

Mehta, Shalin B.; Sheppard, Colin J. R.

2010-05-01

Various methods that use large illumination aperture (i.e. partially coherent illumination) have been developed for making transparent (i.e. phase) specimens visible. These methods were developed to provide qualitative contrast rather than quantitative measurement-coherent illumination has been relied upon for quantitative phase analysis. Partially coherent illumination has some important advantages over coherent illumination and can be used for measurement of the specimen's phase distribution. However, quantitative analysis and image computation in partially coherent systems have not been explored fully due to the lack of a general, physically insightful and computationally efficient model of image formation. We have developed a phase-space model that satisfies these requirements. In this paper, we employ this model (called the phase-space imager) to elucidate five different partially coherent systems mentioned in the title. We compute images of an optical fiber under these systems and verify some of them with experimental images. These results and simulated images of a general phase profile are used to compare the contrast and the resolution of the imaging systems. We show that, for quantitative phase imaging of a thin specimen with matched illumination, differential phase contrast offers linear transfer of specimen information to the image. We also show that the edge enhancement properties of spiral phase contrast are compromised significantly as the coherence of illumination is reduced. The results demonstrate that the phase-space imager model provides a useful framework for analysis, calibration, and design of partially coherent imaging methods.

Phase contrast image synthesis

DEFF Research Database (Denmark)

Glückstad, J.

1996-01-01

A new method is presented for synthesizing arbitrary intensity patterns based on phase contrast imaging. The concept is grounded on an extension of the Zernike phase contrast method into the domain of full range [0; 2 pi] phase modulation. By controlling the average value of the input phase funct...... function and by choosing appropriate phase retardation at the phase contrast filter, a pure phase to intensity imaging is accomplished. The method presented is also directly applicable in dark field image synthesis....

Polarized differential-phase laser scanning microscope

International Nuclear Information System (INIS)

Chou Chien; Lyu, C.-W.; Peng, L.-C.

2001-01-01

A polarized differential-phase laser scanning microscope, which combines a polarized optical heterodyne Mach-Zehnder interferometer and a differential amplifier to scan the topographic image of a surface, is proposed. In the experiment the differential amplifier, which acts as a PM-AM converter, in the experiment, converting phase modulation (PM) into amplitude modulation (AM). Then a novel, to our knowledge, phase demodulator was proposed and implemented for the differential-phase laser scanning microscope. An optical grating (1800 lp/mm) was imaged. The lateral and the depth resolutions of the imaging system were 0.5 μm and 1 nm, respectively. The detection accuracy, which was limited by the reflectivity variation of the test surface, is discussed

High-resolution observation of phase contrast at 1MeV. Amorphous or crystalline objects

International Nuclear Information System (INIS)

Bourret, A.; Desseaux, J.

1975-01-01

Many authors have stressed the possibilities of high voltage to improve resolution, but owing to numerous experimental difficulties the resolution limit at 1MeV, which lies around 1A for conventional lenses, has so far been unattainable. Thus the phase contrast at 1MeV has not been studied on evaporated objects. On the other hand the fringes of crystal planes have been observed at 1MeV. the CEN-G microscope having been considerably modified it has been possible to observe the phase contrast of amorphous or crystalline objects [fr

Laser speckle contrast imaging using light field microscope approach

Science.gov (United States)

Ma, Xiaohui; Wang, Anting; Ma, Fenghua; Wang, Zi; Ming, Hai

2018-01-01

In this paper, a laser speckle contrast imaging (LSCI) system using light field (LF) microscope approach is proposed. As far as we known, it is first time to combine LSCI with LF. To verify this idea, a prototype consists of a modified LF microscope imaging system and an experimental device was built. A commercially used Lytro camera was modified for microscope imaging. Hollow glass tubes with different depth fixed in glass dish were used to simulate the vessels in brain and test the performance of the system. Compared with conventional LSCI, three new functions can be realized by using our system, which include refocusing, extending the depth of field (DOF) and gathering 3D information. Experiments show that the principle is feasible and the proposed system works well.

Stable and simple quantitative phase-contrast imaging by Fresnel biprism

Science.gov (United States)

Ebrahimi, Samira; Dashtdar, Masoomeh; Sánchez-Ortiga, Emilio; Martínez-Corral, Manuel; Javidi, Bahram

2018-03-01

Digital holographic (DH) microscopy has grown into a powerful nondestructive technique for the real-time study of living cells including dynamic membrane changes and cell fluctuations in nanometer and sub-nanometer scales. The conventional DH microscopy configurations require a separately generated coherent reference wave that results in a low phase stability and a necessity to precisely adjust the intensity ratio between two overlapping beams. In this work, we present a compact, simple, and very stable common-path DH microscope, employing a self-referencing configuration. The microscope is implemented by a diode laser as the source and a Fresnel biprism for splitting and recombining the beams simultaneously. In the overlapping area, linear interference fringes with high contrast are produced. The frequency of the interference pattern could be easily adjusted by displacement of the biprism along the optical axis without a decrease in fringe contrast. To evaluate the validity of the method, the spatial noise and temporal stability of the setup are compared with the common off-axis DH microscope based on a Mach-Zehnder interferometer. It is shown that the proposed technique has low mechanical noise as well as superb temporal stability with sub-nanometer precision without any external vibration isolation. The higher temporal stability improves the capabilities of the microscope for studying micro-object fluctuations, particularly in the case of biological specimens. Experimental results are presented using red blood cells and silica microspheres to demonstrate the system performance.

Observation of Phase Objects by Using an X-ray Microscope with a Foucault Knife-Edge

Science.gov (United States)

Watanabe, N.; Sasaya, T.; Imai, Y.; Iwata, S.; Zama, K.; Aoki, S.

2011-09-01

An x-ray microscope with a zone plate was assembled at the synchrotron radiation source of BL3C, Photon Factory. A Foucault knife-edge was set at the back focal plate of the objective zone plate and phase retrieval was tested by scanning the knife-edge. A preliminary result shows that scanning the knife-edge during exposure was effective for phase retrieval. Phase-contrast tomography was investigated using differential projection images calculated from two Schlieren images with the oppositely oriented knife-edges. Fairly good reconstruction images of polystyrene beads and spores could be obtained.

Observation of Phase Objects by Using an X-ray Microscope with a Foucault Knife-Edge

International Nuclear Information System (INIS)

Watanabe, N.; Sasaya, T.; Imai, Y.; Iwata, S.; Zama, K.; Aoki, S.

2011-01-01

An x-ray microscope with a zone plate was assembled at the synchrotron radiation source of BL3C, Photon Factory. A Foucault knife-edge was set at the back focal plate of the objective zone plate and phase retrieval was tested by scanning the knife-edge. A preliminary result shows that scanning the knife-edge during exposure was effective for phase retrieval. Phase-contrast tomography was investigated using differential projection images calculated from two Schlieren images with the oppositely oriented knife-edges. Fairly good reconstruction images of polystyrene beads and spores could be obtained.

Criterion for traffic phases in single vehicle data and empirical test of a microscopic three-phase traffic theory

International Nuclear Information System (INIS)

Kerner, Boris S; Klenov, Sergey L; Hiller, Andreas

2006-01-01

Based on empirical and numerical microscopic analyses, the physical nature of a qualitatively different behaviour of the wide moving jam phase in comparison with the synchronized flow phase-microscopic traffic flow interruption within the wide moving jam phase-is found. A microscopic criterion for distinguishing the synchronized flow and wide moving jam phases in single vehicle data measured at a single freeway location is presented. Based on this criterion, empirical microscopic classification of different local congested traffic states is performed. Simulations made show that the microscopic criterion and macroscopic spatiotemporal objective criteria lead to the same identification of the synchronized flow and wide moving jam phases in congested traffic. Microscopic models in the context of three-phase traffic theory have been tested based on the microscopic criterion for the phases in congested traffic. It is found that microscopic three-phase traffic models can explain both microscopic and macroscopic empirical congested pattern features. It is obtained that microscopic frequency distributions for vehicle speed difference as well as fundamental diagrams and speed correlation functions can depend on the spatial co-ordinate considerably. It turns out that microscopic optimal velocity (OV) functions and time headway distributions are not necessarily qualitatively different, even if local congested traffic states are qualitatively different. The reason for this is that important spatiotemporal features of congested traffic patterns are lost in these as well as in many other macroscopic and microscopic traffic characteristics, which are widely used as the empirical basis for a test of traffic flow models, specifically, cellular automata traffic flow models

Fresnel zone-plate based X-ray microscopy in Zernike phase contrast with sub-50 nm resolution at NSRL

International Nuclear Information System (INIS)

Chen Jie; Li Wenjie; Tian Jinping; Liu Longhua; Xiong Ying; Liu Gang; Wu Ziyu; Tian Yangchao; Liu Yijin; Yue Zhengbo; Yu Hanqing; Wang Chunru

2009-01-01

A transmission X-ray microscope using Fresnel zone-plates (FZPs) has been installed at U7A beamline of National Synchrotron Radiation Laboratory (NSRL). The objective FZP with 45 nm outermost zone width delivers a sub-50 nm resolution. A gold phase ring with 2.5 μm thickness and 4 μm width was placed at the focal plane of the objective FZP at 8 keV to produce a negative Zernike phase contrast. A series of samples were used to test the performance of the Zernike phase contrast X-ray microscopy.

Fresnel zone-plate based X-ray microscopy in Zernike phase contrast with sub-50 nm resolution at NSRL

Energy Technology Data Exchange (ETDEWEB)

Chen Jie; Li Wenjie; Tian Jinping; Liu Longhua; Xiong Ying; Liu Gang; Wu Ziyu; Tian Yangchao [National Synchrotron Radiation Laboratory (China); Liu Yijin [School of Physics (China); Yue Zhengbo; Yu Hanqing [Laboratory of Environmental Engineering, School of Chemistry, University of Science and Technology of China, Hefei Anhui 230029 (China); Wang Chunru, E-mail: ychtian@ustc.edu.c [Institute of Chemistry, Chinese Academy of Sciences, Beijing 10060 (China)

2009-09-01

A transmission X-ray microscope using Fresnel zone-plates (FZPs) has been installed at U7A beamline of National Synchrotron Radiation Laboratory (NSRL). The objective FZP with 45 nm outermost zone width delivers a sub-50 nm resolution. A gold phase ring with 2.5 {mu}m thickness and 4 {mu}m width was placed at the focal plane of the objective FZP at 8 keV to produce a negative Zernike phase contrast. A series of samples were used to test the performance of the Zernike phase contrast X-ray microscopy.

Benchtop phase-contrast X-ray imaging

Energy Technology Data Exchange (ETDEWEB)

Gundogdu, O. [Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)], E-mail: o.gundogdu@surrey.ac.uk; Nirgianaki, E.; Che Ismail, E.; Jenneson, P.M.; Bradley, D.A. [Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

2007-12-15

Clinical radiography has traditionally been based on contrast obtained from absorption when X-rays pass through the body. The contrast obtained from traditional radiography can be rather poor, particularly when it comes to soft tissue. A wide range of media of interest in materials science, biology and medicine exhibit very weak absorption contrast, but they nevertheless produce significant phase shifts with X-rays. The use of phase information for imaging purposes is therefore an attractive prospect. Some of the X-ray phase-contrast imaging methods require highly monochromatic plane wave radiation and sophisticated X-ray optics. However, the propagation-based phase-contrast imaging method adapted in this paper is a relatively simple method to implement, essentially requiring only a microfocal X-ray tube and electronic detection. In this paper, we present imaging results obtained from two different benchtop X-ray sources employing the free space propagation method. X-ray phase-contrast imaging provides higher contrast in many samples, including biological tissues that have negligible absorption contrast.

Transportable and vibration-free full-field low-coherent quantitative phase microscope

Science.gov (United States)

Yamauchi, Toyohiko; Yamada, Hidenao; Goto, Kentaro; Matsui, Hisayuki; Yasuhiko, Osamu; Ueda, Yukio

2018-02-01

We developed a transportable Linnik-type full-field low-coherent quantitative phase microscope that is able to compensate for optical path length (OPL) disturbance due to environmental mechanical noises. Though two-beam interferometers such as Linnik ones suffer from unstable OPL difference, we overcame this problem with a mechanical feedback system based on digital signal-processing that controls the OPL difference in sub-nanometer resolution precisely with a feedback bandwidth of 4 kHz. The developed setup has a footprint of 200 mm by 200 mm, a height of 500 mm, and a weight of 4.5 kilograms. In the transmission imaging mode, cells were cultured on a reflection-enhanced glass-bottom dish, and we obtained interference images sequentially while performing stepwise quarter-wavelength phase-shifting. Real-time image processing, including retrieval of the unwrapped phase from interference images and its background correction, along with the acquisition of interference images, was performed on a laptop computer. Emulation of the phase contrast (PhC) images and the differential interference contrast (DIC) images was also performed in real time. Moreover, our setup was applied for full-field cell membrane imaging in the reflection mode, where the cells were cultured on an anti-reflection (AR)-coated glass-bottom dish. The phase and intensity of the light reflected by the membrane revealed the outer shape of the cells independent of the refractive index. In this paper, we show imaging results on cultured cells in both transmission and reflection modes.

Compressive Phase Contrast Tomography

International Nuclear Information System (INIS)

Maia, Filipe; MacDowell, Alastair; Marchesini, Stefano; Padmore, Howard A.; Parkinson, Dula Y.; Pien, Jack; Schirotzek, Andre; Yang, Chao

2010-01-01

When x-rays penetrate soft matter, their phase changes more rapidly than their amplitude. Interference effects visible with high brightness sources creates higher contrast, edge enhanced images. When the object is piecewise smooth (made of big blocks of a few components), such higher contrast datasets have a sparse solution. We apply basis pursuit solvers to improve SNR, remove ring artifacts, reduce the number of views and radiation dose from phase contrast datasets collected at the Hard X-Ray Micro Tomography Beamline at the Advanced Light Source. We report a GPU code for the most computationally intensive task, the gridding and inverse gridding algorithm (non uniform sampled Fourier transform).

Application of differential interference contrast with inverted microscopes to the in vitro perfused nephron.

Science.gov (United States)

Horster, M; Gundlach, H

1979-12-01

The study of in vitro perfused individual nephron segments requires a microscope which provides: (1) easy access to the specimen for measurement of cellular solute flux and voltage; (2) an image with high resolution and contrast; (3) optical sectioning of the object at different levels; and (4) rapid recording of the morphological phenomena. This paper describes an example of commercially available apparatus meeting the above requirements, and illustrates its efficiency. The microscope is of the inverted type (Zeiss IM 35) equipped with differential-interference-contrast (DIC) with a long working distance, and an automatically controlled camera system. The microscopic image exhibits cellular and intercellular details in the unstained transporting mammalian nephron segments despite their tubular structure and great thickness and makes obvious function-structure correlations (e.g. cell volume changes); luminal and contraluminal cell borders are well resolved for controlled microelectrode impalement.

Phase-contrast X-ray CT

Energy Technology Data Exchange (ETDEWEB)

Momose, Atsushi [Hitachi Ltd., Saitama (Japan). Advanced Research Laboratory; Takeda, Tohoru; Itai, Yuji

1995-12-01

Phase-contrast X-ray computed tomography (CT) enabling the observation of biological soft tissues without contrast enhancement has been developed. The X-ray phase shift caused by an object is measured and input to a standard CT reconstruction algorithm. A thousand times increase in the image sensitivity to soft tissues is achieved compared with the conventional CT using absorption contrast. This is because the X-ray phase shift cross section of light elements is about a thousand times larger than the absorption cross section. The phase shift is detected using an X-ray interferometer and computer analyses of interference patterns. Experiments were performed using a synchrotron X-ray source. Excellent image sensitivity is demonstrated in the observation of cancerous rabbit liver. The CT images distinguish cancer lesion from normal liver tissue and, moreover, visualize the pathological condition in the lesion. Although the X-ray energy employed and the present observation area size are not suitable for medical applications as they are, phase-contrast X-ray CT is promising for investigating the internal structure of soft tissue which is almost transparent for X-rays. The high sensitivity also provides the advantage of reducing X-ray doses. (author).

Holography microscopy as an artifact-free alternative to phase-contrast.

Science.gov (United States)

Pastorek, Lukáš; Venit, Tomáš; Hozák, Pavel

2018-02-01

Artifact-free microscopic images represent a key requirement of multi-parametric image analysis in modern biomedical research. Holography microscopy (HM) is one of the quantitative phase imaging techniques, which has been finding new applications in life science, especially in morphological screening, cell migration, and cancer research. Rather than the classical imaging of absorbing (typically stained) specimens by bright-field microscopy, the information about the light-wave's phase shifts induced by the biological sample is employed for final image reconstruction. In this comparative study, we investigated the usability and the reported advantage of the holography imaging. The claimed halo-free imaging was analyzed compared to the widely used Zernike phase-contrast microscopy. The intensity and phase cross-membrane profiles at the periphery of the cell were quantified. The intensity profile for cells in the phase-contrast images suffers from the significant increase in intensity values around the cell border. On the contrary, no distorted profile is present outside the cell membrane in holography images. The gradual increase in phase shift values is present in the internal part of the cell body projection in holography image. This increase may be related to the increase in the cell internal material according to the dry mass theory. Our experimental data proved the halo-free nature of the holography imaging, which is an important prerequisite of the correct thresholding and cell segmentation, nowadays frequently required in high-content screening and other image-based analysis. Consequently, HM is a method of choice whenever the image analysis relies on the accurate data on cell boundaries.

Atomic force microscope image contrast mechanisms on supported lipid bilayers.

Science.gov (United States)

Schneider, J; Dufrêne, Y F; Barger, W R; Lee, G U

2000-08-01

This work presents a methodology to measure and quantitatively interpret force curves on supported lipid bilayers in water. We then use this method to correlate topographic imaging contrast in atomic force microscopy (AFM) images of phase-separated Langmuir-Blodgett bilayers with imaging load. Force curves collected on pure monolayers of both distearoylphosphatidylethanolamine (DSPE) and monogalactosylethanolamine (MGDG) and dioleoylethanolamine (DOPE) deposited at similar surface pressures onto a monolayer of DSPE show an abrupt breakthrough event at a repeatable, material-dependent force. The breakthrough force for DSPE and MGDG is sizable, whereas the breakthrough force for DOPE is too small to measure accurately. Contact-mode AFM images on 1:1 mixed monolayers of DSPE/DOPE and MGDG/DOPE have a high topographic contrast at loads between the breakthrough force of each phase, and a low topographic contrast at loads above the breakthrough force of both phases. Frictional contrast is inverted and magnified at loads above the breakthrough force of both phases. These results emphasize the important role that surface forces and mechanics can play in imaging multicomponent biomembranes with AFM.

3D widefield light microscope image reconstruction without dyes

Science.gov (United States)

Larkin, S.; Larson, J.; Holmes, C.; Vaicik, M.; Turturro, M.; Jurkevich, A.; Sinha, S.; Ezashi, T.; Papavasiliou, G.; Brey, E.; Holmes, T.

2015-03-01

3D image reconstruction using light microscope modalities without exogenous contrast agents is proposed and investigated as an approach to produce 3D images of biological samples for live imaging applications. Multimodality and multispectral imaging, used in concert with this 3D optical sectioning approach is also proposed as a way to further produce contrast that could be specific to components in the sample. The methods avoid usage of contrast agents. Contrast agents, such as fluorescent or absorbing dyes, can be toxic to cells or alter cell behavior. Current modes of producing 3D image sets from a light microscope, such as 3D deconvolution algorithms and confocal microscopy generally require contrast agents. Zernike phase contrast (ZPC), transmitted light brightfield (TLB), darkfield microscopy and others can produce contrast without dyes. Some of these modalities have not previously benefitted from 3D image reconstruction algorithms, however. The 3D image reconstruction algorithm is based on an underlying physical model of scattering potential, expressed as the sample's 3D absorption and phase quantities. The algorithm is based upon optimizing an objective function - the I-divergence - while solving for the 3D absorption and phase quantities. Unlike typical deconvolution algorithms, each microscope modality, such as ZPC or TLB, produces two output image sets instead of one. Contrast in the displayed image and 3D renderings is further enabled by treating the multispectral/multimodal data as a feature set in a mathematical formulation that uses the principal component method of statistics.

Remote laboratory for phase-aided 3D microscopic imaging and metrology

Science.gov (United States)

Wang, Meng; Yin, Yongkai; Liu, Zeyi; He, Wenqi; Li, Boqun; Peng, Xiang

2014-05-01

In this paper, the establishment of a remote laboratory for phase-aided 3D microscopic imaging and metrology is presented. Proposed remote laboratory consists of three major components, including the network-based infrastructure for remote control and data management, the identity verification scheme for user authentication and management, and the local experimental system for phase-aided 3D microscopic imaging and metrology. The virtual network computer (VNC) is introduced to remotely control the 3D microscopic imaging system. Data storage and management are handled through the open source project eSciDoc. Considering the security of remote laboratory, the fingerprint is used for authentication with an optical joint transform correlation (JTC) system. The phase-aided fringe projection 3D microscope (FP-3DM), which can be remotely controlled, is employed to achieve the 3D imaging and metrology of micro objects.

Microscopic origin of black hole reentrant phase transitions

Science.gov (United States)

Zangeneh, M. Kord; Dehyadegari, A.; Sheykhi, A.; Mann, R. B.

2018-04-01

Understanding the microscopic behavior of the black hole ingredients has been one of the important challenges in black hole physics during the past decades. In order to shed some light on the microscopic structure of black holes, in this paper, we explore a recently observed phenomenon for black holes namely reentrant phase transition, by employing the Ruppeiner geometry. Interestingly enough, we observe two properties for the phase behavior of small black holes that leads to reentrant phase transition. They are correlated and they are of the interaction type. For the range of pressure in which the system underlies reentrant phase transition, it transits from the large black holes phase to the small one which possesses higher correlation than the other ranges of pressures. On the other hand, the type of interaction between small black holes near the large/small transition line differs for usual and reentrant phase transitions. Indeed, for the usual case, the dominant interaction is repulsive whereas for the reentrant case we encounter an attractive interaction. We show that in the reentrant phase transition case, the small black holes behave like a bosonic gas whereas in the usual phase transition case, they behave like a quantum anyon gas.

Microscopy imaging and quantitative phase contrast mapping in turbid microfluidic channels by digital holography.

Science.gov (United States)

Paturzo, Melania; Finizio, Andrea; Memmolo, Pasquale; Puglisi, Roberto; Balduzzi, Donatella; Galli, Andrea; Ferraro, Pietro

2012-09-07

We show that sharp imaging and quantitative phase-contrast microcopy is possible in microfluidics in flowing turbid media by digital holography. In fact, in flowing liquids with suspended colloidal particles, clear vision is hindered and cannot be recovered by any other microscopic imaging technique. On the contrary, using digital holography, clear imaging is possible thanks to the Doppler frequency shift experienced by the photons scattered by the flowing colloidal particles, which do not contribute to the interference process, i.e. the recorded hologram. The method is illustrated and imaging results are demonstrated for pure phase objects, i.e. biological cells in microfluidic channels.

The application of phase contrast X-ray techniques for imaging Li-ion battery electrodes

Science.gov (United States)

Eastwood, D. S.; Bradley, R. S.; Tariq, F.; Cooper, S. J.; Taiwo, O. O.; Gelb, J.; Merkle, A.; Brett, D. J. L.; Brandon, N. P.; Withers, P. J.; Lee, P. D.; Shearing, P. R.

2014-04-01

In order to accelerate the commercialization of fuel cells and batteries across a range of applications, an understanding of the mechanisms by which they age and degrade at the microstructural level is required. Here, the most widely commercialized Li-ion batteries based on porous graphite based electrodes which de/intercalate Li+ ions during charge/discharge are studied by two phase contrast enhanced X-ray imaging modes, namely in-line phase contrast and Zernike phase contrast at the micro (synchrotron) and nano (laboratory X-ray microscope) level, respectively. The rate of charge cycling is directly dependent on the nature of the electrode microstructure, which are typically complex multi-scale 3D geometries with significant microstructural heterogeneities. We have been able to characterise the porosity and the tortuosity by micro-CT as well as the morphology of 5 individual graphite particles by nano-tomography finding that while their volume varied significantly their sphericity was surprisingly similar. The volume specific surface areas of the individual grains measured by nano-CT are significantly larger than the total volume specific surface area of the electrode from the micro-CT imaging, which can be attributed to the greater particle surface area visible at higher resolution.

The application of phase contrast X-ray techniques for imaging Li-ion battery electrodes

International Nuclear Information System (INIS)

Eastwood, D.S.; Bradley, R.S.; Tariq, F.; Cooper, S.J.; Taiwo, O.O.; Gelb, J.; Merkle, A.; Brett, D.J.L.; Brandon, N.P.; Withers, P.J.; Lee, P.D.; Shearing, P.R.

2014-01-01

In order to accelerate the commercialization of fuel cells and batteries across a range of applications, an understanding of the mechanisms by which they age and degrade at the microstructural level is required. Here, the most widely commercialized Li-ion batteries based on porous graphite based electrodes which de/intercalate Li + ions during charge/discharge are studied by two phase contrast enhanced X-ray imaging modes, namely in-line phase contrast and Zernike phase contrast at the micro (synchrotron) and nano (laboratory X-ray microscope) level, respectively. The rate of charge cycling is directly dependent on the nature of the electrode microstructure, which are typically complex multi-scale 3D geometries with significant microstructural heterogeneities. We have been able to characterise the porosity and the tortuosity by micro-CT as well as the morphology of 5 individual graphite particles by nano-tomography finding that while their volume varied significantly their sphericity was surprisingly similar. The volume specific surface areas of the individual grains measured by nano-CT are significantly larger than the total volume specific surface area of the electrode from the micro-CT imaging, which can be attributed to the greater particle surface area visible at higher resolution

Dual focal-spot imaging for phase extraction in phase-contrast radiography

International Nuclear Information System (INIS)

Donnelly, Edwin F.; Price, Ronald R.; Pickens, David R.

2003-01-01

The purpose of this study was to evaluate dual focal spot imaging as a method for extracting the phase component from a phase-contrast radiography image. All measurements were performed using a microfocus tungsten-target x-ray tube with an adjustable focal-spot size (0.01 mm to 0.045 mm). For each object, high-resolution digital radiographs were obtained with two different focal spot sizes to produce matched image pairs in which all other geometric variables as well as total exposure and tube kVp were held constant. For each image pair, a phase extraction was performed using pixel-wise division. The phase-extracted image resulted in an image similar to the standard image processing tool commonly referred to as 'unsharp masking' but with the additional edge-enhancement produced by phase-contrast effects. The phase-extracted image illustrates the differences between the two images whose imaging parameters differ only in focal spot size. The resulting image shows effects from both phase contrast as well as geometric unsharpness. In weakly attenuating materials the phase-contrast effect predominates, while in strongly attenuating materials the phase effects are so small that they are not detectable. The phase-extracted image in the strongly attenuating object reflects differences in geometric unsharpness. The degree of phase extraction depends strongly on the size of the smallest focal spot used. This technique of dual-focal spot phase-contrast radiography provides a simple technique for phase-component (edge) extraction in phase-contrast radiography. In strongly attenuating materials the phase-component is overwhelmed by differences in geometric unsharpness. In these cases the technique provides a form of unsharp masking which also accentuates the edges. Thus, the two effects are complimentary and may be useful in the detection of small objects

Application of phase contrast imaging to mammography

International Nuclear Information System (INIS)

Tohyama, Keiko; Yamada, Katsuhiko; Katafuchi, Tetsuro; Matsuo, Satoru; Morishita, Junji

2005-01-01

Phase contrast images were obtained experimentally by using a customized mammography unit with a nominal focal spot size of 100 μm and variable source-to-image distances of up to 1.5 m. The purpose of this study was to examine the applicability and potential usefulness of phase contrast imaging for mammography. A mammography phantom (ACR156 RMI phantom) was imaged, and its visibility was examined. The optical density of the phantom images was adjusted to approximately 1.3 for both the contact and phase contrast images. Forty-one observers (18 medical doctors and 23 radiological technologists) participated in visual evaluation of the images. Results showed that, in comparison with the images of contact mammography, the phantom images of phase contrast imaging demonstrated statistically significantly superior visibility for fibers, clustered micro-calcifications, and masses. Therefore, phase contrast imaging obtained by using the customized mammography unit would be useful for improving diagnostic accuracy in mammography. (author)

Contrast-to-noise ratio optimization for a prototype phase-contrast computed tomography scanner

International Nuclear Information System (INIS)

Müller, Mark; Yaroshenko, Andre; Velroyen, Astrid; Tapfer, Arne; Bech, Martin; Pauwels, Bart; Bruyndonckx, Peter; Sasov, Alexander; Pfeiffer, Franz

2015-01-01

In the field of biomedical X-ray imaging, novel techniques, such as phase-contrast and dark-field imaging, have the potential to enhance the contrast and provide complementary structural information about a specimen. In this paper, a first prototype of a preclinical X-ray phase-contrast CT scanner based on a Talbot-Lau interferometer is characterized. We present a study of the contrast-to-noise ratios for attenuation and phase-contrast images acquired with the prototype scanner. The shown results are based on a series of projection images and tomographic data sets of a plastic phantom in phase and attenuation-contrast recorded with varying acquisition settings. Subsequently, the signal and noise distribution of different regions in the phantom were determined. We present a novel method for estimation of contrast-to-noise ratios for projection images based on the cylindrical geometry of the phantom. Analytical functions, representing the expected signal in phase and attenuation-contrast for a circular object, are fitted to individual line profiles of the projection data. The free parameter of the fit function is used to estimate the contrast and the goodness of the fit is determined to assess the noise in the respective signal. The results depict the dependence of the contrast-to-noise ratios on the applied source voltages, the number of steps of the phase stepping routine, and the exposure times for an individual step. Moreover, the influence of the number of projection angles on the image quality of CT slices is investigated. Finally, the implications for future imaging purposes with the scanner are discussed

Biological applications of phase-contrast electron microscopy.

Science.gov (United States)

Nagayama, Kuniaki

2014-01-01

Here, I review the principles and applications of phase-contrast electron microscopy using phase plates. First, I develop the principle of phase contrast based on a minimal model of microscopy, introducing a double Fourier-transform process to mathematically formulate the image formation. Next, I explain four phase-contrast (PC) schemes, defocus PC, Zernike PC, Hilbert differential contrast, and schlieren optics, as image-filtering processes in the context of the minimal model, with particular emphases on the Zernike PC and corresponding Zernike phase plates. Finally, I review applications of Zernike PC cryo-electron microscopy to biological systems such as protein molecules, virus particles, and cells, including single-particle analysis to delineate three-dimensional (3D) structures of protein and virus particles and cryo-electron tomography to reconstruct 3D images of complex protein systems and cells.

Phase Contrast Imaging

DEFF Research Database (Denmark)

1996-01-01

The invention relates to a method and a system for synthesizing a prescribed intensity pattern based on phase contrast imaging that is not based on the assumption of prior art methods that the pahase shift phi is less than 1 radian. An improved method based on a simple imaging operation...... phasors attain predetermined values for predetermined spatial frequencies, and the phasor value of the specific resolution element of the spatial phase mask corresponds to a distinct intensity level of the image of the resolution element in the intensity pattern, and a spatial phase filter for phase...... shifting of a part of the electromagntic radiation, in combination with an imaging system for generation of the intensity pattern by interference in the image plane of the imaging system between the part of the electromagnetic raidation that has been phase shifted by the phase filter and the remaining part...

X-ray phase-contrast imaging

Science.gov (United States)

Endrizzi, Marco

2018-01-01

X-ray imaging is a standard tool for the non-destructive inspection of the internal structure of samples. It finds application in a vast diversity of fields: medicine, biology, many engineering disciplines, palaeontology and earth sciences are just few examples. The fundamental principle underpinning the image formation have remained the same for over a century: the X-rays traversing the sample are subjected to different amount of absorption in different parts of the sample. By means of phase-sensitive techniques it is possible to generate contrast also in relation to the phase shifts imparted by the sample and to extend the capabilities of X-ray imaging to those details that lack enough absorption contrast to be visualised in conventional radiography. A general overview of X-ray phase contrast imaging techniques is presented in this review, along with more recent advances in this fast evolving field and some examples of applications.

Reducing charging effects in scanning electron microscope images by Rayleigh contrast stretching method (RCS).

Science.gov (United States)

Wan Ismail, W Z; Sim, K S; Tso, C P; Ting, H Y

2011-01-01

To reduce undesirable charging effects in scanning electron microscope images, Rayleigh contrast stretching is developed and employed. First, re-scaling is performed on the input image histograms with Rayleigh algorithm. Then, contrast stretching or contrast adjustment is implemented to improve the images while reducing the contrast charging artifacts. This technique has been compared to some existing histogram equalization (HE) extension techniques: recursive sub-image HE, contrast stretching dynamic HE, multipeak HE and recursive mean separate HE. Other post processing methods, such as wavelet approach, spatial filtering, and exponential contrast stretching, are compared as well. Overall, the proposed method produces better image compensation in reducing charging artifacts. Copyright © 2011 Wiley Periodicals, Inc.

The application of phase contrast X-ray techniques for imaging Li-ion battery electrodes

Energy Technology Data Exchange (ETDEWEB)

Eastwood, D.S. [Manchester X-ray Imaging Facility, School of Materials, University of Manchester, Manchester M13 9PL (United Kingdom); Research Complex at Harwell, Didcot, Oxon OX11 0FA (United Kingdom); Bradley, R.S. [Manchester X-ray Imaging Facility, School of Materials, University of Manchester, Manchester M13 9PL (United Kingdom); Tariq, F.; Cooper, S.J. [Dept. Earth Science and Engineering, Imperial College London, London SW7 2AZ (United Kingdom); Taiwo, O.O. [Dept. Chemical Engineering, University College London, London WC1E 7JE (United Kingdom); Gelb, J.; Merkle, A. [Carl Zeiss X-ray Microscopy Inc., Pleasanton, CA 94588 (United States); Brett, D.J.L. [Dept. Chemical Engineering, University College London, London WC1E 7JE (United Kingdom); Brandon, N.P. [Dept. Earth Science and Engineering, Imperial College London, London SW7 2AZ (United Kingdom); Withers, P.J.; Lee, P.D. [Manchester X-ray Imaging Facility, School of Materials, University of Manchester, Manchester M13 9PL (United Kingdom); Research Complex at Harwell, Didcot, Oxon OX11 0FA (United Kingdom); Shearing, P.R., E-mail: p.shearing@ucl.ac.uk [Dept. Chemical Engineering, University College London, London WC1E 7JE (United Kingdom)

2014-04-01

In order to accelerate the commercialization of fuel cells and batteries across a range of applications, an understanding of the mechanisms by which they age and degrade at the microstructural level is required. Here, the most widely commercialized Li-ion batteries based on porous graphite based electrodes which de/intercalate Li{sup +} ions during charge/discharge are studied by two phase contrast enhanced X-ray imaging modes, namely in-line phase contrast and Zernike phase contrast at the micro (synchrotron) and nano (laboratory X-ray microscope) level, respectively. The rate of charge cycling is directly dependent on the nature of the electrode microstructure, which are typically complex multi-scale 3D geometries with significant microstructural heterogeneities. We have been able to characterise the porosity and the tortuosity by micro-CT as well as the morphology of 5 individual graphite particles by nano-tomography finding that while their volume varied significantly their sphericity was surprisingly similar. The volume specific surface areas of the individual grains measured by nano-CT are significantly larger than the total volume specific surface area of the electrode from the micro-CT imaging, which can be attributed to the greater particle surface area visible at higher resolution.

The structure of dodecagonal (Ta,V){sub 1.6}Te imaged by phase-contrast scanning transmission electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Krumeich, F., E-mail: krumeich@inorg.chem.ethz.ch [Laboratory of Inorganic Chemistry, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Mueller, E.; Wepf, R.A. [Electron Microscopy ETH Zurich (EMEZ), Wolfgang-Pauli-Strasse 16, 8093 Zurich (Switzerland); Conrad, M.; Reich, C.; Harbrecht, B. [Department of Chemistry and Centre of Materials Science, Philipps-Universitaet, Hans-Meerwein-Strasse, 35032 Marburg (Germany); Nesper, R. [Laboratory of Inorganic Chemistry, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland)

2012-10-15

While HRTEM is the well-established method to characterize the structure of dodecagonal tantalum (vanadium) telluride quasicrystals and their periodic approximants, phase-contrast imaging performed on an aberration-corrected scanning transmission electron microscope (STEM) represents a favorable alternative. The (Ta,V){sub 151}Te{sub 74} clusters, the basic structural unit in all these phases, can be visualized with high resolution. A dependence of the image contrast on defocus and specimen thickness has been observed. In thin areas, the projected crystal potential is basically imaged with either dark or bright contrast at two defocus values close to Scherzer defocus as confirmed by image simulations utilizing the principle of reciprocity. Models for square-triangle tilings describing the arrangement of the basic clusters can be derived from such images. - Graphical abstract: PC-STEM image of a (Ta,V){sub 151}Te{sub 74} cluster. Highlights: Black-Right-Pointing-Pointer C{sub s}-corrected STEM is applied for the characterization of dodecagonal quasicrystals. Black-Right-Pointing-Pointer The projected potential of the structure is mirrored in the images. Black-Right-Pointing-Pointer Phase-contrast STEM imaging depends on defocus and thickness. Black-Right-Pointing-Pointer For simulations of phase-contrast STEM images, the reciprocity theorem is applicable.

Laser projection using generalized phase contrast

DEFF Research Database (Denmark)

Glückstad, Jesper; Palima, Darwin; Rodrigo, Peter John

2007-01-01

is introduced. An arbitrary phase shift filter eliminates the need for high-frequency modulation and conjugate phase encoding. This lowers device performance requirements and allows practical implementation with currently available dynamic spatial light modulators. (c) 2007 Optical Society of America.......We demonstrate experimental laser projection of a gray-level photographic image with 74% light efficiency using the generalized phase contrast (GPC) method. In contrast with a previously proposed technique [Alonzo et al., New J. Phys. 9, 132 (2007)], a new approach to image construction via GPC...

Phase contrast STEM for thin samples: Integrated differential phase contrast.

Science.gov (United States)

Lazić, Ivan; Bosch, Eric G T; Lazar, Sorin

2016-01-01

It has been known since the 1970s that the movement of the center of mass (COM) of a convergent beam electron diffraction (CBED) pattern is linearly related to the (projected) electrical field in the sample. We re-derive a contrast transfer function (CTF) for a scanning transmission electron microscopy (STEM) imaging technique based on this movement from the point of view of image formation and continue by performing a two-dimensional integration on the two images based on the two components of the COM movement. The resulting integrated COM (iCOM) STEM technique yields a scalar image that is linear in the phase shift caused by the sample and therefore also in the local (projected) electrostatic potential field of a thin sample. We confirm that the differential phase contrast (DPC) STEM technique using a segmented detector with 4 quadrants (4Q) yields a good approximation for the COM movement. Performing a two-dimensional integration, just as for the COM, we obtain an integrated DPC (iDPC) image which is approximately linear in the phase of the sample. Beside deriving the CTFs of iCOM and iDPC, we clearly point out the objects of the two corresponding imaging techniques, and highlight the differences to objects corresponding to COM-, DPC-, and (HA) ADF-STEM. The theory is validated with simulations and we present first experimental results of the iDPC-STEM technique showing its capability for imaging both light and heavy elements with atomic resolution and a good signal to noise ratio (SNR). Copyright © 2015 Elsevier B.V. All rights reserved.

X-ray Phase Contrast analysis - Digital wavefront development

International Nuclear Information System (INIS)

Idir, Mourad; Potier, Jonathan; Fricker, Sebastien; Snigirev, Anatoly; Snigireva, Irina; Modi, M. H.

2010-01-01

Optical schemes that enable imaging of the phase shift produced by an object have become popular in the x-ray region, where phase can be the dominant contrast mechanism. The propagation-based technique consists of recording the interference pattern produced by choosing one or several sample-to-detector distances. Pioneering studies, carried out making use of synchrotron radiation, demonstrated that this technique results in a dramatic increase of image contrast and detail visibility, allowing the detection of structures invisible with conventional techniques. An experimental and theoretical study of in-line hard x-ray phase-contrast imaging had been performed. The theoretical description of the technique is based on Fresnel diffraction. As an illustration of the potential of this quantitative imaging technique, high-resolution x-ray phase contrast images of simple objects will be presented.

Absorption and Phase Contrast X-Ray Imaging in Paleontology Using Laboratory and Synchrotron Sources

Energy Technology Data Exchange (ETDEWEB)

Bidola, Pidassa; Stockmar, Marco; Achterhold, Klaus; Pfeiffer, Franz; Pacheco, Mirian L.A.F.; Soriano, Carmen; Beckmann, Felix; Herzen, Julia

2015-10-01

X-ray micro-computed tomography (CT) is commonly used for imaging of samples in biomedical or materials science research. Owing to the ability to visualize a sample in a nondestructive way, X-ray CT is perfectly suited to inspect fossilized specimens, which are mostly unique or rare. In certain regions of the world where important sedimentation events occurred in the Precambrian geological time, several fossilized animals are studied to understand questions related to their origin, environment, and life evolution. This article demonstrates the advantages of applying absorption and phase-contrast CT on the enigmatic fossil Corumbella werneri, one of the oldest known animals capable of building hard parts, originally discovered in Corumba (Brazil). Different tomographic setups were tested to visualize the fossilized inner structures: a commercial laboratory-based CT device, two synchrotron-based imaging setups using conventional absorption and propagation-based phase contrast, and a commercial X-ray microscope with a lens-coupled detector system, dedicated for radiography and tomography. Based on our results we discuss the strengths and weaknesses of the different imaging setups for paleontological studies.

Isotropic differential phase contrast microscopy for quantitative phase bio-imaging.

Science.gov (United States)

Chen, Hsi-Hsun; Lin, Yu-Zi; Luo, Yuan

2018-05-16

Quantitative phase imaging (QPI) has been investigated to retrieve optical phase information of an object and applied to biological microscopy and related medical studies. In recent examples, differential phase contrast (DPC) microscopy can recover phase image of thin sample under multi-axis intensity measurements in wide-field scheme. Unlike conventional DPC, based on theoretical approach under partially coherent condition, we propose a new method to achieve isotropic differential phase contrast (iDPC) with high accuracy and stability for phase recovery in simple and high-speed fashion. The iDPC is simply implemented with a partially coherent microscopy and a programmable thin-film transistor (TFT) shield to digitally modulate structured illumination patterns for QPI. In this article, simulation results show consistency of our theoretical approach for iDPC under partial coherence. In addition, we further demonstrate experiments of quantitative phase images of a standard micro-lens array, as well as label-free live human cell samples. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phase retrieval for X-ray in-line phase contrast imaging

International Nuclear Information System (INIS)

Scattarella, F.; Bellotti, R.; Tangaro, S.; Gargano, G.; Giannini, C.

2011-01-01

A review article about phase retrieval problem in X-ray phase contrast imaging is presented. A simple theoretical framework of Fresnel diffraction imaging by X-rays is introduced. A review of the most important methods for phase retrieval in free-propagation-based X-ray imaging and a new method developed by our collaboration are shown. The proposed algorithm, Combined Mixed Approach (CMA) is based on a mixed transfer function and transport of intensity approach, and it requires at most an initial approximate estimate of the average phase shift introduced by the object as prior knowledge. The accuracy with which this initial estimate is known determines the convenience speed of algorithm. The new proposed algorithm is based on the retrieval of both the object phase and its complex conjugate. The results obtained by the algorithm on simulated data have shown that the obtained reconstructed phase maps are characterized by particularly low normalized mean square errors. The algorithm was also tested on noisy experimental phase contrast data, showing a good efficiency in recovering phase information and enhancing the visibility of details inside soft tissues.

Bi-directional x-ray phase-contrast mammography.

Directory of Open Access Journals (Sweden)

Kai Scherer

Full Text Available Phase-contrast x-ray imaging is a promising improvement of conventional absorption-based mammography for early tumor detection. This potential has been demonstrated recently, utilizing structured gratings to obtain differential phase and dark-field scattering images. However, the inherently anisotropic imaging sensitivity of the proposed mono-directional approach yields only insufficient diagnostic information, and has low diagnostic sensitivity to highly oriented structures. To overcome these limitations, we present a two-directional x-ray phase-contrast mammography approach and demonstrate its advantages by applying it to a freshly dissected, cancerous mastectomy breast specimen. We illustrate that the two-directional scanning procedure overcomes the insufficient diagnostic value of a single scan, and reliably detects tumor structures, independently from their orientation within the breast. Our results indicate the indispensable diagnostic necessity and benefit of a multi-directional approach for x-ray phase-contrast mammography.

Contrast and resolution enhancement of a near-field optical microscope by using a modulation technique

International Nuclear Information System (INIS)

Flaxer, Eli; Palachi, Eldad

2005-01-01

A new design of a tunneling near-field optical microscope (TNOM) combined with an atomic force microscope (AFM) is presented. This design can be used to generate three different images of the sample's surface: a non-contact (tapping mode) AFM image, a conventional TNOM and an image of a modulation signal of the conventional TNOM, which we call AC-TNOM. The images are obtained simultaneously, using a single light source. It is shown that the AC-TNOM has better resolution (∼200 A) and contrast compared to conventional TNOM (∼400 A)

Digital phase-shifting atomic force microscope Moire method

International Nuclear Information System (INIS)

Liu Chiaming; Chen Lienwen

2005-01-01

In this study, the digital atomic force microscope (AFM) Moire method with phase-shifting technology is established to measure the in-plane displacement and strain fields. The Moire pattern is generated by the interference between the specimen grating and the virtual reference grating formed by digital image processes. The overlapped image is filtered by two-dimensional wavelet transformation to obtain the clear interference Moire patterns. The four-step phase-shifting method is realized by translating the phase of the virtual reference grating from 0 to 2π. The principle of the digital AFM Moire method and the phase-shifting technology are described in detail. Experimental results show that this method is convenient to use and efficient in realizing the microscale measurement

Hard x-ray phase contrastmicroscopy - techniques and applications

Science.gov (United States)

Holzner, Christian

In 1918, Einstein provided the first description of the nature of the refractive index for X-rays, showing that phase contrast effects are significant. A century later, most x-ray microscopy and nearly all medical imaging remains based on absorption contrast, even though phase contrast offers orders of magnitude improvements in contrast and reduced radiation exposure at multi-keV x-ray energies. The work presented is concerned with developing practical and quantitative methods of phase contrast for x-ray microscopy. A theoretical framework for imaging in phase contrast is put forward; this is used to obtain quantitative images in a scanning microscope using a segmented detector, and to correct for artifacts in a commercial phase contrast x-ray nano-tomography system. The principle of reciprocity between scanning and full-field microscopes is then used to arrive at a novel solution: Zernike contrast in a scanning microscope. These approaches are compared on a theoretical and experimental basis in direct connection with applications using multi-keV x-ray microscopes at the Advanced Photon Source at Argonne National Laboratory. Phase contrast provides the best means to image mass and ultrastructure of light elements that mainly constitute biological matter, while stimulated x-ray fluorescence provides high sensitivity for studies of the distribution of heavier trace elements, such as metals. These approaches are combined in a complementary way to yield quantitative maps of elemental concentration from 2D images, with elements placed in their ultrastructural context. The combination of x-ray fluorescence and phase contrast poses an ideal match for routine, high resolution tomographic imaging of biological samples in the future. The presented techniques and demonstration experiments will help pave the way for this development.

Spectro-refractometry of individual microscopic objects using swept-source quantitative phase imaging.

Science.gov (United States)

Jung, Jae-Hwang; Jang, Jaeduck; Park, Yongkeun

2013-11-05

We present a novel spectroscopic quantitative phase imaging technique with a wavelength swept-source, referred to as swept-source diffraction phase microscopy (ssDPM), for quantifying the optical dispersion of microscopic individual samples. Employing the swept-source and the principle of common-path interferometry, ssDPM measures the multispectral full-field quantitative phase imaging and spectroscopic microrefractometry of transparent microscopic samples in the visible spectrum with a wavelength range of 450-750 nm and a spectral resolution of less than 8 nm. With unprecedented precision and sensitivity, we demonstrate the quantitative spectroscopic microrefractometry of individual polystyrene beads, 30% bovine serum albumin solution, and healthy human red blood cells.

Phase-contrast tomographic imaging using an X-ray interferometer

Energy Technology Data Exchange (ETDEWEB)

Momose, A. [Hitachi Ltd, Advanced Research Lab., Saitama (Japan); Takeda, T.; Itai, Y. [Univ. of Tsukuba, Inst. of Clinical Medicine, Ibaraki (Japan); Yoneyama, A. [Hitachi Ltd, Central Resarch Lab., Tokyo (Japan); Hirano, K. [High Energy Accelerator Research Organization, Inst. of Materials Structure Science, Ibaraki (Japan)

1998-05-01

Apparatus for phase-contrast X-ray computed tomography using a monolithic X-ray interferometer is presented with some observational results for human breast tissues. Structures characteristic of the tissues were revealed in the phase-contrast tomograms. The procedure of image analysis consists of phase retrieval from X-ray interference patterns and tomographic image reconstruction from the retrieved phase shift. Next, feasibility of phase-contrast imaging using a two-crystal X-ray interferometer was studied aiming at in vivo observation in the future. In a preliminary study, the two-crystal X-ray interferometer was capable of generating fringes of 70% visibility using synchrotron X-rays. 35 refs.

Phase-contrast tomographic imaging using an X-ray interferometer

International Nuclear Information System (INIS)

Momose, A.; Takeda, T.; Itai, Y.; Yoneyama, A.; Hirano, K.

1998-01-01

Apparatus for phase-contrast X-ray computed tomography using a monolithic X-ray interferometer is presented with some observational results for human breast tissues. Structures characteristic of the tissues were revealed in the phase-contrast tomograms. The procedure of image analysis consists of phase retrieval from X-ray interference patterns and tomographic image reconstruction from the retrieved phase shift. Next, feasibility of phase-contrast imaging using a two-crystal X-ray interferometer was studied aiming at in vivo observation in the future. In a preliminary study, the two-crystal X-ray interferometer was capable of generating fringes of 70% visibility using synchrotron X-rays

Spline based iterative phase retrieval algorithm for X-ray differential phase contrast radiography.

Science.gov (United States)

Nilchian, Masih; Wang, Zhentian; Thuering, Thomas; Unser, Michael; Stampanoni, Marco

2015-04-20

Differential phase contrast imaging using grating interferometer is a promising alternative to conventional X-ray radiographic methods. It provides the absorption, differential phase and scattering information of the underlying sample simultaneously. Phase retrieval from the differential phase signal is an essential problem for quantitative analysis in medical imaging. In this paper, we formalize the phase retrieval as a regularized inverse problem, and propose a novel discretization scheme for the derivative operator based on B-spline calculus. The inverse problem is then solved by a constrained regularized weighted-norm algorithm (CRWN) which adopts the properties of B-spline and ensures a fast implementation. The method is evaluated with a tomographic dataset and differential phase contrast mammography data. We demonstrate that the proposed method is able to produce phase image with enhanced and higher soft tissue contrast compared to conventional absorption-based approach, which can potentially provide useful information to mammographic investigations.

Investigations on microstructure of Chinese traditional medicine using phase-contrast imaging with microfocus X-ray tube

International Nuclear Information System (INIS)

Wei Xun; Chinese Academy of Sciences, Beijing; Xiao Tiqiao; Chen Min; Liu Lixiang; Luo Yuyu; Du Guohao; Xu Hongjie

2005-01-01

The microscopic morphology of plant cells and their ergastic substances is an important standard for the identification of Chinese traditional medicine. The authors have developed a new method, X-ray phase-contrast imaging (XPCI) based on the microfocus X-ray tube, to explore microstructures of Chinese herbal medicine. The results indicate that XPCI is capable of distinguishing the structures commonly used in the identification. Non-destructive detection and high sensibility are counted among the major advantages of XPCI. The possibility of future applications of XPCI in the field of medicine identification is discussed. (authors)

A hybrid scanning force and light microscope for surface imaging and three-dimensional optical sectioning in differential interference contrast.

Science.gov (United States)

Stemmer, A

1995-04-01

The design of a scanned-cantilever-type force microscope is presented which is fully integrated into an inverted high-resolution video-enhanced light microscope. This set-up allows us to acquire thin optical sections in differential interference contrast (DIC) or polarization while the force microscope is in place. Such a hybrid microscope provides a unique platform to study how cell surface properties determine, or are affected by, the three-dimensional dynamic organization inside the living cell. The hybrid microscope presented in this paper has proven reliable and versatile for biological applications. It is the only instrument that can image a specimen by force microscopy and high-power DIC without having either to translate the specimen or to remove the force microscope. Adaptation of the design features could greatly enhance the suitability of other force microscopes for biological work.

Phase Contrast Imaging

International Nuclear Information System (INIS)

Menk, Ralf Hendrik

2008-01-01

All standard (medical) x-ray imaging technologies, rely primarily on the amplitude properties of the incident radiation, and do not depend on its phase. This is unchanged since the discovery by Roentgen that the intensity of an x-ray beam, as measured by the exposure on a film, was related to the relative transmission properties of an object. However, recently various imaging techniques have emerged which depend on the phase of the x-rays as well as the amplitude. Phase becomes important when the beam is coherent and the imaging system is sensitive to interference phenomena. Significant new advances have been made in coherent optic theory and techniques, which now promise phase information in medical imaging. The development of perfect crystal optics and the increasing availability of synchrotron radiation facilities have contributed to a significant increase in the application of phase based imaging in materials and life sciences. Unique source characteristics such as high intensity, monochromaticity, coherence and high collimating provide an ideal source for advanced imaging. Phase contrast imaging has been applied in both projection and computed tomography modes, and recent applications have been made in the field of medical imaging. Due to the underlying principle of X-ray detection conventional image receptors register only intensities of wave fields and not their phases. During the last decade basically five different methods were developed that translate the phase information into intensity variations. These methods are based on measuring the phase shift φ directly (using interference phenomena), the gradient ∇ φ , or the Laplacian ∇ 2 φ. All three methods can be applied to polychromatic X-ray sources keeping in mind that the native source is synchrotron radiation, featuring monochromatic and reasonable coherent X-ray beams. Due to the vast difference in the coefficients that are driven absorption and phase effects (factor 1,000-10,000 in the energy

Phase contrast STEM for thin samples: Integrated differential phase contrast

International Nuclear Information System (INIS)

Lazić, Ivan; Bosch, Eric G.T.; Lazar, Sorin

2016-01-01

It has been known since the 1970s that the movement of the center of mass (COM) of a convergent beam electron diffraction (CBED) pattern is linearly related to the (projected) electrical field in the sample. We re-derive a contrast transfer function (CTF) for a scanning transmission electron microscopy (STEM) imaging technique based on this movement from the point of view of image formation and continue by performing a two-dimensional integration on the two images based on the two components of the COM movement. The resulting integrated COM (iCOM) STEM technique yields a scalar image that is linear in the phase shift caused by the sample and therefore also in the local (projected) electrostatic potential field of a thin sample. We confirm that the differential phase contrast (DPC) STEM technique using a segmented detector with 4 quadrants (4Q) yields a good approximation for the COM movement. Performing a two-dimensional integration, just as for the COM, we obtain an integrated DPC (iDPC) image which is approximately linear in the phase of the sample. Beside deriving the CTFs of iCOM and iDPC, we clearly point out the objects of the two corresponding imaging techniques, and highlight the differences to objects corresponding to COM-, DPC-, and (HA) ADF-STEM. The theory is validated with simulations and we present first experimental results of the iDPC-STEM technique showing its capability for imaging both light and heavy elements with atomic resolution and a good signal to noise ratio (SNR). - Highlights: • First DPC-based atomic resolution images of potential and charge density are obtained. • This is enabled by integration and differentiation of 2D DPC signals, respectively. • Integrated DPC (iDPC) based on 4 quadrant imaging is compared to iCOM imaging. • Noise analysis and comparison with standard STEM imaging modes is provided. • iDPC allows direct imaging of light (C, N, O …) and heavy (Ga, Au …) atoms together.

Phase contrast STEM for thin samples: Integrated differential phase contrast

Energy Technology Data Exchange (ETDEWEB)

Lazić, Ivan, E-mail: ivan.lazic@fei.com; Bosch, Eric G.T.; Lazar, Sorin

2016-01-15

It has been known since the 1970s that the movement of the center of mass (COM) of a convergent beam electron diffraction (CBED) pattern is linearly related to the (projected) electrical field in the sample. We re-derive a contrast transfer function (CTF) for a scanning transmission electron microscopy (STEM) imaging technique based on this movement from the point of view of image formation and continue by performing a two-dimensional integration on the two images based on the two components of the COM movement. The resulting integrated COM (iCOM) STEM technique yields a scalar image that is linear in the phase shift caused by the sample and therefore also in the local (projected) electrostatic potential field of a thin sample. We confirm that the differential phase contrast (DPC) STEM technique using a segmented detector with 4 quadrants (4Q) yields a good approximation for the COM movement. Performing a two-dimensional integration, just as for the COM, we obtain an integrated DPC (iDPC) image which is approximately linear in the phase of the sample. Beside deriving the CTFs of iCOM and iDPC, we clearly point out the objects of the two corresponding imaging techniques, and highlight the differences to objects corresponding to COM-, DPC-, and (HA) ADF-STEM. The theory is validated with simulations and we present first experimental results of the iDPC-STEM technique showing its capability for imaging both light and heavy elements with atomic resolution and a good signal to noise ratio (SNR). - Highlights: • First DPC-based atomic resolution images of potential and charge density are obtained. • This is enabled by integration and differentiation of 2D DPC signals, respectively. • Integrated DPC (iDPC) based on 4 quadrant imaging is compared to iCOM imaging. • Noise analysis and comparison with standard STEM imaging modes is provided. • iDPC allows direct imaging of light (C, N, O …) and heavy (Ga, Au …) atoms together.

Microbubbles as contrast agent for in-line x-ray phase-contrast imaging

International Nuclear Information System (INIS)

Xi Yan; Zhao Jun; Tang Rongbiao; Wang Yujie

2011-01-01

In the present study, we investigated the potential of gas-filled microbubbles as contrast agents for in-line x-ray phase-contrast imaging (PCI) in biomedical applications. When imaging parameters are optimized, the microbubbles function as microlenses that focus the incoming x-rays to form bright spots, which can significantly enhance the image contrast. Since microbubbles have been shown to be safe contrast agents in clinical ultrasonography, this contrast-enhancement procedure for PCI may have promising utility in biomedical applications, especially when the dose of radiation is a serious concern. In this study, we performed both numerical simulations and ex vivo experiments to investigate the formation of the contrast and the effectiveness of microbubbles as contrast agents in PCI.

Quantum coherent optical phase modulation in an ultrafast transmission electron microscope.

Science.gov (United States)

Feist, Armin; Echternkamp, Katharina E; Schauss, Jakob; Yalunin, Sergey V; Schäfer, Sascha; Ropers, Claus

2015-05-14

Coherent manipulation of quantum systems with light is expected to be a cornerstone of future information and communication technology, including quantum computation and cryptography. The transfer of an optical phase onto a quantum wavefunction is a defining aspect of coherent interactions and forms the basis of quantum state preparation, synchronization and metrology. Light-phase-modulated electron states near atoms and molecules are essential for the techniques of attosecond science, including the generation of extreme-ultraviolet pulses and orbital tomography. In contrast, the quantum-coherent phase-modulation of energetic free-electron beams has not been demonstrated, although it promises direct access to ultrafast imaging and spectroscopy with tailored electron pulses on the attosecond scale. Here we demonstrate the coherent quantum state manipulation of free-electron populations in an electron microscope beam. We employ the interaction of ultrashort electron pulses with optical near-fields to induce Rabi oscillations in the populations of electron momentum states, observed as a function of the optical driving field. Excellent agreement with the scaling of an equal-Rabi multilevel quantum ladder is obtained, representing the observation of a light-driven 'quantum walk' coherently reshaping electron density in momentum space. We note that, after the interaction, the optically generated superposition of momentum states evolves into a train of attosecond electron pulses. Our results reveal the potential of quantum control for the precision structuring of electron densities, with possible applications ranging from ultrafast electron spectroscopy and microscopy to accelerator science and free-electron lasers.

Image fusion in x-ray differential phase-contrast imaging

Science.gov (United States)

Haas, W.; Polyanskaya, M.; Bayer, F.; Gödel, K.; Hofmann, H.; Rieger, J.; Ritter, A.; Weber, T.; Wucherer, L.; Durst, J.; Michel, T.; Anton, G.; Hornegger, J.

2012-02-01

Phase-contrast imaging is a novel modality in the field of medical X-ray imaging. The pioneer method is the grating-based interferometry which has no special requirements to the X-ray source and object size. Furthermore, it provides three different types of information of an investigated object simultaneously - absorption, differential phase-contrast and dark-field images. Differential phase-contrast and dark-field images represent a completely new information which has not yet been investigated and studied in context of medical imaging. In order to introduce phase-contrast imaging as a new modality into medical environment the resulting information about the object has to be correctly interpreted. The three output images reflect different properties of the same object the main challenge is to combine and visualize these data in such a way that it diminish the information explosion and reduce the complexity of its interpretation. This paper presents an intuitive image fusion approach which allows to operate with grating-based phase-contrast images. It combines information of the three different images and provides a single image. The approach is implemented in a fusion framework which is aimed to support physicians in study and analysis. The framework provides the user with an intuitive graphical user interface allowing to control the fusion process. The example given in this work shows the functionality of the proposed method and the great potential of phase-contrast imaging in medical practice.

Experimental validation of the Wigner distributions theory of phase-contrast imaging

International Nuclear Information System (INIS)

Donnelly, Edwin F.; Price, Ronald R.; Pickens, David R.

2005-01-01

Recently, a new theory of phase-contrast imaging has been proposed by Wu and Liu [Med. Phys. 31, 2378-2384 (2004)]. This theory, based upon Wigner distributions, provides a much stronger foundation for the evaluation of phase-contrast imaging systems than did the prior theories based upon Fresnel-Kirchhoff diffraction theory. In this paper, we compare results of measurements made in our laboratory of phase contrast for different geometries and tube voltages to the predictions of the Wu and Liu model. In our previous publications, we have used an empirical measurement (the edge enhancement index) to parametrize the degree of phase-contrast effects in an image. While the Wu and Liu model itself does not predict image contrast, it does measure the degree of phase contrast that the system can image for a given spatial frequency. We have found that our previously published experimental results relating phase-contrast effects to geometry and x-ray tube voltage are consistent with the predictions of the Wu and Liu model

Imaging of surface plasmon polariton interference using phase-sensitive scanning tunneling microscope

NARCIS (Netherlands)

Jose, J.; Segerink, Franciscus B.; Korterik, Jeroen P.; Herek, Jennifer Lynn; Offerhaus, Herman L.

2011-01-01

We report the surface plasmon polariton interference, generated via a ‘buried’ gold grating, and imaged using a phase-sensitive Photon Scanning Tunneling Microscope (PSTM). The phase-resolved PSTM measurement unravels the complex surface plasmon polariton interference fields at the gold-air

Phase-only optical encryption based on the zeroth-order phase-contrast technique

Science.gov (United States)

Pizolato, José Carlos; Neto, Luiz Gonçalves

2009-09-01

A phase-only encryption/decryption scheme with the readout based on the zeroth-order phase-contrast technique (ZOPCT), without the use of a phase-changing plate on the Fourier plane of an optical system based on the 4f optical correlator, is proposed. The encryption of a gray-level image is achieved by multiplying the phase distribution obtained directly from the gray-level image by a random phase distribution. The robustness of the encoding is assured by the nonlinearity intrinsic to the proposed phase-contrast method and the random phase distribution used in the encryption process. The experimental system has been implemented with liquid-crystal spatial modulators to generate phase-encrypted masks and a decrypting key. The advantage of this method is the easy scheme to recover the gray-level information from the decrypted phase-only mask applying the ZOPCT. An analysis of this decryption method was performed against brute force attacks.

Reconstruction methods for phase-contrast tomography

Energy Technology Data Exchange (ETDEWEB)

Raven, C.

1997-02-01

Phase contrast imaging with coherent x-rays can be distinguished in outline imaging and holography, depending on the wavelength {lambda}, the object size d and the object-to-detector distance r. When r << d{sup 2}{lambda}, phase contrast occurs only in regions where the refractive index fastly changes, i.e. at interfaces and edges in the sample. With increasing object-to-detector distance we come in the area of holographic imaging. The image contrast outside the shadow region of the object is due to interference of the direct, undiffracted beam and a beam diffracted by the object, or, in terms of holography, the interference of a reference wave with the object wave. Both, outline imaging and holography, offer the possibility to obtain three dimensional information of the sample in conjunction with a tomographic technique. But the data treatment and the kind of information one can obtain from the reconstruction is different.

X-ray phase-contrast tomosynthesis for improved breast tissue discrimination

International Nuclear Information System (INIS)

Schleede, Simone; Bech, Martin; Grandl, Susanne; Sztrókay, Aniko; Herzen, Julia; Mayr, Doris; Stockmar, Marco; Potdevin, Guillaume

2014-01-01

Purpose: Attenuation-based tomosynthesis has proven to successfully resolve the glandular tissue overlap present in mammography. However, the ability of tomosynthesis to differentiate tumorous and glandular tissue remains limited, due to the small differences in X-ray attenuation in breast tissue. One possibility to overcome this limitation and to further increase the diagnostic value of tomosynthesis exams, is the application of recently developed grating-based phase-contrast methods, which provide complementary information on the phase shift and the local scattering power of the sample. In this study, we report on first phase-contrast breast tomosynthesis results of a mastectomy sample slice with an invasive ductal carcinoma. Material and methods: A slice of a mastectomy sample with histologically proven invasive ductal cancer was imaged at the synchrotron radiation source ESRF (Grenoble, France). We used a two-grating interferometer setup at the ninth fractional Talbot distance and with an X-ray energy of 23 keV. In grating interferometry absorption, differential phase, and scattering images are recorded simultaneously. The tomosynthesis scan comprises 61 projections. Multimodal tomosynthesis results were reconstructed using a standard filtered back-projection approach. Our findings are supported by a comparison of tomographic views to histopathology. Results: Phase-contrast tomosynthesis combines the advantage of improved soft-tissue discrimination in phase-contrast imaging with the ability of tomosynthesis to provide a third dimension so that improved feature visibility is not hampered by superposition artifacts. Our results indicate superior diagnostic value due to the depth resolution supplied in tomosynthesis imaging; a region of necrotic tissue that is obscured in a projection image can clearly be depicted in one single tomosynthesis slice. Compared to absorption tomosynthesis alone, soft tissue contrast is significantly enhanced in phase-contrast

X-ray phase-contrast tomosynthesis for improved breast tissue discrimination.

Science.gov (United States)

Schleede, Simone; Bech, Martin; Grandl, Susanne; Sztrókay, Aniko; Herzen, Julia; Mayr, Doris; Stockmar, Marco; Potdevin, Guillaume; Zanette, Irene; Rack, Alexander; Weitkamp, Timm; Pfeiffer, Franz

2014-03-01

Attenuation-based tomosynthesis has proven to successfully resolve the glandular tissue overlap present in mammography. However, the ability of tomosynthesis to differentiate tumorous and glandular tissue remains limited, due to the small differences in X-ray attenuation in breast tissue. One possibility to overcome this limitation and to further increase the diagnostic value of tomosynthesis exams, is the application of recently developed grating-based phase-contrast methods, which provide complementary information on the phase shift and the local scattering power of the sample. In this study, we report on first phase-contrast breast tomosynthesis results of a mastectomy sample slice with an invasive ductal carcinoma. A slice of a mastectomy sample with histologically proven invasive ductal cancer was imaged at the synchrotron radiation source ESRF (Grenoble, France). We used a two-grating interferometer setup at the ninth fractional Talbot distance and with an X-ray energy of 23 keV. In grating interferometry absorption, differential phase, and scattering images are recorded simultaneously. The tomosynthesis scan comprises 61 projections. Multimodal tomosynthesis results were reconstructed using a standard filtered back-projection approach. Our findings are supported by a comparison of tomographic views to histopathology. Phase-contrast tomosynthesis combines the advantage of improved soft-tissue discrimination in phase-contrast imaging with the ability of tomosynthesis to provide a third dimension so that improved feature visibility is not hampered by superposition artifacts. Our results indicate superior diagnostic value due to the depth resolution supplied in tomosynthesis imaging; a region of necrotic tissue that is obscured in a projection image can clearly be depicted in one single tomosynthesis slice. Compared to absorption tomosynthesis alone, soft tissue contrast is significantly enhanced in phase-contrast tomosynthesis views, where fibrous structures

Pilot experimental study on continual spectrum thermal neutron in-line phase contrast radiography

International Nuclear Information System (INIS)

Tang Bin; Huo Heyong; Wu Yang

2009-01-01

The in-line phase contrast radiography is one of phase contrast imaging methods. The neutron in-line phase contrast is developed with X-rays phase contrast radiography. In the paper, the principle of in-line phase contrast is introduced briefly and the experimental result of thermal neutron in-line contrast at SPRR-300 is analysed. It shows that thermal neutron can be used as in-line phase contrast radiography and enhances the edge of some sample in radiography and complements the disadvantage of conventional neutron radiography. (authors)

Phase contrast imaging with coherent high energy X-rays

Energy Technology Data Exchange (ETDEWEB)

Snigireva, I. [ESRF, Grenoble (France)

1997-02-01

X-ray imaging concern high energy domain (>6 keV) like a contact radiography, projection microscopy and tomography is used for many years to discern the features of the internal structure non destructively in material science, medicine and biology. In so doing the main contrast formation is absorption that makes some limitations for imaging of the light density materials and what is more the resolution of these techniques is not better than 10-100 {mu}m. It was turned out that there is now way in which to overcome 1{mu}m or even sub-{mu}m resolution limit except phase contrast imaging. It is well known in optics that the phase contrast is realised when interference between reference wave front and transmitted through the sample take place. Examples of this imaging are: phase contrast microscopy suggested by Zernike and Gabor (in-line) holography. Both of this techniques: phase contrast x-ray microscopy and holography are successfully progressing now in soft x-ray region. For imaging in the hard X-rays to enhance the contrast and to be able to resolve phase variations across the beam the high degree of the time and more importantly spatial coherence is needed. Because of this it was reasonable that the perfect crystal optics was involved like Bonse-Hart interferometry, double-crystal and even triple-crystal set-up using Laue and Bragg geometry with asymmetrically cut crystals.

Diffractive generalized phase contrast for adaptive phase imaging and optical security

DEFF Research Database (Denmark)

Palima, Darwin; Glückstad, Jesper

2012-01-01

We analyze the properties of Generalized Phase Contrast (GPC) when the input phase modulation is implemented using diffractive gratings. In GPC applications for patterned illumination, the use of a dynamic diffractive optical element for encoding the GPC input phase allows for onthe- fly optimiza...... security applications and can be used to create phasebased information channels for enhanced information security....

Generalised phase contrast: microscopy, manipulation and more

DEFF Research Database (Denmark)

Palima, Darwin; Glückstad, Jesper

2010-01-01

Generalised phase contrast (GPC) not only leads to more accurate phase imaging beyond thin biological samples, but serves as an enabling framework in developing tools over a wide spectrum of contemporary applications in optics and photonics, including optical trapping and micromanipulation, optic...

Subtraction MR venography acquired from time-resolved contrast-enhanced MR angiography: Comparison with phase-contrast MR venography and single-phase contrast-enhanced MR venography

International Nuclear Information System (INIS)

Jang, Jin Hee; Kim, Bum Soo; KIm, Bom Yi; Choi, Hyun Seok; Jung, So Lyung; Ahn, Kook Jin; Sung, Ji Kyeong

2015-01-01

To evaluate the image characteristics of subtraction magnetic resonance venography (SMRV) from time-resolved contrast-enhanced MR angiography (TRMRA) compared with phase-contrast MR venography (PCMRV) and single-phase contrast-enhanced MR venography (CEMRV). Twenty-one patients who underwent brain MR venography (MRV) using standard protocols (PCMRV, CEMRV, and TRMRA) were included. SMRV was made by subtracting the arterial phase data from the venous phase data in TRMRA. Co-registration and subtraction of the two volume data was done using commercially available software. Image quality and the degree of arterial contamination of the three MRVs were compared. In the three MRVs, 19 pre-defined venous structures (14 dural sinuses and 5 cerebral veins) were evaluated. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the three MRVs were also compared. Single-phase contrast-enhanced MR venography showed better image quality (median score 4 in both reviewers) than did the other two MRVs (p < 0.001), whereas SMRV (median score 3 in both reviewers) and PCMRV (median score 3 in both reviewers) had similar image quality (p ≥ 0.951). SMRV (median score 0 in both reviewers) suppressed arterial signal better than did the other MRVs (median score 1 in CEMRV, median score 2 in PCMRV, both reviewers) (p < 0.001). The dural sinus score of SMRV (median and interquartile range [IQR] 48, 43-50 for reviewer 1, 47, 43-49 for reviewer 2) was significantly higher than for PCMRV (median and IQR 31, 25-34 for reviewer 1, 30, 23-32 for reviewer 2) (p < 0.01) and did not differ from that of CEMRV (median and IQR 50, 47-52 for reviewer 1, 49, 45-51 for reviewer 2) (p = 0.146 in reviewer 1 and 0.123 in reviewer 2). The SNR and CNR of SMRV (median and IQR 104.5, 83.1-121.2 and 104.1, 74.9-120.5, respectively) were between those of CEMRV (median and IQR 150.3, 111-182.6 and 148.4, 108-178.2) and PCMRV (median and IQR 59.4, 49.2-74.9 and 53.6, 43.8-69.2). Subtraction magnetic

Single particle analysis based on Zernike phase contrast transmission electron microscopy.

Science.gov (United States)

Danev, Radostin; Nagayama, Kuniaki

2008-02-01

We present the first application of Zernike phase-contrast transmission electron microscopy to single-particle 3D reconstruction of a protein, using GroEL chaperonin as the test specimen. We evaluated the performance of the technique by comparing 3D models derived from Zernike phase contrast imaging, with models from conventional underfocus phase contrast imaging. The same resolution, about 12A, was achieved by both imaging methods. The reconstruction based on Zernike phase contrast data required about 30% fewer particles. The advantages and prospects of each technique are discussed.

Grating-based X-ray phase contrast for biomedical imaging applications

International Nuclear Information System (INIS)

Pfeiffer, Franz; Willner, Marian; Chabior, Michael; Herzen, Julia; Helmholtz-Zentrum Geesthacht, Geesthacht; Auweter, Sigrid; Reiser, Maximilian; Bamberg, Fabian

2013-01-01

In this review article we describe the development of grating-based X-ray phase-contrast imaging, with particular emphasis on potential biomedical applications of the technology. We review the basics of image formation in grating-based phase-contrast and dark-field radiography and present some exemplary multimodal radiography results obtained with laboratory X-ray sources. Furthermore, we discuss the theoretical concepts to extend grating-based multimodal radiography to quantitative transmission, phase-contrast, and dark-field scattering computed tomography. (orig.)

In-line phase contrast micro-CT reconstruction for biomedical specimens.

Science.gov (United States)

Fu, Jian; Tan, Renbo

2014-01-01

X-ray phase contrast micro computed tomography (micro-CT) can non-destructively provide the internal structure information of soft tissues and low atomic number materials. It has become an invaluable analysis tool for biomedical specimens. Here an in-line phase contrast micro-CT reconstruction technique is reported, which consists of a projection extraction method and the conventional filter back-projection (FBP) reconstruction algorithm. The projection extraction is implemented by applying the Fourier transform to the forward projections of in-line phase contrast micro-CT. This work comprises a numerical study of the method and its experimental verification using a biomedical specimen dataset measured at an X-ray tube source micro-CT setup. The numerical and experimental results demonstrate that the presented technique can improve the imaging contrast of biomedical specimens. It will be of interest for a wide range of in-line phase contrast micro-CT applications in medicine and biology.

Large-area full field x-ray differential phase-contrast imaging using 2D tiled gratings

Science.gov (United States)

Schröter, Tobias J.; Koch, Frieder J.; Kunka, Danays; Meyer, Pascal; Tietze, Sabrina; Engelhardt, Sabine; Zuber, Marcus; Baumbach, Tilo; Willer, Konstantin; Birnbacher, Lorenz; Prade, Friedrich; Pfeiffer, Franz; Reichert, Klaus-Martin; Hofmann, Andreas; Mohr, Jürgen

2017-06-01

Grating-based x-ray differential phase-contrast imaging (DPCI) is capable of acquiring information based on phase-shift and dark-field signal, in addition to conventional x-ray absorption-contrast. Thus DPCI gives an advantage to investigate composite materials with component wise similar absorption properties like soft tissues. Due to technological challenges in fabricating high quality gratings over a large extent, the field of view (FoV) of the imaging systems is limited to a grating area of a couple of square centimeters. For many imaging applications (e.g. in medicine), however, a FoV that ranges over several ten centimeters is needed. In this manuscript we propose to create large area gratings of theoretically any extent by assembling a number of individual grating tiles. We discuss the precision needed for alignment of each microstructure tile in order to reduce image artifacts and to preserve minimum 90% of the sensitivity obtainable with a monolithic grating. To achieve a reliable high precision alignment a semiautomatic assembly system consisting of a laser autocollimator, a digital microscope and a force sensor together with positioning devices was built. The setup was used to tile a first four times four analyzer grating with a size of 200 mm  ×  200 mm together with a two times two phase grating. First imaging results prove the applicability and quality of the tiling concept.

X-ray differential phase-contrast tomographic reconstruction with a phase line integral retrieval filter

International Nuclear Information System (INIS)

Fu, Jian; Hu, Xinhua; Li, Chen

2015-01-01

We report an alternative reconstruction technique for x-ray differential phase-contrast computed tomography (DPC-CT). This approach is based on a new phase line integral projection retrieval filter, which is rooted in the derivative property of the Fourier transform and counteracts the differential nature of the DPC-CT projections. It first retrieves the phase line integral from the DPC-CT projections. Then the standard filtered back-projection (FBP) algorithms popular in x-ray absorption-contrast CT are directly applied to the retrieved phase line integrals to reconstruct the DPC-CT images. Compared with the conventional DPC-CT reconstruction algorithms, the proposed method removes the Hilbert imaginary filter and allows for the direct use of absorption-contrast FBP algorithms. Consequently, FBP-oriented image processing techniques and reconstruction acceleration softwares that have already been successfully used in absorption-contrast CT can be directly adopted to improve the DPC-CT image quality and speed up the reconstruction

A multi-modal stereo microscope based on a spatial light modulator.

Science.gov (United States)

Lee, M P; Gibson, G M; Bowman, R; Bernet, S; Ritsch-Marte, M; Phillips, D B; Padgett, M J

2013-07-15

Spatial Light Modulators (SLMs) can emulate the classic microscopy techniques, including differential interference (DIC) contrast and (spiral) phase contrast. Their programmability entails the benefit of flexibility or the option to multiplex images, for single-shot quantitative imaging or for simultaneous multi-plane imaging (depth-of-field multiplexing). We report the development of a microscope sharing many of the previously demonstrated capabilities, within a holographic implementation of a stereo microscope. Furthermore, we use the SLM to combine stereo microscopy with a refocusing filter and with a darkfield filter. The instrument is built around a custom inverted microscope and equipped with an SLM which gives various imaging modes laterally displaced on the same camera chip. In addition, there is a wide angle camera for visualisation of a larger region of the sample.

X-ray phase-contrast CT of a pancreatic ductal adenocarcinoma mouse model.

Directory of Open Access Journals (Sweden)

Arne Tapfer

Full Text Available To explore the potential of grating-based x-ray phase-contrast computed tomography (CT for preclinical research, a genetically engineered mouse model of pancreatic ductal adenocarcinoma (PDAC was investigated. One ex-vivo mouse specimen was scanned with different grating-based phase-contrast CT imaging setups covering two different settings: i high-resolution synchrotron radiation (SR imaging and ii dose-reduced imaging using either synchrotron radiation or a conventional x-ray tube source. These experimental settings were chosen to assess the potential of phase-contrast imaging for two different types of application: i high-performance imaging for virtual microscopy applications and ii biomedical imaging with increased soft-tissue contrast for in-vivo applications. For validation and as a reference, histological slicing and magnetic resonance imaging (MRI were performed on the same mouse specimen. For each x-ray imaging setup, attenuation and phase-contrast images were compared visually with regard to contrast in general, and specifically concerning the recognizability of lesions and cancerous tissue. To quantitatively assess contrast, the contrast-to-noise ratios (CNR of selected regions of interest (ROI in the attenuation images and the phase images were analyzed and compared. It was found that both for virtual microscopy and for in-vivo applications, there is great potential for phase-contrast imaging: in the SR-based benchmarking data, fine details about tissue composition are accessible in the phase images and the visibility of solid tumor tissue under dose-reduced conditions is markedly superior in the phase images. The present study hence demonstrates improved diagnostic value with phase-contrast CT in a mouse model of a complex endogenous cancer, promoting the use and further development of grating-based phase-contrast CT for biomedical imaging applications.

Phase contrast image segmentation using a Laue analyser crystal

International Nuclear Information System (INIS)

Kitchen, Marcus J; Paganin, David M; Lewis, Robert A; Pavlov, Konstantin M; Uesugi, Kentaro; Allison, Beth J; Hooper, Stuart B

2011-01-01

Dual-energy x-ray imaging is a powerful tool enabling two-component samples to be separated into their constituent objects from two-dimensional images. Phase contrast x-ray imaging can render the boundaries between media of differing refractive indices visible, despite them having similar attenuation properties; this is important for imaging biological soft tissues. We have used a Laue analyser crystal and a monochromatic x-ray source to combine the benefits of both techniques. The Laue analyser creates two distinct phase contrast images that can be simultaneously acquired on a high-resolution detector. These images can be combined to separate the effects of x-ray phase, absorption and scattering and, using the known complex refractive indices of the sample, to quantitatively segment its component materials. We have successfully validated this phase contrast image segmentation (PCIS) using a two-component phantom, containing an iodinated contrast agent, and have also separated the lungs and ribcage in images of a mouse thorax. Simultaneous image acquisition has enabled us to perform functional segmentation of the mouse thorax throughout the respiratory cycle during mechanical ventilation.

Preliminary study on X-ray phase contrast imaging using synchrotron radiation facility

International Nuclear Information System (INIS)

Xiong Zhuang; Wang Jianhua; Yu Yongqiang; Jiang Shiping; Chen Yang; Tian Yulian

2006-01-01

Objective: To study the methodology of X-ray phase contrast imaging using synchrotron radiation, and evaluate the quality of phase contrast images. Methods: Several experiments to obtain phase contrast images and absorption contrast images of various biological samples were conducted in Beijing Synchrotron Radiation Facility (BSRF), and then these images were interpreted to find out the difference between the two kinds of imaging methods. Results: Satisfactory phase contrast images of these various samples were obtained, and the quality of these images was superior to that obtained with absorption contrast imaging. The phase contrast formation is based on the phenomenon of fresnel diffraction which transforms phase shifts into intensity variations upon a simple act of free-space propagation, so it requires highly coherent X-rays and appropriate distance between sample and detector. This method of imaging is very useful in imaging of low-absorption objects or objects with little absorption variation, and its resolution is far higher than that of the conventional X-ray imaging. The photographs obtained showed very fine inner microstructure of the biological samples, and the smallest microstructure to be distinguished is within 30-40 μm. There is no doubt that phase contrast imaging has a practical applicability in medicine. Moreover, it improves greatly the efficiency and the resolution of the existing X-ray diagnostic techniques. Conclusions: X-ray phase contrast imaging can be performed with synchrotron radiation source and has some advantages over the conventional absorption contrast imaging. (authors)

Differential phase microscope and micro-tomography with a Foucault knife-edge scanning filter

Science.gov (United States)

Watanabe, N.; Hashizume, J.; Goto, M.; Yamaguchi, M.; Tsujimura, T.; Aoki, S.

2013-10-01

An x-ray differential phase microscope with a Foucault knife-edge scanning filter was set up at the bending magnet source BL3C, Photon Factory. A reconstructed phase profile from the differential phase image of an aluminium wire at 5.36 keV was fairly good agreement with the numerical simulation. Phase tomography of a biological specimen, such as an Artemia cyst, could be successfully demonstrated.

Hard X-ray Microscopic Imaging Of Human Breast Tissues

Science.gov (United States)

Park, Sung H.; Kim, Hong T.; Kim, Jong K.; Jheon, Sang H.; Youn, Hwa S.

2007-01-01

X-ray microscopy with synchrotron radiation will be a useful tool for innovation of x-ray imaging in clinical and laboratory settings. It helps us observe detailed internal structure of material samples non-invasively in air. And, it also has the potential to solve some tough problems of conventional breast imaging if it could evaluate various conditions of breast tissue effectively. A new hard x-ray microscope with a spatial resolution better than 100 nm was installed at Pohang Light Source, a third generation synchrotron radiation facility in Pohang, Korea. The x-ray energy was set at 6.95 keV, and the x-ray beam was monochromatized by W/B4C monochromator. Condenser and objective zone plates were used as x-ray lenses. Zernike phase plate next to condenser zone plate was introduced for improved contrast imaging. The image of a sample was magnified 30 times by objective zone plate and 20 times by microscope objective, respectively. After additional 10 times digital magnification, the total magnifying power was up to 6000 times in the end. Phase contrast synchrotron images of 10-μm-thick female breast tissue of the normal, fibroadenoma, fibrocystic change and carcinoma cases were obtained. By phase contrast imaging, hard x-rays enable us to observe many structures of breast tissue without sample preparations such as staining or fixation.

Hard X-ray Microscopic Imaging Of Human Breast Tissues

International Nuclear Information System (INIS)

Park, Sung H.; Kim, Hong T.; Kim, Jong K.; Jheon, Sang H.; Youn, Hwa S.

2007-01-01

X-ray microscopy with synchrotron radiation will be a useful tool for innovation of x-ray imaging in clinical and laboratory settings. It helps us observe detailed internal structure of material samples non-invasively in air. And, it also has the potential to solve some tough problems of conventional breast imaging if it could evaluate various conditions of breast tissue effectively. A new hard x-ray microscope with a spatial resolution better than 100 nm was installed at Pohang Light Source, a third generation synchrotron radiation facility in Pohang, Korea. The x-ray energy was set at 6.95 keV, and the x-ray beam was monochromatized by W/B4C monochromator. Condenser and objective zone plates were used as x-ray lenses. Zernike phase plate next to condenser zone plate was introduced for improved contrast imaging. The image of a sample was magnified 30 times by objective zone plate and 20 times by microscope objective, respectively. After additional 10 times digital magnification, the total magnifying power was up to 6000 times in the end. Phase contrast synchrotron images of 10-μm-thick female breast tissue of the normal, fibroadenoma, fibrocystic change and carcinoma cases were obtained. By phase contrast imaging, hard x-rays enable us to observe many structures of breast tissue without sample preparations such as staining or fixation

3D geometric phase analysis and its application in 3D microscopic morphology measurement

Science.gov (United States)

Zhu, Ronghua; Shi, Wenxiong; Cao, Quankun; Liu, Zhanwei; Guo, Baoqiao; Xie, Huimin

2018-04-01

Although three-dimensional (3D) morphology measurement has been widely applied on the macro-scale, there is still a lack of 3D measurement technology on the microscopic scale. In this paper, a microscopic 3D measurement technique based on the 3D-geometric phase analysis (GPA) method is proposed. In this method, with machine vision and phase matching, the traditional GPA method is extended to three dimensions. Using this method, 3D deformation measurement on the micro-scale can be realized using a light microscope. Simulation experiments were conducted in this study, and the results demonstrate that the proposed method has a good anti-noise ability. In addition, the 3D morphology of the necking zone in a tensile specimen was measured, and the results demonstrate that this method is feasible.

Three-dimensional characterization of extreme ultraviolet mask blank defects by interference contrast photoemission electron microscopy.

Science.gov (United States)

Lin, Jingquan; Weber, Nils; Escher, Matthias; Maul, Jochen; Han, Hak-Seung; Merkel, Michael; Wurm, Stefan; Schönhense, Gerd; Kleineberg, Ulf

2008-09-29

A photoemission electron microscope based on a new contrast mechanism "interference contrast" is applied to characterize extreme ultraviolet lithography mask blank defects. Inspection results show that positioning of interference destructive condition (node of standing wave field) on surface of multilayer in the local region of a phase defect is necessary to obtain best visibility of the defect on mask blank. A comparative experiment reveals superiority of the interference contrast photoemission electron microscope (Extreme UV illumination) over a topographic contrast one (UV illumination with Hg discharge lamp) in detecting extreme ultraviolet mask blank phase defects. A depth-resolved detection of a mask blank defect, either by measuring anti-node peak shift in the EUV-PEEM image under varying inspection wavelength condition or by counting interference fringes with a fixed illumination wavelength, is discussed.

Robustness of phase retrieval methods in x-ray phase contrast imaging: A comparison

International Nuclear Information System (INIS)

Yan, Aimin; Wu, Xizeng; Liu, Hong

2011-01-01

Purpose: The robustness of the phase retrieval methods is of critical importance for limiting and reducing radiation doses involved in x-ray phase contrast imaging. This work is to compare the robustness of two phase retrieval methods by analyzing the phase maps retrieved from the experimental images of a phantom. Methods: Two phase retrieval methods were compared. One method is based on the transport of intensity equation (TIE) for phase contrast projections, and the TIE-based method is the most commonly used method for phase retrieval in the literature. The other is the recently developed attenuation-partition based (AP-based) phase retrieval method. The authors applied these two methods to experimental projection images of an air-bubble wrap phantom for retrieving the phase map of the bubble wrap. The retrieved phase maps obtained by using the two methods are compared. Results: In the wrap's phase map retrieved by using the TIE-based method, no bubble is recognizable, hence, this method failed completely for phase retrieval from these bubble wrap images. Even with the help of the Tikhonov regularization, the bubbles are still hardly visible and buried in the cluttered background in the retrieved phase map. The retrieved phase values with this method are grossly erroneous. In contrast, in the wrap's phase map retrieved by using the AP-based method, the bubbles are clearly recovered. The retrieved phase values with the AP-based method are reasonably close to the estimate based on the thickness-based measurement. The authors traced these stark performance differences of the two methods to their different techniques employed to deal with the singularity problem involved in the phase retrievals. Conclusions: This comparison shows that the conventional TIE-based phase retrieval method, regardless if Tikhonov regularization is used or not, is unstable against the noise in the wrap's projection images, while the AP-based phase retrieval method is shown in these

Quantitative phase tomography by using x-ray microscope with Foucault knife-edge scanning filter

Energy Technology Data Exchange (ETDEWEB)

Watanabe, Norio; Tsuburaya, Yuji; Shimada, Akihiro; Aoki, Sadao [Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8573 (Japan)

2016-01-28

Quantitative phase tomography was evaluated by using a differential phase microscope with a Foucault knife-edge scanning filter. A 3D x-ray phase image of polystyrene beads was obtained at 5.4 keV. The reconstructed refractive index was fairly good agreement with the Henke’s tabulated data.

Quantitative phase tomography by using x-ray microscope with Foucault knife-edge scanning filter

International Nuclear Information System (INIS)

Watanabe, Norio; Tsuburaya, Yuji; Shimada, Akihiro; Aoki, Sadao

2016-01-01

Quantitative phase tomography was evaluated by using a differential phase microscope with a Foucault knife-edge scanning filter. A 3D x-ray phase image of polystyrene beads was obtained at 5.4 keV. The reconstructed refractive index was fairly good agreement with the Henke’s tabulated data

Quantitative phase tomography by using x-ray microscope with Foucault knife-edge scanning filter

Science.gov (United States)

Watanabe, Norio; Tsuburaya, Yuji; Shimada, Akihiro; Aoki, Sadao

2016-01-01

Quantitative phase tomography was evaluated by using a differential phase microscope with a Foucault knife-edge scanning filter. A 3D x-ray phase image of polystyrene beads was obtained at 5.4 keV. The reconstructed refractive index was fairly good agreement with the Henke's tabulated data.

Application of phase-contrast cine magnetic resonance imaging in endoscopic aqueductoplasty.

Science.gov (United States)

Chen, Guoqiang; Zheng, Jiaping; Xiao, Qing; Liu, Yunsheng

2013-06-01

The aim of this study was to evaluate the application of phase-contrast cine magnetic resonance imaging (MRI) in endoscopic aqueductoplasty (EA) for patients with obstructive hydrocephalus. The clinical diagnosis of hydrocephalus caused by aqueduct obstruction in 23 patients was confirmed by phase-contrast cine MRI examination. The patients were treated with EA and MRI was repeated during the follow-up. The cerebrospinal fluid (CSF) flow velocity in the aqueduct was measured to determine whether the aqueduct was obstructed. The results of phase-contrast cine MRI examinations indicated that there was no CSF flow in the aqueduct for all patients prior to surgery. Aqueductoplasty was successfully performed in all patients. The results of phase-contrast cine MRI examinations performed a week after surgery demonstrated an average CSF flow velocity of 4.74±1.77 cm/sec. During the follow-up, intracranial hypertension recurred in two patients in whom CSF flow was not observed in the aqueduct by the phase-contrast cine MRI scan. Aqueduct re-occlusion was revealed by an endoscopic exploration. By measuring the CSF flow velocity, phase-contrast cine MRI accurately identifies aqueduct obstruction. Cine MRI is a nontraumatic, simple and reliable method for determining whether the aqueduct is successfully opened following aqueductoplasty.

Laser-wakefield accelerators for medical phase contrast imaging: Monte Carlo simulations and experimental studies

Science.gov (United States)

Cipiccia, S.; Reboredo, D.; Vittoria, Fabio A.; Welsh, G. H.; Grant, P.; Grant, D. W.; Brunetti, E.; Wiggins, S. M.; Olivo, A.; Jaroszynski, D. A.

2015-05-01

X-ray phase contrast imaging (X-PCi) is a very promising method of dramatically enhancing the contrast of X-ray images of microscopic weakly absorbing objects and soft tissue, which may lead to significant advancement in medical imaging with high-resolution and low-dose. The interest in X-PCi is giving rise to a demand for effective simulation methods. Monte Carlo codes have been proved a valuable tool for studying X-PCi including coherent effects. The laser-plasma wakefield accelerators (LWFA) is a very compact particle accelerator that uses plasma as an accelerating medium. Accelerating gradient in excess of 1 GV/cm can be obtained, which makes them over a thousand times more compact than conventional accelerators. LWFA are also sources of brilliant betatron radiation, which are promising for applications including medical imaging. We present a study that explores the potential of LWFA-based betatron sources for medical X-PCi and investigate its resolution limit using numerical simulations based on the FLUKA Monte Carlo code, and present preliminary experimental results.

Grating-based x-ray differential phase contrast imaging with twin peaks in phase-stepping curves—phase retrieval and dewrapping

Energy Technology Data Exchange (ETDEWEB)

Yang, Yi; Xie, Huiqiao; Tang, Xiangyang, E-mail: xiangyang.tang@emory.edu [Imaging and Medical Physics, Department of Radiology and Imaging Sciences, Emory University School of Medicine, 1701 Uppergate Dr., C-5018, Atlanta, Georgia 30322 (United States); Cai, Weixing [Department of Radiation Oncology, Brigham and Women’s Hospital Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115 (United States); Mao, Hui [Laboratory of Functional and Molecular Imaging and Nanomedicine, Department of Radiology and Imaging Sciences, Emory University School of Medicine, 1841 Clifton Road NE, Atlanta, Georgia 30329 (United States)

2016-06-15

Purpose: X-ray differential phase contrast CT implemented with Talbot interferometry employs phase-stepping to extract information of x-ray attenuation, phase shift, and small-angle scattering. Since inaccuracy may exist in the absorption grating G{sub 2} due to an imperfect fabrication, the effective period of G{sub 2} can be as large as twice the nominal period, leading to a phenomenon of twin peaks that differ remarkably in their heights. In this work, the authors investigate how to retrieve and dewrap the phase signal from the phase-stepping curve (PSC) with the feature of twin peaks for x-ray phase contrast imaging. Methods: Based on the paraxial Fresnel–Kirchhoff theory, the analytical formulae to characterize the phenomenon of twin peaks in the PSC are derived. Then an approach to dewrap the retrieved phase signal by jointly using the phases of the first- and second-order Fourier components is proposed. Through an experimental investigation using a prototype x-ray phase contrast imaging system implemented with Talbot interferometry, the authors evaluate and verify the derived analytic formulae and the proposed approach for phase retrieval and dewrapping. Results: According to theoretical analysis, the twin-peak phenomenon in PSC is a consequence of combined effects, including the inaccuracy in absorption grating G{sub 2}, mismatch between phase grating and x-ray source spectrum, and finite size of x-ray tube’s focal spot. The proposed approach is experimentally evaluated by scanning a phantom consisting of organic materials and a lab mouse. The preliminary data show that compared to scanning G{sub 2} over only one single nominal period and correcting the measured phase signal with an intuitive phase dewrapping method that is being used in the field, stepping G{sub 2} over twice its nominal period and dewrapping the measured phase signal with the proposed approach can significantly improve the quality of x-ray differential phase contrast imaging in both

Atomic Force Microscope Image Contrast Mechanisms on Supported Lipid Bilayers

OpenAIRE

Schneider, James; Dufrêne, Yves F.; Barger Jr., William R.; Lee, Gil U.

2000-01-01

This work presents a methodology to measure and quantitatively interpret force curves on supported lipid bilayers in water. We then use this method to correlate topographic imaging contrast in atomic force microscopy (AFM) images of phase-separated Langmuir-Blodgett bilayers with imaging load. Force curves collected on pure monolayers of both distearoylphosphatidylethanolamine (DSPE) and monogalactosylethanolamine (MGDG) and dioleoylethanolamine (DOPE) deposited at similar surface pressures o...

Laser-induced microscopic phase-transition on an ionic liquid

International Nuclear Information System (INIS)

Iguchi, Natsuki; Datta, Alokmay; Yoshikawa, Kenichi; Ma Yue

2009-01-01

Nematic-isotropic transition is induced in a 5 μm 'droplet' within an oriented bulk of a mixture of a liquid crystalline material with a room-temperature ionic liquid, by a laser working at 532 nm with an output power of 200 mW and a beam diameter of 1 μm. No microscopic phase transition is observed either in absence of the ionic liquid or at the other wavelength of 1064 nm, available to the Nd-YAG laser. This indicates the essential role on a resonant transfer of energy to the ionic liquid from the laser radiation, which is subsequently transferred to the liquid crystal. Spectroscopy of the pure liquid crystal and ionic liquid samples confirms this concept. Spatio-temporal image of the droplet growth shows, however, that the phase transition remains confined within the microscopic domain for the first 50 s, and then spreads out rapidly. Since resonant, quantum transitions between molecular levels takes place in less than microseconds, the about seven orders of magnitude slowing down of energy transfer observed here suggests unique hierarchical dynamics including the coupling between the intra-molecular motions in the ionic liquid and the inter-molecular forces between ionic liquid and liquid crystal.

A novel phase-sensitive scanning near-field optical microscope

International Nuclear Information System (INIS)

Wu Xiao-Yu; Lin Sun; Tan Qiao-Feng; Wang Jia

2015-01-01

Phase is one of the most important parameters of electromagnetic waves. It is the phase distribution that determines the propagation, reflection, refraction, focusing, divergence, and coupling features of light, and further affects the intensity distribution. In recent years, the designs of surface plasmon polariton (SPP) devices have mostly been based on the phase modulation and manipulation. Here we demonstrate a phase sensitive multi-parameter heterodyne scanning near-field optical microscope (SNOM) with an aperture probe in the visible range, with which the near field optical phase and amplitude distributions can be simultaneously obtained. A novel architecture combining a spatial optical path and a fiber optical path is employed for stability and flexibility. Two kinds of typical nano-photonic devices are tested with the system. With the phase-sensitive SNOM, the phase and amplitude distributions of any nano-optical field and localized field generated with any SPP nano-structures and irregular phase modulation surfaces can be investigated. The phase distribution and the interference pattern will help us to gain a better understanding of how light interacts with SPP structures and how SPP waves generate, localize, convert, and propagate on an SPP surface. This will be a significant guidance on SPP nano-structure design and optimization. (paper)

In-Line Phase-Contrast X-ray Imaging and Tomography for Materials Science.

Science.gov (United States)

Mayo, Sheridan C; Stevenson, Andrew W; Wilkins, Stephen W

2012-05-24

X-ray phase-contrast imaging and tomography make use of the refraction of X-rays by the sample in image formation. This provides considerable additional information in the image compared to conventional X-ray imaging methods, which rely solely on X-ray absorption by the sample. Phase-contrast imaging highlights edges and internal boundaries of a sample and is thus complementary to absorption contrast, which is more sensitive to the bulk of the sample. Phase-contrast can also be used to image low-density materials, which do not absorb X-rays sufficiently to form a conventional X-ray image. In the context of materials science, X-ray phase-contrast imaging and tomography have particular value in the 2D and 3D characterization of low-density materials, the detection of cracks and voids and the analysis of composites and multiphase materials where the different components have similar X-ray attenuation coefficients. Here we review the use of phase-contrast imaging and tomography for a wide variety of materials science characterization problems using both synchrotron and laboratory sources and further demonstrate the particular benefits of phase contrast in the laboratory setting with a series of case studies.

Quantitative breast tissue characterization using grating-based x-ray phase-contrast imaging

Science.gov (United States)

Willner, M.; Herzen, J.; Grandl, S.; Auweter, S.; Mayr, D.; Hipp, A.; Chabior, M.; Sarapata, A.; Achterhold, K.; Zanette, I.; Weitkamp, T.; Sztrókay, A.; Hellerhoff, K.; Reiser, M.; Pfeiffer, F.

2014-04-01

X-ray phase-contrast imaging has received growing interest in recent years due to its high capability in visualizing soft tissue. Breast imaging became the focus of particular attention as it is considered the most promising candidate for a first clinical application of this contrast modality. In this study, we investigate quantitative breast tissue characterization using grating-based phase-contrast computed tomography (CT) at conventional polychromatic x-ray sources. Different breast specimens have been scanned at a laboratory phase-contrast imaging setup and were correlated to histopathology. Ascertained tumor types include phylloides tumor, fibroadenoma and infiltrating lobular carcinoma. Identified tissue types comprising adipose, fibroglandular and tumor tissue have been analyzed in terms of phase-contrast Hounsfield units and are compared to high-quality, high-resolution data obtained with monochromatic synchrotron radiation, as well as calculated values based on tabulated tissue properties. The results give a good impression of the method’s prospects and limitations for potential tumor detection and the associated demands on such a phase-contrast breast CT system. Furthermore, the evaluated quantitative tissue values serve as a reference for simulations and the design of dedicated phantoms for phase-contrast mammography.

First application experiments with the Stockholm compact soft x-ray microscope

International Nuclear Information System (INIS)

Bertilson, M; Hofsten, O von; Lindblom, M; Holmberg, A; Takman, P; Vogt, U; Hertz, H; Thieme, J

2009-01-01

Most soft x-ray microscopes operating in the water window (λ = 2.3 - 4.4 nm) rely on synchrotron radiation sources. In the future we believe scientists will use soft x-ray microscopes as one imaging tool among others in their own laboratory. For this purpose we have developed a full field soft x-ray microscope with a laser-plasma source compact enough to fit on an optical table. In this contribution we describe the current status of this microscope now featuring stable operation at λ = 3.37 nm or λ 2.48 nm. In-house fabricated single element zone plates offering the possibility to perform phase contrast imaging have been implemented. We also report on the first application experiments for compact soft x-ray microscopy, including results from studies of clay minerals and colloids existing in nature and results from phase optics experiments. Planned upgrades of the microscope include increasing the source brightness, implementing more efficient condenser optics, and installing a cryo sample stage for tomography. These improvements will open up for further applications, especially in the field of biological imaging.

DHM (Digital Holography Microscope) for imaging cells

International Nuclear Information System (INIS)

Emery, Yves; Cuche, Etienne; Colomb, Tristan; Depeursinge, Christian; Rappaz, Benjamin; Marquet, Pierre; Magistretti, Pierre

2007-01-01

Light interaction with a sample modifies both intensity and phase of the illuminating wave. Any available supports for image recording are only sensitive to intensity, but Denis Gabor [P. Marquet, B. Rappaz, P. Magistretti, et. al. Digital Holography for quantitative phase-contrast imaging, Optics Letters, 30, 5, pp 291-93 (2005)] invented in 1948 a way to encode the phase as an intensity variation: the h ologram . Digital Holographic Microscopy (DHM) [D. Gabor, A new microscopic principle, Nature, 1948] implements digitally this powerful hologram. Characterization of various pollen grains and of morphology changes of neurones associated with hypotonic shock demonstrates the potential of DHM for imaging cells

Contrast and decay of cathodoluminescence from phosphor particles in a scanning electron microscope

Energy Technology Data Exchange (ETDEWEB)

Engelsen, Daniel den; Harris, Paul G.; Ireland, Terry G., E-mail: terry.ireland@brunel.ac.uk; Fern, George R.; Silver, Jack

2015-10-15

Cathodoluminescence (CL) studies are reported on phosphors in a field emission scanning electron microscope (FESEM). ZnO: Zn and other luminescent powders manifest a bright ring around the periphery of the particles: this ring enhances the contrast. Additionally, particles resting on top of others are substantially brighter than underlying ones. These phenomena are explained in terms of the combined effects of electrons backscattered out of the particles, together with light absorption by the substrate. The contrast is found to be a function of the particle size and the energy of the primary electrons. Some phosphor materials exhibit a pronounced comet-like structure at high scan rates in a CL-image, because the particle continues to emit light after the electron beam has moved to a position without phosphor material. Image analysis has been used to study the loss of brightness along the tail and hence to determine the decay time of the materials. The effect of phosphor saturation on the determination of decay times by CL-microscopy was also investigated. - Highlights: • Contrast enhancement are observed in secondary electron and cathodoluminescent images of phosphor particles sitting on top of others. • Backscattered electrons largely explain the observed contrast enhancement. • After glow effects in CL-micrographs of phosphors enable the determination of decay times. • Phosphor saturation can be used to determine the decay time of individual spectral transitions.

Characterization of a high-energy in-line phase contrast tomosynthesis prototype.

Science.gov (United States)

Wu, Di; Yan, Aimin; Li, Yuhua; Wong, Molly D; Zheng, Bin; Wu, Xizeng; Liu, Hong

2015-05-01

In this research, a high-energy in-line phase contrast tomosynthesis prototype was developed and characterized through quantitative investigations and phantom studies. The prototype system consists of an x-ray source, a motorized rotation stage, and a CMOS detector with a pixel pitch of 0.05 mm. The x-ray source was operated at 120 kVp for this study, and the objects were mounted on the rotation stage 76.2 cm (R1) from the source and 114.3 cm (R2) from the detector. The large air gap between the object and detector guarantees sufficient phase-shift effects. The quantitative evaluation of this prototype included modulation transfer function and noise power spectrum measurements conducted under both projection mode and tomosynthesis mode. Phantom studies were performed including three custom designed phantoms with complex structures: a five-layer bubble wrap phantom, a fishbone phantom, and a chicken breast phantom with embedded fibrils and mass structures extracted from an ACR phantom. In-plane images of the phantoms were acquired to investigate their image qualities through observation, intensity profile plots, edge enhancement evaluations, and/or contrast-to-noise ratio calculations. In addition, the robust phase-attenuation duality (PAD)-based phase retrieval method was applied to tomosynthesis for the first time in this research. It was utilized as a preprocessing method to fully exhibit phase contrast on the angular projection before reconstruction. The resolution and noise characteristics of this high-energy in-line phase contrast tomosynthesis prototype were successfully investigated and demonstrated. The phantom studies demonstrated that this imaging prototype can successfully remove the structure overlapping in phantom projections, obtain delineate interfaces, and achieve better contrast-to-noise ratio after applying phase retrieval to the angular projections. This research successfully demonstrated a high-energy in-line phase contrast tomosynthesis

Phase-contrast X-ray imaging using an X-ray interferometer for biological imaging

Energy Technology Data Exchange (ETDEWEB)

Momose, Atsushi; Koyama, Ichiro [Tokyo Univ., Dept. of Applied Physics, Tokyo (Japan); Takeda, Tohoru; Itai, Yuji [Tsukuba Univ., Inst. of Clinical Medicine, Tsukuba, Ibaraki (Japan); Yoneyama, Akio [Hitachi Ltd., Advanced Research Laboratory, Saitama (Japan)

2002-04-01

The potential of phase-contrast X-ray imaging using an X-ray interferometer is discussed comparing with other phase-contrast X-ray imaging methods, and its principle of contrast generation is presented including the case of phase-contrast X-ray computed tomography. The status of current instrumentation is described and perspectives for practical applications are discussed. (author)

Microscopic analysis of order parameters in nuclear quantum phase transitions

International Nuclear Information System (INIS)

Li, Z. P.; Niksic, T.; Vretenar, D.; Meng, J.

2009-01-01

Microscopic signatures of nuclear ground-state shape phase transitions in Nd isotopes are studied using excitation spectra and collective wave functions obtained by diagonalization of a five-dimensional Hamiltonian for quadrupole vibrational and rotational degrees of freedom, with parameters determined by constrained self-consistent relativistic mean-field calculations for triaxial shapes. As a function of the physical control parameter, the number of nucleons, energy gaps between the ground state and the excited vibrational states with zero angular momentum, isomer shifts, and monopole transition strengths exhibit sharp discontinuities at neutron number N=90, which is characteristic of a first-order quantum phase transition.

Depiction of blood vessels by x-ray phase contrast

Energy Technology Data Exchange (ETDEWEB)

Momose, Atsushi [School of Engineering, University of Tokyo, Tokyo (Japan); Takeda, Tohoru; Itai, Yuji [Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki (Japan)

2001-04-01

Blood vessels in livers of a mouse and a rat were depicted by phase-contrast x-ray imaging with an x-ray interferometer without using contrast agents. X-ray interference patterns were converted to image mapping x-ray phase shift caused by the livers using the technique of phase-shifting x-ray interferometry. The arteries and veins to and from the livers were tied before excision in order to prevent blood from flowing out of the liver. The x-ray phase shift caused by blood was substantially different from that caused by other soft sues, and consequently trees of blood vessels were revealed in the images. Vessels of diameter smaller than 0.1 mm were detected. This result suggests new possibilities for investigating vascular systems. (author)

About the contrast of δ' precipitates in bulk Al-Cu-Li alloys in reflection mode with a field-emission scanning electron microscope at low accelerating voltage.

Science.gov (United States)

Brodusch, Nicolas; Voisard, Frédéric; Gauvin, Raynald

2017-11-01

Characterising the impact of lithium additions in the precipitation sequence in Al-Li-Cu alloys is important to control the strengthening of the final material. Since now, transmission electron microscopy (TEM) at high beam voltage has been the technique of choice to monitor the size and spatial distribution of δ' precipitates (Al 3 Li). Here we report on the imaging of the δ' phase in such alloys using backscattered electrons (BSE) and low accelerating voltage in a high-resolution field-emission scanning electron microscope. By applying low-energy Ar + ion milling to the surface after mechanical polishing (MP), the MP-induced corroded layers were efficiently removed and permitted the δ's to be visible with a limited impact on the observed microstructure. The resulting BSE contrast between the δ's and the Al matrix was compared with that obtained using Monte Carlo modelling. The artefacts possibly resulting from the sample preparation procedure were reviewed and discussed and permitted to confirm that these precipitates were effectively the metastable δ's. The method described in this report necessitates less intensive sample preparation than that required for TEM and provides a much larger field of view and an easily interpretable contrast compared to the transmission techniques. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Calibrated Phase-Shifting Digital Holographic Microscope Using a Sampling Moiré Technique

Directory of Open Access Journals (Sweden)

Peng Xia

2018-05-01

Full Text Available A calibrated phase-shifting digital holographic microscope system capable of improving the quality of reconstructed images is proposed. Phase-shifting errors are introduced in phase-shifted holograms for numerous reasons, such as the non-linearity of piezoelectric transducers (PZTs, wavelength fluctuations in lasers, and environmental disturbances, leading to poor-quality reconstructions. In our system, in addition to the camera used to record object information, an extra camera is used to record interferograms, which are used to analyze phase-shifting errors using a sampling Moiré technique. The quality of the reconstructed object images can be improved by the phase-shifting error compensation algorithm. Both the numerical simulation and experiment demonstrate the effectiveness of the proposed system.

Dynamic Studies of Lung Fluid Clearance with Phase Contrast Imaging

International Nuclear Information System (INIS)

Kitchen, Marcus J.; Williams, Ivan; Irvine, Sarah C.; Morgan, Michael J.; Paganin, David M.; Lewis, Rob A.; Pavlov, Konstantin; Hooper, Stuart B.; Wallace, Megan J.; Siu, Karen K. W.; Yagi, Naoto; Uesugi, Kentaro

2007-01-01

Clearance of liquid from the airways at birth is a poorly understood process, partly due to the difficulties of observing and measuring the distribution of air within the lung. Imaging dynamic processes within the lung in vivo with high contrast and spatial resolution is therefore a major challenge. However, phase contrast X-ray imaging is able to exploit inhaled air as a contrast agent, rendering the lungs of small animals visible due to the large changes in the refractive index at air/tissue interfaces. In concert with the high spatial resolution afforded by X-ray imaging systems (<100 μm), propagation-based phase contrast imaging is ideal for studying lung development. To this end we have utilized intense, monochromatic synchrotron radiation, together with a fast readout CCD camera, to study fluid clearance from the lungs of rabbit pups at birth. Local rates of fluid clearance have been measured from the dynamic sequences using a single image phase retrieval algorithm

Low-dose quantitative phase contrast medical CT

Science.gov (United States)

Mittone, A.; Bravin, A.; Coan, P.

2018-02-01

X-ray computed tomography (CT) is a powerful and routinely used clinical diagnostic technique, which is well tolerated by patients, and which provides high-resolution images and volumetric information about the body. However, two important limitations still affect this examination procedure: (1) its low sensitivity with respect to soft tissues, and (2) the hazards associated with x-ray exposure. Conventional radiology is based on the detection of the different photon absorption properties that characterize biological tissues, and thus the obtainable image contrast from soft and/or similar tissues is intrinsically limited. In this scenario, x-ray phase contrast imaging (XPCI) has been extensively tested and proven to overcome some of the main issues surrounding standard x-ray imaging. In addition to the absorption signal, XPCI relies on detecting the phase shifts induced by an object. Interestingly, as the order of magnitude of the phase contrast is higher than that of absorption, XPCI can, in principle, offer higher sensitivity at lower radiation doses. However, other technical aspects may counterbalance this gain, and an optimized setup and image processing solutions need to be implemented. The work presented here describes the strategies and developments we have realized, with the aim of controlling the radiation dose for the highly sensitive and quantitative XPCI-CT. Different algorithms for the phase retrieval and CT reconstruction of the XPCI data are presented. The CT algorithms we have implemented, namely the equally sloped tomography and the dictionary learning method, allow the image quality to be preserved while reducing the number of angular projections required by a factor of five. The results applied to breast imaging report accurate reconstructions at clinically compatible doses of the 3D distribution of the refractive properties of full human organs obtained by using three different phase retrieval methods. The described methodologies and the

Contrast and decay of cathodoluminescence from phosphor particles in a scanning electron microscope.

Science.gov (United States)

den Engelsen, Daniel; Harris, Paul G; Ireland, Terry G; Fern, George R; Silver, Jack

2015-10-01

Cathodoluminescence (CL) studies are reported on phosphors in a field emission scanning electron microscope (FESEM). ZnO: Zn and other luminescent powders manifest a bright ring around the periphery of the particles: this ring enhances the contrast. Additionally, particles resting on top of others are substantially brighter than underlying ones. These phenomena are explained in terms of the combined effects of electrons backscattered out of the particles, together with light absorption by the substrate. The contrast is found to be a function of the particle size and the energy of the primary electrons. Some phosphor materials exhibit a pronounced comet-like structure at high scan rates in a CL-image, because the particle continues to emit light after the electron beam has moved to a position without phosphor material. Image analysis has been used to study the loss of brightness along the tail and hence to determine the decay time of the materials. The effect of phosphor saturation on the determination of decay times by CL-microscopy was also investigated. Copyright © 2015 Elsevier B.V. All rights reserved.

Atomic force microscopic imaging of Acanthamoeba castellanii and Balamuthia mandrillaris trophozoites and cysts.

Science.gov (United States)

Aqeel, Yousuf; Siddiqui, Ruqaiyyah; Ateeq, Muhammad; Raza Shah, Muhammad; Kulsoom, Huma; Khan, Naveed Ahmed

2015-01-01

Light microscopy and electron microscopy have been successfully used in the study of microbes, as well as free-living protists. Unlike light microscopy, which enables us to observe living organisms or the electron microscope which provides a two-dimensional image, atomic force microscopy provides a three-dimensional surface profile. Here, we observed two free-living amoebae, Acanthamoeba castellanii and Balamuthia mandrillaris under the phase contrast inverted microscope, transmission electron microscope and atomic force microscope. Although light microscopy was of lower magnification, it revealed functional biology of live amoebae such as motility and osmoregulation using contractile vacuoles of the trophozoite stage, but it is of limited value in defining the cyst stage. In contrast, transmission electron microscopy showed significantly greater magnification and resolution to reveal the ultra-structural features of trophozoites and cysts including intracellular organelles and cyst wall characteristics but it only produced a snapshot in time of a dead amoeba cell. Atomic force microscopy produced three-dimensional images providing detailed topographic description of shape and surface, phase imaging measuring boundary stiffness, and amplitude measurements including width, height and length of A. castellanii and B. mandrillaris trophozoites and cysts. These results demonstrate the importance of the application of various microscopic methods in the biological and structural characterization of the whole cell, ultra-structural features, as well as surface components and cytoskeleton of protist pathogens. © 2014 The Author(s) Journal of Eukaryotic Microbiology © 2014 International Society of Protistologists.

Zernike phase contrast cryo-electron tomography of whole bacterial cells.

Science.gov (United States)

Guerrero-Ferreira, Ricardo C; Wright, Elizabeth R

2014-01-01

Cryo-electron tomography (cryo-ET) provides three-dimensional (3D) structural information of bacteria preserved in a native, frozen-hydrated state. The typical low contrast of tilt-series images, a result of both the need for a low electron dose and the use of conventional defocus phase-contrast imaging, is a challenge for high-quality tomograms. We show that Zernike phase-contrast imaging allows the electron dose to be reduced. This limits movement of gold fiducials during the tilt series, which leads to better alignment and a higher-resolution reconstruction. Contrast is also enhanced, improving visibility of weak features. The reduced electron dose also means that more images at more tilt angles could be recorded, further increasing resolution. Copyright © 2013 Elsevier Inc. All rights reserved.

Phase-Contrast Hounsfield Units of Fixated and Non-Fixated Soft-Tissue Samples

Science.gov (United States)

Willner, Marian; Fior, Gabriel; Marschner, Mathias; Birnbacher, Lorenz; Schock, Jonathan; Braun, Christian; Fingerle, Alexander A.; Noël, Peter B.; Rummeny, Ernst J.; Pfeiffer, Franz; Herzen, Julia

2015-01-01

X-ray phase-contrast imaging is a novel technology that achieves high soft-tissue contrast. Although its clinical impact is still under investigation, the technique may potentially improve clinical diagnostics. In conventional attenuation-based X-ray computed tomography, radiological diagnostics are quantified by Hounsfield units. Corresponding Hounsfield units for phase-contrast imaging have been recently introduced, enabling a setup-independent comparison and standardized interpretation of imaging results. Thus far, the experimental values of few tissue types have been reported; these values have been determined from fixated tissue samples. This study presents phase-contrast Hounsfield units for various types of non-fixated human soft tissues. A large variety of tissue specimens ranging from adipose, muscle and connective tissues to liver, kidney and pancreas tissues were imaged by a grating interferometer with a rotating-anode X-ray tube and a photon-counting detector. Furthermore, we investigated the effects of formalin fixation on the quantitative phase-contrast imaging results. PMID:26322638

X-ray phase contrast imaging: From synchrotrons to conventional sources

International Nuclear Information System (INIS)

Olivo, A.; Castelli, E.

2014-01-01

Phase-based approaches can revolutionize X-ray imaging and remove its main limitation: poor image contrast arising from low attenuation differences. They exploit the unit decrement of the real part of the refractive index, typically 1000 times larger than the imaginary part driving attenuation. This increases the contrast of all details, and enables the detection of features classically considered 'X-ray invisible'. Following pioneering experiments dating back to the mid-sixties, X-ray phase contrast imaging 'exploded' in the mid-nineties, when third generation synchrotron sources became more widely available. Applications were proposed in fields as diverse as material science, palaeontology, biology, food science, cultural heritage preservation, and many others. Among these applications, medicine has been constantly considered the most important; among medical applications, mammography is arguably the one that attracted most attention. Applications to mammography were pioneered by the SYRMEP (SYnchrotron Radiation for MEdical Physics) group in Trieste, which was already active in the area through a combination of innovative ways to do imaging at synchrotrons and development of novel X-ray detectors. This pioneering phase led to the only clinical experience of phase contrast mammography on human patients, and spawned a number of ideas as to how these advances could be translated into clinical practice.

Monte Carlo simulation of grating-based neutron phase contrast imaging at CPHS

International Nuclear Information System (INIS)

Zhang Ran; Chen Zhiqiang; Huang Zhifeng; Xiao Yongshun; Wang Xuewu; Wie Jie; Loong, C.-K.

2011-01-01

Since the launching of the Compact Pulsed Hadron Source (CPHS) project of Tsinghua University in 2009, works have begun on the design and engineering of an imaging/radiography instrument for the neutron source provided by CPHS. The instrument will perform basic tasks such as transmission imaging and computerized tomography. Additionally, we include in the design the utilization of coded-aperture and grating-based phase contrast methodology, as well as the options of prompt gamma-ray analysis and neutron-energy selective imaging. Previously, we had implemented the hardware and data-analysis software for grating-based X-ray phase contrast imaging. Here, we investigate Geant4-based Monte Carlo simulations of neutron refraction phenomena and then model the grating-based neutron phase contrast imaging system according to the classic-optics-based method. The simulated experimental results of the retrieving phase shift gradient information by five-step phase-stepping approach indicate the feasibility of grating-based neutron phase contrast imaging as an option for the cold neutron imaging instrument at the CPHS.

Investigation of the imaging quality of synchrotron-based phase-contrast mammographic tomography

International Nuclear Information System (INIS)

Gureyev, T E; Mayo, S C; Nesterets, Ya I; Mohammadi, S; Menk, R H; Arfelli, F; Tromba, G; Lockie, D; Pavlov, K M; Kitchen, M J; Zanconati, F; Dullin, C

2014-01-01

We report the results of a systematic study of phase-contrast x-ray computed tomography in the propagation-based and analyser-based modes using specially designed phantoms and excised breast tissue samples. The study is aimed at the quantitative evaluation and subsequent optimization, with respect to detection of small tumours in breast tissue, of the effects of phase contrast and phase retrieval on key imaging parameters, such as spatial resolution, contrast-to-noise ratio, x-ray dose and a recently proposed ‘intrinsic quality’ characteristic which combines the image noise with the spatial resolution. We demonstrate that some of the methods evaluated in this work lead to substantial (more than 20-fold) improvement in the contrast-to-noise and intrinsic quality of the reconstructed tomographic images compared with conventional techniques, with the measured characteristics being in good agreement with the corresponding theoretical estimations. This improvement also corresponds to an approximately 400-fold reduction in the x-ray dose, compared with conventional absorption-based tomography, without a loss in the imaging quality. The results of this study confirm and quantify the significant potential benefits achievable in three-dimensional mammography using x-ray phase-contrast imaging and phase-retrieval techniques. (paper)

Visualizing Typical Features of Breast Fibroadenomas Using Phase-Contrast CT: An Ex-Vivo Study

Science.gov (United States)

Grandl, Susanne; Willner, Marian; Herzen, Julia; Sztrókay-Gaul, Anikó; Mayr, Doris; Auweter, Sigrid D.; Hipp, Alexander; Birnbacher, Lorenz; Marschner, Mathias; Chabior, Michael; Reiser, Maximilian; Pfeiffer, Franz; Bamberg, Fabian; Hellerhoff, Karin

2014-01-01

Background Fibroadenoma is the most common benign solid breast lesion type and a very common cause for histologic assessment. To justify a conservative therapy, a highly specific discrimination between fibroadenomas and other breast lesions is crucial. Phase-contrast imaging offers improved soft-tissue contrast and differentiability of fine structures combined with the potential of 3-dimensional imaging. In this study we assessed the potential of grating-based phase-contrast CT imaging for visualizing diagnostically relevant features of fibroadenomas. Materials and Methods Grating-based phase-contrast CT was performed on six ex-vivo formalin-fixed breast specimens containing a fibroadenoma and three samples containing benign changes that resemble fibroadenomas using Talbot Lau interferometry and a polychromatic X-ray source. Phase-contrast and simultaneously acquired absorption-based 3D-datasets were manually matched with corresponding histological slices. The visibility of diagnostically valuable features was assessed in comparison with histology as the gold-standard. Results In all cases, matching of grating-based phase-contrast CT images and histology was successfully completed. Grating-based phase-contrast CT showed greatly improved differentiation of fine structures and provided accurate depiction of strands of fibrous tissue within the fibroadenomas as well as of the diagnostically valuable dilated, branched ductuli of the fibroadenomas. A clear demarcation of tumor boundaries in all cases was provided by phase- but not absorption-contrast CT. Conclusions Pending successful translation of the technology to a clinical setting and considerable reduction of the required dose, the data presented here suggest that grating-based phase-contrast CT may be used as a supplementary non-invasive diagnostic tool in breast diagnostics. Phase-contrast CT may thus contribute to the reduction of false positive findings and reduce the recall and core biopsy rate in population

Combined fluorescence and phase contrast imaging at the Advanced Photon Source

International Nuclear Information System (INIS)

Hornberger, B.; Feser, M.; Jacobsen, C.; Vogt, S.; Legnini, D.; Paterson, D.; Rehak, P.; DeGeronimo, G.; Palmer, B.M.; Experimental Facilities Division; State Univ. of New York at Stony Brook Univ.; BNL; Univ. of Vermont

2006-01-01

X-ray fluorescence microprobes excel at detecting and quantifying trace metals in biological and environmental science samples, but typically do not detect low Z elements such as carbon and nitrogen. Therefore, it is hard to put the trace metals into context with their natural environment. We are implementing phase contrast capabilities with a segmented detector into several microprobes at the Advanced Photon Source (APS) to address this problem. Qualitative differential phase contrast images from a modified soft x-ray detector already provide very useful information for general users. We are also implementing a quantitative method to recover the absolute phase shift by Fourier filtering detector images. New detectors are under development which are optimized for the signal levels present at the APS. In this paper, we concentrate on fundamental signal to noise considerations comparing absorption and differential phase contrast

The Scanning Optical Microscope.

Science.gov (United States)

Sheppard, C. J. R.

1978-01-01

Describes the principle of the scanning optical microscope and explains its advantages over the conventional microscope in the improvement of resolution and contrast, as well as the possibility of producing a picture from optical harmonies generated within the specimen.

Thermal diffusivity imaging with the thermal lens microscope.

Science.gov (United States)

Dada, Oluwatosin O; Feist, Peter E; Dovichi, Norman J

2011-12-01

A coaxial thermal lens microscope was used to generate images based on both the absorbance and thermal diffusivity of histological samples. A pump beam was modulated at frequencies ranging from 50 kHz to 5 MHz using an acousto-optic modulator. The pump and a CW probe beam were combined with a dichroic mirror, directed into an inverted microscope, and focused onto the specimen. The change in the transmitted probe beam's center intensity was detected with a photodiode. The photodiode's signal and a reference signal from the modulator were sent to a high-speed lock-in amplifier. The in-phase and quadrature signals were recorded as a sample was translated through the focused beams and used to generate images based on the amplitude and phase of the lock-in amplifier's signal. The amplitude is related to the absorbance and the phase is related to the thermal diffusivity of the sample. Thin sections of stained liver and bone tissues were imaged; the contrast and signal-to-noise ratio of the phase image was highest at frequencies from 0.1-1 MHz and dropped at higher frequencies. The spatial resolution was 2.5 μm for both amplitude and phase images, limited by the pump beam spot size. © 2011 Optical Society of America

Phase shift extraction and wavefront retrieval from interferograms with background and contrast fluctuations

International Nuclear Information System (INIS)

Liu, Qian; Wang, Yang; He, Jianguo; Ji, Fang

2015-01-01

The fluctuations of background and contrast cause measurement errors in the phase-shifting technique. To extract the phase shifts from interferograms with background and contrast fluctuations, an iterative algorithm is represented. The phase shifts and wavefront phase are calculated in two individual steps with the least-squares method. The fluctuation factors are determined when the phase shifts are calculated, and the fluctuations are compensated when the wavefront phase is calculated. The advantage of the algorithm lies in its ability to extract phase shifts from interferograms with background and contrast fluctuations converging stably and rapidly. Simulations and experiments verify the effectiveness and reliability of the proposed algorithm. The convergence accuracy and speed are demonstrated by the simulation results. The experiment results show its ability for suppressing phase retrieval errors. (paper)

In-line X-ray phase-contrast imaging of murine liver microvasculature ex vivo

International Nuclear Information System (INIS)

Li Beilei; Xu Min; Shi Hongcheng; Chen Shaoliang; Wu Weizhong; Peng Guanyun; Zhang Xi; Peng Yifeng

2012-01-01

Imaging blood vessels is of importance for determining the vascular distribution of organs and tumors. Phase-contrast X-ray imaging can reveal the vessels in much more detail than conventional X-ray absorption method. Visualizing murine liver microvasculature ex vivo with phase-contrast X-ray imaging was performed at Shanghai Synchrotron Radiation Facility. Barium sulfate and physiological saline were used as contrast agents for the blood vessels. Blood vessels of <Φ20 μm could be detected by replacing resident blood with physiological saline or barium sulfate. An entire branch of the portal vein (from the main axial portal vein to the ninth generation of branching) could be captured in a single phase-contrast image. It is demonstrated that selective angiography based on phase contrast X-ray imaging, with a physiological material of low Z elements (such as saline) being the contrast agent, is a viable imaging strategy. Further efforts will be focused on using the technique to image tumor angiogenesis. (authors)

Nonlinear optical response in condensed phases : A microscopic theory using the multipolar Hamiltonian

NARCIS (Netherlands)

Knoester, Jasper; Mukamel, Shaul

1990-01-01

A general scheme is presented for calculating the nonlinear optical response in condensed phases that provides a unified picture of excitons, polaritons, retardation, and local-field effects in crystals and in disordered systems. A fully microscopic starting point is taken by considering the

Ex vivo characterization of pathologic fluids with quantitative phase-contrast computed tomography

Energy Technology Data Exchange (ETDEWEB)

Richter, Vivien, E-mail: vivien.richter@med.uni-tuebingen.de [Department of Diagnostic and Interventional Radiology, Eberhard Karls Universität Tübingen, Hoppe-Seyler-Weg 3, 72076 Tuebingen (Germany); Willner, Marian S., E-mail: marian.willner@ph.tum.de [Department of Physics & Institute of Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching (Germany); Henningsen, John, E-mail: john.henningsen@tum.de [Department of Physics & Institute of Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching (Germany); Birnbacher, Lorenz, E-mail: lorenz.birnbacher@ph.tum.de [Department of Physics & Institute of Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching (Germany); Marschner, Mathias, E-mail: mathias.marschner@ph.tum.de [Department of Physics & Institute of Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching (Germany); Herzen, Julia, E-mail: julia.herzen@ph.tum.de [Department of Physics & Institute of Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching (Germany); Kimm, Melanie A., E-mail: melanie.kimm@tum.de [Department of Diagnostic and Interventional Radiology, Technische Universität München, Ismaninger Str. 22, 81675 Munich (Germany); and others

2017-01-15

Purpose: X-ray phase-contrast imaging (PCI) provides additional information beyond absorption characteristics by detecting the phase shift of the X-ray beam passing through material. The grating-based system works with standard polychromatic X-ray sources, promising a possible clinical implementation. PCI has been shown to provide additional information in soft-tissue samples. The aim of this study was to determine if ex vivo quantitative phase-contrast computed tomography (PCCT) may differentiate between pathologic fluid collections. Materials and methods: PCCT was performed with the grating interferometry method. A protein serial dilution, human blood samples and 17 clinical samples of pathologic fluid retentions were imaged and correlated with clinical chemistry measurements. Conventional and phase-contrast tomography images were reconstructed. Phase-contrast Hounsfield Units (HUp) were used for quantitative analysis analogously to conventional HU. The imaging was analyzed using overall means, ROI values as well as whole-volume-histograms and vertical gradients. Contrast to noise ratios were calculated between different probes and between imaging methods. Results: HUp showed a very good linear correlation with protein concentration in vitro. In clinical samples, HUp correlated rather well with cell count and triglyceride content. PCI was better than absorption imaging at differentiating protein concentrations in the protein samples as well as at differentiating blood plasma from cellular components. PCI also allowed for differentiation of watery samples (such as lymphoceles) from pus. Conclusion: Phase-contrast computed tomography is a promising tool for the differentiation of pathologic fluids that appear homogenous with conventional attenuation imaging.

Recent advances in synchrotron-based hard x-ray phase contrast imaging

International Nuclear Information System (INIS)

Liu, Y; Nelson, J; Andrews, J C; Pianetta, P; Holzner, C

2013-01-01

Ever since the first demonstration of phase contrast imaging (PCI) in the 1930s by Frits Zernike, people have realized the significant advantage of phase contrast over conventional absorption-based imaging in terms of sensitivity to ‘transparent’ features within specimens. Thus, x-ray phase contrast imaging (XPCI) holds great potential in studies of soft biological tissues, typically containing low Z elements such as C, H, O and N. Particularly when synchrotron hard x-rays are employed, the favourable brightness, energy tunability, monochromatic characteristics and penetration depth have dramatically enhanced the quality and variety of XPCI methods, which permit detection of the phase shift associated with 3D geometry of relatively large samples in a non-destructive manner. In this paper, we review recent advances in several synchrotron-based hard x-ray XPCI methods. Challenges and key factors in methodological development are discussed, and biological and medical applications are presented. (paper)

Recent advances in synchrotron-based hard x-ray phase contrast imaging

Science.gov (United States)

Liu, Y.; Nelson, J.; Holzner, C.; Andrews, J. C.; Pianetta, P.

2013-12-01

Ever since the first demonstration of phase contrast imaging (PCI) in the 1930s by Frits Zernike, people have realized the significant advantage of phase contrast over conventional absorption-based imaging in terms of sensitivity to ‘transparent’ features within specimens. Thus, x-ray phase contrast imaging (XPCI) holds great potential in studies of soft biological tissues, typically containing low Z elements such as C, H, O and N. Particularly when synchrotron hard x-rays are employed, the favourable brightness, energy tunability, monochromatic characteristics and penetration depth have dramatically enhanced the quality and variety of XPCI methods, which permit detection of the phase shift associated with 3D geometry of relatively large samples in a non-destructive manner. In this paper, we review recent advances in several synchrotron-based hard x-ray XPCI methods. Challenges and key factors in methodological development are discussed, and biological and medical applications are presented.

Film thickness measurement based on nonlinear phase analysis using a Linnik microscopic white-light spectral interferometer.

Science.gov (United States)

Guo, Tong; Chen, Zhuo; Li, Minghui; Wu, Juhong; Fu, Xing; Hu, Xiaotang

2018-04-20

Based on white-light spectral interferometry and the Linnik microscopic interference configuration, the nonlinear phase components of the spectral interferometric signal were analyzed for film thickness measurement. The spectral interferometric signal was obtained using a Linnik microscopic white-light spectral interferometer, which includes the nonlinear phase components associated with the effective thickness, the nonlinear phase error caused by the double-objective lens, and the nonlinear phase of the thin film itself. To determine the influence of the effective thickness, a wavelength-correction method was proposed that converts the effective thickness into a constant value; the nonlinear phase caused by the effective thickness can then be determined and subtracted from the total nonlinear phase. A method for the extraction of the nonlinear phase error caused by the double-objective lens was also proposed. Accurate thickness measurement of a thin film can be achieved by fitting the nonlinear phase of the thin film after removal of the nonlinear phase caused by the effective thickness and by the nonlinear phase error caused by the double-objective lens. The experimental results demonstrated that both the wavelength-correction method and the extraction method for the nonlinear phase error caused by the double-objective lens improve the accuracy of film thickness measurements.

Phase contrast imaging using a micro focus x-ray source

Science.gov (United States)

Zhou, Wei; Majidi, Keivan; Brankov, Jovan G.

2014-09-01

Phase contrast x-ray imaging, a new technique to increase the imaging contrast for the tissues with close attenuation coefficients, has been studied since mid 1990s. This technique reveals the possibility to show the clear details of the soft tissues and tumors in small scale resolution. A compact and low cost phase contrast imaging system using a conventional x-ray source is described in this paper. Using the conventional x-ray source is of great importance, because it provides the possibility to use the method in hospitals and clinical offices. Simple materials and components are used in the setup to keep the cost in a reasonable and affordable range.Tungsten Kα1 line with the photon energy 59.3 keV was used for imaging. Some of the system design details are discussed. The method that was used to stabilize the system is introduced. A chicken thigh bone tissue sample was used for imaging followed by the image quality, image acquisition time and the potential clinical application discussion. High energy x-ray beam can be used in phase contrast imaging. Therefore the radiation dose to the patients can be greatly decreased compared to the traditional x-ray radiography.

Imaging of metastatic lymph nodes by X-ray phase-contrast micro-tomography.

Directory of Open Access Journals (Sweden)

Torben Haugaard Jensen

Full Text Available Invasive cancer causes a change in density in the affected tissue, which can be visualized by x-ray phase-contrast tomography. However, the diagnostic value of this method has so far not been investigated in detail. Therefore, the purpose of this study was, in a blinded manner, to investigate whether malignancy could be revealed by non-invasive x-ray phase-contrast tomography in lymph nodes from breast cancer patients. Seventeen formalin-fixed paraffin-embedded lymph nodes from 10 female patients (age range 37-83 years diagnosed with invasive ductal carcinomas were analyzed by X-ray phase-contrast tomography. Ten lymph nodes had metastatic deposits and 7 were benign. The phase-contrast images were analyzed according to standards for conventional CT images looking for characteristics usually only visible by pathological examinations. Histopathology was used as reference. The result of this study was that the diagnostic sensitivity of the image analysis for detecting malignancy was 100% and the specificity was 87%. The positive predictive value was 91% for detecting malignancy and the negative predictive value was 100%. We conclude that x-ray phase-contrast imaging can accurately detect density variations to obtain information regarding lymph node involvement previously inaccessible with standard absorption x-ray imaging.

PHASE QUANTIZATION STUDY OF SPATIAL LIGHT MODULATOR FOR EXTREME HIGH-CONTRAST IMAGING

Energy Technology Data Exchange (ETDEWEB)

Dou, Jiangpei; Ren, Deqing, E-mail: jpdou@niaot.ac.cn, E-mail: jiangpeidou@gmail.com [Physics and Astronomy Department, California State University Northridge, 18111 Nordhoff Street, Northridge, CA 91330 (United States)

2016-11-20

Direct imaging of exoplanets by reflected starlight is extremely challenging due to the large luminosity ratio to the primary star. Wave-front control is a critical technique to attenuate the speckle noise in order to achieve an extremely high contrast. We present a phase quantization study of a spatial light modulator (SLM) for wave-front control to meet the contrast requirement of detection of a terrestrial planet in the habitable zone of a solar-type star. We perform the numerical simulation by employing the SLM with different phase accuracy and actuator numbers, which are related to the achievable contrast. We use an optimization algorithm to solve the quantization problems that is matched to the controllable phase step of the SLM. Two optical configurations are discussed with the SLM located before and after the coronagraph focal plane mask. The simulation result has constrained the specification for SLM phase accuracy in the above two optical configurations, which gives us a phase accuracy of 0.4/1000 and 1/1000 waves to achieve a contrast of 10{sup -10}. Finally, we have demonstrated that an SLM with more actuators can deliver a competitive contrast performance on the order of 10{sup -10} in comparison to that by using a deformable mirror.

Noninvasive 3D Structural Analysis of Arthropod by Synchrotron X-Ray Phase Contrast Tomography

International Nuclear Information System (INIS)

Yao, S.; Zong, Y.; Fan, J.; Sun, Z.; Jiang, H.

2015-01-01

X-ray imaging techniques significantly advanced our understanding of materials and biology, among which phase contrast X-ray microscopy has obvious advantages in imaging biological specimens which have low contrast by conventional absorption contrast microscopy. In this paper, three-dimensional microstructure of arthropod with high contrast has been demonstrated by synchrotron X-ray in-line phase contrast tomography. The external morphology and internal structures of an earthworm were analyzed based upon tomographic reconstructions with and without phase retrieval. We also identified and characterized various fine structural details such as the musculature system, the digestive system, the nervous system, and the circulatory system. This work exhibited the high efficiency, high precision, and wide potential applications of synchrotron X-ray phase contrast tomography in nondestructive investigation of low-density materials and biology.

Applications of phase-contrast x-ray imaging to medicine using an x-ray interferometer

Science.gov (United States)

Momose, Atsushi; Yoneyama, Akio; Takeda, Tohoru; Itai, Yuji; Tu, Jinhong; Hirano, Keiichi

1999-10-01

We are investigating possible medical applications of phase- contrast X-ray imaging using an X-ray interferometer. This paper introduces the strategy of the research project and the present status. The main subject is to broaden the observation area to enable in vivo observation. For this purpose, large X-ray interferometers were developed, and 2.5 cm X 1.5 cm interference patterns were generated using synchrotron X-rays. An improvement of the spatial resolution is also included in the project, and an X-ray interferometer designed for high-resolution phase-contrast X-ray imaging was fabricated and tested. In parallel with the instrumental developments, various soft tissues are observed by phase- contrast X-ray CT to find correspondence between the generated contrast and our histological knowledge. The observation done so far suggests that cancerous tissues are differentiated from normal tissues and that blood can produce phase contrast. Furthermore, this project includes exploring materials that modulate phase contrast for selective imaging.

Simulation of single grid-based phase-contrast x-ray imaging (g-PCXI)

Energy Technology Data Exchange (ETDEWEB)

Lim, H.W.; Lee, H.W. [Department of Radiation Convergence Engineering, iTOMO Group, Yonsei University, 1 Yonseidae-gil, Wonju, Gangwon-do 26493 (Korea, Republic of); Cho, H.S., E-mail: hscho1@yonsei.ac.kr [Department of Radiation Convergence Engineering, iTOMO Group, Yonsei University, 1 Yonseidae-gil, Wonju, Gangwon-do 26493 (Korea, Republic of); Je, U.K.; Park, C.K.; Kim, K.S.; Kim, G.A.; Park, S.Y.; Lee, D.Y.; Park, Y.O.; Woo, T.H. [Department of Radiation Convergence Engineering, iTOMO Group, Yonsei University, 1 Yonseidae-gil, Wonju, Gangwon-do 26493 (Korea, Republic of); Lee, S.H.; Chung, W.H.; Kim, J.W.; Kim, J.G. [R& D Center, JPI Healthcare Co., Ltd., Ansan 425-833 (Korea, Republic of)

2017-04-01

Single grid-based phase-contrast x-ray imaging (g-PCXI) technique, which was recently proposed by Wen et al. to retrieve absorption, scattering, and phase-gradient images from the raw image of the examined object, seems a practical method for phase-contrast imaging with great simplicity and minimal requirements on the setup alignment. In this work, we developed a useful simulation platform for g-PCXI and performed a simulation to demonstrate its viability. We also established a table-top setup for g-PCXI which consists of a focused-linear grid (200-lines/in strip density), an x-ray tube (100-μm focal spot size), and a flat-panel detector (48-μm pixel size) and performed a preliminary experiment with some samples to show the performance of the simulation platform. We successfully obtained phase-contrast x-ray images of much enhanced contrast from both the simulation and experiment and the simulated contract seemed similar to the experimental contrast, which shows the performance of the developed simulation platform. We expect that the simulation platform will be useful for designing an optimal g-PCXI system. - Highlights: • It is proposed for the single grid-based phase-contrast x-ray imaging (g-PCXI) technique. • We implemented for a numerical simulation code. • The preliminary experiment with several samples to compare is performed. • It is expected to be useful to design an optimal g-PCXI system.

Observation of human tissue with phase-contrast x-ray computed tomography

Science.gov (United States)

Momose, Atsushi; Takeda, Tohoru; Itai, Yuji; Tu, Jinhong; Hirano, Keiichi

1999-05-01

Human tissues obtained from cancerous kidneys fixed in formalin were observed with phase-contrast X-ray computed tomography (CT) using 17.7-keV synchrotron X-rays. By measuring the distributions of the X-ray phase shift caused by samples using an X-ray interferometer, sectional images that map the distribution of the refractive index were reconstructed. Because of the high sensitivity of phase- contrast X-ray CT, a cancerous lesion was differentiated from normal tissue and a variety of other structures were revealed without the need for staining.

Analyser-based phase contrast image reconstruction using geometrical optics

International Nuclear Information System (INIS)

Kitchen, M J; Pavlov, K M; Siu, K K W; Menk, R H; Tromba, G; Lewis, R A

2007-01-01

Analyser-based phase contrast imaging can provide radiographs of exceptional contrast at high resolution (<100 μm), whilst quantitative phase and attenuation information can be extracted using just two images when the approximations of geometrical optics are satisfied. Analytical phase retrieval can be performed by fitting the analyser rocking curve with a symmetric Pearson type VII function. The Pearson VII function provided at least a 10% better fit to experimentally measured rocking curves than linear or Gaussian functions. A test phantom, a hollow nylon cylinder, was imaged at 20 keV using a Si(1 1 1) analyser at the ELETTRA synchrotron radiation facility. Our phase retrieval method yielded a more accurate object reconstruction than methods based on a linear fit to the rocking curve. Where reconstructions failed to map expected values, calculations of the Takagi number permitted distinction between the violation of the geometrical optics conditions and the failure of curve fitting procedures. The need for synchronized object/detector translation stages was removed by using a large, divergent beam and imaging the object in segments. Our image acquisition and reconstruction procedure enables quantitative phase retrieval for systems with a divergent source and accounts for imperfections in the analyser

Phase-contrast x-ray computed tomography for observing biological specimens and organic materials

Science.gov (United States)

Momose, Atsushi; Takeda, Tohoru; Itai, Yuji

1995-02-01

A novel three-dimensional x-ray imaging method has been developed by combining a phase-contrast x-ray imaging technique with x-ray computed tomography. This phase-contrast x-ray computed tomography (PCX-CT) provides sectional images of organic specimens that would produce absorption-contrast x-ray CT images with little contrast. Comparing PCX-CT images of rat cerebellum and cancerous rabbit liver specimens with corresponding absorption-contrast CT images shows that PCX-CT is much more sensitive to the internal structure of organic specimens.

Simple and reliable identification of the human round spermatid by inverted phase-contrast microscopy.

Science.gov (United States)

Verheyen, G; Crabbé, E; Joris, H; Van Steirteghem, A

1998-06-01

Based on the results of animal studies, round spermatid injection (ROSI) has been introduced into the clinical practice of several in-vitro fertilization (IVF) centres. The efficiency of this procedure in terms of fertilization rates and pregnancy rates, however, remains very poor. An essential aspect which does not receive enough attention is the correct identification of this type of round cell within a heterogeneous population of testicular cells. A Nikon inverted microscope equipped with phase-contrast optics (DLL) provided a clear image which allowed reliable recognition of round spermatids in cell suspensions smeared at the glass bottom of the dish. Fluorescent in-situ hybridization confirmed the haploid status of the selected cells. However, exploration of several biopsies from patients with non-obstructive azoospermia showing no spermatozoa after extensive search did not reveal any round spermatids. This observation questions whether enough effort is spent on searching for mature spermatozoa or late spermatids. Experimental investigations should precede the introduction of ROSI into the clinical practice of any IVF centre.

High sensitivity phase retrieval method in grating-based x-ray phase contrast imaging

Energy Technology Data Exchange (ETDEWEB)

Wu, Zhao; Gao, Kun; Chen, Jian; Wang, Dajiang; Wang, Shenghao; Chen, Heng; Bao, Yuan; Shao, Qigang; Wang, Zhili, E-mail: wangnsrl@ustc.edu.cn [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Zhang, Kai [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Zhu, Peiping; Wu, Ziyu, E-mail: wuzy@ustc.edu.cn [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China and Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

2015-02-15

Purpose: Grating-based x-ray phase contrast imaging is considered as one of the most promising techniques for future medical imaging. Many different methods have been developed to retrieve phase signal, among which the phase stepping (PS) method is widely used. However, further practical implementations are hindered, due to its complex scanning mode and high radiation dose. In contrast, the reverse projection (RP) method is a novel fast and low dose extraction approach. In this contribution, the authors present a quantitative analysis of the noise properties of the refraction signals retrieved by the two methods and compare their sensitivities. Methods: Using the error propagation formula, the authors analyze theoretically the signal-to-noise ratios (SNRs) of the refraction images retrieved by the two methods. Then, the sensitivities of the two extraction methods are compared under an identical exposure dose. Numerical experiments are performed to validate the theoretical results and provide some quantitative insight. Results: The SNRs of the two methods are both dependent on the system parameters, but in different ways. Comparison between their sensitivities reveals that for the refraction signal, the RP method possesses a higher sensitivity, especially in the case of high visibility and/or at the edge of the object. Conclusions: Compared with the PS method, the RP method has a superior sensitivity and provides refraction images with a higher SNR. Therefore, one can obtain highly sensitive refraction images in grating-based phase contrast imaging. This is very important for future preclinical and clinical implementations.

High sensitivity phase retrieval method in grating-based x-ray phase contrast imaging

International Nuclear Information System (INIS)

Wu, Zhao; Gao, Kun; Chen, Jian; Wang, Dajiang; Wang, Shenghao; Chen, Heng; Bao, Yuan; Shao, Qigang; Wang, Zhili; Zhang, Kai; Zhu, Peiping; Wu, Ziyu

2015-01-01

Purpose: Grating-based x-ray phase contrast imaging is considered as one of the most promising techniques for future medical imaging. Many different methods have been developed to retrieve phase signal, among which the phase stepping (PS) method is widely used. However, further practical implementations are hindered, due to its complex scanning mode and high radiation dose. In contrast, the reverse projection (RP) method is a novel fast and low dose extraction approach. In this contribution, the authors present a quantitative analysis of the noise properties of the refraction signals retrieved by the two methods and compare their sensitivities. Methods: Using the error propagation formula, the authors analyze theoretically the signal-to-noise ratios (SNRs) of the refraction images retrieved by the two methods. Then, the sensitivities of the two extraction methods are compared under an identical exposure dose. Numerical experiments are performed to validate the theoretical results and provide some quantitative insight. Results: The SNRs of the two methods are both dependent on the system parameters, but in different ways. Comparison between their sensitivities reveals that for the refraction signal, the RP method possesses a higher sensitivity, especially in the case of high visibility and/or at the edge of the object. Conclusions: Compared with the PS method, the RP method has a superior sensitivity and provides refraction images with a higher SNR. Therefore, one can obtain highly sensitive refraction images in grating-based phase contrast imaging. This is very important for future preclinical and clinical implementations

Analyser-based phase contrast image reconstruction using geometrical optics.

Science.gov (United States)

Kitchen, M J; Pavlov, K M; Siu, K K W; Menk, R H; Tromba, G; Lewis, R A

2007-07-21

Analyser-based phase contrast imaging can provide radiographs of exceptional contrast at high resolution (geometrical optics are satisfied. Analytical phase retrieval can be performed by fitting the analyser rocking curve with a symmetric Pearson type VII function. The Pearson VII function provided at least a 10% better fit to experimentally measured rocking curves than linear or Gaussian functions. A test phantom, a hollow nylon cylinder, was imaged at 20 keV using a Si(1 1 1) analyser at the ELETTRA synchrotron radiation facility. Our phase retrieval method yielded a more accurate object reconstruction than methods based on a linear fit to the rocking curve. Where reconstructions failed to map expected values, calculations of the Takagi number permitted distinction between the violation of the geometrical optics conditions and the failure of curve fitting procedures. The need for synchronized object/detector translation stages was removed by using a large, divergent beam and imaging the object in segments. Our image acquisition and reconstruction procedure enables quantitative phase retrieval for systems with a divergent source and accounts for imperfections in the analyser.

Slit-scanning differential phase-contrast mammography: first experimental results

Science.gov (United States)

Roessl, Ewald; Daerr, Heiner; Koehler, Thomas; Martens, Gerhard; van Stevendaal, Udo

2014-03-01

The demands for a large field-of-view (FOV) and the stringent requirements for a stable acquisition geometry rank among the major obstacles for the translation of grating-based, differential phase-contrast techniques from the laboratory to clinical applications. While for state-of-the-art Full-Field-Digital Mammography (FFDM) FOVs of 24 cm x 30 cm are common practice, the specifications for mechanical stability are naturally derived from the detector pixel size which ranges between 50 and 100 μm. However, in grating-based, phasecontrast imaging, the relative placement of the gratings in the interferometer must be guaranteed to within micro-meter precision. In this work we report on first experimental results on a phase-contrast x-ray imaging system based on the Philips MicroDose L30 mammography unit. With the proposed approach we achieve a FOV of about 65 mm x 175 mm by the use of the slit-scanning technique. The demand for mechanical stability on a micrometer scale was relaxed by the specific interferometer design, i.e., a rigid, actuator-free mount of the phase-grating G1 with respect to the analyzer-grating G2 onto a common steel frame. The image acquisition and formation processes are described and first phase-contrast images of a test object are presented. A brief discussion of the shortcomings of the current approach is given, including the level of remaining image artifacts and the relatively inefficient usage of the total available x-ray source output.

Scanning Color Laser Microscope

Science.gov (United States)

Awamura, D.; Ode, T.; Yonezawa, M.

1988-01-01

A confocal color laser microscope which utilizes a three color laser light source (Red: He-Ne, Green: Ar, Blue: Ar) has been developed and is finding useful applications in the semiconductor field. The color laser microscope, when compared to a conventional microscope, offers superior color separation, higher resolution, and sharper contrast. Recently some new functions including a Focus Scan Memory, a Surface Profile Measurement System, a Critical Dimension Measurement system (CD) and an Optical Beam Induced Current Function (OBIC) have been developed for the color laser microscope. This paper will discuss these new features.

Development of phase-contrast imaging technique for material science and medical science applications

International Nuclear Information System (INIS)

Kashyap, Y.S.; Roy, Tushar; Sarkar, P.S; Shukla, Mayank; Yadav, P.S; Sinha, Amar; Verma, Vishnu; Ghosh, A.K.

2007-07-01

In-line phase contrast imaging technique is an emerging method for study of materials such as carbon fibres, carbon composite materials, polymers etc. These represent the class of materials for which x-ray attenuation cross-section is very small. Similarly, this technique is also well suited for imaging of soft materials such as tissues, distinguishing between tumour and normal tissue. Thus this method promises a far better contrast for low x-ray absorbing substances than the conventional radiography method for material and medical science applications. Though the conventional radiography technique has been carried out for decades, the phase-imaging technique is being demonstrated for the first time within, the country. We have set up an experimental facility for phase contrast imaging using a combination of x-ray CCD detector and a microfocus x-ray source. This facility is dedicated for micro-imaging experiments such as micro-tomography and high resolution phase contrast experiments. In this report, the results of phase contrast imaging using microfocus source and ELETTRA, synchrotron source are discussed. We have also discussed the basic design and heat load calculation for upcoming imaging beamline at Indus-II, RRCAT, Indore. (author)

Synchrotron Based Phase Contrast Tomography of Hyper cholesteromic Rat Liver

Directory of Open Access Journals (Sweden)

Fatima A

2017-05-01

Full Text Available X-ray phase contrast imaging technique has been applied for the study of morphological variations in soft tissues. The effect of an antioxidant, α-lipoic acid in reducing hypercholesterolemia in rats is investigated. The experiment was conducted to measure serum lipid profile and diameter of vessels in rat liver, as liver is the most vital organ in hypolipidemic activity studies. Methods: Four groups of male Wistar rats, control (Group I, hyperlipidemic (Group II, positive control (Group III and treated Group IV were studied for serum lipid profile and liver vessels with synchrotron X-ray phase tomography. The Group I rats received chow diet, in Group II rats, administration of 20% butter rich diet induced hyperlipidemia. Group III, treated rats received hypolipidemic drug Atorvastatin and Group IV animals received a potent antioxidant DL-α-Lipoic acid. The excised liver tissue immersed in 10% formalin. X-ray phase contrast tomography was performed for comparison of diameter of liver vessels. Results: Among the four group of animals, the diameter of liver vessels was much larger in hypercholesterolemic rat (Group II. The liver vessel diameter comparison with X-ray phase contrast tomography and the lipid profile shows reduction in serum lipids and lipoproteins by ALA treatment.

First principles study of the optical contrast in phase change materials

Energy Technology Data Exchange (ETDEWEB)

Caravati, S; Parrinello, M [Department of Chemistry and Applied Biosciences, ETH Zurich, USI Campus, Via Giuseppe Buffi 13, 6900 Lugano (Switzerland); Bernasconi, M, E-mail: marco.bernasconi@mater.unimib.i [Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via R Cozzi 53, I-20125, Milano (Italy)

2010-08-11

We study from first principles the optical properties of the phase change materials Ge{sub 2}Sb{sub 2}Te{sub 5} (GST), GeTe and Sb{sub 2}Te{sub 3} in the crystalline phase and in realistic models of the amorphous phase generated by quenching from the melt in ab initio molecular dynamics simulations. The calculations reproduce the strong optical contrast between the crystalline and amorphous phases measured experimentally and exploited in optical data storage. It is demonstrated that the optical contrast is due to a change in the optical matrix elements across the phase change in all the compounds. It is concluded that the reduction of the optical matrix elements in the amorphous phases is due to angular disorder in p-bonding which dominates the amorphous network in agreement with previous proposals (Huang and Robertson 2010 Phys. Rev. B 81 081204) based on calculations on crystalline models.

Selective scanning tunneling microscope light emission from rutile phase of VO2.

Science.gov (United States)

Sakai, Joe; Kuwahara, Masashi; Hotsuki, Masaki; Katano, Satoshi; Uehara, Yoichi

2016-09-28

We observed scanning tunneling microscope light emission (STM-LE) induced by a tunneling current at the gap between an Ag tip and a VO2 thin film, in parallel to scanning tunneling spectroscopy (STS) profiles. The 34 nm thick VO2 film grown on a rutile TiO2 (0 0 1) substrate consisted of both rutile (R)- and monoclinic (M)-structure phases of a few 10 nm-sized domains at room temperature. We found that STM-LE with a certain photon energy of 2.0 eV occurs selectively from R-phase domains of VO2, while no STM-LE was observed from M-phase. The mechanism of STM-LE from R-phase VO2 was determined to be an interband transition process rather than inverse photoemission or inelastic tunneling processes.

Effects of intraarticular contrast media on synovial membrane and cartilage: An electron microscopic evaluation in rabbit knees

International Nuclear Information System (INIS)

Kose, N.; Inan, U.; Omeroglu, H.; Seber, S.; Baycu, C.; Omeroglu, H.

2007-01-01

To evaluate the histological and ultrastructural alterations in rabbit knee joint cartilage and synovia induced by intraarticular injections of 2 water soluble contrast agents. The study was conducted at the Department of Orthopedics and Traumatology, Medical Faculty, Osmangazi University, Eskisehir, Turkey in January 2002. To examine the effect of contrast agents on articular cartilage and synovial membrane, rabbit model was used. Specimens from 62 knee joints were examined by light microscopy and transmission electron microscopy one hour, one day, one week and 2 weeks after intraarticular administration of gadolinium-diethylenetriamine pentaacetic acid, iopromide or saline. In the knees injected with saline, light microscopic changes of the synovium consisted of edema only. Edema and hyperemia were seen in contrast agent injected knees. Ultrastructurally, numerous and large pinocytotic vesicles in A cells of the synovial membrane were seen in contrast agent injected groups. In the knees injected with saline the cartilage were ultrastructurally normal but contrast agent injected knees showed increased activation of chondrocytes with increase of dense glycogen accumulation, large lipid vacuoles and matrix material. There were very rare pycnotic cells in these samples. The rating scale has been used and the means of the total scores were determined for the groups. The effects of contrast agents reduced gradually on the cartilage and synovium in general but did not become completely normal in the observation period. (author)

Phase zone plates as condensers for the Gottingen scanning x-ray microscope

International Nuclear Information System (INIS)

Hilkenbach, R.; Thieme

1987-01-01

With the Gottingen scanning x-ray microscope the synchrotron source is image by x-ray optics into a monochromatic small scan spot, through which a specimen can be moved. Hereby one part of the optics, the condenser zone plate and a pinhole, works as a linear monochromator in the wavelength region of λ = 2.36 nm to λ = 4.5 nm. The efficiency of such a condenser should be as high as possible to minimize the loss of radiation. Phase zone plates have a four times higher efficiency in the first order of diffraction than amplitude zone plates. Two condenser zone plates, KZP4 and KZP5, have been constructed so that they are well suited for the use in the scanning microscope. These zone plates have been made holographically by superposing two wavefronts of laser light in an specific designed optical arrangement and exposing the zone plate structure into a photoresist. Using reactive ion etching (RIE) the structure has been transformed into Germanium. The thickness of the zone plate has been chosen to show at λ = 2.36 nm a phase effect. The efficiency has been measured at the Berliner Elektronenspeircherring Gesellschaft fur Synchrotronstrahlung m.b.H., Berlin

The phase accumulation and antenna near field of microscopic propagating spin wave devices

Energy Technology Data Exchange (ETDEWEB)

Chang, Crosby S.; Kostylev, Mikhail, E-mail: mikhail.kostylev@uwa.edu.au; Ivanov, Eugene [School of Physics M013, The University of Western Australia, Crawley, WA 6009 (Australia); Ding, Junjia; Adeyeye, Adekunle O. [Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore (Singapore)

2014-01-20

We studied phase accumulation by the highly non-reciprocal magnetostatic surface spin waves in thin Permalloy microstripes excited and received by microscopic coplanar antennae. We find that the experimentally measured characteristic length of the near field of the antenna is smaller than the total width of the coplanar. This is confirmed by our numerical simulations. Consequently, the distance over which the spin wave accumulates its phase while travelling between the input and output antennae coincides with the distance between the antennae symmetry axes with good accuracy.

The phase accumulation and antenna near field of microscopic propagating spin wave devices

International Nuclear Information System (INIS)

Chang, Crosby S.; Kostylev, Mikhail; Ivanov, Eugene; Ding, Junjia; Adeyeye, Adekunle O.

2014-01-01

We studied phase accumulation by the highly non-reciprocal magnetostatic surface spin waves in thin Permalloy microstripes excited and received by microscopic coplanar antennae. We find that the experimentally measured characteristic length of the near field of the antenna is smaller than the total width of the coplanar. This is confirmed by our numerical simulations. Consequently, the distance over which the spin wave accumulates its phase while travelling between the input and output antennae coincides with the distance between the antennae symmetry axes with good accuracy

Initial studies of synchrotron radiation phase-contrast imaging in the field of medicine

International Nuclear Information System (INIS)

Chen Shaoliang; Zhang Xi; Peng Yifeng; Li Beilei; Cheng Aiping; Zhu Peiping; Yuan Xiqing; Huang Wanxia

2010-01-01

Recently,research on using X-ray phase information in medicine has been growing remarkably fast. Phase-contrast imaging with synchrotron radiation can reveal inner soft tissues such as tendons, cartilage, ligaments, adipose tissue, vessels and nerves without a contrast agent. We have visualized the liver, bile duct, lung, kidney, stomach and intestine, heart, blood vessel, bone and arthrosis, and tumor tissues using 'in-line' phase contrast imaging and diffraction-enhanced imaging. It is seen that the synchrotron radiation graphs show much higher resolution. This method is especially suitable for studying soft tissue structure and blood vessels. (authors)

A phase contrast interferometer on DIII-D

International Nuclear Information System (INIS)

Coda, S.; Porkolab, M.; Carlstrom, T.N.

1992-04-01

A novel imaging diagnostic has recently become operational on the DIII-D tokamak for the study of density fluctuations at the outer edge of the plasma. The phase contrast imaging approach overcomes the limitations of conventional scattering techniques in the spectral range of interest for transport-related phenomena, by allowing detection of long wavelength modes (up to 7.6 cm) with excellent spatial resolution (5 mm) in the radial direction. Additional motivation for the diagnostic is provided by wave-plasma interactions during heating and current drive experiments in the Ion Cyclotron range of frequencies. Density perturbations of 4 x 10 7 cm -3 with a 1 MHz bandwidth can be resolved. The diagnostic employs a 7.6 cm diameter CO 2 laser beam launched vertically across the plasma edge. An image of the plasma is then created on a 16-element detector array: the detector signals are directly proportional to the density fluctuations integrated along each chord. Wavelengths and correlation lengths can be inferred from the spatial mapping. The phase contrast method and its application to DIII-D are described and tests and first plasma data are presented

Analyzer-based x-ray phase-contrast microscopy combining channel-cut and asymmetrically cut crystals

International Nuclear Information System (INIS)

Hoennicke, M. G.; Cusatis, C.

2007-01-01

An analyzer-based x-ray phase-contrast microscopy (ABM) setup combining a standard analyzer-based x-ray phase-contrast imaging (ABI) setup [nondispersive 4-crystal setup (Bonse-Hart setup)] and diffraction by asymmetrically cut crystals is presented here. An attenuation-contrast microscopy setup with conventional x-ray source and asymmetrically cut crystals is first analyzed. Edge-enhanced effects attributed to phase jumps or refraction/total external reflection on the fiber borders were detected. However, the long exposure times and the possibility to achieve high contrast microscopies by using extremely low attenuation-contrast samples motivated us to assemble the ABM setup using a synchrotron source. This setup was found to be useful for low contrast attenuation samples due to the low exposure time, high contrast, and spatial resolution found. Moreover, thanks to the combination with the nondispersive ABI setup, the diffraction-enhanced x-ray imaging algorithm could be applied

Cumulative phase delay imaging for contrast-enhanced ultrasound tomography

International Nuclear Information System (INIS)

Demi, Libertario; Van Sloun, Ruud J G; Wijkstra, Hessel; Mischi, Massimo

2015-01-01

Standard dynamic-contrast enhanced ultrasound (DCE-US) imaging detects and estimates ultrasound-contrast-agent (UCA) concentration based on the amplitude of the nonlinear (harmonic) components generated during ultrasound (US) propagation through UCAs. However, harmonic components generation is not specific to UCAs, as it also occurs for US propagating through tissue. Moreover, nonlinear artifacts affect standard DCE-US imaging, causing contrast to tissue ratio reduction, and resulting in possible misclassification of tissue and misinterpretation of UCA concentration. Furthermore, no contrast-specific modality exists for DCE-US tomography; in particular speed-of-sound changes due to UCAs are well within those caused by different tissue types. Recently, a new marker for UCAs has been introduced. A cumulative phase delay (CPD) between the second harmonic and fundamental component is in fact observable for US propagating through UCAs, and is absent in tissue. In this paper, tomographic US images based on CPD are for the first time presented and compared to speed-of-sound US tomography. Results show the applicability of this marker for contrast specific US imaging, with cumulative phase delay imaging (CPDI) showing superior capabilities in detecting and localizing UCA, as compared to speed-of-sound US tomography. Cavities (filled with UCA) which were down to 1 mm in diameter were clearly detectable. Moreover, CPDI is free of the above mentioned nonlinear artifacts. These results open important possibilities to DCE-US tomography, with potential applications to breast imaging for cancer localization. (fast track communication)

Combined mixed approach algorithm for in-line phase-contrast x-ray imaging

International Nuclear Information System (INIS)

De Caro, Liberato; Scattarella, Francesco; Giannini, Cinzia; Tangaro, Sabina; Rigon, Luigi; Longo, Renata; Bellotti, Roberto

2010-01-01

Purpose: In the past decade, phase-contrast imaging (PCI) has been applied to study different kinds of tissues and human body parts, with an increased improvement of the image quality with respect to simple absorption radiography. A technique closely related to PCI is phase-retrieval imaging (PRI). Indeed, PCI is an imaging modality thought to enhance the total contrast of the images through the phase shift introduced by the object (human body part); PRI is a mathematical technique to extract the quantitative phase-shift map from PCI. A new phase-retrieval algorithm for the in-line phase-contrast x-ray imaging is here proposed. Methods: The proposed algorithm is based on a mixed transfer-function and transport-of-intensity approach (MA) and it requires, at most, an initial approximate estimate of the average phase shift introduced by the object as prior knowledge. The accuracy in the initial estimate determines the convergence speed of the algorithm. The proposed algorithm retrieves both the object phase and its complex conjugate in a combined MA (CMA). Results: Although slightly less computationally effective with respect to other mixed-approach algorithms, as two phases have to be retrieved, the results obtained by the CMA on simulated data have shown that the obtained reconstructed phase maps are characterized by particularly low normalized mean square errors. The authors have also tested the CMA on noisy experimental phase-contrast data obtained by a suitable weakly absorbing sample consisting of a grid of submillimetric nylon fibers as well as on a strongly absorbing object made of a 0.03 mm thick lead x-ray resolution star pattern. The CMA has shown a good efficiency in recovering phase information, also in presence of noisy data, characterized by peak-to-peak signal-to-noise ratios down to a few dBs, showing the possibility to enhance with phase radiography the signal-to-noise ratio for features in the submillimetric scale with respect to the attenuation

Regularized iterative integration combined with non-linear diffusion filtering for phase-contrast x-ray computed tomography.

Science.gov (United States)

Burger, Karin; Koehler, Thomas; Chabior, Michael; Allner, Sebastian; Marschner, Mathias; Fehringer, Andreas; Willner, Marian; Pfeiffer, Franz; Noël, Peter

2014-12-29

Phase-contrast x-ray computed tomography has a high potential to become clinically implemented because of its complementarity to conventional absorption-contrast.In this study, we investigate noise-reducing but resolution-preserving analytical reconstruction methods to improve differential phase-contrast imaging. We apply the non-linear Perona-Malik filter on phase-contrast data prior or post filtered backprojected reconstruction. Secondly, the Hilbert kernel is replaced by regularized iterative integration followed by ramp filtered backprojection as used for absorption-contrast imaging. Combining the Perona-Malik filter with this integration algorithm allows to successfully reveal relevant sample features, quantitatively confirmed by significantly increased structural similarity indices and contrast-to-noise ratios. With this concept, phase-contrast imaging can be performed at considerably lower dose.

Comparison of post contrast CT urography phases in bladder cancer detection

Energy Technology Data Exchange (ETDEWEB)

Helenius, Malin; Dahlman, Par; Lonnemark, Maria; Magnusson, Anders [Uppsala University Hospital, Department of Surgical Sciences, Section of Radiology, Uppsala (Sweden); Brekkan, Einar [Uppsala University Hospital, Department of Surgical Sciences, Section of Urology, Uppsala (Sweden); Wernroth, Lisa [Uppsala University Hospital, Uppsala Clinical Research Center, Uppsala (Sweden)

2016-02-15

The aim of this study was to investigate which post-contrast phase(s) in a four-phase CT urography protocol is (are) most suitable for bladder cancer detection. The medical records of 106 patients with visible haematuria who underwent a CT urography examination, including unenhanced, enhancement-triggered corticomedullary (CMP), nephrographic (NP) and excretory (EP) phases, were reviewed. The post-contrast phases (n = 318 different phases) were randomized into an evaluation order and blindly reviewed by two uroradiologists. Twenty-one patients were diagnosed with bladder cancer. Sensitivity for bladder cancer detection was 0.95 in CMP, 0.83 in NP and 0.81 in EP. Negative predictive value (NPV) was 0.99 in CMP, 0.96 in NP and 0.95 in EP. The sensitivity was higher in CMP than in both NP (p-value 0.016) and EP (p-value 0.0003). NPV was higher in CMP than in NP (p-value 0.024) and EP (p-value 0.002). In the CT urography protocol with enhancement-triggered scan, sensitivity and NPV were highest in the corticomedullary phase, and this phase should be used for bladder assessment. (orig.)

Comparison of post contrast CT urography phases in bladder cancer detection

International Nuclear Information System (INIS)

Helenius, Malin; Dahlman, Par; Lonnemark, Maria; Magnusson, Anders; Brekkan, Einar; Wernroth, Lisa

2016-01-01

The aim of this study was to investigate which post-contrast phase(s) in a four-phase CT urography protocol is (are) most suitable for bladder cancer detection. The medical records of 106 patients with visible haematuria who underwent a CT urography examination, including unenhanced, enhancement-triggered corticomedullary (CMP), nephrographic (NP) and excretory (EP) phases, were reviewed. The post-contrast phases (n = 318 different phases) were randomized into an evaluation order and blindly reviewed by two uroradiologists. Twenty-one patients were diagnosed with bladder cancer. Sensitivity for bladder cancer detection was 0.95 in CMP, 0.83 in NP and 0.81 in EP. Negative predictive value (NPV) was 0.99 in CMP, 0.96 in NP and 0.95 in EP. The sensitivity was higher in CMP than in both NP (p-value 0.016) and EP (p-value 0.0003). NPV was higher in CMP than in NP (p-value 0.024) and EP (p-value 0.002). In the CT urography protocol with enhancement-triggered scan, sensitivity and NPV were highest in the corticomedullary phase, and this phase should be used for bladder assessment. (orig.)

The second-order differential phase contrast and its retrieval for imaging with x-ray Talbot interferometry

International Nuclear Information System (INIS)

Yang Yi; Tang Xiangyang

2012-01-01

Purpose: The x-ray differential phase contrast imaging implemented with the Talbot interferometry has recently been reported to be capable of providing tomographic images corresponding to attenuation-contrast, phase-contrast, and dark-field contrast, simultaneously, from a single set of projection data. The authors believe that, along with small-angle x-ray scattering, the second-order phase derivative Φ ″ s (x) plays a role in the generation of dark-field contrast. In this paper, the authors derive the analytic formulae to characterize the contribution made by the second-order phase derivative to the dark-field contrast (namely, second-order differential phase contrast) and validate them via computer simulation study. By proposing a practical retrieval method, the authors investigate the potential of second-order differential phase contrast imaging for extensive applications. Methods: The theoretical derivation starts at assuming that the refractive index decrement of an object can be decomposed into δ=δ s +δ f , where δ f corresponds to the object's fine structures and manifests itself in the dark-field contrast via small-angle scattering. Based on the paraxial Fresnel-Kirchhoff theory, the analytic formulae to characterize the contribution made by δ s , which corresponds to the object's smooth structures, to the dark-field contrast are derived. Through computer simulation with specially designed numerical phantoms, an x-ray differential phase contrast imaging system implemented with the Talbot interferometry is utilized to evaluate and validate the derived formulae. The same imaging system is also utilized to evaluate and verify the capability of the proposed method to retrieve the second-order differential phase contrast for imaging, as well as its robustness over the dimension of detector cell and the number of steps in grating shifting. Results: Both analytic formulae and computer simulations show that, in addition to small-angle scattering, the

Clinical implementation of x-ray phase-contrast imaging: Theoretical foundations and design considerations

International Nuclear Information System (INIS)

Wu Xizeng; Liu Hong

2003-01-01

Theoretical foundation and design considerations of a clinical feasible x-ray phase contrast imaging technique were presented in this paper. Different from the analysis of imaging phase object with weak absorption in literature, we proposed a new formalism for in-line phase-contrast imaging to analyze the effects of four clinically important factors on the phase contrast. These are the body parts attenuation, the spatial coherence of spherical waves from a finite-size focal spot, and polychromatic x-ray and radiation doses to patients for clinical applications. The theory presented in this paper can be applied widely in diagnostic x-ray imaging procedures. As an example, computer simulations were conducted and optimal design parameters were derived for clinical mammography. The results of phantom experiments were also presented which validated the theoretical analysis and computer simulations

Microscopical advances in assisted reproduction.

Science.gov (United States)

Baccetti, B

2004-01-01

In a series of papers carried out by this laboratory it was demonstrated that the quality of sterile males sperm, assessed submicroscopically and mathematically, is closely correlated with the success of the various procedures of assisted reproduction. If we attempt to select hypothetically optimal spermatozoa destined to the ICSI by light inverted microscopy, a considerable amount of ultrastructural information is lost and our selection is merely based on the motility. In this study we apply polarization microscopy to the ICSI technique, introducing polarizing and analyzing lenses in an inverted microscope model, operating in a transparent container. The retardation of the birefringence in the various organelles is evaluated by compensators, and the images are transmitted to a video system, and stored in a computer. Spermatozoa are maintained alive and perfectly motile in this polarizing inverted microscope, and the character of the birefringence is the same as in fixed and sectioned biological material examined by polarization microscopy. The birefringence of the sperm structures allows a sperm analysis closer to TEM than to phase contrast light microscopy analysis.

Grating-based phase contrast tomosynthesis imaging: Proof-of-concept experimental studies

International Nuclear Information System (INIS)

Li, Ke; Ge, Yongshuai; Garrett, John; Bevins, Nicholas; Zambelli, Joseph; Chen, Guang-Hong

2014-01-01

Purpose: This paper concerns the feasibility of x-ray differential phase contrast (DPC) tomosynthesis imaging using a grating-based DPC benchtop experimental system, which is equipped with a commercial digital flat-panel detector and a medical-grade rotating-anode x-ray tube. An extensive system characterization was performed to quantify its imaging performance. Methods: The major components of the benchtop system include a diagnostic x-ray tube with a 1.0 mm nominal focal spot size, a flat-panel detector with 96 μm pixel pitch, a sample stage that rotates within a limited angular span of ±30°, and a Talbot-Lau interferometer with three x-ray gratings. A total of 21 projection views acquired with 3° increments were used to reconstruct three sets of tomosynthetic image volumes, including the conventional absorption contrast tomosynthesis image volume (AC-tomo) reconstructed using the filtered-backprojection (FBP) algorithm with the ramp kernel, the phase contrast tomosynthesis image volume (PC-tomo) reconstructed using FBP with a Hilbert kernel, and the differential phase contrast tomosynthesis image volume (DPC-tomo) reconstructed using the shift-and-add algorithm. Three inhouse physical phantoms containing tissue-surrogate materials were used to characterize the signal linearity, the signal difference-to-noise ratio (SDNR), the three-dimensional noise power spectrum (3D NPS), and the through-plane artifact spread function (ASF). Results: While DPC-tomo highlights edges and interfaces in the image object, PC-tomo removes the differential nature of the DPC projection data and its pixel values are linearly related to the decrement of the real part of the x-ray refractive index. The SDNR values of polyoxymethylene in water and polystyrene in oil are 1.5 and 1.0, respectively, in AC-tomo, and the values were improved to 3.0 and 2.0, respectively, in PC-tomo. PC-tomo and AC-tomo demonstrate equivalent ASF, but their noise characteristics quantified by the 3D NPS

Grating-based phase contrast tomosynthesis imaging: Proof-of-concept experimental studies

Science.gov (United States)

Li, Ke; Ge, Yongshuai; Garrett, John; Bevins, Nicholas; Zambelli, Joseph; Chen, Guang-Hong

2014-01-01

Purpose: This paper concerns the feasibility of x-ray differential phase contrast (DPC) tomosynthesis imaging using a grating-based DPC benchtop experimental system, which is equipped with a commercial digital flat-panel detector and a medical-grade rotating-anode x-ray tube. An extensive system characterization was performed to quantify its imaging performance. Methods: The major components of the benchtop system include a diagnostic x-ray tube with a 1.0 mm nominal focal spot size, a flat-panel detector with 96 μm pixel pitch, a sample stage that rotates within a limited angular span of ±30°, and a Talbot-Lau interferometer with three x-ray gratings. A total of 21 projection views acquired with 3° increments were used to reconstruct three sets of tomosynthetic image volumes, including the conventional absorption contrast tomosynthesis image volume (AC-tomo) reconstructed using the filtered-backprojection (FBP) algorithm with the ramp kernel, the phase contrast tomosynthesis image volume (PC-tomo) reconstructed using FBP with a Hilbert kernel, and the differential phase contrast tomosynthesis image volume (DPC-tomo) reconstructed using the shift-and-add algorithm. Three inhouse physical phantoms containing tissue-surrogate materials were used to characterize the signal linearity, the signal difference-to-noise ratio (SDNR), the three-dimensional noise power spectrum (3D NPS), and the through-plane artifact spread function (ASF). Results: While DPC-tomo highlights edges and interfaces in the image object, PC-tomo removes the differential nature of the DPC projection data and its pixel values are linearly related to the decrement of the real part of the x-ray refractive index. The SDNR values of polyoxymethylene in water and polystyrene in oil are 1.5 and 1.0, respectively, in AC-tomo, and the values were improved to 3.0 and 2.0, respectively, in PC-tomo. PC-tomo and AC-tomo demonstrate equivalent ASF, but their noise characteristics quantified by the 3D NPS

Non-destructive characterisation of polymers and Al-alloys by polychromatic cone-beam phase contrast tomography

International Nuclear Information System (INIS)

Kastner, Johann; Plank, Bernhard; Requena, Guillermo

2012-01-01

X-ray computed tomography (XCT) has become a very important tool for the non-destructive characterisation of materials. Continuous improvements in the quality and performance of X-ray tubes and detectors have led to cone-beam XCT systems that can now achieve spatial resolutions down to 1 μm and even below. Since not only the amplitude but also the phase of an X-ray beam is altered while passing through an object, phase contrast effects can occur even for polychromatic sources when the spatial coherence due to a small focal spot size is high enough. This can lead to significant improvements over conventional attenuation-based X-ray computed tomography. Phase contrast can increase by edge enhancement the visibility of small structures and of features which are only slightly different in attenuation. We report on the possibilities of polychromatic cone-beam phase contrast tomography for non-destructive characterisation of materials. A carbon fibre-reinforced polymer and the Al-alloys AlMg5Si7 and AlSi18 were investigated with high resolution cone-beam X-ray computed tomography with a polychromatic tube source. Under certain conditions strong phase contrast resulting in an upward and downward overshooting of the grey values across edges was observed. The phase effects are much stronger for the polymer than for the Al-alloys. The influence on the phase contrast of the parameters, including source-detector distance, focal spot size and tube acceleration voltage is presented. Maximum phase contrast was observed for a maximum distance between the source and the detector, for a low voltage and a minimum focal spot size at the X-ray source. The detectability of the different phases is improved by the edge enhancement and the resulting improvement of sharpness. Thus, a better segmentation of the carbon fibres in the fibre-reinforced polymer and of the Mg 2 Si-phase in the AlMg5Si7-alloy is achieved. Primary and eutectic Si cannot be detected by attenuation-based X

Phase-contrast enhanced mammography: A new diagnostic tool for breast imaging

International Nuclear Information System (INIS)

Wang Zhentian; Thuering, Thomas; David, Christian; Roessl, Ewald; Trippel, Mafalda; Kubik-Huch, Rahel A.; Singer, Gad; Hohl, Michael K.; Hauser, Nik; Stampanoni, Marco

2012-01-01

Phase contrast and scattering-based X-ray imaging can potentially revolutionize the radiological approach to breast imaging by providing additional and complementary information to conventional, absorption-based methods. We investigated native, non-fixed whole breast samples using a grating interferometer with an X-ray tube-based configuration. Our approach simultaneously recorded absorption, differential phase contrast and small-angle scattering signals. The results show that this novel technique - combined with a dedicated image fusion algorithm - has the potential to deliver enhanced breast imaging with complementary information for an improved diagnostic process.

Phase-contrast enhanced mammography: A new diagnostic tool for breast imaging

Energy Technology Data Exchange (ETDEWEB)

Wang Zhentian; Thuering, Thomas; David, Christian; Roessl, Ewald; Trippel, Mafalda; Kubik-Huch, Rahel A.; Singer, Gad; Hohl, Michael K.; Hauser, Nik; Stampanoni, Marco [Swiss Light Source, Paul Scherrer Institut, 5232 Villigen (Switzerland); Laboratory for Micro and Nanotechnology, Paul Scherrer Institut, 5232 Villigen (Switzerland); Philips Technologie GmbH, Roentgenstrasse 24, 22335 Hamburg (Germany); Institute of Pathology, Kantonsspital Baden, 5404 Baden (Switzerland); Department of Radiology, Kantonsspital Baden, 5404 Baden (Switzerland); Institute of Pathology, Kantonsspital Baden, 5404 Baden (Switzerland); Department of Gynecology and Obstetrics, Interdisciplinary Breast Center Baden, Kantonsspital Baden, 5404 Baden (Switzerland); Swiss Light Source, Paul Scherrer Institut, 5232 Villigen, Switzerland and Institute for Biomedical Engineering, University and ETH Zuerich, 8092 Zuerich (Switzerland)

2012-07-31

Phase contrast and scattering-based X-ray imaging can potentially revolutionize the radiological approach to breast imaging by providing additional and complementary information to conventional, absorption-based methods. We investigated native, non-fixed whole breast samples using a grating interferometer with an X-ray tube-based configuration. Our approach simultaneously recorded absorption, differential phase contrast and small-angle scattering signals. The results show that this novel technique - combined with a dedicated image fusion algorithm - has the potential to deliver enhanced breast imaging with complementary information for an improved diagnostic process.

Evidence of a fractional quantum Hall nematic phase in a microscopic model

Science.gov (United States)

Regnault, N.; Maciejko, J.; Kivelson, S. A.; Sondhi, S. L.

2017-07-01

At small momenta, the Girvin-MacDonald-Platzman (GMP) mode in the fractional quantum Hall (FQH) effect can be identified with gapped nematic fluctuations in the isotropic FQH liquid. This correspondence would be exact as the GMP mode softens upon approach to the putative point of a quantum phase transition to a FQH nematic. Motivated by these considerations as well as by suggestive evidence of an FQH nematic in tilted field experiments, we have sought evidence of such a nematic FQHE in a microscopic model of interacting electrons in the lowest Landau level at filling factor 1/3. Using a family of anisotropic Laughlin states as trial wave functions, we find a continuous quantum phase transition between the isotropic Laughlin liquid and the FQH nematic. Results of numerical exact diagonalization also suggest that rotational symmetry is spontaneously broken, and that the phase diagram of the model contains both a nematic and a stripe phase.

Fabrication of optical multilayer for two-color phase plate in super-resolution microscope.

Science.gov (United States)

Iketaki, Yoshinori; Kitagawa, Katsuichi; Hidaka, Kohjiro; Kato, Naoki; Hirabayashi, Akira; Bokor, Nandor

2014-07-01

In super-resolution microscopy based on fluorescence depletion, the two-color phase plate (TPP) is an indispensable optical element, which can independently control the phase shifts for two beams of different color, i.e., the pump and erase beams. By controlling a phase shift of the erase beam through the TPP, the erase beam can be modulated into a doughnut shape, while the pump beam maintains the initial Gaussian shape. To obtain a reliable optical multiplayer (ML) for the TPP, we designed a ML with only two optical layers by performing numerical optimization. The measured phase shifts generated by the fabricated ML using interferometry correspond to the design values. The beam profiles in the focal plane are also consistent with theoretical results. Although the fabricated ML consists of only two optical layers, the ML can provide a suitable phase modulation function for the TPP in a practical super-resolution microscope.

Fabrication of optical multilayer for two-color phase plate in super-resolution microscope

International Nuclear Information System (INIS)

Iketaki, Yoshinori; Kitagawa, Katsuichi; Hidaka, Kohjiro; Kato, Naoki; Hirabayashi, Akira; Bokor, Nandor

2014-01-01

In super-resolution microscopy based on fluorescence depletion, the two-color phase plate (TPP) is an indispensable optical element, which can independently control the phase shifts for two beams of different color, i.e., the pump and erase beams. By controlling a phase shift of the erase beam through the TPP, the erase beam can be modulated into a doughnut shape, while the pump beam maintains the initial Gaussian shape. To obtain a reliable optical multiplayer (ML) for the TPP, we designed a ML with only two optical layers by performing numerical optimization. The measured phase shifts generated by the fabricated ML using interferometry correspond to the design values. The beam profiles in the focal plane are also consistent with theoretical results. Although the fabricated ML consists of only two optical layers, the ML can provide a suitable phase modulation function for the TPP in a practical super-resolution microscope

Low dose reconstruction algorithm for differential phase contrast imaging.

Science.gov (United States)

Wang, Zhentian; Huang, Zhifeng; Zhang, Li; Chen, Zhiqiang; Kang, Kejun; Yin, Hongxia; Wang, Zhenchang; Marco, Stampanoni

2011-01-01

Differential phase contrast imaging computed tomography (DPCI-CT) is a novel x-ray inspection method to reconstruct the distribution of refraction index rather than the attenuation coefficient in weakly absorbing samples. In this paper, we propose an iterative reconstruction algorithm for DPCI-CT which benefits from the new compressed sensing theory. We first realize a differential algebraic reconstruction technique (DART) by discretizing the projection process of the differential phase contrast imaging into a linear partial derivative matrix. In this way the compressed sensing reconstruction problem of DPCI reconstruction can be transformed to a resolved problem in the transmission imaging CT. Our algorithm has the potential to reconstruct the refraction index distribution of the sample from highly undersampled projection data. Thus it can significantly reduce the dose and inspection time. The proposed algorithm has been validated by numerical simulations and actual experiments.

Microscopic Mechanism of Doping-Induced Kinetically Constrained Crystallization in Phase-Change Materials.

Science.gov (United States)

Lee, Tae Hoon; Loke, Desmond; Elliott, Stephen R

2015-10-07

A comprehensive microscopic mechanism of doping-induced kinetically constrained crystallization in phase-change materials is provided by investigating structural and dynamical dopant characteristics via ab initio molecular dynamics simulations. The information gained from this study may provide a basis for a fast screening of dopant species for electronic memory devices, or for understanding the general physics involved in the crystallization of doped glasses. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

X-ray imaging with monochromatic synchrotron radiation. Fluorescent and phase-contrast method

Energy Technology Data Exchange (ETDEWEB)

Takeda, Tohoru; Itai, Yuji [Tsukuba Univ., Ibaraki (Japan). Inst. of Clinical Medicine

2002-05-01

To obtain the high sensitive x-ray images of biomedical object, new x-ray imaging techniques using fluorescent x-ray and phase-contrast x-ray are being developed in Japan. Fluorescent x-ray CT can detect very small amounts of specific elements in the order of ppm at one pixel, whereas phase-contrast x-ray imaging with interferometer can detect minute differences of biological object. Here, our recent experimental results are presented. (author)

Evaluation on correction factor for in-line X-ray phase contrast computed tomography

Energy Technology Data Exchange (ETDEWEB)

Jin, Mingli; Huang, Zhifeng; Zhang, Li; Zhang, Ran [Tsinghua Univ., Beijing (China). Dept. of Engineering Physics; Ministry of Education, Beijing (China). Key Laboratory of Particle and Radiation Imaging; Yin, Hongxia; Liu, Yunfu; Wang, Zhenchang [Capital Medical Univ., Beijing (China). Medical Imaging Center; Xiao, Tiqiao [Chinese Academy of Sciences, Shanghai (China). Shanghai Inst. of Applied Physics

2011-07-01

X-ray in-line phase contrast computed tomography (CT) is an effective nondestructive tool, providing 3D distribution of the refractive index of weakly absorbing low-Z object with high resolution and image contrast, especially with high-brilliance third-generation synchrotron radiation sources. Modified Bronnikov's algorithm (MBA), one of the in-line phase contrast CT reconstruction algorithms, can reconstruct the refractive index distribution of a pure phase object with a single computed tomographic data set. The key idea of the MBA is to use a correction factor in the filter function to stabilize the behavior at low frequencies. In this paper, we evaluate the influences of the correction factor to the final reconstruction results of the absorption-phase-mixed objects with analytical simulation and actual experiments. The limitations of the MBA are discussed finally. (orig.)

Quantitative evaluation of a single-distance phase-retrieval method applied on in-line phase-contrast images of a mouse lung

International Nuclear Information System (INIS)

Mohammadi, Sara; Larsson, Emanuel; Alves, Frauke; Dal Monego, Simeone; Biffi, Stefania; Garrovo, Chiara; Lorenzon, Andrea; Tromba, Giuliana; Dullin, Christian

2014-01-01

Quantitative analysis concerning the application of a single-distance phase-retrieval algorithm on in-line phase-contrast images of a mouse lung at different sample-to-detector distances is presented. Propagation-based X-ray phase-contrast computed tomography (PBI) has already proven its potential in a great variety of soft-tissue-related applications including lung imaging. However, the strong edge enhancement, caused by the phase effects, often hampers image segmentation and therefore the quantitative analysis of data sets. Here, the benefits of applying single-distance phase retrieval prior to the three-dimensional reconstruction (PhR) are discussed and quantified compared with three-dimensional reconstructions of conventional PBI data sets in terms of contrast-to-noise ratio (CNR) and preservation of image features. The PhR data sets show more than a tenfold higher CNR and only minor blurring of the edges when compared with PBI in a predominately absorption-based set-up. Accordingly, phase retrieval increases the sensitivity and provides more functionality in computed tomography imaging

Laser scanning confocal microscope with programmable amplitude, phase, and polarization of the illumination beam.

Science.gov (United States)

Boruah, B R; Neil, M A A

2009-01-01

We describe the design and construction of a laser scanning confocal microscope with programmable beam forming optics. The amplitude, phase, and polarization of the laser beam used in the microscope can be controlled in real time with the help of a liquid crystal spatial light modulator, acting as a computer generated hologram, in conjunction with a polarizing beam splitter and two right angled prisms assembly. Two scan mirrors, comprising an on-axis fast moving scan mirror for line scanning and an off-axis slow moving scan mirror for frame scanning, configured in a way to minimize the movement of the scanned beam over the pupil plane of the microscope objective, form the XY scan unit. The confocal system, that incorporates the programmable beam forming unit and the scan unit, has been implemented to image in both reflected and fluorescence light from the specimen. Efficiency of the system to programmably generate custom defined vector beams has been demonstrated by generating a bottle structured focal volume, which in fact is the overlap of two cross polarized beams, that can simultaneously improve both the lateral and axial resolutions if used as the de-excitation beam in a stimulated emission depletion confocal microscope.

Trial on MR portal blood flow measurement with phase contrast technique

International Nuclear Information System (INIS)

Tsunoda, Masatoshi; Kimoto, Shin; Togami, Izumi

1991-01-01

Portal blood flow measurement is considered to be important for the analysis of hemodynamics in various liver diseases. The Doppler ultrasound method has been used extensively during the past several years for measuring portal blood flow, as a non-invasive method. However, the Doppler ultrasound technique do not allow the portal blood flow to be measured in cases of obesity, with much intestinal gas, and so on. In this study, we attempted to measure the blood flow in the main trunk of portal vein as an application of MR phase contrast technique to the abdominal region. In the flow phantom study, the flow volumes and the velocities measured by phase contrast technique showed a close correlation with those measured by electromagnetic flowmeter. In the clinical study with 10 healthy volunteers, various values of portal blood flow were obtained. Mean portal blood flow could be measured within the measuring time (about 8 minutes) under natural breathing conditions. Phase contrast technique is considered to be useful for the non-invasive measurement of portal blood flow. (author)

High frequency write head measurement with the phase detection magnetic force microscope

International Nuclear Information System (INIS)

Abe, M.; Tanaka, Y.

2001-01-01

We demonstrated the measurement of the high frequency (HF) magnetic field of a write head with the phase detection magnetic force microscope. An amplitude-modulated current was applied to the head coil to detect the force gradient induced by the HF magnetic field. Spatial resolution of this method was higher than that of the deflection detection method previously proposed. By the phase detection method, dynamic HF magnetic fields at the poles of the write heads were clearly imaged. HF magnetic field leakage was observed along the P2 pole shape on the air-bearing surface. The frequency dependence of the write head dynamics up to 350 MHz was also investigated. [copyright] 2001 American Institute of Physics

Optimization of X-ray phase-contrast imaging based on in-line holography

International Nuclear Information System (INIS)

Wu Xizeng; Liu Hong; Yan Aimin

2005-01-01

This paper introduces a newly conceived formalism for clinical in-line phase-contrast X-ray imaging. The new formalism applies not only to ideal 'thin' objects analyzed in previous studies, but also applies to the real-world tissues used in actual clinical practice. Moreover we have identified the four clinically important factors that affect phase-contrast characteristics. These factors are: (1) body part attenuation (2) the spatial coherence of incident X-rays from an X-ray tube (3) the polychromatic nature of the X-ray source and (4) radiation dose to patients for clinical applications. Techniques of phase image-reconstruction based on the new X-ray in-line holography theory are discussed. Numerical simulations are described which were used to validate the theory. The design parameters of an optimal clinical phase-contrast mammographic imaging system which were determined based on the new theory, and validated in the simulations, are presented. The theory, image reconstruction algorithms, and numerical simulation techniques presented in this paper can be applied widely to clinical diagnostic X-ray imaging applications

The QCD phase transition. From the microscopic mechanism to signals

International Nuclear Information System (INIS)

Shuryak, E.V.

1997-01-01

This talk consists of two very different parts: the first one deals with non-perturbative QCD and physics of the chiral restoration, the second with rather low-key (and still unfinished) work aiming at obtaining EOS and other properties of hot/dense hadronic matter from data on heavy ion collisions. The microscopic mechanism for chiral restoration phase transition is a transition from randomly placed tunneling events (instantons) at low T to a set of strongly correlated tunneling-anti-tunneling events (known as instanton-anti-instanton molecules) at high T. Many features of the transition can be explained in this simple picture, especially the critical line and its dependence on quark masses. This scenario predicts qualitative change of the basic quark-quark interactions around the phase transition line, with some states (such as pion-sigma ones) probably surviving event at T > T c . In the second half of the talk experimental data on collective flow in heavy ion collision are discussed its hydro-based description and relation to equation of state (EOS). A distinct feature of the QCD phase transition region is high degree of 'softness', (small ratio pressure/energy density). (author)

Optimization and stability of the contrast transfer function in aberration-corrected electron microscopy

International Nuclear Information System (INIS)

Tromp, R.M.; Schramm, S.M.

2013-01-01

The Contrast Transfer Function (CTF) describes the manner in which the electron microscope modifies the object exit wave function as a result of objective lens aberrations. For optimum resolution in C 3 -corrected microscopes it is well established that a small negative value of C 3 , offset by positive values of C 5 and defocus C 1 results in the most optimal instrument resolution, and optimization of the CTF has been the subject of several studies. Here we describe a simple design procedure for the CTF that results in a most even transfer of information below the resolution limit. We address not only the resolution of the instrument, but also the stability of the CTF in the presence of small disturbances in C 1 and C 3 . We show that resolution can be traded for stability in a rational and transparent fashion. These topics are discussed quantitatively for both weak-phase and strong-phase (or amplitude) objects. The results apply equally to instruments at high electron energy (TEM) and at very low electron energy (LEEM), as the basic optical properties of the imaging lenses are essentially identical. - Highlights: ► An optimized Contrast Transfer Function for aberration corrected electron microscopes is proposed. ► Based on the properties of the CTF near optimum settings, we address its stability. ► Over some range of parameters resolution can be traded for stability. ► These issues are addressed for weak-phase objects, as well as strong-phase and amplitude object. ► We compare our results with CTF settings previously proposed

High-throughput, high-resolution X-ray phase contrast tomographic microscopy for visualisation of soft tissue

Energy Technology Data Exchange (ETDEWEB)

McDonald, S A; Marone, F; Hintermueller, C; Stampanoni, M [Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Bensadoun, J-C; Aebischer, P, E-mail: samuel.mcdonald@psi.c [EPFL, School of Life Sciences, Station 15, 1015 Lausanne (Switzerland)

2009-09-01

The use of conventional absorption based X-ray microtomography can become limited for samples showing only very weak absorption contrast. However, a wide range of samples studied in biology and materials science can produce significant phase shifts of the X-ray beam, and thus the use of the phase signal can provide substantially increased contrast and therefore new and otherwise inaccessible information. The application of two approaches for high-throughput, high-resolution X-ray phase contrast tomography, both available on the TOMCAT beamline of the SLS, is illustrated. Differential Phase Contrast (DPC) imaging uses a grating interferometer and a phase-stepping technique. It has been integrated into the beamline environment on TOMCAT in terms of the fast acquisition and reconstruction of data and the availability to scan samples within an aqueous environment. The second phase contrast approach is a modified transfer of intensity approach that can yield the 3D distribution of the phase (refractive index) of a weakly absorbing object from a single tomographic dataset. These methods are being used for the evaluation of cell integrity in 3D, with the specific aim of following and analyzing progressive cell degeneration to increase knowledge of the mechanistic events of neurodegenerative disorders such as Parkinson's disease.

Breast tumor segmentation in high resolution x-ray phase contrast analyzer based computed tomography.

Science.gov (United States)

Brun, E; Grandl, S; Sztrókay-Gaul, A; Barbone, G; Mittone, A; Gasilov, S; Bravin, A; Coan, P

2014-11-01

Phase contrast computed tomography has emerged as an imaging method, which is able to outperform present day clinical mammography in breast tumor visualization while maintaining an equivalent average dose. To this day, no segmentation technique takes into account the specificity of the phase contrast signal. In this study, the authors propose a new mathematical framework for human-guided breast tumor segmentation. This method has been applied to high-resolution images of excised human organs, each of several gigabytes. The authors present a segmentation procedure based on the viscous watershed transform and demonstrate the efficacy of this method on analyzer based phase contrast images. The segmentation of tumors inside two full human breasts is then shown as an example of this procedure's possible applications. A correct and precise identification of the tumor boundaries was obtained and confirmed by manual contouring performed independently by four experienced radiologists. The authors demonstrate that applying the watershed viscous transform allows them to perform the segmentation of tumors in high-resolution x-ray analyzer based phase contrast breast computed tomography images. Combining the additional information provided by the segmentation procedure with the already high definition of morphological details and tissue boundaries offered by phase contrast imaging techniques, will represent a valuable multistep procedure to be used in future medical diagnostic applications.

High contrast imaging and flexible photomanipulation for quantitative in vivo multiphoton imaging with polygon scanning microscope.

Science.gov (United States)

Li, Yongxiao; Montague, Samantha J; Brüstle, Anne; He, Xuefei; Gillespie, Cathy; Gaus, Katharina; Gardiner, Elizabeth E; Lee, Woei Ming

2018-02-28

In this study, we introduce two key improvements that overcome limitations of existing polygon scanning microscopes while maintaining high spatial and temporal imaging resolution over large field of view (FOV). First, we proposed a simple and straightforward means to control the scanning angle of the polygon mirror to carry out photomanipulation without resorting to high speed optical modulators. Second, we devised a flexible data sampling method directly leading to higher image contrast by over 2-fold and digital images with 100 megapixels (10 240 × 10 240) per frame at 0.25 Hz. This generates sub-diffraction limited pixels (60 nm per pixels over the FOV of 512 μm) which increases the degrees of freedom to extract signals computationally. The unique combined optical and digital control recorded fine fluorescence recovery after localized photobleaching (r ~10 μm) within fluorescent giant unilamellar vesicles and micro-vascular dynamics after laser-induced injury during thrombus formation in vivo. These new improvements expand the quantitative biological-imaging capacity of any polygon scanning microscope system. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct imaging of phase objects enables conventional deconvolution in bright field light microscopy.

Directory of Open Access Journals (Sweden)

Carmen Noemí Hernández Candia

Full Text Available In transmitted optical microscopy, absorption structure and phase structure of the specimen determine the three-dimensional intensity distribution of the image. The elementary impulse responses of the bright field microscope therefore consist of separate absorptive and phase components, precluding general application of linear, conventional deconvolution processing methods to improve image contrast and resolution. However, conventional deconvolution can be applied in the case of pure phase (or pure absorptive objects if the corresponding phase (or absorptive impulse responses of the microscope are known. In this work, we present direct measurements of the phase point- and line-spread functions of a high-aperture microscope operating in transmitted bright field. Polystyrene nanoparticles and microtubules (biological polymer filaments serve as the pure phase point and line objects, respectively, that are imaged with high contrast and low noise using standard microscopy plus digital image processing. Our experimental results agree with a proposed model for the response functions, and confirm previous theoretical predictions. Finally, we use the measured phase point-spread function to apply conventional deconvolution on the bright field images of living, unstained bacteria, resulting in improved definition of cell boundaries and sub-cellular features. These developments demonstrate practical application of standard restoration methods to improve imaging of phase objects such as cells in transmitted light microscopy.

Ideal-observer detectability in photon-counting differential phase-contrast imaging using a linear-systems approach

Energy Technology Data Exchange (ETDEWEB)

Fredenberg, Erik; Danielsson, Mats; Stayman, J. Webster; Siewerdsen, Jeffrey H.; Aslund, Magnus [Research and Development, Philips Women' s Healthcare, Smidesvaegen 5, SE-171 41 Solna, Sweden and Department of Physics, Royal Institute of Technology, AlbaNova, SE-106 91 Stockholm (Sweden); Department of Physics, Royal Institute of Technology, AlbaNova, SE-106 91 Stockholm (Sweden); Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Department of Biomedical Engineering and Department of Radiology, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Research and Development, Philips Women' s Healthcare, Smidesvaegen 5, SE-171 41 Solna (Sweden)

2012-09-15

Purpose: To provide a cascaded-systems framework based on the noise-power spectrum (NPS), modulation transfer function (MTF), and noise-equivalent number of quanta (NEQ) for quantitative evaluation of differential phase-contrast imaging (Talbot interferometry) in relation to conventional absorption contrast under equal-dose, equal-geometry, and, to some extent, equal-photon-economy constraints. The focus is a geometry for photon-counting mammography. Methods: Phase-contrast imaging is a promising technology that may emerge as an alternative or adjunct to conventional absorption contrast. In particular, phase contrast may increase the signal-difference-to-noise ratio compared to absorption contrast because the difference in phase shift between soft-tissue structures is often substantially larger than the absorption difference. We have developed a comprehensive cascaded-systems framework to investigate Talbot interferometry, which is a technique for differential phase-contrast imaging. Analytical expressions for the MTF and NPS were derived to calculate the NEQ and a task-specific ideal-observer detectability index under assumptions of linearity and shift invariance. Talbot interferometry was compared to absorption contrast at equal dose, and using either a plane wave or a spherical wave in a conceivable mammography geometry. The impact of source size and spectrum bandwidth was included in the framework, and the trade-off with photon economy was investigated in some detail. Wave-propagation simulations were used to verify the analytical expressions and to generate example images. Results: Talbot interferometry inherently detects the differential of the phase, which led to a maximum in NEQ at high spatial frequencies, whereas the absorption-contrast NEQ decreased monotonically with frequency. Further, phase contrast detects differences in density rather than atomic number, and the optimal imaging energy was found to be a factor of 1.7 higher than for absorption

Ideal-observer detectability in photon-counting differential phase-contrast imaging using a linear-systems approach

International Nuclear Information System (INIS)

Fredenberg, Erik; Danielsson, Mats; Stayman, J. Webster; Siewerdsen, Jeffrey H.; Åslund, Magnus

2012-01-01

Purpose: To provide a cascaded-systems framework based on the noise-power spectrum (NPS), modulation transfer function (MTF), and noise-equivalent number of quanta (NEQ) for quantitative evaluation of differential phase-contrast imaging (Talbot interferometry) in relation to conventional absorption contrast under equal-dose, equal-geometry, and, to some extent, equal-photon-economy constraints. The focus is a geometry for photon-counting mammography. Methods: Phase-contrast imaging is a promising technology that may emerge as an alternative or adjunct to conventional absorption contrast. In particular, phase contrast may increase the signal-difference-to-noise ratio compared to absorption contrast because the difference in phase shift between soft-tissue structures is often substantially larger than the absorption difference. We have developed a comprehensive cascaded-systems framework to investigate Talbot interferometry, which is a technique for differential phase-contrast imaging. Analytical expressions for the MTF and NPS were derived to calculate the NEQ and a task-specific ideal-observer detectability index under assumptions of linearity and shift invariance. Talbot interferometry was compared to absorption contrast at equal dose, and using either a plane wave or a spherical wave in a conceivable mammography geometry. The impact of source size and spectrum bandwidth was included in the framework, and the trade-off with photon economy was investigated in some detail. Wave-propagation simulations were used to verify the analytical expressions and to generate example images. Results: Talbot interferometry inherently detects the differential of the phase, which led to a maximum in NEQ at high spatial frequencies, whereas the absorption-contrast NEQ decreased monotonically with frequency. Further, phase contrast detects differences in density rather than atomic number, and the optimal imaging energy was found to be a factor of 1.7 higher than for absorption

Binocular contrast-gain control for natural scenes: Image structure and phase alignment.

Science.gov (United States)

Huang, Pi-Chun; Dai, Yu-Ming

2018-05-01

In the context of natural scenes, we applied the pattern-masking paradigm to investigate how image structure and phase alignment affect contrast-gain control in binocular vision. We measured the discrimination thresholds of bandpass-filtered natural-scene images (targets) under various types of pedestals. Our first experiment had four pedestal types: bandpass-filtered pedestals, unfiltered pedestals, notch-filtered pedestals (which enabled removal of the spatial frequency), and misaligned pedestals (which involved rotation of unfiltered pedestals). Our second experiment featured six types of pedestals: bandpass-filtered, unfiltered, and notch-filtered pedestals, and the corresponding phase-scrambled pedestals. The thresholds were compared for monocular, binocular, and dichoptic viewing configurations. The bandpass-filtered pedestal and unfiltered pedestals showed classic dipper shapes; the dipper shapes of the notch-filtered, misaligned, and phase-scrambled pedestals were weak. We adopted a two-stage binocular contrast-gain control model to describe our results. We deduced that the phase-alignment information influenced the contrast-gain control mechanism before the binocular summation stage and that the phase-alignment information and structural misalignment information caused relatively strong divisive inhibition in the monocular and interocular suppression stages. When the pedestals were phase-scrambled, the elimination of the interocular suppression processing was the most convincing explanation of the results. Thus, our results indicated that both phase-alignment information and similar image structures cause strong interocular suppression. Copyright © 2018 Elsevier Ltd. All rights reserved.

The optics of microscope image formation.

Science.gov (United States)

Wolf, David E

2013-01-01

Although geometric optics gives a good understanding of how the microscope works, it fails in one critical area, which is explaining the origin of microscope resolution. To accomplish this, one must consider the microscope from the viewpoint of physical optics. This chapter describes the theory of the microscope-relating resolution to the highest spatial frequency that a microscope can collect. The chapter illustrates how Huygens' principle or construction can be used to explain the propagation of a plane wave. It is shown that this limit increases with increasing numerical aperture (NA). As a corollary to this, resolution increases with decreasing wavelength because of how NA depends on wavelength. The resolution is higher for blue light than red light. Resolution is dependent on contrast, and the higher the contrast, the higher the resolution. This last point relates to issues of signal-to-noise and dynamic range. The use of video and new digital cameras has necessitated redefining classical limits such as those of Rayleigh's criterion. Copyright © 2007 Elsevier Inc. All rights reserved.

Measurements and simulations analysing the noise behaviour of grating-based X-ray phase-contrast imaging

Energy Technology Data Exchange (ETDEWEB)

Weber, T., E-mail: thomas.weber@physik.uni-erlangen.de [University of Erlangen-Nuremberg, ECAP - Erlangen Center for Astroparticle Physics, Erwin-Rommel-Str. 1, 91058 Erlangen (Germany); Bartl, P.; Durst, J. [University of Erlangen-Nuremberg, ECAP - Erlangen Center for Astroparticle Physics, Erwin-Rommel-Str. 1, 91058 Erlangen (Germany); Haas, W. [University of Erlangen-Nuremberg, ECAP - Erlangen Center for Astroparticle Physics, Erwin-Rommel-Str. 1, 91058 Erlangen (Germany); University of Erlangen-Nuremberg, Pattern Recognition Lab, Martensstr. 3, 91058 Erlangen (Germany); Michel, T.; Ritter, A.; Anton, G. [University of Erlangen-Nuremberg, ECAP - Erlangen Center for Astroparticle Physics, Erwin-Rommel-Str. 1, 91058 Erlangen (Germany)

2011-08-21

In the last decades, phase-contrast imaging using a Talbot-Lau grating interferometer is possible even with a low-brilliance X-ray source. With the potential of increasing the soft-tissue contrast, this method is on its way into medical imaging. For this purpose, the knowledge of the underlying physics of this technique is necessary. With this paper, we would like to contribute to the understanding of grating-based phase-contrast imaging by presenting results on measurements and simulations regarding the noise behaviour of the differential phases. These measurements were done using a microfocus X-ray tube with a hybrid, photon-counting, semiconductor Medipix2 detector. The additional simulations were performed by our in-house developed phase-contrast simulation tool 'SPHINX', combining both wave and particle contributions of the simulated photons. The results obtained by both of these methods show the same behaviour. Increasing the number of photons leads to a linear decrease of the standard deviation of the phase. The number of used phase steps has no influence on the standard deviation, if the total number of photons is held constant. Furthermore, the probability density function (pdf) of the reconstructed differential phases was analysed. It turned out that the so-called von Mises distribution is the physically correct pdf, which was also confirmed by measurements. This information advances the understanding of grating-based phase-contrast imaging and can be used to improve image quality.

Theory and preliminary experimental verification of quantitative edge illumination x-ray phase contrast tomography.

Science.gov (United States)

Hagen, C K; Diemoz, P C; Endrizzi, M; Rigon, L; Dreossi, D; Arfelli, F; Lopez, F C M; Longo, R; Olivo, A

2014-04-07

X-ray phase contrast imaging (XPCi) methods are sensitive to phase in addition to attenuation effects and, therefore, can achieve improved image contrast for weakly attenuating materials, such as often encountered in biomedical applications. Several XPCi methods exist, most of which have already been implemented in computed tomographic (CT) modality, thus allowing volumetric imaging. The Edge Illumination (EI) XPCi method had, until now, not been implemented as a CT modality. This article provides indications that quantitative 3D maps of an object's phase and attenuation can be reconstructed from EI XPCi measurements. Moreover, a theory for the reconstruction of combined phase and attenuation maps is presented. Both reconstruction strategies find applications in tissue characterisation and the identification of faint, weakly attenuating details. Experimental results for wires of known materials and for a biological object validate the theory and confirm the superiority of the phase over conventional, attenuation-based image contrast.

Breast tumor segmentation in high resolution x-ray phase contrast analyzer based computed tomography

Energy Technology Data Exchange (ETDEWEB)

Brun, E., E-mail: emmanuel.brun@esrf.fr [European Synchrotron Radiation Facility (ESRF), Grenoble 380000, France and Department of Physics, Ludwig-Maximilians University, Garching 85748 (Germany); Grandl, S.; Sztrókay-Gaul, A.; Gasilov, S. [Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, 81377 Munich (Germany); Barbone, G. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Mittone, A.; Coan, P. [Department of Physics, Ludwig-Maximilians University, Garching 85748, Germany and Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, 81377 Munich (Germany); Bravin, A. [European Synchrotron Radiation Facility (ESRF), Grenoble 380000 (France)

2014-11-01

Purpose: Phase contrast computed tomography has emerged as an imaging method, which is able to outperform present day clinical mammography in breast tumor visualization while maintaining an equivalent average dose. To this day, no segmentation technique takes into account the specificity of the phase contrast signal. In this study, the authors propose a new mathematical framework for human-guided breast tumor segmentation. This method has been applied to high-resolution images of excised human organs, each of several gigabytes. Methods: The authors present a segmentation procedure based on the viscous watershed transform and demonstrate the efficacy of this method on analyzer based phase contrast images. The segmentation of tumors inside two full human breasts is then shown as an example of this procedure’s possible applications. Results: A correct and precise identification of the tumor boundaries was obtained and confirmed by manual contouring performed independently by four experienced radiologists. Conclusions: The authors demonstrate that applying the watershed viscous transform allows them to perform the segmentation of tumors in high-resolution x-ray analyzer based phase contrast breast computed tomography images. Combining the additional information provided by the segmentation procedure with the already high definition of morphological details and tissue boundaries offered by phase contrast imaging techniques, will represent a valuable multistep procedure to be used in future medical diagnostic applications.

Optimization of in-line phase contrast particle image velocimetry using a laboratory x-ray source

International Nuclear Information System (INIS)

Ng, I.; Fouras, A.; Paganin, D. M.

2012-01-01

Phase contrast particle image velocimetry (PIV) using a laboratory x-ray microfocus source is investigated using a numerical model. Phase contrast images of 75 μm air bubbles, embedded within water exhibiting steady-state vortical flow, are generated under the paraxial approximation using a tungsten x-ray spectrum at 30 kVp. Propagation-based x-ray phase-contrast speckle images at a range of source-object and object-detector distances are generated, and used as input into a simulated PIV measurement. The effects of source-size-induced penumbral blurring, together with the finite dynamic range of the detector, are accounted for in the simulation. The PIV measurement procedure involves using the cross-correlation between temporally sequential speckle images to estimate the transverse displacement field for the fluid. The global error in the PIV reconstruction, for the set of simulations that was performed, suggests that geometric magnification is the key parameter for designing a laboratory-based x-ray phase-contrast PIV system. For the modeled system, x-ray phase-contrast PIV data measurement can be optimized to obtain low error ( 15 μm) of the detector, high geometric magnification (>2.5) is desired, while for large source size system (FWHM > 30 μm), low magnification (<1.5) would be suggested instead. The methods developed in this paper can be applied to optimizing phase-contrast velocimetry using a variety of laboratory x-ray sources.

Image contrast enhancement of Ni/YSZ anode during the slice-and-view process in FIB-SEM.

Science.gov (United States)

Liu, Shu-Sheng; Takayama, Akiko; Matsumura, Syo; Koyama, Michihisa

2016-03-01

Focused ion beam-scanning electron microscopy (FIB-SEM) is a widely used and easily operational equipment for three-dimensional reconstruction with flexible analysis volume. It has been using successfully and increasingly in the field of solid oxide fuel cell. However, the phase contrast of the SEM images is indistinct in many cases, which will bring difficulties to the image processing. Herein, the phase contrast of a conventional Ni/yttria stabilized zirconia anode is tuned in an FIB-SEM with In-Lens secondary electron (SE) and backscattered electron detectors. Two accessories, tungsten probe and carbon nozzle, are inserted during the observation. The former has no influence on the contrast. When the carbon nozzle is inserted, best and distinct contrast can be obtained by In-Lens SE detector. This method is novel for contrast enhancement. Phase segmentation of the image can be automatically performed. The related mechanism for different images is discussed. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Variation in supratentorial cerebrospinal fluid production rate in one day. Measurement by nontriggered phase-contrast magnetic resonance imaging

International Nuclear Information System (INIS)

Takahashi, Hiroto; Tanaka, Hisashi; Fujita, Norihiko; Murase, Kenya; Tomiyama, Noriyuki

2011-01-01

Measuring the cerebrospinal fluid (CSF) production rate is important for understanding the physiology related to normal conditions and neurological disorders. Triggered phase-contrast magnetic resonance imaging (MRI) has been used to measure CSF production rate, but the use of nontriggered phase-contrast MRI has not been reported. The purposes of this study were to assess the feasibility of using nontriggered phase-contrast MRI to measure CSF flow and to determine whether CSF production exhibits circadian rhythm. The feasibility of phase-contrast MRI was assessed with a phantom simulated human cerebral aqueduct. CSF flow through the cerebral aqueduct was measured with nontriggered phase-contrast MRI four times during 1 day in 10 normal volunteers. In the phantom study, linear regression analysis gave the following measured values (ml/h): 0.80 x (value of steady flow)-10.0 for triggered phase-contrast MRI and 1.27 x (value of steady flow)-12.2 for nontriggered phase-contrast MRI. One-factor analysis of variance showed no significant effect of the time of the measurements (P=0.47). The supratentorial CSF production rate was 510±549 ml/day (mean ± SD). Nontriggered phase-contrast MRI provided good estimates of the flow rate in the phantom study. We observed no circadian rhythm in CSF production. (author)

Differential X-ray phase-contrast imaging with a grating interferometer using a laboratory X-ray micro-focus tube

Energy Technology Data Exchange (ETDEWEB)

Yoon, Kwon-Ha; Ryu, Jong-Hyun; Jung, Chang-Won [Wonkwang University School of Medicine, Iksan (Korea, Republic of); Ryu, Cheol-Woo; Kim, Young-Jo; Kwon, Young-Man [Jeonbuk Technopark, Iksan (Korea, Republic of); Park, Mi-Ran; Cho, Seung-Ryong [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Chon, Kwon-Su [Catholic University of Daegu, Gyeongsan (Korea, Republic of)

2014-12-15

X-ray phase-contrast imaging can provide images with much greater soft-tissue contrast than conventional absorption-based images. In this paper, we describe differential X-ray phase-contrast images of insect specimens that were obtained using a grating-based Talbot interferometer and a laboratory X-ray source with a spot size of a few tens of micrometers. We developed the interferometer on the basis of the wavelength, periods, and height of the gratings; the field of view depends on the size of the grating, considering the refractive index of the specimen. The phase-contrast images were acquired using phase-stepping methods. The phase contrast imaging provided a significantly enhanced soft-tissue contrast compared with the attenuation data. The contour of the sample was clearly visible because the refraction from the edges of the object was strong in the differential phase-contrast image. Our results demonstrate that a grating-based Talbot interferometer with a conventional X-ray tube may be attractive as an X-ray imaging system for generating phase images. X-ray phase imaging obviously has sufficient potential and is expected to soon be a great tool for medical diagnostics.

Differential X-ray phase-contrast imaging with a grating interferometer using a laboratory X-ray micro-focus tube

International Nuclear Information System (INIS)

Yoon, Kwon-Ha; Ryu, Jong-Hyun; Jung, Chang-Won; Ryu, Cheol-Woo; Kim, Young-Jo; Kwon, Young-Man; Park, Mi-Ran; Cho, Seung-Ryong; Chon, Kwon-Su

2014-01-01

X-ray phase-contrast imaging can provide images with much greater soft-tissue contrast than conventional absorption-based images. In this paper, we describe differential X-ray phase-contrast images of insect specimens that were obtained using a grating-based Talbot interferometer and a laboratory X-ray source with a spot size of a few tens of micrometers. We developed the interferometer on the basis of the wavelength, periods, and height of the gratings; the field of view depends on the size of the grating, considering the refractive index of the specimen. The phase-contrast images were acquired using phase-stepping methods. The phase contrast imaging provided a significantly enhanced soft-tissue contrast compared with the attenuation data. The contour of the sample was clearly visible because the refraction from the edges of the object was strong in the differential phase-contrast image. Our results demonstrate that a grating-based Talbot interferometer with a conventional X-ray tube may be attractive as an X-ray imaging system for generating phase images. X-ray phase imaging obviously has sufficient potential and is expected to soon be a great tool for medical diagnostics

Imaging of metastatic lymph nodes by X-ray phase-contrast micro-tomography

DEFF Research Database (Denmark)

Jensen, Torben Haugaard; Bech, Martin; Binderup, Tina

2013-01-01

-contrast tomography. Ten lymph nodes had metastatic deposits and 7 were benign. The phase-contrast images were analyzed according to standards for conventional CT images looking for characteristics usually only visible by pathological examinations. Histopathology was used as reference. The result of this study...

A method for fast automated microscope image stitching.

Science.gov (United States)

Yang, Fan; Deng, Zhen-Sheng; Fan, Qiu-Hong

2013-05-01

Image stitching is an important technology to produce a panorama or larger image by combining several images with overlapped areas. In many biomedical researches, image stitching is highly desirable to acquire a panoramic image which represents large areas of certain structures or whole sections, while retaining microscopic resolution. In this study, we develop a fast normal light microscope image stitching algorithm based on feature extraction. At first, an algorithm of scale-space reconstruction of speeded-up robust features (SURF) was proposed to extract features from the images to be stitched with a short time and higher repeatability. Then, the histogram equalization (HE) method was employed to preprocess the images to enhance their contrast for extracting more features. Thirdly, the rough overlapping zones of the images preprocessed were calculated by phase correlation, and the improved SURF was used to extract the image features in the rough overlapping areas. Fourthly, the features were corresponded by matching algorithm and the transformation parameters were estimated, then the images were blended seamlessly. Finally, this procedure was applied to stitch normal light microscope images to verify its validity. Our experimental results demonstrate that the improved SURF algorithm is very robust to viewpoint, illumination, blur, rotation and zoom of the images and our method is able to stitch microscope images automatically with high precision and high speed. Also, the method proposed in this paper is applicable to registration and stitching of common images as well as stitching the microscope images in the field of virtual microscope for the purpose of observing, exchanging, saving, and establishing a database of microscope images. Copyright © 2013 Elsevier Ltd. All rights reserved.

A new method for information retrieval in two-dimensional grating-based X-ray phase contrast imaging

International Nuclear Information System (INIS)

Wang Zhi-Li; Gao Kun; Chen Jian; Ge Xin; Tian Yang-Chao; Wu Zi-Yu; Zhu Pei-Ping

2012-01-01

Grating-based X-ray phase contrast imaging has been demonstrated to be an extremely powerful phase-sensitive imaging technique. By using two-dimensional (2D) gratings, the observable contrast is extended to two refraction directions. Recently, we have developed a novel reverse-projection (RP) method, which is capable of retrieving the object information efficiently with one-dimensional (1D) grating-based phase contrast imaging. In this contribution, we present its extension to the 2D grating-based X-ray phase contrast imaging, named the two-dimensional reverse-projection (2D-RP) method, for information retrieval. The method takes into account the nonlinear contributions of two refraction directions and allows the retrieval of the absorption, the horizontal and the vertical refraction images. The obtained information can be used for the reconstruction of the three-dimensional phase gradient field, and for an improved phase map retrieval and reconstruction. Numerical experiments are carried out, and the results confirm the validity of the 2D-RP method

Microscopic deformation and strain hardening analysis of ferrite–bainite dual-phase steels using micro-grid method

International Nuclear Information System (INIS)

Ishikawa, Nobuyuki; Yasuda, Kyono; Sueyoshi, Hitoshi; Endo, Shigeru; Ikeda, Hiroshi; Morikawa, Tatsuya; Higashida, Kenji

2015-01-01

The local strain measurement method using nanometer-scaled micro grids printed on the surface of a specimen by an electron lithography technique (the micro-grid method) has been established. Microscopic deformation behavior of the ferrite–bainite steels with different bainite volume fraction, 16% and 40% of bainite, was evaluated. Strain localization in the ferrite phase adjacent to the ferrite/bainite boundary was clearly observed and visualized. Highly strained regions expanded toward the inner region of the ferrite phase and connected each other with an increase of macroscopic strain. The existence of hard bainite phase plays an important role for inducing strain localization in the ferrite phase by plastic constraint in the boundary parallel to the tensile direction. In order to obtain further understanding of microscopic deformation behavior, finite element analysis using the representative volume element, which is expressed by the axisymmetric unit cell containing a hard phase surrounded by a soft phase matrix, was conducted. It was found that the macroscopic stress–strain behavior of ferrite–bainite steels was well simulated by the unit cell models. Strain concentration in the ferrite phase was highly enhanced for the ferrite-40% bainite steel, and this imposed higher internal stress in the bainite phase, resulting in higher strain hardening rate in the early stage of the deformation. However, smaller ferrite volume fraction of ferrite-40% bainite steel induced bainite plastic deformation in order to fulfill the macroscopic strain of the steel. Accordingly, strain hardening capacity of the ferrite-40% bainite steel was reduced to a significant degree, resulting in a smaller uniform elongation than the ferrite-16% bainite steel

X-ray elastography: Modification of x-ray phase contrast images using ultrasonic radiation pressure

International Nuclear Information System (INIS)

Hamilton, Theron J.; Bailat, Claude; Rose-Petruck, Christoph; Diebold, Gerald J.; Gehring, Stephan; Laperle, Christopher M.; Wands, Jack

2009-01-01

The high resolution characteristic of in-line x-ray phase contrast imaging can be used in conjunction with directed ultrasound to detect small displacements in soft tissue generated by differential acoustic radiation pressure. The imaging method is based on subtraction of two x-ray images, the first image taken with, and the second taken without the presence of ultrasound. The subtraction enhances phase contrast features and, to a large extent, removes absorption contrast so that differential movement of tissues with different acoustic impedances or relative ultrasonic absorption is highlighted in the image. Interfacial features of objects with differing densities are delineated in the image as a result of both the displacement introduced by the ultrasound and the inherent sensitivity of x-ray phase contrast imaging to density variations. Experiments with ex vivo murine tumors and human tumor phantoms point out a diagnostic capability of the method for identifying tumors.

Analytical evaluation of the signal and noise propagation in x-ray differential phase-contrast computed tomography

International Nuclear Information System (INIS)

Raupach, Rainer; Flohr, Thomas G

2011-01-01

We analyze the signal and noise propagation of differential phase-contrast computed tomography (PCT) compared with conventional attenuation-based computed tomography (CT) from a theoretical point of view. This work focuses on grating-based differential phase-contrast imaging. A mathematical framework is derived that is able to analytically predict the relative performance of both imaging techniques in the sense of the relative contrast-to-noise ratio for the contrast of any two materials. Two fundamentally different properties of PCT compared with CT are identified. First, the noise power spectra show qualitatively different characteristics implying a resolution-dependent performance ratio. The break-even point is derived analytically as a function of system parameters such as geometry and visibility. A superior performance of PCT compared with CT can only be achieved at a sufficiently high spatial resolution. Second, due to periodicity of phase information which is non-ambiguous only in a bounded interval statistical phase wrapping can occur. This effect causes a collapse of information propagation for low signals which limits the applicability of phase-contrast imaging at low dose.

Phase-contrast imaging and tomography at 60 keV using a conventional x-ray tube source

International Nuclear Information System (INIS)

Donath, Tilman; Bunk, Oliver; Groot, Waldemar; Bednarzik, Martin; Gruenzweig, Christian; David, Christian; Pfeiffer, Franz; Hempel, Eckhard; Popescu, Stefan; Hoheisel, Martin

2009-01-01

Phase-contrast imaging at laboratory-based x-ray sources using grating interferometers has been developed over the last few years for x-ray energies of up to 28 keV. Here, we show first phase-contrast projection and tomographic images recorded at significantly higher x-ray energies, produced by an x-ray tube source operated at 100 kV acceleration voltage. We find our measured tomographic phase images in good agreement with tabulated data. The extension of phase-contrast imaging to this significantly higher x-ray energy opens up many applications of the technique in medicine and industrial nondestructive testing.

Application of Fourier-wavelet regularized deconvolution for improving image quality of free space propagation x-ray phase contrast imaging.

Science.gov (United States)

Zhou, Zhongxing; Gao, Feng; Zhao, Huijuan; Zhang, Lixin

2012-11-21

New x-ray phase contrast imaging techniques without using synchrotron radiation confront a common problem from the negative effects of finite source size and limited spatial resolution. These negative effects swamp the fine phase contrast fringes and make them almost undetectable. In order to alleviate this problem, deconvolution procedures should be applied to the blurred x-ray phase contrast images. In this study, three different deconvolution techniques, including Wiener filtering, Tikhonov regularization and Fourier-wavelet regularized deconvolution (ForWaRD), were applied to the simulated and experimental free space propagation x-ray phase contrast images of simple geometric phantoms. These algorithms were evaluated in terms of phase contrast improvement and signal-to-noise ratio. The results demonstrate that the ForWaRD algorithm is most appropriate for phase contrast image restoration among above-mentioned methods; it can effectively restore the lost information of phase contrast fringes while reduce the amplified noise during Fourier regularization.

High-resolution short-exposure small-animal laboratory x-ray phase-contrast tomography

Science.gov (United States)

Larsson, Daniel H.; Vågberg, William; Yaroshenko, Andre; Yildirim, Ali Önder; Hertz, Hans M.

2016-12-01

X-ray computed tomography of small animals and their organs is an essential tool in basic and preclinical biomedical research. In both phase-contrast and absorption tomography high spatial resolution and short exposure times are of key importance. However, the observable spatial resolutions and achievable exposure times are presently limited by system parameters rather than more fundamental constraints like, e.g., dose. Here we demonstrate laboratory tomography with few-ten μm spatial resolution and few-minute exposure time at an acceptable dose for small-animal imaging, both with absorption contrast and phase contrast. The method relies on a magnifying imaging scheme in combination with a high-power small-spot liquid-metal-jet electron-impact source. The tomographic imaging is demonstrated on intact mouse, phantoms and excised lungs, both healthy and with pulmonary emphysema.

Insight into the microscopic structure of an AdS black hole from a thermodynamical phase transition.

Science.gov (United States)

Wei, Shao-Wen; Liu, Yu-Xiao

2015-09-11

Comparing with an ordinary thermodynamic system, we investigate the possible microscopic structure of a charged anti-de Sitter black hole completely from the thermodynamic viewpoint. The number density of the black hole molecules is introduced to measure the microscopic degrees of freedom of the black hole. We found that the number density suffers a sudden change accompanied by a latent heat when the black hole system crosses the small-large black hole coexistence curve, while when the system passes the critical point, it encounters a second-order phase transition with a vanishing latent heat due to the continuous change of the number density. Moreover, the thermodynamic scalar curvature suggests that there is a weak attractive interaction between two black hole molecules. These phenomena might cast new insight into the underlying microscopic structure of a charged anti-de Sitter black hole.

Angle selective backscattered electron contrast in the low-voltage scanning electron microscope: Simulation and experiment for polymers

Energy Technology Data Exchange (ETDEWEB)

Wan, Q., E-mail: qwan2@sheffield.ac.uk [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Masters, R.C. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Lidzey, D. [Department of Physics and Astronomy, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Abrams, K.J. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Dapor, M. [European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT-FBK) and Trento Institute for Fundamental Physics and Applications (TIFPA-INFN), via Sommarive 18, I-38123 Trento (Italy); Plenderleith, R.A. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Rimmer, S. [Department of Chemistry, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Claeyssens, F.; Rodenburg, C. [Department of Material Science and Engineering, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom)

2016-12-15

Recently developed detectors can deliver high resolution and high contrast images of nanostructured carbon based materials in low voltage scanning electron microscopes (LVSEM) with beam deceleration. Monte Carlo Simulations are also used to predict under which exact imaging conditions purely compositional contrast can be obtained and optimised. This allows the prediction of the electron signal intensity in angle selective conditions for back-scattered electron (BSE) imaging in LVSEM and compares it to experimental signals. Angle selective detection with a concentric back scattered (CBS) detector is considered in the model in the absence and presence of a deceleration field, respectively. The validity of the model prediction for both cases was tested experimentally for amorphous C and Cu and applied to complex nanostructured carbon based materials, namely a Poly(N-isopropylacrylamide)/Poly(ethylene glycol) Diacrylate (PNIPAM/PEGDA) semi-interpenetration network (IPN) and a Poly(3-hexylthiophene-2,5-diyl) (P3HT) film, to map nano-scale composition and crystallinity distribution by avoiding experimental imaging conditions that lead to a mixed topographical and compositional contrast - Highlights: • An optimised model for nano-scale analysis of beam sensitive materials by LVSEM. • Simulation and separation of composition and topography in a CBS detector. • Selective angle backscattered electron collection for mapping of polymers.

Angle selective backscattered electron contrast in the low-voltage scanning electron microscope: Simulation and experiment for polymers

International Nuclear Information System (INIS)

Wan, Q.; Masters, R.C.; Lidzey, D.; Abrams, K.J.; Dapor, M.; Plenderleith, R.A.; Rimmer, S.; Claeyssens, F.; Rodenburg, C.

2016-01-01

Recently developed detectors can deliver high resolution and high contrast images of nanostructured carbon based materials in low voltage scanning electron microscopes (LVSEM) with beam deceleration. Monte Carlo Simulations are also used to predict under which exact imaging conditions purely compositional contrast can be obtained and optimised. This allows the prediction of the electron signal intensity in angle selective conditions for back-scattered electron (BSE) imaging in LVSEM and compares it to experimental signals. Angle selective detection with a concentric back scattered (CBS) detector is considered in the model in the absence and presence of a deceleration field, respectively. The validity of the model prediction for both cases was tested experimentally for amorphous C and Cu and applied to complex nanostructured carbon based materials, namely a Poly(N-isopropylacrylamide)/Poly(ethylene glycol) Diacrylate (PNIPAM/PEGDA) semi-interpenetration network (IPN) and a Poly(3-hexylthiophene-2,5-diyl) (P3HT) film, to map nano-scale composition and crystallinity distribution by avoiding experimental imaging conditions that lead to a mixed topographical and compositional contrast - Highlights: • An optimised model for nano-scale analysis of beam sensitive materials by LVSEM. • Simulation and separation of composition and topography in a CBS detector. • Selective angle backscattered electron collection for mapping of polymers.

In-line phase-contrast stereoscopic X-ray imaging for radiological purposes: An initial experimental study

International Nuclear Information System (INIS)

Siegbahn, E.A.; Coan, P.; Zhou, S.-A.; Bravin, A.; Brahme, A.

2011-01-01

We report results from a pilot study in which the in-line propagation-based phase-contrast imaging technique is combined with the stereoscopic method. Two phantoms were imaged at several sample-detector distances using monochromatic, 30 keV, X-rays. High contrast- and spatial-resolution phase-contrast stereoscopic pairs of X-ray images were constructed using the anaglyph approach and a vivid stereoscopic effect was demonstrated. On the other hand, images of the same phantoms obtained with a shorter sample-to-detector distance, but otherwise the same experimental conditions (i.e. the same X-ray energy and absorbed radiation dose), corresponding to the conventional attenuation-based imaging mode, hardly revealed stereoscopic effects because of the lower image contrast produced. These results have confirmed our hypothesis that stereoscopic X-ray images of samples with objects composed of low-atomic-number elements are considerably improved if phase-contrast imaging is used. It is our belief that the high-resolution phase-contrast stereoscopic method will be a valuable new medical imaging tool for radiologists and that it will be of help to enhance the diagnostic capability in the examination of patients in future clinical practice, even though further efforts will be needed to optimize the system performance.

Design of a compact high-energy setup for x-ray phase-contrast imaging

Science.gov (United States)

Schüttler, Markus; Yaroshenko, Andre; Bech, Martin; Potdevin, Guillaume; Malecki, Andreas; Chabior, Michael; Wolf, Johannes; Tapfer, Arne; Meiser, Jan; Kunka, Danays; Amberger, Maximilian; Mohr, Jürgen; Pfeiffer, Franz

2014-03-01

The main shortcoming of conventional biomedical x-ray imaging is the weak soft-tissue contrast caused by the small differences in the absorption coefficients between different materials. This issue can be addressed by x-ray phasesensitive imaging approaches, e.g. x-ray Talbot-Lau grating interferometry. The advantage of the three-grating Talbot-Lau approach is that it allows to acquire x-ray phase-contrast and dark-field images with a conventional lab source. However, through the introduction of the grating interferometer some constraints are imposed on the setup geometry. In general, the grating pitch and the mean x-ray energy determine the setup dimensions. The minimal length of the setup increases linearly with energy and is proportional to p2, where p is the grating pitch. Thus, a high-energy (100 keV) compact grating-based setup for x-ray imaging can be realized only if gratings with aspect-ratio of approximately 300 and a pitch of 1-2 μm were available. However, production challenges limit the availability of such gratings. In this study we consider the use of non-binary phase-gratings as means of designing a more compact grating interferometer for phase-contrast imaging. We present simulation and experimental data for both monochromatic and polychromatic case. The results reveal that phase-gratings with triangular-shaped structures yield visibilities that can be used for imaging purposes at significantly shorter distances than binary gratings. This opens the possibility to design a high-energy compact setup for x-ray phase-contrast imaging. Furthermore, we discuss different techniques to achieve triangular-shaped phase-shifting structures.

A user-friendly LabVIEW software platform for grating based X-ray phase-contrast imaging.

Science.gov (United States)

Wang, Shenghao; Han, Huajie; Gao, Kun; Wang, Zhili; Zhang, Can; Yang, Meng; Wu, Zhao; Wu, Ziyu

2015-01-01

X-ray phase-contrast imaging can provide greatly improved contrast over conventional absorption-based imaging for weakly absorbing samples, such as biological soft tissues and fibre composites. In this study, we introduced an easy and fast way to develop a user-friendly software platform dedicated to the new grating-based X-ray phase-contrast imaging setup at the National Synchrotron Radiation Laboratory of the University of Science and Technology of China. The control of 21 motorized stages, of a piezoelectric stage and of an X-ray tube are achieved with this software, it also covers image acquisition with a flat panel detector for automatic phase stepping scan. Moreover, a data post-processing module for signals retrieval and other custom features are in principle available. With a seamless integration of all the necessary functions in one software package, this platform greatly facilitate users' activities during experimental runs with this grating based X-ray phase contrast imaging setup.

In situ transmission electron microscope studies of ion irradiation-induced and irradiation-enhanced phase changes

International Nuclear Information System (INIS)

Allen, C.W.

1992-01-01

Motivated at least initially by materials needs for nuclear reactor development, extensive irradiation effects studies employing transmission electron microscopes (TEM) have been performed for several decades, involving irradiation-induced and irradiation-enhanced microstructural changes, including phase transformations such as precipitation, dissolution, crystallization, amorphization, and order-disorder phenomena. From the introduction of commercial high voltage electron microscopes (HVEM) in the mid-1960s, studies of electron irradiation effects have constituted a major aspect of HVEM application in materials science. For irradiation effects studies two additional developments have had particularly significant impact; the development of TEM specimen holder sin which specimen temperature can be controlled in the range 10-2200 K and the interfacing of ion accelerators which allows in situ TEM studies of irradiation effects and the ion beam modification of materials within this broad temperature range. This paper treats several aspects of in situ studies of electron and ion beam-induced and enhanced phase changes and presents two case studies involving in situ experiments performed in an HVEM to illustrate the strategies of such an approach of the materials research of irradiation effects

Matched filtering Generalized Phase Contrast using binary phase for dynamic spot- and line patterns in biophotonics and structured lighting

DEFF Research Database (Denmark)

Bañas, Andrew Rafael; Aabo, Thomas; Palima, Darwin

2013-01-01

as a combination of Generalized Phase Contrast and phase-only correlation. Such an analysis makes it convenient to optimize an mGPC system for different setup conditions. Results showing binary-only phase generation of dynamic spot arrays and line patterns are presented. © 201 Optical Society of America...

In Vitro Validation of an Artefact Suppression Algorithm in X-Ray Phase-Contrast Computed Tomography.

Science.gov (United States)

Sunaguchi, Naoki; Yuasa, Tetsuya; Hirano, Shin-Ichi; Gupta, Rajiv; Ando, Masami

2015-01-01

X-ray phase-contrast tomography can significantly increase the contrast-resolution of conventional attenuation-contrast imaging, especially for soft-tissue structures that have very similar attenuation. Just as in attenuation-based tomography, phase contrast tomography requires a linear dependence of aggregate beam direction on the incremental direction alteration caused by individual voxels along the path of the X-ray beam. Dense objects such as calcifications in biological specimens violate this condition. There are extensive beam deflection artefacts in the vicinity of such structures because they result in large distortion of wave front due to the large difference of refractive index; for such large changes in beam direction, the transmittance of the silicon analyzer crystal saturates and is no longer linearly dependent on the angle of refraction. This paper describes a method by which these effects can be overcome and excellent soft-tissue contrast of phase tomography can be preserved in the vicinity of such artefact-producing structures.

High-energy x-ray grating-based phase-contrast radiography of human anatomy

Science.gov (United States)

Horn, Florian; Hauke, Christian; Lachner, Sebastian; Ludwig, Veronika; Pelzer, Georg; Rieger, Jens; Schuster, Max; Seifert, Maria; Wandner, Johannes; Wolf, Andreas; Michel, Thilo; Anton, Gisela

2016-03-01

X-ray grating-based phase-contrast Talbot-Lau interferometry is a promising imaging technology that has the potential to raise soft tissue contrast in comparison to conventional attenuation-based imaging. Additionally, it is sensitive to attenuation, refraction and scattering of the radiation and thus provides complementary and otherwise inaccessible information due to the dark-field image, which shows the sub-pixel size granularity of the measured object. Until recent progress the method has been mainly limited to photon energies below 40 keV. Scaling the method to photon energies that are sufficient to pass large and spacious objects represents a challenging task. This is caused by increasing demands regarding the fabrication process of the gratings and the broad spectra that come along with the use of polychromatic X-ray sources operated at high acceleration voltages. We designed a setup that is capable to reach high visibilities in the range from 50 to 120 kV. Therefore, spacious and dense parts of the human body with high attenuation can be measured, such as a human knee. The authors will show investigations on the resulting attenuation, differential phase-contrast and dark-field images. The images experimentally show that X-ray grating-based phase-contrast radiography is feasible with highly absorbing parts of the human body containing massive bones.

Phase contrast X-ray imaging at the bone-cartilage interface

International Nuclear Information System (INIS)

Che Ismail, E.; Gundogdu, O.; Bradley, D.A.

2008-01-01

Full text: Phase contrast X-ray imaging is a simple technique to investigate various biological samples. At Surrey, the bone-cartilage interface is one of the biological samples which actively been studied. Bone-cartilage interface study gives a particular interest in this research as the degeneration of cartilage is the hallmark of the degenerative joint disease such as osteoarthritis. We have been applying the phase contrast imaging technique in studying the bone-cartilage interface, obtaining information on anatomical features such as the cartilage, blood vessel, tide mark and cement line. Our samples range from dry bone-cartilage to wet bone-cartilage tissue. This work will briefly review the basic supporting physics of the study. It also shows some of the images and other results that we have obtained to-date. Fig. 1 shows examples obtained using the X-ray tube system at the University of Surrey

Virtual dissection of Thoropa miliaris tadpole using phase-contrast synchrotron microtomography

Science.gov (United States)

Fidalgo, G.; Colaço, M. V.; Nogueira, L. P.; Braz, D.; Silva, H. R.; Colaço, G.; Barroso, R. C.

2018-05-01

In this work, in-line phase-contrast synchrotron microtomography was used in order to study the external and internal morphology of Thoropa miliaris tadpoles. Whole-specimens of T. miliaris in larval stages of development 28, 37 and 42, collected in the municipality of Mangaratiba (Rio de Janeiro, Brazil) were used for the study. The samples were scanned in microtomography beamline (IMX) at the Brazilian Synchrotron Light Laboratory (LNLS). The phase-contrast technique allowed us to obtain high quality images which made possible the structures segmentation on the rendered volume by the Avizo graphic image editing software. The combination of high quality images and segmentation process provides adequate visualization of different organs and soft (liver, notochord, brain, crystalline, cartilages) and hard (elements of the bone skeleton) tissues.

X-ray phase contrast imaging of the bone-cartilage interface

International Nuclear Information System (INIS)

Ismail, Elna Che; Kaabar, W.; Garrity, D.; Gundogdu, O.; Bunk, O.; Pfeiffer, F.; Farquharson, M.J.; Bradley, D.A.

2010-01-01

Synovial joints articulate in a lubricating environment, the system providing for smooth articulation. The articular cartilage overlying the bone consists of a network of collagen fibres. This network is essential to cartilage integrity, suffering damage in degenerative joint disease such as osteoarthritis. At Surrey and also in work conducted by this group at the Paul Scherrer Institute (PSI) synchrotron site we have been applying a number of techniques to study the bone-cartilage interface and of changes occurring in this with disease. One of the techniques attracting particular interest is X-ray phase contrast imaging, yielding information on anatomical features that manifest from the large scale organisation of collagen and the mineralised phase contained within the collagen fibres in the deep cartilage zone. This work briefly reviews some of the basic supporting physics of X-ray phase contrast imaging and then shows example images of the articular surface and subchondral bone and other supporting results obtained to-date. Present results have been obtained on sections of bone not displaying evidence of an osteoarthritic lesion and can be used as a baseline against which diseased bone can be compared.

X-ray phase contrast imaging of the bone-cartilage interface

Energy Technology Data Exchange (ETDEWEB)

Ismail, Elna Che; Kaabar, W.; Garrity, D.; Gundogdu, O. [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Bunk, O. [Paul Scherrer Institut, CH-5232 Villigen (Switzerland); Pfeiffer, F. [Paul Scherrer Institut, CH-5232 Villigen (Switzerland); Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Farquharson, M.J. [Department of Radiography, City University, London EC1V OHB (United Kingdom); Bradley, D.A. [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom)], E-mail: d.a.bradley@surrey.ac.uk

2010-04-15

Synovial joints articulate in a lubricating environment, the system providing for smooth articulation. The articular cartilage overlying the bone consists of a network of collagen fibres. This network is essential to cartilage integrity, suffering damage in degenerative joint disease such as osteoarthritis. At Surrey and also in work conducted by this group at the Paul Scherrer Institute (PSI) synchrotron site we have been applying a number of techniques to study the bone-cartilage interface and of changes occurring in this with disease. One of the techniques attracting particular interest is X-ray phase contrast imaging, yielding information on anatomical features that manifest from the large scale organisation of collagen and the mineralised phase contained within the collagen fibres in the deep cartilage zone. This work briefly reviews some of the basic supporting physics of X-ray phase contrast imaging and then shows example images of the articular surface and subchondral bone and other supporting results obtained to-date. Present results have been obtained on sections of bone not displaying evidence of an osteoarthritic lesion and can be used as a baseline against which diseased bone can be compared.

In-focus electron microscopy of frozen-hydrated biological samples with a Boersch phase plate

Energy Technology Data Exchange (ETDEWEB)

Barton, B.; Rhinow, D.; Walter, A.; Schroeder, R. [Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main (Germany); Benner, G.; Majorovits, E.; Matijevic, M.; Niebel, H. [Carl Zeiss NTS GmbH, D-73447 Oberkochen (Germany); Mueller, H.; Haider, M. [CEOS GmbH, Englerstr. 26, 69126 Heidleberg (Germany); Lacher, M.; Schmitz, S.; Holik, P. [Caesar Research Center, Ludwig-Erhard-Allee 2, D-53175 Bonn (Germany); Kuehlbrandt, W., E-mail: werner.kuehlbrandt@mpibp-frankfurt.mpg.de [Max Planck Institute of Biophysics, Max-von-Laue Str. 3, 60438 Frankfurt am Main (Germany)

2011-12-15

We report the implementation of an electrostatic Einzel lens (Boersch) phase plate in a prototype transmission electron microscope dedicated to aberration-corrected cryo-EM. The combination of phase plate, C{sub s} corrector and Diffraction Magnification Unit (DMU) as a new electron-optical element ensures minimal information loss due to obstruction by the phase plate and enables in-focus phase contrast imaging of large macromolecular assemblies. As no defocussing is necessary and the spherical aberration is corrected, maximal, non-oscillating phase contrast transfer can be achieved up to the information limit of the instrument. A microchip produced by a scalable micro-fabrication process has 10 phase plates, which are positioned in a conjugate, magnified diffraction plane generated by the DMU. Phase plates remained fully functional for weeks or months. The large distance between phase plate and the cryo sample permits the use of an effective anti-contaminator, resulting in ice contamination rates of <0.6 nm/h at the specimen. Maximal in-focus phase contrast was obtained by applying voltages between 80 and 700 mV to the phase plate electrode. The phase plate allows for in-focus imaging of biological objects with a signal-to-noise of 5-10 at a resolution of 2-3 nm, as demonstrated for frozen-hydrated virus particles and purple membrane at liquid-nitrogen temperature. -- Highlights: Black-Right-Pointing-Pointer We implement an electrostatic Boersch phase plate into a dedicated prototypical TEM. Black-Right-Pointing-Pointer Phase contrast aberration-corrected electron microscope (PACEM) includes a diffraction magnification unit (DMU). Black-Right-Pointing-Pointer DMU minimizes obstruction of low spatial frequencies by the phase plate. Black-Right-Pointing-Pointer In-focus phase contrast generation is demonstrated for frozen-hydrated biological specimens.

Development of x-ray laminography under an x-ray microscopic condition

International Nuclear Information System (INIS)

Hoshino, Masato; Uesugi, Kentaro; Takeuchi, Akihisa; Suzuki, Yoshio; Yagi, Naoto

2011-01-01

An x-ray laminography system under an x-ray microscopic condition was developed to obtain a three-dimensional structure of laterally-extended planar objects which were difficult to observe by x-ray tomography. An x-ray laminography technique was introduced to an x-ray transmission microscope with zone plate optics. Three prototype sample holders were evaluated for x-ray imaging laminography. Layered copper grid sheets were imaged as a laminated sample. Diatomite powder on a silicon nitride membrane was measured to confirm the applicability of this method to non-planar micro-specimens placed on the membrane. The three-dimensional information of diatom shells on the membrane was obtained at a spatial resolution of sub-micron. Images of biological cells on the membrane were also obtained by using a Zernike phase contrast technique.

Quantification of signal detection performance degradation induced by phase-retrieval in propagation-based x-ray phase-contrast imaging

Science.gov (United States)

Chou, Cheng-Ying; Anastasio, Mark A.

2016-04-01

In propagation-based X-ray phase-contrast (PB XPC) imaging, the measured image contains a mixture of absorption- and phase-contrast. To obtain separate images of the projected absorption and phase (i.e., refractive) properties of a sample, phase retrieval methods can be employed. It has been suggested that phase-retrieval can always improve image quality in PB XPC imaging. However, when objective (task-based) measures of image quality are employed, this is not necessarily true and phase retrieval can be detrimental. In this work, signal detection theory is utilized to quantify the performance of a Hotelling observer (HO) for detecting a known signal in a known background. Two cases are considered. In the first case, the HO acts directly on the measured intensity data. In the second case, the HO acts on either the retrieved phase or absorption image. We demonstrate that the performance of the HO is superior when acting on the measured intensity data. The loss of task-specific information induced by phase-retrieval is quantified by computing the efficiency of the HO as the ratio of the test statistic signal-to-noise ratio (SNR) for the two cases. The effect of the system geometry on this efficiency is systematically investigated. Our findings confirm that phase-retrieval can impair signal detection performance in XPC imaging.

Hepatic hemangioma: contrast enhancement patterns on two-phase spiral CT

International Nuclear Information System (INIS)

Yun, Eun Joo; Choi, Byung Ihn; Han, Joon Koo; Jang, Hyun Jung; Kim, Tae Kyoung; Kim, Ah Young; Lee, Ki Yeol

1998-01-01

To evaluate contrast enhancement patterns of hemangioma according to size, as seen during the arterial and portal venous phase of spiral CT. Overall, the most common enhancement pattern was peripheral high (44/82, 53.7%), during the arterial and portal venous phase. The second and third most common patterns were uniform high (11/82, 13.4%) and peripheral high-uniform high (9/82, 11.0%), also during the arterial and portal venous phase. In tumors smaller than 20 mm, low-low attenuation was seen in eight (9.8%), and iso-low attenuation in two (2.4%), during the arterial and portal venous phase, respectively. On two-phase spiral CT, the most common enhancement pattern of hemangioma was peripheral high, seen during the arterial and portal venous phase. However, a small hemangioma less than 2cm may show atypical patterns, including low and iso attenuation. (author). 23 refs., 1 tab., 4 figs

A phase contrast imaging system for TEXT-U

International Nuclear Information System (INIS)

Chatterjee, R.; Hallock, G.A.; Gartman, M.L.

1994-01-01

A diagnostic to study plasma density fluctuations, Phase Contrast Imaging (PCI) has been developed for the Texas Experimental Tokamak-Upgrade. The diagnostic has a sensitivity of about 10 -4 n e0 and is capable of detecting a wide range of wavenumbers (0.5 cm -1 - 12 cm -1 ) with a bandwidth of 500 Khz. The design of the diagnostic, some results of acoustic calibration tests and preliminary results of simulation of expected spectra are presented

Observations of a human hair shaft with an x-ray microscope

Energy Technology Data Exchange (ETDEWEB)

Youn, Hwa Shik [Pohang Accelerator Laboratory, Pohang University of Science and Technology, 31 San, Hyoja-dong, Pohang, KyungBuk, 790-784 (Korea, Republic of); Jung, Suk-Won [Nano Mechatronics Research Center, Korea Electronics Technology Institute, 455-6 Masan-ri, Jinwi-myon, Pyungtaek, Kyungki-do, 451-865 (Korea, Republic of)

2005-11-21

We observed the internal structures of a human hair shaft using x-ray microscopes with a spatial resolution in the range from a few microns to less than 100 nm. The energy of the x-ray used is 6.95 keV. The Zernike phase contrast together with a spatial resolution better than 100 nm enabled us to see the cuticles of scales, the cortex of macrofibrils and the medulla. All these internal features and more can easily be observed with no sample preparation including staining.

Observations of a human hair shaft with an x-ray microscope

International Nuclear Information System (INIS)

Youn, Hwa Shik; Jung, Suk-Won

2005-01-01

We observed the internal structures of a human hair shaft using x-ray microscopes with a spatial resolution in the range from a few microns to less than 100 nm. The energy of the x-ray used is 6.95 keV. The Zernike phase contrast together with a spatial resolution better than 100 nm enabled us to see the cuticles of scales, the cortex of macrofibrils and the medulla. All these internal features and more can easily be observed with no sample preparation including staining

Preliminary research on dual-energy X-ray phase-contrast imaging

Science.gov (United States)

Han, Hua-Jie; Wang, Sheng-Hao; Gao, Kun; Wang, Zhi-Li; Zhang, Can; Yang, Meng; Zhang, Kai; Zhu, Pei-Ping

2016-04-01

Dual-energy X-ray absorptiometry (DEXA) has been widely applied to measure the bone mineral density (BMD) and soft-tissue composition of the human body. However, the use of DEXA is greatly limited for low-Z materials such as soft tissues due to their weak absorption, while X-ray phase-contrast imaging (XPCI) shows significantly improved contrast in comparison with the conventional standard absorption-based X-ray imaging for soft tissues. In this paper, we propose a novel X-ray phase-contrast method to measure the area density of low-Z materials, including a single-energy method and a dual-energy method. The single-energy method is for the area density calculation of one low-Z material, while the dual-energy method aims to calculate the area densities of two low-Z materials simultaneously. Comparing the experimental and simulation results with the theoretical ones, the new method proves to have the potential to replace DEXA in area density measurement. The new method sets the prerequisites for a future precise and low-dose area density calculation method for low-Z materials. Supported by Major State Basic Research Development Program (2012CB825800), Science Fund for Creative Research Groups (11321503) and National Natural Science Foundation of China (11179004, 10979055, 11205189, 11205157)

Implementation of neutron phase contrast imaging at FRM-II

Energy Technology Data Exchange (ETDEWEB)

Lorenz, Klaus

2008-11-12

At ANTARES, the beam line for neutron imaging at the Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II) in Garching, the option to do phase contrast imaging besides conventional absorption based neutron imaging was implemented and successfully used for the non-destructive testing of various types of objects. The used propagation-based technique is based on the interference of neutron waves in the detector plane that were differently strong diffracted by the sample. A comparison with other phase-sensitive neutron imaging techniques highlights assets and drawbacks of the different methods. In preliminary measurements at ANTARES and the spallation source SINQ at PSI in Villigen, the influence of the beam geometry, the neutron spectrum and the detector on the quality of the phase contrast measurements were investigated systematically. It was demonstrated that gamma radiation and epithermal neutrons in the beam contribute severely to background noise in measurements, which motivated the installation of a remotely controlled filter wheel for a quick and precise positioning of different crystal filters in the beam. By the installation of a similar aperture wheel, a quick change between eight different beam geometries was made possible. Besides pinhole and slit apertures, coded apertures based on non redundant arrays were investigated. The possibilities, which arise by the exploitation of the real part of the refractive index in neutron imaging, were demonstrated in experiments with especially designed test samples and in measurements with ordinary, industrial components. (orig.)

Implementation of neutron phase contrast imaging at FRM-II

International Nuclear Information System (INIS)

Lorenz, Klaus

2008-01-01

At ANTARES, the beam line for neutron imaging at the Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II) in Garching, the option to do phase contrast imaging besides conventional absorption based neutron imaging was implemented and successfully used for the non-destructive testing of various types of objects. The used propagation-based technique is based on the interference of neutron waves in the detector plane that were differently strong diffracted by the sample. A comparison with other phase-sensitive neutron imaging techniques highlights assets and drawbacks of the different methods. In preliminary measurements at ANTARES and the spallation source SINQ at PSI in Villigen, the influence of the beam geometry, the neutron spectrum and the detector on the quality of the phase contrast measurements were investigated systematically. It was demonstrated that gamma radiation and epithermal neutrons in the beam contribute severely to background noise in measurements, which motivated the installation of a remotely controlled filter wheel for a quick and precise positioning of different crystal filters in the beam. By the installation of a similar aperture wheel, a quick change between eight different beam geometries was made possible. Besides pinhole and slit apertures, coded apertures based on non redundant arrays were investigated. The possibilities, which arise by the exploitation of the real part of the refractive index in neutron imaging, were demonstrated in experiments with especially designed test samples and in measurements with ordinary, industrial components. (orig.)

Holography microscopy as an artifact-free alternative to phase-contrast

Czech Academy of Sciences Publication Activity Database

Pastorek, Lukáš; Venit, Tomáš; Hozák, Pavel

2018-01-01

Roč. 149, č. 2 (2018), s. 179-186 ISSN 0948-6143 R&D Projects: GA MŠk(CZ) LM2015062 Institutional support: RVO:68378050 Keywords : Holography microscopy * Phase-contrast * Halo effect Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Cell biology Impact factor: 2.553, year: 2016

Height measurement of transparent objects by adopting differential interference contrast technology

International Nuclear Information System (INIS)

Yu, Sheng-Kang; Liu, Ting-Kun; Lin, Shih-Chieh

2010-01-01

In this study, the differential interference contrast (DIC) approach originally used for image enhancement to increase the contrast between a transparent object and the background is adopted for the dimension measurement of transparent structures. With the phase difference image retrieved using the DIC technique, the phase map of the examined object can be approximated by integrating the phase difference. The need of integration accuracy is much higher for measurement than for image enhancement. In this study, a modified Fourier phase integration is proposed to reduce the effects of noise on surface profile reconstruction. The simulation results show that the proposed approach can effectively reduce the effects of noise. Experimental results are also conducted to study the feasibility of using the transmitted DIC with the proposed integration method for transparent object measurement. The results show that the height of a transparent structure measured using the DIC method is quite close to those measured using an atomic force microscope, while those measured using the white-light interference method result in a much larger measurement than all others.

Accelerated 4D phase contrast MRI in skeletal muscle contraction.

Science.gov (United States)

Mazzoli, Valentina; Gottwald, Lukas M; Peper, Eva S; Froeling, Martijn; Coolen, Bram F; Verdonschot, Nico; Sprengers, Andre M; van Ooij, Pim; Strijkers, Gustav J; Nederveen, Aart J

2018-03-05

3D time-resolved (4D) phase contrast MRI can be used to study muscle contraction. However, 3D coverage with sufficient spatiotemporal resolution can only be achieved by interleaved acquisitions during many repetitions of the motion task, resulting in long scan times. The aim of this study was to develop a compressed sensing accelerated 4D phase contrast MRI technique for quantification of velocities and strain rate of the muscles in the lower leg during active plantarflexion/dorsiflexion. Nine healthy volunteers were scanned during active dorsiflexion/plantarflexion task. For each volunteer, we acquired a reference scan, as well as 4 different accelerated scans (k-space undersampling factors: 3.14X, 4.09X, 4.89X, and 6.41X) obtained using Cartesian Poisson disk undersampling schemes. The data was reconstructed using a compressed sensing pipeline. For each scan, velocity and strain rate values were quantified in the gastrocnemius lateralis, gastrocnemius medialis, tibialis anterior, and soleus. No significant differences in velocity values were observed as a function acceleration factor in the investigated muscles. The strain rate calculation resulted in one positive (s + ) and one negative (s - ) eigenvalue, whereas the third eigenvalue (s 3 ) was consistently 0 for all the acquisitions. No significant differences were observed for the strain rate eigenvalues as a function of acceleration factor. Data undersampling combined with compressed sensing reconstruction allowed obtainment of time-resolved phase contrast acquisitions with 3D coverage and quantitative information comparable to the reference scan. The 3D sensitivity of the method can help in understanding the connection between muscle architecture and muscle function in future studies. © 2018 International Society for Magnetic Resonance in Medicine.

A reconstruction method for cone-beam differential x-ray phase-contrast computed tomography.

Science.gov (United States)

Fu, Jian; Velroyen, Astrid; Tan, Renbo; Zhang, Junwei; Chen, Liyuan; Tapfer, Arne; Bech, Martin; Pfeiffer, Franz

2012-09-10

Most existing differential phase-contrast computed tomography (DPC-CT) approaches are based on three kinds of scanning geometries, described by parallel-beam, fan-beam and cone-beam. Due to the potential of compact imaging systems with magnified spatial resolution, cone-beam DPC-CT has attracted significant interest. In this paper, we report a reconstruction method based on a back-projection filtration (BPF) algorithm for cone-beam DPC-CT. Due to the differential nature of phase contrast projections, the algorithm restrains from differentiation of the projection data prior to back-projection, unlike BPF algorithms commonly used for absorption-based CT data. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a micro-focus x-ray tube source. Moreover, the numerical simulation and experimental results demonstrate that the proposed method can deal with several classes of truncated cone-beam datasets. We believe that this feature is of particular interest for future medical cone-beam phase-contrast CT imaging applications.

Quantitative differential phase contrast imaging at high resolution with radially asymmetric illumination.

Science.gov (United States)

Lin, Yu-Zi; Huang, Kuang-Yuh; Luo, Yuan

2018-06-15

Half-circle illumination-based differential phase contrast (DPC) microscopy has been utilized to recover phase images through a pair of images along multiple axes. Recently, the half-circle based DPC using 12-axis measurements significantly provides a circularly symmetric phase transfer function to improve accuracy for more stable phase recovery. Instead of using half-circle-based DPC, we propose a new scheme of DPC under radially asymmetric illumination to achieve circularly symmetric phase transfer function and enhance the accuracy of phase recovery in a more stable and efficient fashion. We present the design, implementation, and experimental image data demonstrating the ability of our method to obtain quantitative phase images of microspheres, as well as live fibroblast cell samples.

Quantitative hard x-ray phase contrast imaging of micropipes in SiC

International Nuclear Information System (INIS)

Kohn, V. G.; Argunova, T. S.; Je, J. H.

2013-01-01

Peculiarities of quantitative hard x-ray phase contrast imaging of micropipes in SiC are discussed. The micropipe is assumed as a hollow cylinder with an elliptical cross section. The major and minor diameters can be restored using the least square fitting procedure by comparing the experimental data, i.e. the profile across the micropipe axis, with those calculated based on phase contrast theory. It is shown that one projection image gives an information which does not allow a complete determination of the elliptical cross section, if an orientation of micropipe is not known. Another problem is a weak accuracy in estimating the diameters, partly because of using pink synchrotron radiation, which is necessary because a monochromatic beam intensity is not sufficient to reveal the weak contrast from a very small object. The general problems of accuracy in estimating the two diameters using the least square procedure are discussed. Two experimental examples are considered to demonstrate small as well as modest accuracies in estimating the diameters

Hard-x-ray phase-difference microscopy with a low-brilliance laboratory x-ray source

International Nuclear Information System (INIS)

Kuwabara, Hiroaki; Yashiro, Wataru; Harasse, Sebastien; Momose, Atsushi; Mizutani, Haruo

2011-01-01

We have developed a hard-X-ray phase-imaging microscopy method using a low-brilliance X-ray source. The microscope consists of a sample, a Fresnel zone plate, a transmission grating, and a source grating creating an array of mutually incoherent X-ray sources. The microscope generates an image exhibiting twin features of the sample with opposite signs separated by a distance, which is processed to generate a phase image. The method is quantitative even for non-weak-phase objects that are difficult to be quantitatively examined by the widely used Zernike phase-contrast microscopy, and it has potentially broad applications in the material and biological science fields. (author)

The influence of microscopic and macroscopic non-stoichiometry on interfacial planarity during the solid-phase epitaxial growth of amorphized GaAs

International Nuclear Information System (INIS)

Belay, K.B.; Ridgway, M.C.; Llewellyn, D.J.

1996-01-01

The influence of microscopic and macroscopic non-stoichiometry on the Solid-Phase Epitaxial Growth of GaAs has been studied. Ion implantation has been employed to produce microscopic non-stoichiometry via Ga and As implants and macroscopic non-stoichiometry via Ga or As implants. In-situ Time Resolved Reflectivity and Transmission Electron Microscopy and ex-situ Rutherford Backscattering Spectroscopy and Channeling have been used to investigate the regrowth of amorphized GaAs layers. As non-stoichiometry shifts from microscopic to macroscopic the interface loses its planar nature and subsequently gets rougher. 7 refs., 3 figs

The influence of microscopic and macroscopic non-stoichiometry on interfacial planarity during the solid-phase epitaxial growth of amorphized GaAs

Energy Technology Data Exchange (ETDEWEB)

Belay, K.B.; Ridgway, M.C.; Llewellyn, D.J. [Australian National Univ., Canberra, ACT (Australia). Dept. of Physics

1996-12-31

The influence of microscopic and macroscopic non-stoichiometry on the Solid-Phase Epitaxial Growth of GaAs has been studied. Ion implantation has been employed to produce microscopic non-stoichiometry via Ga and As implants and macroscopic non-stoichiometry via Ga or As implants. In-situ Time Resolved Reflectivity and Transmission Electron Microscopy and ex-situ Rutherford Backscattering Spectroscopy and Channeling have been used to investigate the regrowth of amorphized GaAs layers. As non-stoichiometry shifts from microscopic to macroscopic the interface loses its planar nature and subsequently gets rougher. 7 refs., 3 figs.

The influence of microscopic and macroscopic non-stoichiometry on interfacial planarity during the solid-phase epitaxial growth of amorphized GaAs

Energy Technology Data Exchange (ETDEWEB)

Belay, K B; Ridgway, M C; Llewellyn, D J [Australian National Univ., Canberra, ACT (Australia). Dept. of Physics

1997-12-31

The influence of microscopic and macroscopic non-stoichiometry on the Solid-Phase Epitaxial Growth of GaAs has been studied. Ion implantation has been employed to produce microscopic non-stoichiometry via Ga and As implants and macroscopic non-stoichiometry via Ga or As implants. In-situ Time Resolved Reflectivity and Transmission Electron Microscopy and ex-situ Rutherford Backscattering Spectroscopy and Channeling have been used to investigate the regrowth of amorphized GaAs layers. As non-stoichiometry shifts from microscopic to macroscopic the interface loses its planar nature and subsequently gets rougher. 7 refs., 3 figs.

Variable-temperature Microwave Impedance Microscope with Light Stimulation for Research on Photo-induced Phase Transitions

Science.gov (United States)

2017-07-24

SECURITY CLASSIFICATION OF: The DURIP program "Variable-temperature Microwave Impedance Microscope with Light Stimulation for Research on Photo... Stimulation for Research on Photo- induced Phase Transitions The views, opinions and/or findings contained in this report are those of the author(s) and should...reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions

Accelerated three-dimensional cine phase contrast imaging using randomly undersampled echo planar imaging with compressed sensing reconstruction.

Science.gov (United States)

Basha, Tamer A; Akçakaya, Mehmet; Goddu, Beth; Berg, Sophie; Nezafat, Reza

2015-01-01

The aim of this study was to implement and evaluate an accelerated three-dimensional (3D) cine phase contrast MRI sequence by combining a randomly sampled 3D k-space acquisition sequence with an echo planar imaging (EPI) readout. An accelerated 3D cine phase contrast MRI sequence was implemented by combining EPI readout with randomly undersampled 3D k-space data suitable for compressed sensing (CS) reconstruction. The undersampled data were then reconstructed using low-dimensional structural self-learning and thresholding (LOST). 3D phase contrast MRI was acquired in 11 healthy adults using an overall acceleration of 7 (EPI factor of 3 and CS rate of 3). For comparison, a single two-dimensional (2D) cine phase contrast scan was also performed with sensitivity encoding (SENSE) rate 2 and approximately at the level of the pulmonary artery bifurcation. The stroke volume and mean velocity in both the ascending and descending aorta were measured and compared between two sequences using Bland-Altman plots. An average scan time of 3 min and 30 s, corresponding to an acceleration rate of 7, was achieved for 3D cine phase contrast scan with one direction flow encoding, voxel size of 2 × 2 × 3 mm(3) , foot-head coverage of 6 cm and temporal resolution of 30 ms. The mean velocity and stroke volume in both the ascending and descending aorta were statistically equivalent between the proposed 3D sequence and the standard 2D cine phase contrast sequence. The combination of EPI with a randomly undersampled 3D k-space sampling sequence using LOST reconstruction allows a seven-fold reduction in scan time of 3D cine phase contrast MRI without compromising blood flow quantification. Copyright © 2014 John Wiley & Sons, Ltd.

Generalized Phase contrast and matched filtering for speckle‐free patterned illumination

DEFF Research Database (Denmark)

Palima, Darwin; Bañas, Andrew Rafael; Villangca, Mark Jayson

2013-01-01

Generalized Phase Contrast (GPC) and matched‐filtering GPC use tandem diffractive phase elements on Fourier‐conjugate planes of a 4f optical processor to efficiently reshape incident light into a pattern that resembles the input phase modulation pattern. The synthesized patterns are inherently...... to optically trap and mechanically manipulate microparticles, GPC has also been applied for laser beamshaping, optical phase cryptography, and greyscale image projection. Recent reports from our collaborators highlight that GPC‐based spatial lightshaping, when combined with temporal focusing and multiphoton...... excitation, exhibits some robustness against light scattering and, hence, makes a promising tool for spatially precise targeting of deeper subsurface neurons using minimally speckled patterned illumination for multiphoton excitation....

Gastric stromal tumor: two-phase dynamic CT findings with water as oral contrast agents

International Nuclear Information System (INIS)

Lee, Se Hyo; Cho, June Sik; Shin, Kyung Sook; Jeong, Ki Ho; Park, Jin Yong; Yu, Ho Jun; Kim, Young Min; Jeon, Kwang Jin

2000-01-01

To evaluate two-phase dynamic CT with water as oral contrast agents in the CT diagnosis of gastric stromal tumors. We retrospectively reviewed the CT findings in 21 patients with pathologically proven gastric stromal tumors. Six were found to be benign, twelve were malignant, and there were three cases of STUMP (stromal tumor uncertain malignant potential). Two-phase dynamic CT scans with water as oral contrast agents were obtained 60-70 secs (portal phase) and 3 mins (equilibrium phase) after the start of IV contrast administration. We determined the size, growth pattern, and enhancement pattern of the tumors and overlying mucosa, the presence or absence of ulceration and necrosis, tumor extent, and lymph nod and distant metastasis. The CT and pathologic findings were correlated. All six benign tumors and three STUMP were less than 5.5 cm in size, and during the portal phase showed round endogastric masses with highly enhanced, intact overlying mucosa. Twelve malignant tumors were 4.5-15.5 cm in size (mean, 11.5 cm); an endogastric mass was seen in three cases, an exogastric mass in one, and a mixed pattern in eight. On portal phase images the tumors were not significantly enhanced, but highly enhanced feeding vessels were noted in five larger tumors (greater than 10 cm). All 12 malignant tumors showed ulceration and necrosis, and interruption of overlying mucosa was clearly seen during the portal phase. We were readily able to evaluate tumor extent during this phase, and in ten malignant tumors there was no invasion of adjacent organs. Seven malignant tumors showed air density within their necrotic portion (p less than 0.05). On equilibrium phase images, all malignant tumors showed heterogeneous enhancement due to necrosis, and poorly enhanced overlying mucosa. Dynamic CT during the portal phase with water as oral contrast agents was useful for depicting the submucosal origin of gastric stromal tumors and for evaluating the extent of malignant stromal tumors. Our

Microscopic interplay of superconducting and magnetic order parameters in ferropnictides

Energy Technology Data Exchange (ETDEWEB)

Maeter, H.; Goltz, T.; Spehling, J.; Klauss, H.H. [Institut fuer Festkoerperphysik, TU Dresden (Germany); Bendele, M.; Luetkens, H.; Khasanov, R.; Pascua, G.; Shermadini, Z.; Amato, A. [Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, Villigen (Switzerland); Aswartham, S.; Hamann-Borrero, J.E.; Kondrat, A.; Hess, C.; Wolter, A.; Wurmehl, S.; Behr, G.; Buechner, B. [Leibniz-Institut fuer Festkoerper- und Werkstoffforschung Dresden (Germany); Wiesenmayer, E.; Johrendt, D. [Department Chemie, Ludwig-Maximilians-Universitaet Muenchen (Germany); Potts, H.; Banusch, B. [Swiss Nanoscience Institute, Universitaet Basel (Switzerland)

2012-07-01

We present results of {mu}SR experiments of Ba{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} that show a large coupling of the superconducting and magnetic order parameters. This is unexpected in light of the phase separation in Ba{sub 1-x}K{sub x}Fe{sub 2}As{sub 2}. However, in a {mu}SR study of Ba{sub 1-x}K{sub x}Fe{sub 2}As{sub 2} we unambiguously showed microscopic coexistence, even though there are many reports of phase separation in this system. In FeSe{sub 1-x} the interplay of phase separation and microscopic coexistence is also evident, here pressure can induce a change from microscopic coexistence to a combination of both. In light of the {mu}SR results it seems likely that phase separation and microscopic coexistence depend on the microscopic properties much more than on disorder.

Correlation between resistance-change effect in transition-metal oxides and secondary-electron contrast of scanning electron microscope images

International Nuclear Information System (INIS)

Kinoshita, K.; Kishida, S.; Yoda, T.

2011-01-01

Conductive atomic-force microscopy (C-AFM) writing is attracting attention as a technique for clarifying the switching mechanism of resistive random-access memory by providing a wide area filled with filaments, which can be regarded as one filament with large radius. The writing area on a nickel-oxide (NiO) film formed by conductive atomic-force microscopy was observed by scanning electron microscope, and a correlation between the contrast in a secondary-electron image (SEI) and the resistance written by C-AFM was revealed. In addition, the dependence of the SEI contrast on the beam accelerating voltage (V accel ) suggests that the resistance-change effect occurs near the surface of the NiO film. As for the effects of electron irradiation and vacuum annealing on the C-AFM writing area, it was shown that the resistance-change effect is caused by exchange of oxygen with the atmosphere at the surface of the NiO film. This result suggests that the low-resistance and high-resistance areas are, respectively, p-type Ni 1+δ O (δ 1+δ O (δ≥ 0).

Simultaneous Scanning Electron Microscope Imaging of Topographical and Chemical Contrast Using In-Lens, In-Column, and Everhart-Thornley Detector Systems.

Science.gov (United States)

Zhang, Xinming; Cen, Xi; Ravichandran, Rijuta; Hughes, Lauren A; van Benthem, Klaus

2016-06-01

The scanning electron microscope provides a platform for subnanometer resolution characterization of material morphology with excellent topographic and chemical contrast dependent on the used detectors. For imaging applications, the predominantly utilized signals are secondary electrons (SEs) and backscattered electrons (BSEs) that are emitted from the sample surface. Recent advances in detector technology beyond the traditional Everhart-Thornley geometry have enabled the simultaneous acquisition and discrimination of SE and BSE signals. This study demonstrates the imaging capabilities of a recently introduced new detector system that consists of the combination of two in-lens (I-L) detectors and one in-column (I-C) detector. Coupled with biasing the sample stage to reduce electron-specimen interaction volumes, this trinity of detector geometry allows simultaneous acquisition of signals to distinguish chemical contrast from topographical changes of the sample, including the identification of surface contamination. The I-C detector provides 4× improved topography, whereas the I-L detector closest to the sample offers excellent simultaneous chemical contrast imaging while not limiting the minimization of working distance to obtain optimal lateral resolution. Imaging capabilities and contrast mechanisms for all three detectors are discussed quantitatively in direct comparison to each other and the conventional Everhart-Thornley detector.

The microscopic twins and their crystal phase in the high Tc Y-Ba-Cu-O and Dy-Ba-Cu-O superconductive ceramics

International Nuclear Information System (INIS)

Zu, Z.J.; Chen, Y.L.

1988-01-01

Most consider that the structure of Y-Ba- Cu-O and Dy-Ba-Cu-O stable superconductive crystals with high Tc is associated with the right-angled phase. The superconductivity is closely connected with the right-angled character of the crystalline texture; the better the right- angled character, the better the superconductivity. From statistical investigations of examples the authors have discovered that most of the Y-Ba-Cu-O and Dy-Ba-Cu-O superconductivity with high Tc ceramic crystals is in the monoclinic phase, which, consists of microscopic, lamellar, single twins. The long-columnar grains consisting of lamellar twin slabs show the optical characteristics of right-angled phase. The microscopic twinning and grain morphologies are summarized in this paper

Differential phase contrast setup for a non coherent beamline at HASYLAB using hard X-ray grating interferometer

Energy Technology Data Exchange (ETDEWEB)

Herzen, Julia; Beckmann, Felix; Haibel, Astrid; Schreyer, Andreas [GKSS Research Centre, Geesthacht (Germany); Donath, Tilman; David, Christian; Gruenzweig, Christian [Paul Scherrer Institute, Villigen PSI (Switzerland); Pfeiffer, Franz [Paul Scherrer Institute, Villigen PSI (Switzerland); EPF Lausanne, Lausanne (Switzerland)

2009-07-01

Phase-contrast imaging is a common technique to visualize soft tissue with much higher contrast than the conventional absorption-contrast imaging. Differential phase contrast (DPC), developed at PSI, Switzerland, makes use of a hard x-ray grating interferometer and allows for phase-contrast imaging with high brilliance synchrotron sources as well as with conventional x-ray tubes. It is recently reported also to provide dark field information that is very sensitive to micro structures like porosity within the materials. Here we present the plans to adopt the DPC technique to the HARWI-II materials science beamline, operated by GKSS Research Centre, in cooperation with DESY, Hamburg. This will offer an amount of new applications especially in the field of materials science like for example characterizing new light weight materials like magnesium and studying its corrosion as implant material.

In vivo x-ray phase contrast analyzer-based imaging for longitudinal osteoarthritis studies in guinea pigs

Energy Technology Data Exchange (ETDEWEB)

Coan, Paola [Faculty of Medicine and Institute of Clinical Radiology, Ludwig-Maximilians University, Munich (Germany); Wagner, Andreas; Mollenhauer, Juergen [Department of Orthopaedics of the University of Jena, Rudolf-Elle-Hospital Eisenberg (Germany); Bravin, Alberto; Diemoz, Paul C; Keyrilaeinen, Jani, E-mail: Paola.Coan@physik.uni-muenchen.d [European Synchrotron Radiation Facility (ESRF), Grenoble (France)

2010-12-21

Over the last two decades phase contrast x-ray imaging techniques have been extensively studied for applications in the biomedical field. Published results demonstrate the high capability of these imaging modalities of improving the image contrast of biological samples with respect to standard absorption-based radiography and routinely used clinical imaging techniques. A clear depiction of the anatomic structures and a more accurate disease diagnosis may be provided by using radiation doses comparable to or lower than those used in current clinical methods. In the literature many works show images of phantoms and excised biological samples proving the high sensitivity of the phase contrast imaging methods for in vitro investigations. In this scenario, the applications of the so-called analyzer-based x-ray imaging (ABI) phase contrast technique are particularly noteworthy. The objective of this work is to demonstrate the feasibility of in vivo x-ray ABI phase contrast imaging for biomedical applications and in particular with respect to joint anatomic depiction and osteoarthritis detection. ABI in planar and tomographic modes was performed in vivo on articular joints of guinea pigs in order to investigate the animals with respect to osteoarthritis by using highly monochromatic x-rays of 52 keV and a low noise detector with a pixel size of 47 x 47 {mu}m{sup 2}. Images give strong evidence of the ability of ABI in depicting both anatomic structures in complex systems as living organisms and all known signs of osteoarthritis with high contrast, high spatial resolution and with an acceptable radiation dose. This paper presents the first proof of principle study of in vivo application of ABI. The technical challenges encountered when imaging an animal in vivo are discussed. This experimental study is an important step toward the study of clinical applications of phase contrast x-ray imaging techniques.

Baseline correction of phase-contrast images in congenital cardiovascular magnetic resonance

Directory of Open Access Journals (Sweden)

Lai Wyman W

2010-03-01

Full Text Available Abstract Background One potential source of error in phase contrast (PC congenital CMR flow measurements is caused by phase offsets due to local non-compensated eddy currents. Phantom correction of these phase offset errors has been shown to result in more accurate measurements of blood flow in adults with structurally normal hearts. We report the effect of phantom correction on PC flow measurements at a clinical congenital CMR program. Results Flow was measured in the ascending aorta, main pulmonary artery, and right and left pulmonary arteries as clinically indicated, and additional values such as Qp/Qs were derived from these measurements. Phantom correction in our study population of 149 patients resulted in clinically significant changes in 13% to 48% of these phase-contrast measurements in patients with known or suspected heart disease. Overall, 640 measurements or calculated values were analyzed, and clinically significant changes were found in 31%. Larger vessels were associated with greater phase offset errors, with 22% of the changes in PC flow measurements attributed to the size of the vessel measured. In patients with structurally normal hearts, the pulmonary-to-systemic flow ratio after phantom correction was closer to 1.0 than before phantom correction. There was no significant difference in the effect of phantom correction for patients with tetralogy of Fallot as compared to the group as a whole. Conclusions Phantom correction often resulted in clinically significant changes in PC blood flow measurements in patients with known or suspected congenital heart disease. In laboratories performing clinical CMR with suspected phase offset errors of significance, the routine use of phantom correction for PC flow measurements should be considered.

Benchmarking the x-ray phase contrast imaging for ICF DT ice characterization using roughened surrogates

Energy Technology Data Exchange (ETDEWEB)

Dewald, E; Kozioziemski, B; Moody, J; Koch, J; Mapoles, E; Montesanti, R; Youngblood, K; Letts, S; Nikroo, A; Sater, J; Atherton, J

2008-06-26

We use x-ray phase contrast imaging to characterize the inner surface roughness of DT ice layers in capsules planned for future ignition experiments. It is therefore important to quantify how well the x-ray data correlates with the actual ice roughness. We benchmarked the accuracy of our system using surrogates with fabricated roughness characterized with high precision standard techniques. Cylindrical artifacts with azimuthally uniform sinusoidal perturbations with 100 um period and 1 um amplitude demonstrated 0.02 um accuracy limited by the resolution of the imager and the source size of our phase contrast system. Spherical surrogates with random roughness close to that required for the DT ice for a successful ignition experiment were used to correlate the actual surface roughness to that obtained from the x-ray measurements. When comparing average power spectra of individual measurements, the accuracy mode number limits of the x-ray phase contrast system benchmarked against surface characterization performed by Atomic Force Microscopy are 60 and 90 for surrogates smoother and rougher than the required roughness for the ice. These agreement mode number limits are >100 when comparing matching individual measurements. We will discuss the implications for interpreting DT ice roughness data derived from phase-contrast x-ray imaging.

X-ray phase-contrast tomography for high-spatial-resolution zebrafish muscle imaging

Science.gov (United States)

Vågberg, William; Larsson, Daniel H.; Li, Mei; Arner, Anders; Hertz, Hans M.

2015-11-01

Imaging of muscular structure with cellular or subcellular detail in whole-body animal models is of key importance for understanding muscular disease and assessing interventions. Classical histological methods for high-resolution imaging methods require excision, fixation and staining. Here we show that the three-dimensional muscular structure of unstained whole zebrafish can be imaged with sub-5 μm detail with X-ray phase-contrast tomography. Our method relies on a laboratory propagation-based phase-contrast system tailored for detection of low-contrast 4-6 μm subcellular myofibrils. The method is demonstrated on 20 days post fertilization zebrafish larvae and comparative histology confirms that we resolve individual myofibrils in the whole-body animal. X-ray imaging of healthy zebrafish show the expected structured muscle pattern while specimen with a dystrophin deficiency (sapje) displays an unstructured pattern, typical of Duchenne muscular dystrophy. The method opens up for whole-body imaging with sub-cellular detail also of other types of soft tissue and in different animal models.

Revising the lower statistical limit of x-ray grating-based phase-contrast computed tomography.

Science.gov (United States)

Marschner, Mathias; Birnbacher, Lorenz; Willner, Marian; Chabior, Michael; Herzen, Julia; Noël, Peter B; Pfeiffer, Franz

2017-01-01

Phase-contrast x-ray computed tomography (PCCT) is currently investigated as an interesting extension of conventional CT, providing high soft-tissue contrast even if examining weakly absorbing specimen. Until now, the potential for dose reduction was thought to be limited compared to attenuation CT, since meaningful phase retrieval fails for scans with very low photon counts when using the conventional phase retrieval method via phase stepping. In this work, we examine the statistical behaviour of the reverse projection method, an alternative phase retrieval approach and compare the results to the conventional phase retrieval technique. We investigate the noise levels in the projections as well as the image quality and quantitative accuracy of the reconstructed tomographic volumes. The results of our study show that this method performs better in a low-dose scenario than the conventional phase retrieval approach, resulting in lower noise levels, enhanced image quality and more accurate quantitative values. Overall, we demonstrate that the lower statistical limit of the phase stepping procedure as proposed by recent literature does not apply to this alternative phase retrieval technique. However, further development is necessary to overcome experimental challenges posed by this method which would enable mainstream or even clinical application of PCCT.

Quantitative tracking of tumor cells in phase-contrast microscopy exploiting halo artifact pattern

Science.gov (United States)

Kang, Mi-Sun; Song, Soo-Min; Lee, Hana; Kim, Myoung-Hee

2012-03-01

Tumor cell morphology is closely related to its invasiveness characteristics and migratory behaviors. An invasive tumor cell has a highly irregular shape, whereas a spherical cell is non-metastatic. Thus, quantitative analysis of cell features is crucial to determine tumor malignancy or to test the efficacy of anticancer treatment. We use phase-contrast microscopy to analyze single cell morphology and to monitor its change because it enables observation of long-term activity of living cells without photobleaching and phototoxicity, which is common in other fluorescence-labeled microscopy. Despite this advantage, there are image-level drawbacks to phase-contrast microscopy, such as local light effect and contrast interference ring, among others. Thus, we first applied a local filter to compensate for non-uniform illumination. Then, we used intensity distribution information to detect the cell boundary. In phase-contrast microscopy images, the cell normally appears as a dark region surrounded by a bright halo. As the halo artifact around the cell body is minimal and has an asymmetric diffusion pattern, we calculated the cross-sectional plane that intersected the center of each cell and was orthogonal to the first principal axis. Then, we extracted the dark cell region by level set. However, a dense population of cultured cells still rendered single-cell analysis difficult. Finally, we measured roundness and size to classify tumor cells into malignant and benign groups. We validated segmentation accuracy by comparing our findings with manually obtained results.

Determination of the parameters of a microscopic object from a complex response of a differential microscope

International Nuclear Information System (INIS)

Baranov, D V; Egorov, Alexander A; Zolotov, Evgenii M; Svidzinsky, K K

1998-01-01

An analysis of the amplitude and phase of a complex response of a heterodyne differential microscope was used to demonstrate experimentally the feasibility of determination of the parameters of a composite microscopic object representing a combination of a step with a groove. (laser applications and other topics in quantum electronics)

Biofilm imaging in porous media by laboratory X-Ray tomography: Combining a non-destructive contrast agent with propagation-based phase-contrast imaging tools.

Science.gov (United States)

Carrel, Maxence; Beltran, Mario A; Morales, Verónica L; Derlon, Nicolas; Morgenroth, Eberhard; Kaufmann, Rolf; Holzner, Markus

2017-01-01

X-ray tomography is a powerful tool giving access to the morphology of biofilms, in 3D porous media, at the mesoscale. Due to the high water content of biofilms, the attenuation coefficient of biofilms and water are very close, hindering the distinction between biofilms and water without the use of contrast agents. Until now, the use of contrast agents such as barium sulfate, silver-coated micro-particles or 1-chloronaphtalene added to the liquid phase allowed imaging the biofilm 3D morphology. However, these contrast agents are not passive and potentially interact with the biofilm when injected into the sample. Here, we use a natural inorganic compound, namely iron sulfate, as a contrast agent progressively bounded in dilute or colloidal form into the EPS matrix during biofilm growth. By combining a very long source-to-detector distance on a X-ray laboratory source with a Lorentzian filter implemented prior to tomographic reconstruction, we substantially increase the contrast between the biofilm and the surrounding liquid, which allows revealing the 3D biofilm morphology. A comparison of this new method with the method proposed by Davit et al (Davit et al., 2011), which uses barium sulfate as a contrast agent to mark the liquid phase was performed. Quantitative evaluations between the methods revealed substantial differences for the volumetric fractions obtained from both methods. Namely, contrast agent-biofilm interactions (e.g. biofilm detachment) occurring during barium sulfate injection caused a reduction of the biofilm volumetric fraction of more than 50% and displacement of biofilm patches elsewhere in the column. Two key advantages of the newly proposed method are that passive addition of iron sulfate maintains the integrity of the biofilm prior to imaging, and that the biofilm itself is marked by the contrast agent, rather than the liquid phase as in other available methods. The iron sulfate method presented can be applied to understand biofilm development

Analysis of an automated background correction method for cardiovascular MR phase contrast imaging in children and young adults

Energy Technology Data Exchange (ETDEWEB)

Rigsby, Cynthia K.; Hilpipre, Nicholas; Boylan, Emma E.; Popescu, Andrada R.; Deng, Jie [Ann and Robert H. Lurie Children' s Hospital of Chicago, Department of Medical Imaging, Chicago, IL (United States); McNeal, Gary R. [Siemens Medical Solutions USA Inc., Customer Solutions Group, Cardiovascular MR R and D, Chicago, IL (United States); Zhang, Gang [Ann and Robert H. Lurie Children' s Hospital of Chicago Research Center, Biostatistics Research Core, Chicago, IL (United States); Choi, Grace [Ann and Robert H. Lurie Children' s Hospital of Chicago, Department of Pediatrics, Chicago, IL (United States); Greiser, Andreas [Siemens AG Healthcare Sector, Erlangen (Germany)

2014-03-15

Phase contrast magnetic resonance imaging (MRI) is a powerful tool for evaluating vessel blood flow. Inherent errors in acquisition, such as phase offset, eddy currents and gradient field effects, can cause significant inaccuracies in flow parameters. These errors can be rectified with the use of background correction software. To evaluate the performance of an automated phase contrast MRI background phase correction method in children and young adults undergoing cardiac MR imaging. We conducted a retrospective review of patients undergoing routine clinical cardiac MRI including phase contrast MRI for flow quantification in the aorta (Ao) and main pulmonary artery (MPA). When phase contrast MRI of the right and left pulmonary arteries was also performed, these data were included. We excluded patients with known shunts and metallic implants causing visible MRI artifact and those with more than mild to moderate aortic or pulmonary stenosis. Phase contrast MRI of the Ao, mid MPA, proximal right pulmonary artery (RPA) and left pulmonary artery (LPA) using 2-D gradient echo Fast Low Angle SHot (FLASH) imaging was acquired during normal respiration with retrospective cardiac gating. Standard phase image reconstruction and the automatic spatially dependent background-phase-corrected reconstruction were performed on each phase contrast MRI dataset. Non-background-corrected and background-phase-corrected net flow, forward flow, regurgitant volume, regurgitant fraction, and vessel cardiac output were recorded for each vessel. We compared standard non-background-corrected and background-phase-corrected mean flow values for the Ao and MPA. The ratio of pulmonary to systemic blood flow (Qp:Qs) was calculated for the standard non-background and background-phase-corrected data and these values were compared to each other and for proximity to 1. In a subset of patients who also underwent phase contrast MRI of the MPA, RPA, and LPA a comparison was made between standard non

Simultaneous acquisition of dual analyser-based phase contrast X-ray images for small animal imaging

International Nuclear Information System (INIS)

Kitchen, Marcus J.; Pavlov, Konstantin M.; Hooper, Stuart B.; Vine, David J.; Siu, Karen K.W.; Wallace, Megan J.; Siew, Melissa L.L.; Yagi, Naoto; Uesugi, Kentaro; Lewis, Rob A.

2008-01-01

Analyser-based phase contrast X-ray imaging can provide high-contrast images of biological tissues with exquisite sensitivity to the boundaries between tissues. The phase and absorption information can be extracted by processing multiple images acquired at different analyser orientations. Recording both the transmitted and diffracted beams from a thin Laue analyser crystal can make phase retrieval possible for dynamic systems by allowing full field imaging. This technique was used to image the thorax of a mechanically ventilated newborn rabbit pup using a 25 keV beam from the SPring-8 synchrotron radiation facility. The diffracted image was produced from the (1 1 1) planes of a 50 mm x 40 mm, 100 μm thick Si analyser crystal in the Laue geometry. The beam and analyser were large enough to image the entire chest, making it possible to observe changes in anatomy with high contrast and spatial resolution

Simultaneous acquisition of dual analyser-based phase contrast X-ray images for small animal imaging

Energy Technology Data Exchange (ETDEWEB)

Kitchen, Marcus J. [School of Physics, Monash University, Victoria 3800 (Australia)], E-mail: Marcus.Kitchen@sci.monash.edu.au; Pavlov, Konstantin M. [School of Physics, Monash University, Victoria 3800 (Australia); Monash Centre for Synchrotron Science, Monash University, Victoria 3800 (Australia); Physics and Electronics, School of Science and Technology, University of New England, NSW 2351 (Australia)], E-mail: Konstantin.Pavlov@sci.monash.edu.au; Hooper, Stuart B. [Department of Physiology, Monash University, Victoria 3800 (Australia)], E-mail: Stuart.Hooper@med.monash.edu.au; Vine, David J. [School of Physics, Monash University, Victoria 3800 (Australia)], E-mail: David.Vine@sci.monash.edu.au; Siu, Karen K.W. [School of Physics, Monash University, Victoria 3800 (Australia); Monash Centre for Synchrotron Science, Monash University, Victoria 3800 (Australia)], E-mail: Karen.Siu@sci.monash.edu.au; Wallace, Megan J. [Department of Physiology, Monash University, Victoria 3800 (Australia)], E-mail: Megan.Wallace@med.monash.edu.au; Siew, Melissa L.L. [Department of Physiology, Monash University, Victoria 3800 (Australia)], E-mail: Melissa.Siew@med.monash.edu.au; Yagi, Naoto [SPring-8/JASRI, Sayo (Japan)], E-mail: yagi@spring8.or.jp; Uesugi, Kentaro [SPring-8/JASRI, Sayo (Japan)], E-mail: ueken@spring8.or.jp; Lewis, Rob A. [School of Physics, Monash University, Victoria 3800 (Australia); Monash Centre for Synchrotron Science, Monash University, Victoria 3800 (Australia)], E-mail: Rob.Lewis@sync.monash.edu.au

2008-12-15

Analyser-based phase contrast X-ray imaging can provide high-contrast images of biological tissues with exquisite sensitivity to the boundaries between tissues. The phase and absorption information can be extracted by processing multiple images acquired at different analyser orientations. Recording both the transmitted and diffracted beams from a thin Laue analyser crystal can make phase retrieval possible for dynamic systems by allowing full field imaging. This technique was used to image the thorax of a mechanically ventilated newborn rabbit pup using a 25 keV beam from the SPring-8 synchrotron radiation facility. The diffracted image was produced from the (1 1 1) planes of a 50 mm x 40 mm, 100 {mu}m thick Si analyser crystal in the Laue geometry. The beam and analyser were large enough to image the entire chest, making it possible to observe changes in anatomy with high contrast and spatial resolution.

Speckle-free and halo-free low coherent Mach-Zehnder quantitative-phase-imaging module as a replacement of objective lens in conventional inverted microscopes

Science.gov (United States)

Yamauchi, Toyohiko; Yamada, Hidenao; Matsui, Hisayuki; Yasuhiko, Osamu; Ueda, Yukio

2018-02-01

We developed a compact Mach-Zehnder interferometer module to be used as a replacement of the objective lens in a conventional inverted microscope (Nikon, TS100-F) in order to make them quantitative phase microscopes. The module has a 90-degree-flipped U-shape; the dimensions of the module are 160 mm by 120 mm by 40 mm and the weight is 380 grams. The Mach-Zehnder interferometer equipped with the separate reference and sample arms was implemented in this U-shaped housing and the path-length difference between the two arms was manually adjustable. The sample under test was put on the stage of the microscope and a sample light went through it. Both arms had identical achromatic lenses for image formation and the lateral positions of them were also manually adjustable. Therefore, temporally and spatially low coherent illumination was applicable because the users were able to balance precisely the path length of the two arms and to overlap the two wavefronts. In the experiment, spectrally filtered LED light for illumination (wavelength = 633 nm and bandwidth = 3 nm) was input to the interferometer module via a 50 micrometer core optical fiber. We have successfully captured full-field interference images by a camera put on the trinocular tube of the microscope and constructed quantitative phase images of the cultured cells by means of the quarter-wavelength phase shifting algorithm. The resultant quantitative phase images were speckle-free and halo-free due to spectrally and spatially low coherent illumination.

Grating-based X-ray phase-contrast tomography of atherosclerotic plaque at high photon energies

Energy Technology Data Exchange (ETDEWEB)

Hetterich, Holger; Fill, Sandra [Klinikum der Ludwig-Maximilians-Univ., Muenchen (Germany). Inst. fuer Klinische Radiologie; Herzen, Julia [Technische Univ. Muenchen, Garching (Germany). Physik-Dept. und Inst. fuer Medizintechnik; Helmholtz-Zentrum Geesthacht, Geesthacht (Germany). Zentrum fuer Materialforschung] [and others

2013-10-01

Background: Tissue characterization of atherosclerosis by absorption-based imaging methods is limited due to low soft-tissue contrast. Grating-based phase-contrast computed tomography (PC-CT) may become an alternative for plaque assessment if the phase signal can be retrieved at clinically applicable photon energies. The aims of this feasibility study were (i) to characterize arterial vessels at low and high photon energies, (ii) to extract qualitative features and (iii) quantitative phase-contrast Hounsfield units (HU-phase) of plaque components at 53 keV using histopathology as gold standard. Materials and methods: Five human carotid artery specimens underwent grating-based PC-CT using synchrotron radiation of either 23 keV or 53 keV and histological work-up. Specimens without advanced atherosclerosis were used to extract signal criteria of vessel layers. Diseased specimens were screened for important plaque components including fibrous tissue (FT), lipid (LIP), necrotic core (NEC), intraplaque hemorrhage (IPH), inflammatory cell infiltration (INF) and calcifications (CA). Qualitative features as well as quantitative HU-phase were analyzed. Results: Thirty-three regions in 6 corresponding PC-CT scans and histology sections were identified. Healthy samples had the same signal characteristics at 23 keV and 53 keV with bright tunica intima and adventitia and dark media. Plaque components showed differences in signal intensity and texture at 53 keV. Quantitative analysis demonstrated the highest HU-phase of soft plaque in dense FT. Less organized LIP, NEC and INF were associated with lower HU-phase values. The highest HU-phase were measured in CA. Conclusion: PC-CT of atherosclerosis is feasible at high, clinically relevant photon energies and provides detailed information about plaque structure including features of high risk vulnerable plaques. (orig.)

Phase-contrast X-ray CT imaging of the kidney. Differences between ethanol fixation and formalin fixation

International Nuclear Information System (INIS)

Shirai, Ryota; Kunii, Takuya; Maruyama, Hiroko; Takeda, Tohoru; Yoneyama, Akio; Lwin, Thet Thet

2012-01-01

A phase-contrast X-ray imaging technique using an X-ray interferometer that provides approximately 1000 times higher sensitivity than the conventional X-ray imaging method for low-atomic number elements based on the difference in the mass attenuation coefficient has recently been developed. In the present study, we compared rat kidneys fixed in 100% ethanol and in 10% formalin to evaluate the effects of ethanol in enhancing image contrast in phase-contrast imaging because ethanol causes significant dehydration of tissues and enhances density differences between tissue components. The experiments were conducted at the Photon Factory in Tsukuba, and the X-ray energy was set at 35 keV. Fine anatomical structures in the kidney such as the glomeruli, tubules, and vessels were observed. Particularly clear renal images were obtained with ethanol fixation. The pixel value ratio between the cortex and medulla was about 43% in ethanol-fixed kidneys and 21% in formalin-fixed kidneys. In other words, the contrast in ethanol-fixed kidneys was about two times higher than that in formalin-fixed kidneys. Histological examination showed significantly condensed features in the cortex. The results of this study suggest that the ethanol fixation technique may be useful for enhancing the image contrast of renal structures in the phase-contrast X-ray imaging technique. (author)

Approximated transport-of-intensity equation for coded-aperture x-ray phase-contrast imaging.

Science.gov (United States)

Das, Mini; Liang, Zhihua

2014-09-15

Transport-of-intensity equations (TIEs) allow better understanding of image formation and assist in simplifying the "phase problem" associated with phase-sensitive x-ray measurements. In this Letter, we present for the first time to our knowledge a simplified form of TIE that models x-ray differential phase-contrast (DPC) imaging with coded-aperture (CA) geometry. The validity of our approximation is demonstrated through comparison with an exact TIE in numerical simulations. The relative contributions of absorption, phase, and differential phase to the acquired phase-sensitive intensity images are made readily apparent with the approximate TIE, which may prove useful for solving the inverse phase-retrieval problem associated with these CA geometry based DPC.

Orientation and phase mapping in the transmission electron microscope using precession-assisted diffraction spot recognition: state-of-the-art results.

Science.gov (United States)

Viladot, D; Véron, M; Gemmi, M; Peiró, F; Portillo, J; Estradé, S; Mendoza, J; Llorca-Isern, N; Nicolopoulos, S

2013-10-01

A recently developed technique based on the transmission electron microscope, which makes use of electron beam precession together with spot diffraction pattern recognition now offers the possibility to acquire reliable orientation/phase maps with a spatial resolution down to 2 nm on a field emission gun transmission electron microscope. The technique may be described as precession-assisted crystal orientation mapping in the transmission electron microscope, precession-assisted crystal orientation mapping technique-transmission electron microscope, also known by its product name, ASTAR, and consists in scanning the precessed electron beam in nanoprobe mode over the specimen area, thus producing a collection of precession electron diffraction spot patterns, to be thereafter indexed automatically through template matching. We present a review on several application examples relative to the characterization of microstructure/microtexture of nanocrystalline metals, ceramics, nanoparticles, minerals and organics. The strengths and limitations of the technique are also discussed using several application examples. ©2013 The Authors. Journal of Microscopy published by John Wiley & Sons Ltd on behalf of Royal Microscopical Society.

Novel X-ray phase-contrast tomography method for quantitative studies of heat induced structural changes in meat

DEFF Research Database (Denmark)

Miklos, Rikke; Nielsen, Mikkel Schou; Einarsdottir, Hildur

2014-01-01

The objective of this study was to evaluate the use of X-ray phase-contrast tomography combined with 3D image segmentation to investigate the heat induced structural changes in meat. The measurements were performed at the Swiss synchrotron radiation light source using a grating interferometric...... and separated into a water phase and a gel phase formed by the sarcoplasmic proteins in the exudate. The results show that X-ray phase contrast tomography offers unique possibilities in studies both the meat structure and the different meat component such as water, fat, connective tissue and myofibrils...

Functional analysis of third ventriculostomy patency with phase-contrast MRI velocity measurements

International Nuclear Information System (INIS)

Lev, S.; Bhadelia, R.A.; Estin, D.; Heilman, C.B.; Wolpert, S.M.

1997-01-01

Our purpose was to explore the utility of cine phase-contrast MRI velocity measurements in determining the functional status of third ventriculostomies, and to correlate the quantitative velocity data with clinical follow-up. We examined six patients with third ventriculostomies and 12 normal subjects by phase-contrast MRI. The maximum craniocaudal to maximum caudocranial velocity range was measured at regions of interest near the third ventricular floor, and in cerebrospinal fluid anterior to the upper pons and spinal cord on midline sagittal images. Ratios of the velocities of both the third ventricle and prepontine space to the space anterior to the spinal cord were obtained. The velocities near the third ventricular floor and in the pontine cistern were significantly higher in patients than in normal subjects, but the velocity anterior to the spinal cord was similar between the groups. The velocity ratios, used to normalize individual differences, were also higher in patients than in controls. Two patients had lower velocity ratios than their fellows at the third ventricular floor and in the pontine cistern; one required a shunt 11 months later, while in the other, who had a third ventricular/thalamic tumor, the lower values probably reflect distortion of the third ventricular floor. We conclude that phase-contrast MR velocity measurements, specifically the velocity ratio between the high pontine cistern and the space anterior to the spinal cord, can help determine the functional status of third ventriculostomies. (orig.)

Detectability index of differential phase contrast CT compared with conventional CT: a preliminary channelized Hotelling observer study

Science.gov (United States)

Tang, Xiangyang; Yang, Yi; Tang, Shaojie

2013-03-01

Under the framework of model observer with signal and background exactly known (SKE/BKE), we investigate the detectability of differential phase contrast CT compared with that of the conventional attenuation-based CT. Using the channelized Hotelling observer and the radially symmetric difference-of-Gaussians channel template , we investigate the detectability index and its variation over the dimension of object and detector cells. The preliminary data show that the differential phase contrast CT outperforms the conventional attenuation-based CT significantly in the detectability index while both the object to be detected and the cell of detector used for data acquisition are relatively small. However, the differential phase contrast CT's dominance in the detectability index diminishes with increasing dimension of either object or detector cell, and virtually disappears while the dimension of object or detector cell approaches a threshold, respectively. It is hoped that the preliminary data reported in this paper may provide insightful understanding of the differential phase contrast CT's characteristic in the detectability index and its comparison with that of the conventional attenuation-based CT.

Computer simulation for precipitation process of θ (Ni3V) and γ' (Ni3Al) with microscopic phase-field method

Institute of Scientific and Technical Information of China (English)

HOU Hua; XU Hong; ZHAO Yu-hong

2006-01-01

With the microscopic phase-field model, the precipitation process of aged alloys was explored by computer simulation, which could clarify some discussional views on the precipitation mechanisms of alloys. The precipitation process of Ni75Al2.5V22.5 alloy was studied. From the simulated atomic pictures, calculated order parameters and volume fraction of different precipitates, it's found that the θ ordered phase precipitates earlier than γ' ordered phase by congruent ordering+spinodal decomposition mechanism and thus produces a nonstoicheometric θ single ordered phase. Then, the nonstoicheometric γ' phase is precipitated by a non-classical nucleation and growth mechanism at the APBS of θ phases. Meanwhile, both of them transform to stoicheometric ordered phases.

Numerical design of in-line X-ray phase-contrast imaging based on ellipsoidal single-bounce monocapillary

Energy Technology Data Exchange (ETDEWEB)

Sun, Weiyuan; Liu, Zhiguo [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Sun, Tianxi, E-mail: stx@bnu.edu.cn [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Peng, Song [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Ma, Yongzhong [Center for Disease Control and Prevention of Beijing, Beijing 100013 (China); Ding, Xunliang [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China)

2014-05-11

A new device using an ellipsoidal single-bounce monocapillary X-ray optics was numerically designed to realize in-line X-ray phase-contrast imaging by using conventional laboratory X-ray source with a large spot. Numerical simulation results validated the effectiveness of the proposed device and approach. The ellipsoidal single-bounce monocapillary X-ray optics had potential applications in the in-line phase contrast imaging with polychromatic X-rays.

Numerical design of in-line X-ray phase-contrast imaging based on ellipsoidal single-bounce monocapillary

International Nuclear Information System (INIS)

Sun, Weiyuan; Liu, Zhiguo; Sun, Tianxi; Peng, Song; Ma, Yongzhong; Ding, Xunliang

2014-01-01

A new device using an ellipsoidal single-bounce monocapillary X-ray optics was numerically designed to realize in-line X-ray phase-contrast imaging by using conventional laboratory X-ray source with a large spot. Numerical simulation results validated the effectiveness of the proposed device and approach. The ellipsoidal single-bounce monocapillary X-ray optics had potential applications in the in-line phase contrast imaging with polychromatic X-rays

Low density contrast agents for x-ray phase contrast imaging: the use of ambient air for x-ray angiography of excised murine liver tissue

International Nuclear Information System (INIS)

Laperle, Christopher M; Wintermeyer, Philip; Derdak, Zoltan; Wands, Jack R; Hamilton, Theron J; Walker, Evan J; Diebold, Gerald; Rose-Petruck, Christoph; Shi, Daxin; Anastasio, Mark A

2008-01-01

We report a new preparative method for providing contrast through reduction in electron density that is uniquely suited for propagation-based differential x-ray phase contrast imaging. The method, which results in an air or fluid filled vasculature, makes possible visualization of the smallest microvessels, roughly down to 15 μm, in an excised murine liver, while preserving the tissue for subsequent histological workup. We show the utility of spatial frequency filtering for increasing the visibility of minute features characteristic of phase contrast imaging, and the capability of tomographic reconstruction to reveal microvessel structure and three-dimensional visualization of the sample. The effect of water evaporation from livers during x-ray imaging on the visibility of blood vessels is delineated. The deformed vascular tree in a cancerous murine liver is imaged.

Microscopic description of magnetized plasma: quasiparticle concept

International Nuclear Information System (INIS)

Sosenko, P.P.; Decyk, V.K.

1993-01-01

A quasiparticle concept is developed systematically, from first principles, within the context of microscopic description of magnetized plasma. It is argued that the zeroth velocity-gyroangle harmonic of the microscopic particle distribution function under the gyrokinetic change of variables can be taken as a microscopic quasi-particle density in a reduced phase space. The nature of quasiparticles is discussed and equations of their motion are derived within both exact and reduced microscopic descriptions. The reduced one employs explicitly the separation of interesting time scales. (orig.)

Segmentation of clustered cells in negative phase contrast images with integrated light intensity and cell shape information.

Science.gov (United States)

Wang, Y; Wang, C; Zhang, Z

2018-05-01

Automated cell segmentation plays a key role in characterisations of cell behaviours for both biology research and clinical practices. Currently, the segmentation of clustered cells still remains as a challenge and is the main reason for false segmentation. In this study, the emphasis was put on the segmentation of clustered cells in negative phase contrast images. A new method was proposed to combine both light intensity and cell shape information through the construction of grey-weighted distance transform (GWDT) within preliminarily segmented areas. With the constructed GWDT, the clustered cells can be detected and then separated with a modified region skeleton-based method. Moreover, a contour expansion operation was applied to get optimised detection of cell boundaries. In this paper, the working principle and detailed procedure of the proposed method are described, followed by the evaluation of the method on clustered cell segmentation. Results show that the proposed method achieves an improved performance in clustered cell segmentation compared with other methods, with 85.8% and 97.16% accuracy rate for clustered cells and all cells, respectively. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Volumetric Arterial Wall Shear Stress Calculation Based on Cine Phase Contrast MRI

NARCIS (Netherlands)

Potters, Wouter V.; van Ooij, Pim; Marquering, Henk; VanBavel, Ed; Nederveen, Aart J.

2015-01-01

PurposeTo assess the accuracy and precision of a volumetric wall shear stress (WSS) calculation method applied to cine phase contrast magnetic resonance imaging (PC-MRI) data. Materials and MethodsVolumetric WSS vectors were calculated in software phantoms. WSS algorithm parameters were optimized

Automated Method for the Rapid and Precise Estimation of Adherent Cell Culture Characteristics from Phase Contrast Microscopy Images

Science.gov (United States)

Jaccard, Nicolas; Griffin, Lewis D; Keser, Ana; Macown, Rhys J; Super, Alexandre; Veraitch, Farlan S; Szita, Nicolas

2014-01-01

The quantitative determination of key adherent cell culture characteristics such as confluency, morphology, and cell density is necessary for the evaluation of experimental outcomes and to provide a suitable basis for the establishment of robust cell culture protocols. Automated processing of images acquired using phase contrast microscopy (PCM), an imaging modality widely used for the visual inspection of adherent cell cultures, could enable the non-invasive determination of these characteristics. We present an image-processing approach that accurately detects cellular objects in PCM images through a combination of local contrast thresholding and post hoc correction of halo artifacts. The method was thoroughly validated using a variety of cell lines, microscope models and imaging conditions, demonstrating consistently high segmentation performance in all cases and very short processing times (image). Based on the high segmentation performance, it was possible to precisely determine culture confluency, cell density, and the morphology of cellular objects, demonstrating the wide applicability of our algorithm for typical microscopy image processing pipelines. Furthermore, PCM image segmentation was used to facilitate the interpretation and analysis of fluorescence microscopy data, enabling the determination of temporal and spatial expression patterns of a fluorescent reporter. We created a software toolbox (PHANTAST) that bundles all the algorithms and provides an easy to use graphical user interface. Source-code for MATLAB and ImageJ is freely available under a permissive open-source license. Biotechnol. Bioeng. 2014;111: 504–517. © 2013 Wiley Periodicals, Inc. PMID:24037521

Sub-nanosecond time-resolved near-field scanning magneto-optical microscope.

Science.gov (United States)

Rudge, J; Xu, H; Kolthammer, J; Hong, Y K; Choi, B C

2015-02-01

We report on the development of a new magnetic microscope, time-resolved near-field scanning magneto-optical microscope, which combines a near-field scanning optical microscope and magneto-optical contrast. By taking advantage of the high temporal resolution of time-resolved Kerr microscope and the sub-wavelength spatial resolution of a near-field microscope, we achieved a temporal resolution of ∼50 ps and a spatial resolution of microscope, the magnetic field pulse induced gyrotropic vortex dynamics occurring in 1 μm diameter, 20 nm thick CoFeB circular disks has been investigated. The microscope provides sub-wavelength resolution magnetic images of the gyrotropic motion of the vortex core at a resonance frequency of ∼240 MHz.

On thermodynamic and microscopic reversibility

International Nuclear Information System (INIS)

Crooks, Gavin E

2011-01-01

The word 'reversible' has two (apparently) distinct applications in statistical thermodynamics. A thermodynamically reversible process indicates an experimental protocol for which the entropy change is zero, whereas the principle of microscopic reversibility asserts that the probability of any trajectory of a system through phase space equals that of the time reversed trajectory. However, these two terms are actually synonymous: a thermodynamically reversible process is microscopically reversible, and vice versa

Teachable, high-content analytics for live-cell, phase contrast movies.

Science.gov (United States)

Alworth, Samuel V; Watanabe, Hirotada; Lee, James S J

2010-09-01

CL-Quant is a new solution platform for broad, high-content, live-cell image analysis. Powered by novel machine learning technologies and teach-by-example interfaces, CL-Quant provides a platform for the rapid development and application of scalable, high-performance, and fully automated analytics for a broad range of live-cell microscopy imaging applications, including label-free phase contrast imaging. The authors used CL-Quant to teach off-the-shelf universal analytics, called standard recipes, for cell proliferation, wound healing, cell counting, and cell motility assays using phase contrast movies collected on the BioStation CT and BioStation IM platforms. Similar to application modules, standard recipes are intended to work robustly across a wide range of imaging conditions without requiring customization by the end user. The authors validated the performance of the standard recipes by comparing their performance with truth created manually, or by custom analytics optimized for each individual movie (and therefore yielding the best possible result for the image), and validated by independent review. The validation data show that the standard recipes' performance is comparable with the validated truth with low variation. The data validate that the CL-Quant standard recipes can provide robust results without customization for live-cell assays in broad cell types and laboratory settings.

Analytical electron microscope study of the omega phase transformation in a zirconium--niobium alloy

Energy Technology Data Exchange (ETDEWEB)

Zaluzec, N.J.

1979-06-01

An in-situ study of the as-quenched omega phase transformation in Zr--15% Nb was conducted between the temperatures of 77 and 300/sup 0/K using analytical electron microscopy. The domain size of the omega regions observed in this investigation was on the order of 30 A, consistent with previous observations in this system. No alignment of omega domains along <222> directions of the bcc lattice was observed and in-situ thermal cycling experiments failed to produce a long period structure of alternating ..beta.. and ..omega.. phase regions as predicted by one theory of this transformation. Several techniques of microstructural analysis were developed, refined, and standardized. Grouped under the general classification of Analytical Electron Microscopy (AEM) they provide the experimentalist with a unique tool for the microcharacterization of solids, allowing semiquantitative to quantitative analysis of the morphology, crystallography, elemental composition, and electronic structure of regions as small as 20 A in diameter. These techniques have complications, and it was necessary to study the AEM system used in this work so that instrumental artifacts which invalidate the information produced in the microscope environment might be eliminated. Once these factors had been corrected, it was possible to obtain a wealth of information about the microvolume of material under investigation. The microanalytical techniques employed during this research include: energy dispersive x-ray spectroscopy (EDS) using both conventional and scanning transmission electron microscopy (CTEM, STEM), transmission scanning electron diffraction (TSED), the stationary diffraction pattern technique, and electron energy loss spectroscopy (ELS) using a dedicated scanning transmission electron microscope (DSTEM).

Analytical electron microscope study of the omega phase transformation in a zirconium--niobium alloy

International Nuclear Information System (INIS)

Zaluzec, N.J.

1979-06-01

An in-situ study of the as-quenched omega phase transformation in Zr--15% Nb was conducted between the temperatures of 77 and 300 0 K using analytical electron microscopy. The domain size of the omega regions observed in this investigation was on the order of 30 A, consistent with previous observations in this system. No alignment of omega domains along directions of the bcc lattice was observed and in-situ thermal cycling experiments failed to produce a long period structure of alternating β and ω phase regions as predicted by one theory of this transformation. Several techniques of microstructural analysis were developed, refined, and standardized. Grouped under the general classification of Analytical Electron Microscopy (AEM) they provide the experimentalist with a unique tool for the microcharacterization of solids, allowing semiquantitative to quantitative analysis of the morphology, crystallography, elemental composition, and electronic structure of regions as small as 20 A in diameter. These techniques have complications, and it was necessary to study the AEM system used in this work so that instrumental artifacts which invalidate the information produced in the microscope environment might be eliminated. Once these factors had been corrected, it was possible to obtain a wealth of information about the microvolume of material under investigation. The microanalytical techniques employed during this research include: energy dispersive x-ray spectroscopy (EDS) using both conventional and scanning transmission electron microscopy (CTEM, STEM), transmission scanning electron diffraction (TSED), the stationary diffraction pattern technique, and electron energy loss spectroscopy (ELS) using a dedicated scanning transmission electron microscope

From Relativistic Electrons to X-ray Phase Contrast Imaging

Energy Technology Data Exchange (ETDEWEB)

Lumpkin, A. H. [Fermilab; Garson, A. B. [Washington U., St. Louis; Anastasio, M. A. [Washington U., St. Louis

2017-10-09

We report the initial demonstrations of the use of single crystals in indirect x-ray imaging for x-ray phase contrast imaging at the Washington University in St. Louis Computational Bioimaging Laboratory (CBL). Based on single Gaussian peak fits to the x-ray images, we observed a four times smaller system point spread function (21 μm (FWHM)) with the 25-mm diameter single crystals than the reference polycrystalline phosphor’s 80-μm value. Potential fiber-optic plate depth-of-focus aspects and 33-μm diameter carbon fiber imaging are also addressed.

Phase contrast imaging diagnostic for the Wendelstein 7-X stellarator

Energy Technology Data Exchange (ETDEWEB)

Boettger, Lukas-Georg; Grulke, Olaf [Max Planck Institute for Plasma Physics, 17491 Greifswald (Germany)

2016-07-01

The phase contrast imaging (PCI) diagnostic allows for non-invasive measurements of density fluctuations in high temperature plasmas. Since the index of refraction in a plasma is a function of the electron density, an incoming laser beam experiences a phase shift, which can be converted to intensity variations via interference after passing a phase plate. Generally speaking, the signal contains only the line-integrated information along the beam path. This limitation can be circumvented by using the fact that the density fluctuations form filamentary structures that are well aligned with the local magnetic field. If the magnetic field direction significantly varies along the beam path, optical filtering allows for localization of the density fluctuations. In order to identify the best diagnostic position regarding localization performance three figures of merit are introduced. They allow for quantitative comparison of different lines of sight and different magnetic field configurations. The results of the optimization process and a comparison with other fusion experiments are shown in this contribution.

Differential phase-contrast dark-field electron holography for strain mapping

Energy Technology Data Exchange (ETDEWEB)

Denneulin, Thibaud, E-mail: thibaud.denneulin@cemes.fr; Houdellier, Florent, E-mail: florent.houdellier@cemes.fr; Hÿtch, Martin, E-mail: martin.hytch@cemes.fr

2016-01-15

Strain mapping is an active area of research in transmission electron microscopy. Here we introduce a dark-field electron holographic technique that shares several aspects in common with both off-axis and in-line holography. Two incident and convergent plane waves are produced in front of the specimen thanks to an electrostatic biprism in the condenser system of a transmission electron microscope. The interference of electron beams diffracted by the illuminated crystal is then recorded in a defocused plane. The differential phase recovered from the hologram is directly proportional to the strain in the sample. The strain can be quantified if the separation of the images due to the defocus is precisely determined. The present technique has the advantage that the derivative of the phase is measured directly which allows us to avoid numerical differentiation. The distribution of the noise in the reconstructed strain maps is isotropic and more homogeneous. This technique was used to investigate different samples: a Si/SiGe superlattice, transistors with SiGe source/drain and epitaxial PZT thin films. - Highlights: • DPC dark-field electron holography is set up with a condenser biprism. • The DPC phase is directly proportional to the lattice deformation. • The technique is illustrated with epitaxial SiGe and Pb(Zr,Ti)O{sub 3} samples. • The defocus allows us to control the strain sensitivity and the spatial resolution. • A solution is proposed to setup this technique with a post-specimen biprism.

Phase-contrast computed tomography for quantification of structural changes in lungs of asthma mouse models of different severity

International Nuclear Information System (INIS)

Dullin, Christian; Larsson, Emanuel; Tromba, Giuliana; Markus, Andrea M.; Alves, Frauke

2015-01-01

Synchrotron inline phase-contrast computed tomography in combination with single-distance phase retrieval enables quantification of morphological alterations in lungs of mice with mild and severe experimental allergic airways disease in comparison with healthy controls. Lung imaging in mouse disease models is crucial for the assessment of the severity of airway disease but remains challenging due to the small size and the high porosity of the organ. Synchrotron inline free-propagation phase-contrast computed tomography (CT) with its intrinsic high soft-tissue contrast provides the necessary sensitivity and spatial resolution to analyse the mouse lung structure in great detail. Here, this technique has been applied in combination with single-distance phase retrieval to quantify alterations of the lung structure in experimental asthma mouse models of different severity. In order to mimic an in vivo situation as close as possible, the lungs were inflated with air at a constant physiological pressure. Entire mice were embedded in agarose gel and imaged using inline free-propagation phase-contrast CT at the SYRMEP beamline (Synchrotron Light Source, ‘Elettra’, Trieste, Italy). The quantification of the obtained phase-contrast CT data sets revealed an increasing lung soft-tissue content in mice correlating with the degree of the severity of experimental allergic airways disease. In this way, it was possible to successfully discriminate between healthy controls and mice with either mild or severe allergic airway disease. It is believed that this approach may have the potential to evaluate the efficacy of novel therapeutic strategies that target airway remodelling processes in asthma

Phase-contrast computed tomography for quantification of structural changes in lungs of asthma mouse models of different severity

Energy Technology Data Exchange (ETDEWEB)

Dullin, Christian, E-mail: christian.dullin@med.uni-goettingen.de [University Medical Center Goettingen, Robert Koch Strasse 40, Goettingen, Lower Saxony 37075 (Germany); Larsson, Emanuel [Elettra-Sincrotrone Trieste, Strada Statale 14, km 163,5 in AREA Science Park, Basovizza (Trieste) 34149 (Italy); University of Trieste, Trieste (Italy); Linkoeping University, SE-581 83 Linkoeping (Sweden); Tromba, Giuliana [Elettra-Sincrotrone Trieste, Strada Statale 14, km 163,5 in AREA Science Park, Basovizza (Trieste) 34149 (Italy); Markus, Andrea M. [University Medical Center Goettingen, Robert Koch Strasse 40, Goettingen, Lower Saxony 37075 (Germany); Alves, Frauke [University Medical Center Goettingen, Robert Koch Strasse 40, Goettingen, Lower Saxony 37075 (Germany); University Medical Center Goettingen, Robert Koch Strasse 40, Goettingen, Lower Saxony 37075 (Germany); Max Planck Institut for Experimental Medicine, Hermann-Rein-Strasse 3, Goettingen, Lower Saxony 37075 (Germany)

2015-06-17

Synchrotron inline phase-contrast computed tomography in combination with single-distance phase retrieval enables quantification of morphological alterations in lungs of mice with mild and severe experimental allergic airways disease in comparison with healthy controls. Lung imaging in mouse disease models is crucial for the assessment of the severity of airway disease but remains challenging due to the small size and the high porosity of the organ. Synchrotron inline free-propagation phase-contrast computed tomography (CT) with its intrinsic high soft-tissue contrast provides the necessary sensitivity and spatial resolution to analyse the mouse lung structure in great detail. Here, this technique has been applied in combination with single-distance phase retrieval to quantify alterations of the lung structure in experimental asthma mouse models of different severity. In order to mimic an in vivo situation as close as possible, the lungs were inflated with air at a constant physiological pressure. Entire mice were embedded in agarose gel and imaged using inline free-propagation phase-contrast CT at the SYRMEP beamline (Synchrotron Light Source, ‘Elettra’, Trieste, Italy). The quantification of the obtained phase-contrast CT data sets revealed an increasing lung soft-tissue content in mice correlating with the degree of the severity of experimental allergic airways disease. In this way, it was possible to successfully discriminate between healthy controls and mice with either mild or severe allergic airway disease. It is believed that this approach may have the potential to evaluate the efficacy of novel therapeutic strategies that target airway remodelling processes in asthma.

The Digital Microscope and Its Image Processing Utility

Directory of Open Access Journals (Sweden)

Tri Wahyu Supardi

2011-12-01

Full Text Available Many institutions, including high schools, own a large number of analog or ordinary microscopes. These microscopes are used to observe small objects. Unfortunately, object observations on the ordinary microscope require precision and visual acuity of the user. This paper discusses the development of a high-resolution digital microscope from an analog microscope, including the image processing utility, which allows the digital microscope users to capture, store and process the digital images of the object being observed. The proposed microscope is constructed from hardware components that can be easily found in Indonesia. The image processing software is capable of performing brightness adjustment, contrast enhancement, histogram equalization, scaling and cropping. The proposed digital microscope has a maximum magnification of 1600x, and image resolution can be varied from 320x240 pixels up to 2592x1944 pixels. The microscope was tested with various objects with a variety of magnification, and image processing was carried out on the image of the object. The results showed that the digital microscope and its image processing system were capable of enhancing the observed object and other operations in accordance with the user need. The digital microscope has eliminated the need for direct observation by human eye as with the traditional microscope.

Equilibrium-phase MR angiography: Comparison of unspecific extracellular and protein-binding gadolinium-based contrast media with respect to image quality.

Science.gov (United States)

Erb-Eigner, Katharina; Taupitz, Matthias; Asbach, Patrick

2016-01-01

The purpose of this study was to compare contrast and image quality of whole-body equilibrium-phase high-spatial-resolution MR angiography using a non-protein-binding unspecific extracellular gadolinium-based contrast medium with that of two contrast media with different protein-binding properties. 45 patients were examined using either 15 mL of gadobutrol (non-protein-binding, n = 15), 32 mL of gadobenate dimeglumine (weakly protein binding, n = 15) or 11 mL gadofosveset trisodium (protein binding, n = 15) followed by equilibrium-phase high-spatial-resolution MR-angiography of four consecutive anatomic regions. The time elapsed between the contrast injection and the beginning of the equilibrium-phase image acquisition in the respective region was measured and was up to 21 min. Signal intensity was measured in two vessels per region and in muscle tissue. Relative contrast (RC) values were calculated. Vessel contrast, artifacts and image quality were rated by two radiologists in consensus on a five-point scale. Compared with gadobutrol, gadofosveset trisodium revealed significantly higher RC values only when acquired later than 15 min after bolus injection. Otherwise, no significant differences between the three contrast media were found regarding vascular contrast and image quality. Equilibrium-phase high-spatial-resolution MR-angiography using a weakly protein-binding or even non-protein-binding contrast medium is equivalent to using a stronger protein-binding contrast medium when image acquisition is within the first 15 min after contrast injection, and allows depiction of the vasculature with high contrast and image quality. The protein-binding contrast medium was superior for imaging only later than 15 min after contrast medium injection. Copyright © 2015 John Wiley & Sons, Ltd.

Surface features on Sahara soil dust particles made visible by atomic force microscope (AFM) phase images

OpenAIRE

G. Helas; M. O. Andreae

2008-01-01

We show that atomic force microscopy (AFM) phase images can reveal surface features of soil dust particles, which are not evident using other microscopic methods. The non-contact AFM method is able to resolve topographical structures in the nanometer range as well as to uncover repulsive atomic forces and attractive van der Waals' forces, and thus gives insight to surface properties. Though the method does not allow quantitative assignment in terms of chemical compound description, it clearly...

A line scanned light-sheet microscope with phase shaped self-reconstructing beams.

Science.gov (United States)

Fahrbach, Florian O; Rohrbach, Alexander

2010-11-08

We recently demonstrated that Microscopy with Self-Reconstructing Beams (MISERB) increases both image quality and penetration depth of illumination beams in strongly scattering media. Based on the concept of line scanned light-sheet microscopy, we present an add-on module to a standard inverted microscope using a scanned beam that is shaped in phase and amplitude by a spatial light modulator. We explain technical details of the setup as well as of the holograms for the creation, positioning and scaling of static light-sheets, Gaussian beams and Bessel beams. The comparison of images from identical sample areas illuminated by different beams allows a precise assessment of the interconnection between beam shape and image quality. The superior propagation ability of Bessel beams through inhomogeneous media is demonstrated by measurements on various scattering media.

Detection of hepatic VX2 tumors in rabbits: comparison of conventional US and phase- inversion harmonic US during the liver- specific late phase of contrast enhancement

International Nuclear Information System (INIS)

Lee, Jeong Min; Youk, Ji Hyun; Lee, Young Hwan; Kim, Young Kon; Kim, Chong Soo; Li, Chun Ai

2003-01-01

To compare phase-inversion sonography during the liver-specific phase of contrast enhancement using a microbubble contrast agent with conventional B-mode sonography for the detection of VX2 liver tumors. Twenty-three rabbits, 18 of which had VX2 liver tumor implants, received a bolus injection of 0.6 g of Levovist (200 mg/ml). During the liver-specific phase of this agent, they were evaluated using both conventional sonography and contrast-enhanced phase-inversion harmonic imaging (CEPIHI). Following sacrifice of the animals, pathologic analysis was performed and the reference standard thus obtained. The conspicuity, size and number of the tumors before and after contrast administration, as determined by a sonographer, were compared between the two modes and with the pathologic findings. CE-PIHI demonstrated marked hepatic parenchymal enhancement in all rabbits. For VX2 tumors detected at both conventional US and CE- PIHI, conspicuity was improved by contrast-enhanced PIHI. On examination of gross specimens, 52 VX2 tumors were identified. Conventional US correctly detected 18 of the 52 (34.6%), while PIHI detected 35 (67.3%) (p < 0.05). In particular, conventional US detected only three (8.3%) of the 36 tumors less than 10 mm in diameter, but CE-PIHI detected 19 such tumors (52.8%) (p < 0.05). Compared to conventional sonography, PIHI performed during the liver-specific phase after intravenous injection of Levovist is markedly better at detecting VX2 liver tumors

Proper alignment of the microscope.

Science.gov (United States)

Rottenfusser, Rudi

2013-01-01

The light microscope is merely the first element of an imaging system in a research facility. Such a system may include high-speed and/or high-resolution image acquisition capabilities, confocal technologies, and super-resolution methods of various types. Yet more than ever, the proverb "garbage in-garbage out" remains a fact. Image manipulations may be used to conceal a suboptimal microscope setup, but an artifact-free image can only be obtained when the microscope is optimally aligned, both mechanically and optically. Something else is often overlooked in the quest to get the best image out of the microscope: Proper sample preparation! The microscope optics can only do its job when its design criteria are matched to the specimen or vice versa. The specimen itself, the mounting medium, the cover slip, and the type of immersion medium (if applicable) are all part of the total optical makeup. To get the best results out of a microscope, understanding the functions of all of its variable components is important. Only then one knows how to optimize these components for the intended application. Different approaches might be chosen to discuss all of the microscope's components. We decided to follow the light path which starts with the light source and ends at the camera or the eyepieces. To add more transparency to this sequence, the section up to the microscope stage was called the "Illuminating Section", to be followed by the "Imaging Section" which starts with the microscope objective. After understanding the various components, we can start "working with the microscope." To get the best resolution and contrast from the microscope, the practice of "Koehler Illumination" should be understood and followed by every serious microscopist. Step-by-step instructions as well as illustrations of the beam path in an upright and inverted microscope are included in this chapter. A few practical considerations are listed in Section 3. Copyright © 2013 Elsevier Inc. All rights

Measurement of dew droplets in initial deposition at dew point by using a phase-shift interference microscope

Science.gov (United States)

Matsumoto, Shigeaki; Toyooka, Satoru; Hoshino, Mitsuo

2002-09-01

In order to measure the total mass per unit area of dew droplets deposited on a metal plate in the dew-point hygrometer, the shape of a dew droplet deposited on a copper plate was measured accurately by using an interference microscope that employed a phase-shift technique. The microscope was constructed by adding a piezoelectric transducer to an usual interference microscope. A simple method that uses a conventional speaker horn and an optical fiber cable was introduced to depress speckle noise. The shape of a dew droplet deposited on the copper plate surface with 0.1 μm in average roughness was measured with an accuracy of +/-3nm. The mass of a dew droplet could be calculated numerically from the volume of its shape and was of the order of 10-9 g. The total mass of dew droplets deposited per unit area and the deposition velocity were obtained under a gentle wind. The total mass was the order of 10-5 g/cm2 at the beginning of deposition and the deposition velocity was ranged from 2x10-6 to 6x10-5 g/cm2.min.

Microscopic modelling of doped manganites

International Nuclear Information System (INIS)

Weisse, Alexander; Fehske, Holger

2004-01-01

Colossal magneto-resistance manganites are characterized by a complex interplay of charge, spin, orbital and lattice degrees of freedom. Formulating microscopic models for these compounds aims at meeting two conflicting objectives: sufficient simplification without excessive restrictions on the phase space. We give a detailed introduction to the electronic structure of manganites and derive a microscopic model for their low-energy physics. Focusing on short-range electron-lattice and spin-orbital correlations we supplement the modelling with numerical simulations

ZEUS: a cophasing sensor based on the Zernike phase contrast method

Science.gov (United States)

Dohlen, Kjetil; Langlois, Maud; Lanzoni, Patrick; Mazzanti, Silvio; Vigan, Arthur; Montoya, Luzma; Hernandez, Elvio; Reyes, Marcos; Surdej, Isabel; Yaitskova, Natalya

2006-06-01

We describe the ZEUS phasing camera for future extremely large telescopes (ELTs) based on the Zernike phase contrast method. A prototype instrument is under construction for implementation in the Active Phasing Experiment (APE), a VLT test bed scheduled for operation in 2007. The paper describes theoretical aspects of the method and its experimental validation, as well as the instrumental implementation for APE. Aspects of its implementation in an ELT are also discussed. While the classical Zernike method uses a phase mask with diameter approximately equal to the Airy disk, we employ a mask the size of the seeing disk. This allows us to overcome the problems related to atmospheric turbulence, whose low spatial frequency phase errors are much larger than the co-phasing errors to be measured. The thickness (OPD) of the mask can be set to lambda/4 - as in the classical case - for maximum signal strength, but for initial phasing where phase errors are much larger than the sensor's linear range (+/-lambda/4), a thinner mask produces a cleaner signal more easily exploitable, leaving the signal analysis more robust. A multi wavelength approach is implemented in order to extend the capture range of the sensor, and the ultimate precision is reached using an iterative approach. End-to-end simulations indicating an achievable precision within the required precision will be shown.

Wide-area phase-contrast X-ray imaging using large X-ray interferometers

Energy Technology Data Exchange (ETDEWEB)

Momose, Atsushi E-mail: momose@exp.t.u-tokyo.ac.jp; Takeda, Tohoru; Yoneyama, Akio; Koyama, Ichiro; Itai, Yuji

2001-07-21

Large X-ray interferometers are developed for phase-contrast X-ray imaging aiming at medical applications. A monolithic X-ray interferometer and a separate one are studied, and currently a 25 mmx20 mm view area can be generated. This paper describes the strategy of our research program and some recent developments.

Wide-area phase-contrast X-ray imaging using large X-ray interferometers

Science.gov (United States)

Momose, Atsushi; Takeda, Tohoru; Yoneyama, Akio; Koyama, Ichiro; Itai, Yuji

2001-07-01

Large X-ray interferometers are developed for phase-contrast X-ray imaging aiming at medical applications. A monolithic X-ray interferometer and a separate one are studied, and currently a 25 mm×20 mm view area can be generated. This paper describes the strategy of our research program and some recent developments.

Microscope and method of use

Science.gov (United States)

Bongianni, Wayne L.

1984-01-01

A method and apparatus for electronically focusing and electronically scanning microscopic specimens are given. In the invention, visual images of even moving, living, opaque specimens can be acoustically obtained and viewed with virtually no time needed for processing (i.e., real time processing is used). And planar samples are not required. The specimens (if planar) need not be moved during scanning, although it will be desirable and possible to move or rotate nonplanar specimens (e.g., laser fusion targets) against the lens of the apparatus. No coupling fluid is needed, so specimens need not be wetted. A phase acoustic microscope is also made from the basic microscope components together with electronic mixers.

Path-separated electron interferometry in a scanning transmission electron microscope

Science.gov (United States)

Yasin, Fehmi S.; Harvey, Tyler R.; Chess, Jordan J.; Pierce, Jordan S.; McMorran, Benjamin J.

2018-05-01

We report a path-separated electron interferometer within a scanning transmission electron microscope. In this setup, we use a nanofabricated grating as an amplitude-division beamsplitter to prepare multiple spatially separated, coherent electron probe beams. We achieve path separations of 30 nm. We pass the  +1 diffraction order probe through amorphous carbon while passing the 0th and  ‑1 orders through vacuum. The probes are then made to interfere via imaging optics, and we observe an interference pattern at the CCD detector with up to 39.7% fringe visibility. We show preliminary experimental results in which the interference pattern was recorded during a 1D scan of the diffracted probes across a test phase object. These results qualitatively agree with a modeled interference predicted by an independent measurement of the specimen thickness. This experimental design can potentially be applied to phase contrast imaging and fundamental physics experiments, such as an exploration of electron wave packet coherence length.

Phase-contrast X-ray computed tomography of non-formalin fixed biological objects

Energy Technology Data Exchange (ETDEWEB)

Takeda, Tohoru E-mail: ttakeda@md.tsukuba.ac.jp; Momose, Atsushi; Wu, Jin; Zeniya, Tsutomu; Yu Quanwen; Thet Thet Lwin; Itai, Yuji

2001-07-21

Using a monolithic X-ray interferometer having the view size of 25 mmx25 mm, phase-contrast X-ray CT (PCCT) was performed for non-formalin fixed livers of two normal rats and a rabbit transplanted with VX-2 cancer. PCCT images of liver and cancer lesions resembled well those obtained by formalin fixed samples.

Techniques for improving material fidelity and contrast consistency in secondary electron mode helium ion microscope (HIM) imaging

Science.gov (United States)

Thompson, William; Stern, Lewis; Ferranti, Dave; Huynh, Chuong; Scipioni, Larry; Notte, John; Sanford, Colin

2010-06-01

Recent helium ion microscope (HIM) imaging studies have shown the strong sensitivity of HIM induced secondary electron (SE) yields [1] to the sample physical and chemical properties and to its surface topography. This SE yield sensitivity is due to the low recoil energy of the HIM initiated electrons and their resulting short mean free path. Additionally, a material's SE escape probability is modulated by changes in the material's work function and surface potential. Due to the escape electrons' roughly 2eV mean energy and their nanometer range mean free path, HIM SE mode image contrast has significant material and surface sensitivity. The latest generation of HIM has a 0.35 nanometer resolution specification and is equipped with a plasma cleaning process to mitigate the effects of hydrocarbon contamination. However, for surfaces that may have native oxide chemistries influencing the secondary electron yield, a new process of low energy, shallow angle argon sputtering, was evaluated. The intent of this work was to study the effect of removing pre-existing native oxides and any in-situ deposited surface contaminants. We will introduce the sputter yield predictions of two established computer models and the sputter yield and sample modification forecasts of the molecular dynamics program, Kalypso. We will review the experimental technique applied to copper samples and show the copper grain contrast improvement that resulted when argon cleaned samples were imaged in HIM SE mode.

A feasibility study of X-ray phase-contrast mammographic tomography at the Imaging and Medical beamline of the Australian Synchrotron.

Science.gov (United States)

Nesterets, Yakov I; Gureyev, Timur E; Mayo, Sheridan C; Stevenson, Andrew W; Thompson, Darren; Brown, Jeremy M C; Kitchen, Marcus J; Pavlov, Konstantin M; Lockie, Darren; Brun, Francesco; Tromba, Giuliana

2015-11-01

Results are presented of a recent experiment at the Imaging and Medical beamline of the Australian Synchrotron intended to contribute to the implementation of low-dose high-sensitivity three-dimensional mammographic phase-contrast imaging, initially at synchrotrons and subsequently in hospitals and medical imaging clinics. The effect of such imaging parameters as X-ray energy, source size, detector resolution, sample-to-detector distance, scanning and data processing strategies in the case of propagation-based phase-contrast computed tomography (CT) have been tested, quantified, evaluated and optimized using a plastic phantom simulating relevant breast-tissue characteristics. Analysis of the data collected using a Hamamatsu CMOS Flat Panel Sensor, with a pixel size of 100 µm, revealed the presence of propagation-based phase contrast and demonstrated significant improvement of the quality of phase-contrast CT imaging compared with conventional (absorption-based) CT, at medically acceptable radiation doses.

Feasibility of measuring renal blood flow by phase-contrast magnetic resonance imaging in patients with autosomal dominant polycystic kidney disease.

Science.gov (United States)

Spithoven, E M; Meijer, E; Borns, C; Boertien, W E; Gaillard, C A J M; Kappert, P; Greuter, M J W; van der Jagt, E; Vart, P; de Jong, P E; Gansevoort, R T

2016-03-01

Renal blood flow (RBF) has been shown to predict disease progression in autosomal dominant polycystic kidney disease (ADPKD). We investigated the feasibility and accuracy of phase-contrast RBF by MRI (RBFMRI) in ADPKD patients with a wide range of estimated glomerular filtration rate (eGFR) values. First, we validated RBFMRI measurement using phantoms simulating renal artery hemodynamics. Thereafter, we investigated in a test-set of 21 patients intra- and inter-observer coefficient of variation of RBFMRI. After validation, we measured RBFMRI in a cohort of 91 patients and compared the variability explained by characteristics indicative for disease severity for RBFMRI and RBF measured by continuous hippuran infusion. The correlation in flow measurement using phantoms by phase-contrast MRI was high and fluid collection was high (CCC=0.969). Technical problems that precluded RBFMRI measurement occurred predominantly in patients with a lower eGFR (34% vs. 16%). In subjects with higher eGFRs, variability in RBF explained by disease characteristics was similar for RBFMRI compared to RBFHip, whereas in subjects with lower eGFRs, this was significantly less for RBFMRI. Our study shows that RBF can be measured accurately in ADPKD patients by phase-contrast, but this technique may be less feasible in subjects with a lower eGFR. Renal blood flow (RBF) can be accurately measured by phase-contrast MRI in ADPKD patients. RBF measured by phase-contrast is associated with ADPKD disease severity. RBF measurement by phase-contrast MRI may be less feasible in patients with an impaired eGFR.

Improved phase sensitivity in spectral domain phase microscopy using line-field illumination and self phase-referencing

Science.gov (United States)

Yaqoob, Zahid; Choi, Wonshik; Oh, Seungeun; Lue, Niyom; Park, Yongkeun; Fang-Yen, Christopher; Dasari, Ramachandra R.; Badizadegan, Kamran; Feld, Michael S.

2010-01-01

We report a quantitative phase microscope based on spectral domain optical coherence tomography and line-field illumination. The line illumination allows self phase-referencing method to reject common-mode phase noise. The quantitative phase microscope also features a separate reference arm, permitting the use of high numerical aperture (NA > 1) microscope objectives for high resolution phase measurement at multiple points along the line of illumination. We demonstrate that the path-length sensitivity of the instrument can be as good as 41 pm/Hz, which makes it suitable for nanometer scale study of cell motility. We present the detection of natural motions of cell surface and two-dimensional surface profiling of a HeLa cell. PMID:19550464

Phase-contrast X-ray computed tomography of non-formalin fixed biological objects

Science.gov (United States)

Takeda, Tohoru; Momose, Atsushi; Wu, Jin; Zeniya, Tsutomu; Yu, Quanwen; Thet-Thet-Lwin; Itai, Yuji

2001-07-01

Using a monolithic X-ray interferometer having the view size of 25 mm×25 mm, phase-contrast X-ray CT (PCCT) was performed for non-formalin fixed livers of two normal rats and a rabbit transplanted with VX-2 cancer. PCCT images of liver and cancer lesions resembled well those obtained by formalin fixed samples.

First application of liquid-metal-jet sources for small-animal imaging: High-resolution CT and phase-contrast tumor demarcation

Energy Technology Data Exchange (ETDEWEB)

Larsson, Daniel H.; Lundstroem, Ulf; Burvall, Anna; Hertz, Hans M. [Department of Applied Physics, KTH Royal Institute of Technology/Albanova, 10691 Stockholm (Sweden); Westermark, Ulrica K.; Arsenian Henriksson, Marie [Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, 17177 Stockholm (Sweden)

2013-02-15

Purpose: Small-animal studies require images with high spatial resolution and high contrast due to the small scale of the structures. X-ray imaging systems for small animals are often limited by the microfocus source. Here, the authors investigate the applicability of liquid-metal-jet x-ray sources for such high-resolution small-animal imaging, both in tomography based on absorption and in soft-tissue tumor imaging based on in-line phase contrast. Methods: The experimental arrangement consists of a liquid-metal-jet x-ray source, the small-animal object on a rotating stage, and an imaging detector. The source-to-object and object-to-detector distances are adjusted for the preferred contrast mechanism. Two different liquid-metal-jet sources are used, one circulating a Ga/In/Sn alloy and the other an In/Ga alloy for higher penetration through thick tissue. Both sources are operated at 40-50 W electron-beam power with {approx}7 {mu}m x-ray spots, providing high spatial resolution in absorption imaging and high spatial coherence for the phase-contrast imaging. Results: High-resolution absorption imaging is demonstrated on mice with CT, showing 50 {mu}m bone details in the reconstructed slices. High-resolution phase-contrast soft-tissue imaging shows clear demarcation of mm-sized tumors at much lower dose than is required in absorption. Conclusions: This is the first application of liquid-metal-jet x-ray sources for whole-body small-animal x-ray imaging. In absorption, the method allows high-resolution tomographic skeletal imaging with potential for significantly shorter exposure times due to the power scalability of liquid-metal-jet sources. In phase contrast, the authors use a simple in-line arrangement to show distinct tumor demarcation of few-mm-sized tumors. This is, to their knowledge, the first small-animal tumor visualization with a laboratory phase-contrast system.

Quantitative measurement of portal blood flow by magnetic resonance phase contrast. Comparative study of flow phantom and Doppler ultrasound in vivo

International Nuclear Information System (INIS)

Tsunoda, Masatoshi; Kimoto, Shin; Hamazaki, Keisuke; Takeda, Yoshihiro; Hiraki, Yoshio.

1994-01-01

A non-invasive method for measuring portal blood flow by magnetic resonance (MR) phase contrast was evaluated in a flow phantom and 20 healthy volunteers. In a flow phantom study, the flow volumes and mean flow velocities measured by MR phase contrast showed close correlations with those measured by electromagnetic flow-metry. In 20 healthy volunteers, the cross-sectional areas, flow volumes and mean flow velocities measured by MR phase contrast correlated well with those measured by the Doppler ultrasound method. Portal blood flow averaged during the imaging time could be measured under natural breathing conditions by using a large number of acquisitions without the limitations imposed on the Doppler ultrasound method. MR phase contrast is considered to be useful for the non-invasive measurement of portal blood flow. (author)

When the non-contrast-enhanced phase is unnecessary in abdominal computed tomography scans? A retrospective analysis of 244 cases

Energy Technology Data Exchange (ETDEWEB)

Costa, Danilo Manuel Cerqueira; Salvadori, Priscila Silveira; Monjardim, Rodrigo da Fonseca; Bretas, Elisa Almeida Sathler; Torres, Lucas Rios; Caldana, Rogerio Pedreschi; Shigueoka, David Carlos; Medeiros, Regina Bitelli; D' ippolito, Giuseppe, E-mail: giuseppe_dr@uol.com.br [Universidade Federal de Sao Paulo (EPM/UNIFESP), Sao Paulo, SP (Brazil). Escola Paulista de Medicina. Departamento de Diagnostico por Imagem

2013-06-15

Objective: to evaluate the necessity of the non contrast-enhanced phase in abdominal computed tomography scans. Materials and Methods: A retrospective, cross-sectional, observational study was developed, evaluating 244 consecutive abdominal computed tomography scans both with and without contrast injection. Initially, the contrast-enhanced images were analyzed (first analysis). Subsequently, the observers had access to the non-contrast-enhanced images for a second analysis. The primary and secondary diagnoses were established as a function of the clinical indications for each study (such as tumor staging, acute abdomen, investigation for abdominal collection and hepatocellular carcinoma, among others). Finally, the changes in the diagnoses resulting from the addition of the non-contrast-enhanced phase were evaluated. Results: Only one (0.4%; p > 0.999; non-statistically significant) out of the 244 reviewed cases had the diagnosis changed after the reading of non-contrast-enhanced images. As the secondary diagnoses are considered, 35 (14%) cases presented changes after the second analysis, as follows: nephrolithiasis (10%), steatosis (3%), adrenal nodule (0.7%) and cholelithiasis (0.3%). Conclusion: For the clinical indications of tumor staging, acute abdomen, investigation of abdominal collections and hepatocellular carcinoma, the non-contrast-enhanced phase can be excluded from abdominal computed tomography studies with no significant impact on the diagnosis. (author)

Noise analysis of grating-based x-ray differential phase-contrast imaging with angular signal radiography

International Nuclear Information System (INIS)

Faiz, Wali; Gao Kun; Wu Zhao; Wei Chen-Xi; Zan Gui-Bin; Tian Yang-Chao; Bao Yuan; Zhu Pei-Ping

2017-01-01

X-ray phase-contrast imaging is one of the novel techniques, and has potential to enhance image quality and provide the details of inner structures nondestructively. In this work, we investigate quantitatively signal-to-noise ratio (SNR) of grating-based x-ray phase contrast imaging (GBPCI) system by employing angular signal radiography (ASR). Moreover, photon statistics and mechanical error that is a major source of noise are investigated in detail. Results show the dependence of SNR on the system parameters and the effects on the extracted absorption, refraction and scattering images. Our conclusions can be used to optimize the system design for upcoming practical applications in the areas such as material science and biomedical imaging. (paper)

SU-F-I-19: MRI Positive Contrast Visualization of Prostate Brachytherapy Seeds Using An Integrated Laplacian-Based Phase Processing

Energy Technology Data Exchange (ETDEWEB)

Soliman, A; Safigholi, H [Sunnybrook Research Institute, Toronto, ON (Canada); Sunnybrook Health Sciences Center, Toronto, ON (Canada); Nosrati, R [Sunnybrook Health Sciences Center, Toronto, ON (Canada); Ryerson University, Toronto, ON (Canada); Owrangi, A; Morton, G [Sunnybrook Health Sciences Center, Toronto, ON (Canada); University of Toronto, Toronto, ON (Canada); Song, W [Sunnybrook Research Institute, Toronto, ON (Canada); Sunnybrook Health Sciences Center, Toronto, ON (Canada); Ryerson University, Toronto, ON (Canada); University of Toronto, Toronto, ON (Canada)

2016-06-15

Purpose: To propose a new method that provides a positive contrast visualization of the prostate brachytherapy seeds using the phase information from MR images. Additionally, the feasibility of using the processed phase information to distinguish seeds from calcifications is explored. Methods: A gel phantom was constructed using 2% agar dissolved in 1 L of distilled water. Contrast agents were added to adjust the relaxation times. Four iodine-125 (Eckert & Ziegler SML86999) dummy seeds were placed at different orientations with respect to the main magnetic field (B0). Calcifications were obtained from a sheep femur cortical bone due to its close similarity to human bone tissue composition. Five samples of calcifications were shaped into different dimensions with lengths ranging between 1.2 – 6.1 mm.MR imaging was performed on a 3T Philips Achieva using an 8-channel head coil. Eight images were acquired at eight echo-times using a multi-gradient echo sequence. Spatial resolution was 0.7 × 0.7 × 2 mm, TR/TE/dTE = 20.0/2.3/2.3 ms and BW = 541 Hz/pixel. Complex images were acquired and fed into a two-step processing pipeline: the first includes phase unwrapping and background phase removal using Laplacian operator (Wei et al. 2013). The second step applies a specific phase mask on the resulting tissue phase from the first step to provide the desired positive contrast of the seeds and to, potentially, differentiate them from the calcifications. Results: The phase-processing was performed in less than 30 seconds. The proposed method has successfully resulted in a positive contrast of the brachytherapy seeds. Additionally, the final processed phase image showed difference between the appearance of seeds and calcifications. However, the shape of the seeds was slightly distorted compared to the original dimensions. Conclusion: It is feasible to provide a positive contrast of the seeds from MR images using Laplacian operator-based phase processing.

Bone histomorphometric quantification by X-ray phase contrast and transmission 3D SR microcomputed tomography

International Nuclear Information System (INIS)

Nogueira, L.P.; Pinheiro, C.J.G.; Braz, D.; Oliveira, L.F.; Barroso, R.C.

2008-01-01

Full text: Conventional histomorphometry is an important method for quantitative evaluation of bone microstructure. X-ray computed tomography is a noninvasive technique, which can be used to evaluate histomorphometric indices. In this technique, the output 3D images are used to quantify the whole sample, differently from the conventional one, in which the quantification is performed in 2D slices and extrapolated for 3D case. Looking for better resolutions and visualization of soft tissues, X-ray phase contrast imaging technique was developed. The objective of this work was to perform histomorphometric quantification of human cancellous bone using 3D synchrotron X ray computed microtomography, using two distinct techniques: transmission and phase contrast, in order to compare the results and evaluate the viability of applying the same methodology of quantification for both technique. All experiments were performed at the ELETTRA Synchrotron Light Laboratory in Trieste (Italy). MicroCT data sets were collected using the CT set-up on the SYRMEP (Synchrotron Radiation for Medical Physics) beamline. Results showed that there is a better correlation between histomorphometric parameters of both techniques when morphological filters had been used. However, using these filters, some important information given by phase contrast are lost and they shall be explored by new techniques of quantification

Can X-ray spectrum imaging replace backscattered electrons for compositional contrast in the scanning electron microscope?

Science.gov (United States)

Newbury, Dale E; Ritchie, Nicholas W M

2011-01-01

The high throughput of the silicon drift detector energy dispersive X-ray spectrometer (SDD-EDS) enables X-ray spectrum imaging (XSI) in the scanning electron microscope to be performed in frame times of 10-100 s, the typical time needed to record a high-quality backscattered electron (BSE) image. These short-duration XSIs can reveal all elements, except H, He, and Li, present as major constituents, defined as 0.1 mass fraction (10 wt%) or higher, as well as minor constituents in the range 0.01-0.1 mass fraction, depending on the particular composition and possible interferences. Although BSEs have a greater abundance by a factor of 100 compared with characteristic X-rays, the strong compositional contrast in element-specific X-ray maps enables XSI mapping to compete with BSE imaging to reveal compositional features. Differences in the fraction of the interaction volume sampled by the BSE and X-ray signals lead to more delocalization of the X-ray signal at abrupt compositional boundaries, resulting in poorer spatial resolution. Improved resolution in X-ray elemental maps occurs for the case of a small feature composed of intermediate to high atomic number elements embedded in a matrix of lower atomic number elements. XSI imaging strongly complements BSE imaging, and the SDD-EDS technology enables an efficient combined BSE-XSI measurement strategy that maximizes the compositional information. If 10 s or more are available for the measurement of an area of interest, the analyst should always record the combined BSE-XSI information to gain the advantages of both measures of compositional contrast. Copyright © 2011 Wiley Periodicals, Inc.

4-D flow magnetic resonance imaging: blood flow quantification compared to 2-D phase-contrast magnetic resonance imaging and Doppler echocardiography

Energy Technology Data Exchange (ETDEWEB)

Gabbour, Maya [Ann and Robert H. Lurie Children' s Hospital of Chicago, Department of Medical Imaging 9, Chicago, IL (United States); Schnell, Susanne [Northwestern University Feinberg School of Medicine, Department of Radiology, Chicago, IL (United States); Jarvis, Kelly [Northwestern University, Department of Biomedical Engineering, McCormick School of Engineering, Evanston, IL (United States); Robinson, Joshua D. [Ann and Robert H. Lurie Children' s Hospital of Chicago, Department of Pediatrics, Division of Pediatric Cardiology, Chicago, IL (United States); Northwestern University Feinberg School of Medicine, Department of Pediatrics, Chicago, IL (United States); Markl, Michael [Northwestern University Feinberg School of Medicine, Department of Radiology, Chicago, IL (United States); Northwestern University, Department of Biomedical Engineering, McCormick School of Engineering, Evanston, IL (United States); Rigsby, Cynthia K. [Ann and Robert H. Lurie Children' s Hospital of Chicago, Department of Medical Imaging 9, Chicago, IL (United States); Northwestern University Feinberg School of Medicine, Department of Radiology, Chicago, IL (United States)

2015-06-15

Doppler echocardiography (echo) is the reference standard for blood flow velocity analysis, and two-dimensional (2-D) phase-contrast magnetic resonance imaging (MRI) is considered the reference standard for quantitative blood flow assessment. However, both clinical standard-of-care techniques are limited by 2-D acquisitions and single-direction velocity encoding and may make them inadequate to assess the complex three-dimensional hemodynamics seen in congenital heart disease. Four-dimensional flow MRI (4-D flow) enables qualitative and quantitative analysis of complex blood flow in the heart and great arteries. The objectives of this study are to compare 4-D flow with 2-D phase-contrast MRI for quantification of aortic and pulmonary flow and to evaluate the advantage of 4-D flow-based volumetric flow analysis compared to 2-D phase-contrast MRI and echo for peak velocity assessment in children and young adults. Two-dimensional phase-contrast MRI of the aortic root, main pulmonary artery (MPA), and right and left pulmonary arteries (RPA, LPA) and 4-D flow with volumetric coverage of the aorta and pulmonary arteries were performed in 50 patients (mean age: 13.1 ± 6.4 years). Four-dimensional flow analyses included calculation of net flow and regurgitant fraction with 4-D flow analysis planes similarly positioned to 2-D planes. In addition, 4-D flow volumetric assessment of aortic root/ascending aorta and MPA peak velocities was performed and compared to 2-D phase-contrast MRI and echo. Excellent correlation and agreement were found between 2-D phase-contrast MRI and 4-D flow for net flow (r = 0.97, P < 0.001) and excellent correlation with good agreement was found for regurgitant fraction (r = 0.88, P < 0.001) in all vessels. Two-dimensional phase-contrast MRI significantly underestimated aortic (P = 0.032) and MPA (P < 0.001) peak velocities compared to echo, while volumetric 4-D flow analysis resulted in higher (aortic: P = 0.001) or similar (MPA: P = 0.98) peak

Phase-contrast MR angiography of intracranial dural arteriovenous fistulae

International Nuclear Information System (INIS)

Cellerini, M.; Mascalchi, M.; Mangiafico, S.; Ferrito, G.P.; Scardigli, V.; Pellicano, G.; Quilici, N.

1999-01-01

MRI and phase-contrast MR angiography (PC MRA) were obtained in 13 patients with angiographically confirmed intracranial dural arteriovenous fistulae (DAVF). Three- and two-dimensional PC MRA was obtained with low (6-20 cm/s) and high (>40 cm/s) velocity encoding along the three main body axes. MRI showed focal or diffuse signal abnormalities in the brain parenchyma in six patients, dilated cortical veins in seven, venous pouches in four with type IV DAVF and enlargement of the superior ophthalmic vein in three patients with DAVF of the cavernous sinus. However, it showed none of the fistula sites and did not allow reliable identification of feeding arteries. 3D PC MRA enabled identification of the fistula and enlarged feeding arteries in six cases each. Stenosis or occlusion of the dural sinuses was detected in six of eight cases on 3D PC MRA with low velocity encoding. In six patients with type II DAVF phase reconstruction of 2D PC MRA demonstrated flow reversal in the dural sinuses or superior ophthalmic vein. (orig.)

An iterative method for near-field Fresnel region polychromatic phase contrast imaging

Science.gov (United States)

Carroll, Aidan J.; van Riessen, Grant A.; Balaur, Eugeniu; Dolbnya, Igor P.; Tran, Giang N.; Peele, Andrew G.

2017-07-01

We present an iterative method for polychromatic phase contrast imaging that is suitable for broadband illumination and which allows for the quantitative determination of the thickness of an object given the refractive index of the sample material. Experimental and simulation results suggest the iterative method provides comparable image quality and quantitative object thickness determination when compared to the analytical polychromatic transport of intensity and contrast transfer function methods. The ability of the iterative method to work over a wider range of experimental conditions means the iterative method is a suitable candidate for use with polychromatic illumination and may deliver more utility for laboratory-based x-ray sources, which typically have a broad spectrum.

4D phase contrast flow imaging for in-stent flow visualization and assessment of stent patency in peripheral vascular stents--a phantom study.

Science.gov (United States)

Bunck, Alexander C; Jüttner, Alena; Kröger, Jan Robert; Burg, Matthias C; Kugel, Harald; Niederstadt, Thomas; Tiemann, Klaus; Schnackenburg, Bernhard; Crelier, Gerard R; Heindel, Walter; Maintz, David

2012-09-01

4D phase contrast flow imaging is increasingly used to study the hemodynamics in various vascular territories and pathologies. The aim of this study was to assess the feasibility and validity of MRI based 4D phase contrast flow imaging for the evaluation of in-stent blood flow in 17 commonly used peripheral stents. 17 different peripheral stents were implanted into a MR compatible flow phantom. In-stent visibility, maximal velocity and flow visualization were assessed and estimates of in-stent patency obtained from 4D phase contrast flow data sets were compared to a conventional 3D contrast-enhanced magnetic resonance angiography (CE-MRA) as well as 2D PC flow measurements. In all but 3 of the tested stents time-resolved 3D particle traces could be visualized inside the stent lumen. Quality of 4D flow visualization and CE-MRA images depended on stent type and stent orientation relative to the magnetic field. Compared to the visible lumen area determined by 3D CE-MRA, estimates of lumen patency derived from 4D flow measurements were significantly higher and less dependent on stent type. A higher number of stents could be assessed for in-stent patency by 4D phase contrast flow imaging (n=14) than by 2D phase contrast flow imaging (n=10). 4D phase contrast flow imaging in peripheral vascular stents is feasible and appears advantageous over conventional 3D contrast-enhanced MR angiography and 2D phase contrast flow imaging. It allows for in-stent flow visualization and flow quantification with varying quality depending on stent type. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

X-ray phase contrast imaging of the bone-cartilage interface

International Nuclear Information System (INIS)

Ismail, E.C.; Kaabar, W.; Garrity, D.; Gundogdu, O.; Bradley, D.A.; Bunk, O.; Pfeiffer, F.; Farquharson, M.J.

2008-01-01

Full text: Synovial joints articulate in a lubricating environment, the system providing for smooth articulation. The articular cartilage overlying the bone consists of a network of collagen fibres. This network is essential to cartilage integrity, suffering damage in degenerative joint disease such as osteoarthritis. At Surrey and also in work conducted by this group at the Paul Scherrer Institute (PSI) synchrotron site we have been applying a number of techniques in studying the bone-cartilage interface and of changes occurring in this with disease. One technique attracting particular interest is X-ray phase contrast imaging, yielding information on anatomical features that manifest from the large scale organisation of collagen and the mineralised phase contained within the collagen fibres in the deep cartilage zone. This work will briefly review some of the basic supporting physics and then shows some of the images and other results that we have obtained to-date

Multi-technology Integration Based on Low-contrast Microscopic Image Enhancement

Directory of Open Access Journals (Sweden)

Haoge Ma

2014-01-01

Full Text Available Microscopic image enhancement is an important issue of image processing technique, which is used to improve the visual quality of image. This paper describes a novel multi resolution image segmentation algorithm for low DOF images. The algorithm is designed to separate a sharply focused object of interest from other foreground or background objects. The algorithm is fully automatic in that all parameters are image in dependent. A multiscale-approach based on high frequency wavelet coefficients and their statistics is used to perform context dependent classification of individual blocks of the image. Compared with the state of the art algorithms, this new algorithm provides better accuracy at higher speed.

Scanning tunneling microscope for magneto-optical imaging

NARCIS (Netherlands)

Prins, M.W.J.; Groeneveld, R.H.M.; Abraham, D.L.; Schad, R.; Kempen, van H.; Kesteren, van H.W.

1996-01-01

Images of magnetic bits written in a Pt/Co multilayer are presented. Using photosensitive semiconducting tips in a scanning tunneling microscope the surface topography as well as the polarization-dependent optical transmission are measured. Magnetic contrast is achieved by detection of the Faraday

Interfacial orientation and misorientation relationships in nanolamellar Cu/Nb composites using transmission-electron-microscope-based orientation and phase mapping

International Nuclear Information System (INIS)

Liu, X.; Nuhfer, N.T.; Rollett, A.D.; Sinha, S.; Lee, S.-B.; Carpenter, J.S.; LeDonne, J.E.; Darbal, A.; Barmak, K.

2014-01-01

A transmission-electron-microscope-based orientation mapping technique that makes use of beam precession to achieve near-kinematical conditions was used to map the phase and crystal orientations in nanolamellar Cu/Nb composites with average layer thicknesses of 86, 30 and 18 nm. Maps of high quality and reliability were obtained by comparing the recorded diffraction patterns with pre-calculated templates. Particular care was taken in optimizing the dewarping parameters and in calibrating the frames of reference. Layers with thicknesses as low as 4 nm were successfully mapped. Heterophase interface plane and character distributions (HIPD and HICD, respectively) of Cu and Nb phases from the samples were determined from the orientation maps. In addition, local orientation relation stereograms of the Cu/Nb interfaces were calculated, and these revealed the detailed layer-to-layer texture information. The results are in agreement with previously reported neutron-diffraction-based and precession-electron-diffraction-based measurements on an accumulated roll bonding (ARB)-fabricated Cu/Nb sample with an average layer thickness of 30 nm as well as scanning-electron-microscope-based electron backscattered diffraction HIPD/HICD plots of ARB-fabricated Cu/Nb samples with layer thicknesses between 200 and 600 nm

Estimation of pulmonary vascular resistance in patients with pulmonary fibrosis by phase-contrast magnetic resonance imaging

International Nuclear Information System (INIS)

Ayukawa, Yuichiro; Murayama, Sadayuki; Tsuchiya, Nanae; Yara, Satomi; Fujita, Jiro

2011-01-01

The aim of this study was to assess pulmonary vascular resistance (PVR) in patients with pulmonary fibrosis (PF) by phase-contrast magnetic resonance imaging (MRI). Subjects were 11 healthy volunteers and 11 patients with PF. Using phase-contrast MRI, we measured pulmonary arterial blood flow and calculated the parameters of PVR. Parameters were compared between volunteers and patients using unpaired t-tests. The diagnostic capability of the parameters was evaluated by receiver operating characteristic (ROC) curve analysis. Patients underwent respiratory function tests (RFTs) and chest computed tomography (CT), and they were correlated with MRI parameters. Most MRI parameters were significantly different between volunteers and patients (t-test P values were <0.05 in 9 of 10 parameters). Regarding the RFT and CT visual score, only the %DLco/VA and acceleration time and the CT visual score and average flow volume had significant correlation [r=-0.667 (P=0.024) and r=-0.6 (P=0.031)], respectively. Our findings suggest that PVR derived from phase-contrast MRI is significantly higher in patients with PF than in volunteers. However, all but two of these parameters may not correlate with the severity of PF. (author)

Preliminary comparison of grating-based and in-line phase contrast X-ray imaging with synchrotron radiation for mouse kidney at TOMCAT

International Nuclear Information System (INIS)

Sun, J; Liu, P; Xu, L X; Irvine, S; Pinzer, B; Stampanoni, M

2013-01-01

Phase contrast imaging has been demonstrated to be advantageous in revealing detailed structures inside biological specimens without contrast agents. Grating-based differential phase contrast (DPC) and in-line phase contrast (ILPC) X-ray imaging are the two modalities frequently used at the beamline of TOmographic Microscopy and Coherent rAdiology experimenTs (TOMCAT) at the Swiss Light Source (SLS). In this paper, we preliminarily compared the abilities of two types of phase contrast imaging in distinguishing micro structures in mouse kidneys. The 3D reconstructions showed that the microstructures in kidney, such as micro vessels and renal tubules, were displayed clearly with both imaging modalities. The two techniques may be viewed as complementary. For larger features with very small density variations DPC is the desirable method. In cases where dose and time limits may prohibit the multiple steps required for DPC, and when the focus is on finer features, the ILPC method may be considered as a more viable alternative. Moreover, high resolution ILPC images are comparable with histological results.

Development of a SEM-based low-energy in-line electron holography microscope for individual particle imaging.

Science.gov (United States)

Adaniya, Hidehito; Cheung, Martin; Cassidy, Cathal; Yamashita, Masao; Shintake, Tsumoru

2018-05-01

A new SEM-based in-line electron holography microscope has been under development. The microscope utilizes conventional SEM and BF-STEM functionality to allow for rapid searching of the specimen of interest, seamless interchange between SEM, BF-STEM and holographic imaging modes, and makes use of coherent low-energy in-line electron holography to obtain low-dose, high-contrast images of light element materials. We report here an overview of the instrumentation and first experimental results on gold nano-particles and carbon nano-fibers for system performance tests. Reconstructed images obtained from the holographic imaging mode of the new microscope show substantial image contrast and resolution compared to those acquired by SEM and BF-STEM modes, demonstrating the feasibility of high-contrast imaging via low-energy in-line electron holography. The prospect of utilizing the new microscope to image purified biological specimens at the individual particle level is discussed and electron optical issues and challenges to further improve resolution and contrast are considered. Copyright © 2018 Elsevier B.V. All rights reserved.

Invited Review Article: Methods for imaging weak-phase objects in electron microscopy

International Nuclear Information System (INIS)

Glaeser, Robert M.

2013-01-01

Contrast has traditionally been produced in electron-microscopy of weak phase objects by simply defocusing the objective lens. There now is renewed interest, however, in using devices that apply a uniform quarter-wave phase shift to the scattered electrons relative to the unscattered beam, or that generate in-focus image contrast in some other way. Renewed activity in making an electron-optical equivalent of the familiar “phase-contrast” light microscope is based in part on the improved possibilities that are now available for device microfabrication. There is also a better understanding that it is important to take full advantage of contrast that can be had at low spatial frequency when imaging large, macromolecular objects. In addition, a number of conceptually new phase-plate designs have been proposed, thus increasing the number of options that are available for development. The advantages, disadvantages, and current status of each of these options is now compared and contrasted. Experimental results that are, indeed, superior to what can be accomplished with defocus-based phase contrast have been obtained recently with two different designs of phase-contrast aperture. Nevertheless, extensive work also has shown that fabrication of such devices is inconsistent, and that their working lifetime is short. The main limitation, in fact, appears to be electrostatic charging of any device that is placed into the electron diffraction pattern. The challenge in fabricating phase plates that are practical to use for routine work in electron microscopy thus may be more in the area of materials science than in the area of electron optics

Increasing the darkfield contrast-to-noise ratio using a deconvolution-based information retrieval algorithm in X-ray grating-based phase-contrast imaging.

Science.gov (United States)

Weber, Thomas; Pelzer, Georg; Bayer, Florian; Horn, Florian; Rieger, Jens; Ritter, André; Zang, Andrea; Durst, Jürgen; Anton, Gisela; Michel, Thilo

2013-07-29

A novel information retrieval algorithm for X-ray grating-based phase-contrast imaging based on the deconvolution of the object and the reference phase stepping curve (PSC) as proposed by Modregger et al. was investigated in this paper. We applied the method for the first time on data obtained with a polychromatic spectrum and compared the results to those, received by applying the commonly used method, based on a Fourier analysis. We confirmed the expectation, that both methods deliver the same results for the absorption and the differential phase image. For the darkfield image, a mean contrast-to-noise ratio (CNR) increase by a factor of 1.17 using the new method was found. Furthermore, the dose saving potential was estimated for the deconvolution method experimentally. It is found, that for the conventional method a dose which is higher by a factor of 1.66 is needed to obtain a similar CNR value compared to the novel method. A further analysis of the data revealed, that the improvement in CNR and dose efficiency is due to the superior background noise properties of the deconvolution method, but at the cost of comparability between measurements at different applied dose values, as the mean value becomes dependent on the photon statistics used.

Study of microscopic phase separation in La2CuO4+y by μSR

International Nuclear Information System (INIS)

Pomyakushin, V.Yu.; Duginov, V.N.; Amato, A.; Gygax, F.N.; Schenck, A.; Herlach, D.

1996-01-01

Electron spin-freezing at T f =8K has been detected in superconducting (T c =12K) single crystal La 2 CuO 4+y (y≅0.03) by μSR. According to the diffraction data the crystal is in the Bmab phase and macroscopically homogeneous without any traces of structural phase separation. At T f part of crystal enters spin-glass-like state, and at T=3K the 'frozen' fraction amounts about half of the crystal volume. μSR-experiment in the external magnetic field has shown that no Abrikosov flux line lattice is formed below T c . The obtained data allow to assume that magnetic and superconducting regions in the crystal are space separated on the microscopic scales ∼10 2 A. Large (>1000ppm) external field induced broadening of the Knight shift distribution on the muon found at all temperatures T ∼ <130K indicates that the crystal contains micro-regions possessing enhanced magnetic susceptibility. 31 refs., 13 figs

Combining Generalized Phase Contrast with matched filtering into a versatile beam shaping approach

DEFF Research Database (Denmark)

Glückstad, Jesper; Palima, Darwin

2010-01-01

We adapt concepts from matched filtering to propose a method for generating reconfigurable multiple beams. Combined with the Generalized Phase Contrast (GPC) technique, the proposed method coined mGPC can yield dynamically reconfigurable optical beam arrays with high light efficiency for optical...... manipulation, high-speed sorting and other parallel spatial light applications [1]....

X-ray phase contrast with injected gas for tumor microangiography

International Nuclear Information System (INIS)

Lundström, U; Larsson, D H; Burvall, A; Hertz, H M; Westermark, U K; Henriksson, M Arsenian

2014-01-01

We show that the microvasculature of mouse tumors can be visualized using propagation-based phase-contrast x-ray imaging with gas as the contrast agent. The large density difference over the gas–tissue interface provides high contrast, allowing the imaging of small-diameter blood vessels with relatively short exposure times and low dose using a compact liquid-metal-jet x-ray source. The method investigated is applied to tumors (E1A/Ras-transformed mouse embryonic fibroblasts) grown in mouse ears, demonstrating sub-15-µm-diameter imaging of their blood vessels. The exposure time for a 2D projection image is a few seconds and a full tomographic 3D map takes some minutes. The method relies on the strength of the vasculature to withstand the gas pressure. Given that tumor vessels are known to be more fragile than normal vessels, we investigate the tolerance of the vasculature of 12 tumors to gas injection and find that a majority withstand 200 mbar pressures, enough to fill 12-µm-diameter vessels with gas. A comparison of the elasticity of tumorous and non-tumorous vessels supports the assumption of tumor vessels being more fragile. Finally, we conclude that the method has the potential to be extended to the imaging of 15 µm vessels in thick tissue, including mouse imaging, making it of interest for, e.g., angiogenesis research. (paper)

Contrast enhanced liver MRI in patients with primary sclerosing cholangitis: inverse appearance of focal confluent fibrosis on delayed phase MR images with hepatocyte specific versus extracellular gadolinium based contrast agents.

Science.gov (United States)

Husarik, Daniela B; Gupta, Rajan T; Ringe, Kristina I; Boll, Daniel T; Merkle, Elmar M

2011-12-01

To assess the enhancement pattern of focal confluent fibrosis (FCF) on contrast-enhanced hepatic magnetic resonance imaging (MRI) using hepatocyte-specific (Gd-EOB-DTPA) and extracellular (ECA) gadolinium-based contrast agents in patients with primary sclerosing cholangitis (PSC). After institutional review board approval, 10 patients with PSC (6 male, 4 female; 33-61 years) with 13 FCF were included in this retrospective study. All patients had a Gd-EOB-DTPA-enhanced liver MRI exam, and a comparison ECA-enhanced MRI. On each T1-weighted dynamic dataset, the signal intensity (SI) of FCF and the surrounding liver as well as the paraspinal muscle (M) were measured. In the Gd-EOB-DTPA group, hepatocyte phase images were also included. SI FCF/SI M, SI liver/SI M, and [(SI liver - SI FCF)/SI liver] were compared between the different contrast agents for each dynamic phase using the paired Student's t-test. There was no significant difference in SI FCF/SI M in all imaging phases. SI liver/SI M was significantly higher for the Gd-EOB-DTPA group in the delayed phase (P DTPA group, mean [(SI liver - SI FCF)/SI liver] were as follows (values for ECA group in parentheses): unenhanced phase: 0.26 (0.26); arterial phase: 0.01 (-0.31); portal venous phase (PVP): -0.05 (-0.26); delayed phase (DP): 0.14 (-0.54); and hepatocyte phase: 0.26. Differences were significant for the DP (P DTPA-enhanced images. Copyright © 2011 AUR. Published by Elsevier Inc. All rights reserved.

Computational fluid dynamics simulations of blood flow regularized by 3D phase contrast MRI

DEFF Research Database (Denmark)

Rispoli, Vinicius C; Nielsen, Jon; Nayak, Krishna S

2015-01-01

BACKGROUND: Phase contrast magnetic resonance imaging (PC-MRI) is used clinically for quantitative assessment of cardiovascular flow and function, as it is capable of providing directly-measured 3D velocity maps. Alternatively, vascular flow can be estimated from model-based computation fluid dyn...

Hard X-Ray Phase-Contrast Imaging for Medical Applications - Physicist's Dream or Radiologist's Mainstream?

International Nuclear Information System (INIS)

Wilkins, S. W.; Gureyev, T. E.; Mayo, S. C.; Nesterets, Ya. I.; Pogany, A.; Stevenson, A. W.; Paganin, D. M.

2007-01-01

We briefly review currently practiced methods of X-ray phase contrast imaging and consider some of their relative features, especially in regard to applicability to clinical medical studies. Various related technological issues and promising future areas of development are also briefly discussed

Effects of microchannel confinement on acoustic vaporisation of ultrasound phase change contrast agents

Science.gov (United States)

Lin, Shengtao; Zhang, Ge; Hau Leow, Chee; Tang, Meng-Xing

2017-09-01

The sub-micron phase change contrast agent (PCCA) composed of a perfluorocarbon liquid core can be activated into gaseous state and form stable echogenic microbubbles for contrast-enhanced ultrasound imaging. It has shown great promise in imaging microvasculature, tumour microenvironment, and cancer cells. Although PCCAs have been extensively studied for different diagnostic and therapeutic applications, the effect of biologically geometrical confinement on the acoustic vaporisation of PCCAs is still not clear. We have investigated the difference in PCCA-produced ultrasound contrast enhancement after acoustic activation with and without a microvessel confinement on a microchannel phantom. The experimental results indicated more than one-order of magnitude less acoustic vaporisation in a microchannel than that in a free environment taking into account the attenuation effect of the vessel on the microbubble scattering. This may provide an improved understanding in the applications of PCCAs in vivo.

Generalized phase contrast-enhanced diffractive coupling to light-driven microtools

DEFF Research Database (Denmark)

Villangca, Mark Jayson; Bañas, Andrew Rafael; Palima, Darwin

2015-01-01

capability of the microtools, the applied spatial light modulator has been illuminated with a properly matched input beam cross section based on the generalized phase contrast method. Our results show a significant gain in the output at the tip of each microtool as measured from the fluorescence signal...... of the coupling spots is done in real time following the position of each microtool with the aid of an object tracking routine. This approach allows continuous coupling of light through the microtools which can be useful in a variety of biophotonics applications. To complement the targeted-light delivery...

An efficient reconstruction algorithm for differential phase-contrast tomographic images from a limited number of views

International Nuclear Information System (INIS)

Sunaguchi, Naoki; Yuasa, Tetsuya; Gupta, Rajiv; Ando, Masami

2015-01-01

The main focus of this paper is reconstruction of tomographic phase-contrast image from a set of projections. We propose an efficient reconstruction algorithm for differential phase-contrast computed tomography that can considerably reduce the number of projections required for reconstruction. The key result underlying this research is a projection theorem that states that the second derivative of the projection set is linearly related to the Laplacian of the tomographic image. The proposed algorithm first reconstructs the Laplacian image of the phase-shift distribution from the second-derivative of the projections using total variation regularization. The second step is to obtain the phase-shift distribution by solving a Poisson equation whose source is the Laplacian image previously reconstructed under the Dirichlet condition. We demonstrate the efficacy of this algorithm using both synthetically generated simulation data and projection data acquired experimentally at a synchrotron. The experimental phase data were acquired from a human coronary artery specimen using dark-field-imaging optics pioneered by our group. Our results demonstrate that the proposed algorithm can reduce the number of projections to approximately 33% as compared with the conventional filtered backprojection method, without any detrimental effect on the image quality

Environmental TEM in an Aberration Corrected Microscope

DEFF Research Database (Denmark)

Hansen, Thomas Willum; Wagner, Jakob Birkedal

‐resolution imaging. A gaseous atmosphere in the pole‐piece gap of the objective lens of the microscope alters both the incoming electron wave prior to interaction with the sample and the outgoing wave below the sample. Whereas conventional TEM samples are usually thin (below 10‐20 nm), the gas in the environmental...... the microscope column. The effects of gas on the electron wave in the objective lens are not well understood and needs further attention. Imaging samples with a simple geometry, such as gold particles on a flat graphene substrate and analyzing the variations in contrast, provides a means for understanding...... results from imaging in various elemental as well as di‐molecular gases and their effect on imaging and spectroscopy in the environmental transmission electron microscope....

Synchrotron radiation phase-contrast X-ray CT imaging of acupuncture points

Energy Technology Data Exchange (ETDEWEB)

Zhang, Dongming; Yan, Xiaohui; Zhang, Xinyi [Fudan University, Synchrotron Radiation Research Center, State Key Laboratory of Surface Physics and Department of Physics, Shanghai (China); Liu, Chenglin [Physics Department of Yancheng Teachers' College, Yancheng (China); Dang, Ruishan [The Second Military Medical University, Shanghai (China); Xiao, Tiqiao [Chinese Academy of Sciences, Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Shanghai (China); Zhu, Peiping [Chinese Academy of Sciences, Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Beijing (China)

2011-08-15

Three-dimensional (3D) topographic structures of acupuncture points were investigated by using synchrotron radiation in-line X-ray phase contrast computerized tomography. Two acupuncture points, named Zhongji (RN3) and Zusanli (ST36), were studied. We found an accumulation of microvessels at each acupuncture point region. Images of the tissues surrounding the acupuncture points do not show such kinds of structure. This is the first time that 3D images have revealed the specific structures of acupuncture points. (orig.)

Synchrotron radiation phase-contrast X-ray CT imaging of acupuncture points

International Nuclear Information System (INIS)

Zhang, Dongming; Yan, Xiaohui; Zhang, Xinyi; Liu, Chenglin; Dang, Ruishan; Xiao, Tiqiao; Zhu, Peiping

2011-01-01

Three-dimensional (3D) topographic structures of acupuncture points were investigated by using synchrotron radiation in-line X-ray phase contrast computerized tomography. Two acupuncture points, named Zhongji (RN3) and Zusanli (ST36), were studied. We found an accumulation of microvessels at each acupuncture point region. Images of the tissues surrounding the acupuncture points do not show such kinds of structure. This is the first time that 3D images have revealed the specific structures of acupuncture points. (orig.)

Matched-filtering generalized phase contrast using LCoS pico-projectors for beam-forming.

Science.gov (United States)

Bañas, Andrew; Palima, Darwin; Glückstad, Jesper

2012-04-23

We report on a new beam-forming system for generating high intensity programmable optical spikes using so-called matched-filtering Generalized Phase Contrast (mGPC) applying two consumer handheld pico-projectors. Such a system presents a low-cost alternative for optical trapping and manipulation, optical lattices and other beam-shaping applications usually implemented with high-end spatial light modulators. Portable pico-projectors based on liquid crystal on silicon (LCoS) devices are used as binary phase-only spatial light modulators by carefully setting the appropriate polarization of the laser illumination. The devices are subsequently placed into the object and Fourier plane of a standard 4f-setup according to the mGPC spatial filtering configuration. Having a reconfigurable spatial phase filter, instead of a fixed and fabricated one, allows the beam shaper to adapt to different input phase patterns suited for different requirements. Despite imperfections in these consumer pico-projectors, the mGPC approach tolerates phase aberrations that would have otherwise been hard to overcome by standard phase projection. © 2012 Optical Society of America

Penalized maximum likelihood reconstruction for x-ray differential phase-contrast tomography

International Nuclear Information System (INIS)

Brendel, Bernhard; Teuffenbach, Maximilian von; Noël, Peter B.; Pfeiffer, Franz; Koehler, Thomas

2016-01-01

Purpose: The purpose of this work is to propose a cost function with regularization to iteratively reconstruct attenuation, phase, and scatter images simultaneously from differential phase contrast (DPC) acquisitions, without the need of phase retrieval, and examine its properties. Furthermore this reconstruction method is applied to an acquisition pattern that is suitable for a DPC tomographic system with continuously rotating gantry (sliding window acquisition), overcoming the severe smearing in noniterative reconstruction. Methods: We derive a penalized maximum likelihood reconstruction algorithm to directly reconstruct attenuation, phase, and scatter image from the measured detector values of a DPC acquisition. The proposed penalty comprises, for each of the three images, an independent smoothing prior. Image quality of the proposed reconstruction is compared to images generated with FBP and iterative reconstruction after phase retrieval. Furthermore, the influence between the priors is analyzed. Finally, the proposed reconstruction algorithm is applied to experimental sliding window data acquired at a synchrotron and results are compared to reconstructions based on phase retrieval. Results: The results show that the proposed algorithm significantly increases image quality in comparison to reconstructions based on phase retrieval. No significant mutual influence between the proposed independent priors could be observed. Further it could be illustrated that the iterative reconstruction of a sliding window acquisition results in images with substantially reduced smearing artifacts. Conclusions: Although the proposed cost function is inherently nonconvex, it can be used to reconstruct images with less aliasing artifacts and less streak artifacts than reconstruction methods based on phase retrieval. Furthermore, the proposed method can be used to reconstruct images of sliding window acquisitions with negligible smearing artifacts

Experimental and theoretical contributions to X-ray phase-contrast techniques for medical imaging

International Nuclear Information System (INIS)

Diemoz, P.C.

2011-01-01

Several X-ray phase-contrast techniques have recently been developed. Unlike conventional X-ray methods, which measure the absorption properties of the tissues, these techniques derive contrast also from the modulation of the phase produced by the sample. Since the phase shift can be significant even for small details characterized by weak or absent absorption, the achievable image contrast can be greatly increased, notably for the soft biological tissues. These methods are therefore very promising for applications in the medical domain. The aim of this work is to contribute to a deeper understanding of these techniques, in particular propagation-based imaging (PBI), analyzer-based imaging (ABI) and grating interferometry (GIFM), and to study their potential and the best practical implementation for medical imaging applications. An important part of this work is dedicated to the use of mathematical algorithms for the extraction, from the acquired images, of quantitative sample information (the absorption, refraction and scattering sample properties). In particular, five among the most known algorithms based on the geometrical optics approximation have been theoretically analysed and experimentally compared, in planar and tomographic modalities, by using geometrical phantoms and human bone-cartilage and breast samples. A semi-quantitative method for the acquisition and reconstruction of tomographic images in the ABI and GIFM techniques has also been proposed. The validity conditions are analyzed in detail and the method, enabling a considerable simplification of the imaging procedure, has been experimentally checked on phantoms and human samples. Finally, a theoretical and experimental comparison of the PBI, ABI and GIFM techniques is presented. The advantages and drawbacks of each of these techniques are discussed. The results obtained from this analysis can be very useful for determining the most adapted technique for a given application. (author)

All-optical optoacoustic microscope based on wideband pulse interferometry.

Science.gov (United States)

Wissmeyer, Georg; Soliman, Dominik; Shnaiderman, Rami; Rosenthal, Amir; Ntziachristos, Vasilis

2016-05-01

Optical and optoacoustic (photoacoustic) microscopy have been recently joined in hybrid implementations that resolve extended tissue contrast compared to each modality alone. Nevertheless, the application of the hybrid technique is limited by the requirement to combine an optical objective with ultrasound detection collecting signal from the same micro-volume. We present an all-optical optoacoustic microscope based on a pi-phase-shifted fiber Bragg grating (π-FBG) with coherence-restored pulsed interferometry (CRPI) used as the interrogation method. The sensor offers an ultra-small footprint and achieved higher sensitivity over piezoelectric transducers of similar size. We characterize the spectral bandwidth of the ultrasound detector and interrogate the imaging performance on phantoms and tissues. We show the first optoacoustic images of biological specimen recorded with π-FBG sensors. We discuss the potential uses of π-FBG sensors based on CRPI.

High transmittance contrast in amorphous to hexagonal phase of Ge2Sb2Te5: Reversible NIR-window

Science.gov (United States)

Singh, Palwinder; Singh, A. P.; Kanda, Neetu; Mishra, Monu; Gupta, Govind; Thakur, Anup

2017-12-01

Ge2Sb2Te5 (GST) is one of the best phase change materials because of its splendid set of properties, viz., high thermal stability, fast crystallization speed, good endurance, scalability, and reliability. Phase transition [amorphous → face centered cubic (fcc) → hexagonal close packed (hcp)] of GST thin films with annealing was studied using X-ray diffraction. Thin films in amorphous, fcc, and hcp phases are highly, medium, and negligible transparent in the near infra-red region, respectively. The optical transmission in amorphous, fcc, and hcp phases is ˜92%, ˜46%, and ˜2%, respectively, at the wavelength of 2740 nm. At 2740 nm, a high transmission contrast (˜90%) is observed with phase transition from the amorphous to hcp phase. By utilizing large transmission contrast, it is demonstrated that GST can be availed as a potential candidate for reversible near infra-red-window. The sharp change in optical transmission with phase transition can be understood from the change in density of states in the valence band.

Quantitative measurement of total cerebral blood flow using 2D phase-contrast MRI and doppler ultrasound

Energy Technology Data Exchange (ETDEWEB)

Seo, Keum Soo; Choi, Sun Seob; Lee, Young Il [Dong-A Univ., College of Medicine, Busan (Korea, Republic of)

2001-12-01

To compare of quantitative measurement of the total cerebral blood flow using two-dimensional phase-contrast MR imaging and Doppler ultrasound. In 16 volunteers (mean age, 26 years; mean body weight, 66 kg) without abnormal medical histories, two-dimensional phase-contrast MR imaging was performed at the level of the C2-3 inter vertebral disc for flow measurement of the internal carotid arteries and the vertebral arteries. Volume flow measurements using Doppler ultrasound were also performed at the internal carotid arteries 2cm above the carotid bifurcation, and at the vertebral arteries at the level of the upper pole of the thyroid gland. Flows in the four vessels measured by the two methods were compared using Wilcoxon's correlation analysis and the median score. Total cerebral blood flows were calculated by summing these four vessel flows, and mean values for the 16 volunteers were calculated. Cerebral blood flows measured by 2-D phase-contrast MR imaging and Doppler ultrasounds were 233 and 239 ml/min in the right internal carotid artery, 250 and 248 ml/min in the left internal carotid artery, 62 and 56 ml/min in the right vertebral artery, and 83 and 68 ml/min in the left vertebral artery. Correlation coefficients of the blood flows determined by the two methods were 0.48, 0.54, 0.49, and 0.62 in each vessel, while total cerebral blood flows were 628{+-}68 (range, 517 to 779) ml/min and 612{+-}79 (range, 482 to 804)ml/min, respectively. Total cerebral blood flow was easily measured using 2-D phase-contrast MR imaging and Doppler ultrasound, and the two noninvasive methods can therefore be used clinically for the measurement of total cerebral blood flow.

Simple non-Markovian microscopic models for the depolarizing channel of a single qubit

International Nuclear Information System (INIS)

Fonseca Romero, K M; Lo Franco, R

2012-01-01

The archetypal one-qubit noisy channels - depolarizing, phase-damping and amplitude-damping channels - describe both Markovian and non-Markovian evolution. Simple microscopic models for the depolarizing channel, both classical and quantum, are considered. Microscopic models that describe phase-damping and amplitude-damping channels are briefly reviewed.

4D phase contrast flow imaging for in-stent flow visualization and assessment of stent patency in peripheral vascular stents – A phantom study

International Nuclear Information System (INIS)

Bunck, Alexander C.; Jüttner, Alena; Kröger, Jan Robert; Burg, Matthias C.; Kugel, Harald; Niederstadt, Thomas; Tiemann, Klaus; Schnackenburg, Bernhard; Crelier, Gerard R.

2012-01-01

Purpose: 4D phase contrast flow imaging is increasingly used to study the hemodynamics in various vascular territories and pathologies. The aim of this study was to assess the feasibility and validity of MRI based 4D phase contrast flow imaging for the evaluation of in-stent blood flow in 17 commonly used peripheral stents. Materials and methods: 17 different peripheral stents were implanted into a MR compatible flow phantom. In-stent visibility, maximal velocity and flow visualization were assessed and estimates of in-stent patency obtained from 4D phase contrast flow data sets were compared to a conventional 3D contrast-enhanced magnetic resonance angiography (CE-MRA) as well as 2D PC flow measurements. Results: In all but 3 of the tested stents time-resolved 3D particle traces could be visualized inside the stent lumen. Quality of 4D flow visualization and CE-MRA images depended on stent type and stent orientation relative to the magnetic field. Compared to the visible lumen area determined by 3D CE-MRA, estimates of lumen patency derived from 4D flow measurements were significantly higher and less dependent on stent type. A higher number of stents could be assessed for in-stent patency by 4D phase contrast flow imaging (n = 14) than by 2D phase contrast flow imaging (n = 10). Conclusions: 4D phase contrast flow imaging in peripheral vascular stents is feasible and appears advantageous over conventional 3D contrast-enhanced MR angiography and 2D phase contrast flow imaging. It allows for in-stent flow visualization and flow quantification with varying quality depending on stent type

Refining Students' Explanations of an Unfamiliar Physical Phenomenon-Microscopic Friction

Science.gov (United States)

Corpuz, Edgar De Guzman; Rebello, N. Sanjay

2017-08-01

The first phase of this multiphase study involves modeling of college students' thinking of friction at the microscopic level. Diagnostic interviews were conducted with 11 students with different levels of physics backgrounds. A phenomenographic approach of data analysis was used to generate categories of responses which subsequently were used to generate a model of explanation. Most of the students interviewed consistently used mechanical interactions in explaining microscopic friction. According to these students, friction is due to the interlocking or rubbing of atoms. Our data suggest that students' explanations of microscopic friction are predominantly influenced by their macroscopic experiences. In the second phase of the research, teaching experiment was conducted with 18 college students to investigate how students' explanations of microscopic friction can be refined by a series of model-building activities. Data were analyzed using Redish's two-level transfer framework. Our results show that through sequences of hands-on and minds-on activities, including cognitive dissonance and resolution, it is possible to facilitate the refinement of students' explanations of microscopic friction. The activities seemed to be productive in helping students activate associations that refine their ideas about microscopic friction.

Microscopic Superconductivity and Room Temperature Electronics of High-Tc Cuprates

International Nuclear Information System (INIS)

Liu Fusui; Chen Wanfang

2008-01-01

This paper points out that the Landau criterion for macroscopic superfluidity of He II is only a criterion for microscopic superfluidity of 4 He, extends the Landau criterion to microscopic superconductivity in fermions (electron and hole) system and system with Cooper pairs without long-range phase coherence. This paper gives another three non-superconductive systems that are of microscopic superconductivity. This paper demonstrates that one application of microscopic superconductivity is to establish room temperature electronics of the high-T c cuprates

Experimental and theoretical contributions to X-ray phase-contrast techniques for medical imaging; Contributions experimentales et theoriques aux techniques de contraste de phase pour l'imagerie medicale par rayons X

Energy Technology Data Exchange (ETDEWEB)

Diemoz, P.C.

2011-02-28

Several X-ray phase-contrast techniques have recently been developed. Unlike conventional X-ray methods, which measure the absorption properties of the tissues, these techniques derive contrast also from the modulation of the phase produced by the sample. Since the phase shift can be significant even for small details characterized by weak or absent absorption, the achievable image contrast can be greatly increased, notably for the soft biological tissues. These methods are therefore very promising for applications in the medical domain. The aim of this work is to contribute to a deeper understanding of these techniques, in particular propagation-based imaging (PBI), analyzer-based imaging (ABI) and grating interferometry (GIFM), and to study their potential and the best practical implementation for medical imaging applications. An important part of this work is dedicated to the use of mathematical algorithms for the extraction, from the acquired images, of quantitative sample information (the absorption, refraction and scattering sample properties). In particular, five among the most known algorithms based on the geometrical optics approximation have been theoretically analysed and experimentally compared, in planar and tomographic modalities, by using geometrical phantoms and human bone-cartilage and breast samples. A semi-quantitative method for the acquisition and reconstruction of tomographic images in the ABI and GIFM techniques has also been proposed. The validity conditions are analyzed in detail and the method, enabling a considerable simplification of the imaging procedure, has been experimentally checked on phantoms and human samples. Finally, a theoretical and experimental comparison of the PBI, ABI and GIFM techniques is presented. The advantages and drawbacks of each of these techniques are discussed. The results obtained from this analysis can be very useful for determining the most adapted technique for a given application. (author)

Concomitant use of polarization and positive phase contrast microscopy for the study of microbial cells

Czech Academy of Sciences Publication Activity Database

Žižka, Zdeněk; Gabriel, Jiří

2015-01-01

Roč. 60, č. 6 (2015), s. 545-550 ISSN 0015-5632 Institutional support: RVO:61388971 Keywords : polarization microscopy * microbial cells * positive phase contrast Subject RIV: EE - Microbiology, Virology Impact factor: 1.335, year: 2015

Phase contrast imaging of the breast. Basic principles and steps towards clinical implementation; Phasenkontrastbildgebung der Brust. Grundlagen und Schritte zur klinischen Implementierbarkeit

Energy Technology Data Exchange (ETDEWEB)

Grandl, S.; Sztrokay-Gaul, A.; Auweter, S.D.; Hellerhoff, K. [Klinikum der Ludwig-Maximilians-Universitaet Muenchen, Campus Grosshadern, Institut fuer Klinische Radiologie, Muenchen (Germany)

2014-03-15

Breast cancer is the most common cancer and the leading cause of cancer deaths in women worldwide. Mammography is the only imaging technique approved for nationwide breast cancer screening. Digital full field mammography has improved mammographic image quality. Nevertheless, mammography has a low positive predictive value and a low sensitivity especially in mammographically dense breasts. One of the major limitations is the inherently low contrast between healthy breast parenchyma and breast cancer. Phase contrast imaging is based on the phase shift that occurs when X-rays encounter a change in refractive index between different materials. The improved soft tissue contrast makes the technology particularly promising for breast diagnostics. The studies presented here suggest that phase contrast imaging provides additional diagnostic information both using phase contrast mammography and phase contrast computed tomography (CT). This paper provides an overview of the basic principles of the phase contrast imaging and describes recent developments towards in vivo and ex vivo phase contrast imaging of the breast. (orig.) [German] Brustkrebs ist weltweit die haeufigste Tumorerkrankung und die haeufigste Krebstodesursache der Frau. Die Mammographie ist die einzige zugelassene bildgebende Methode zur Brustkrebsfrueherkennung im Rahmen flaechendeckender Screeningprogramme. Trotz Verbesserung der Bildqualitaet und der Befundungsperformance durch die Einfuehrung der digitalen Vollfeldmammographie sind der positiv-praediktive Wert und die Sensitivitaet der Mammographie insbesondere bei mammographisch dichtem Druesenkoerper eingeschraenkt. Dies ist u. a. auf die geringen Dichteunterschiede zwischen gesundem Brustdruesengewebe und intramammaeren Malignomen zurueckzufuehren. Die Phasenkontrastbildgebung macht sich die Phasenverschiebung von Roentgenstrahlen zunutze, die an Materialgrenzen mit unterschiedlichen Brechungsindizes entsteht. Die Technik bietet einen potenziell

Recent observations with phase-contrast x-ray computed tomography

Science.gov (United States)

Momose, Atsushi; Takeda, Tohoru; Itai, Yuji; Tu, Jinhong; Hirano, Keiichi

1999-09-01

Recent development in phase-contrast X-ray computed tomography using an X-ray interferometer is reported. To observe larger samples than is possible with our previous X-ray interferometer, a large monolithic X-ray interferometer and a separated-type X-ray interferometer were studied. At the present time, 2.5 cm X 1.5 cm interference patterns have been generated with the X-ray interferometers using synchrotron X-rays. The large monolithic X-ray interferometer has produced interference fringes with 80% visibility, and has been used to measure various tissues. To produce images with higher spatial resolution, we fabricated another X-ray interferometer whose wafer was partially thinned by chemical etching. A preliminary test suggested that the spatial resolution has been improved.

Low-dose phase contrast tomography with conventional x-ray sources

Energy Technology Data Exchange (ETDEWEB)

Hagen, C. K., E-mail: charlotte.hagen.10@ucl.ac.uk; Endrizzi, M.; Diemoz, P. C.; Olivo, A. [Department of Medical Physics and Bioengineering, University College London, Malet Place, Gower Street, London WC1E 6BT (United Kingdom); Munro, P. R. T. [Optical + Biomedical Engineering Laboratory, School of Electrical, Electronic and Computer Engineering, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia and Centre for Microscopy, Characterisation, and Analysis, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009 (Australia)

2014-07-15

Purpose: The edge illumination (EI) x-ray phase contrast imaging (XPCi) method has been recently further developed to perform tomographic and, thus, volumetric imaging. In this paper, the first tomographic EI XPCi images acquired with a conventional x-ray source at dose levels below that used for preclinical small animal imaging are presented. Methods: Two test objects, a biological sample and a custom-built phantom, were imaged with a laboratory-based EI XPCi setup in tomography mode. Tomographic maps that show the phase shift and attenuating properties of the object were reconstructed, and analyzed in terms of signal-to-noise ratio and quantitative accuracy. Dose measurements using thermoluminescence devices were performed. Results: The obtained images demonstrate that phase based imaging methods can provide superior results compared to attenuation based modalities for weakly attenuating samples also in 3D. Moreover, and, most importantly, they demonstrate the feasibility of low-dose imaging. In addition, the experimental results can be considered quantitative within the constraints imposed by polychromaticity. Conclusions: The results, together with the method's dose efficiency and compatibility with conventional x-ray sources, indicate that tomographic EI XPCi can become an important tool for the routine imaging of biomedical samples.

Efficient phase contrast imaging in STEM using a pixelated detector. Part 1: Experimental demonstration at atomic resolution

Energy Technology Data Exchange (ETDEWEB)

Pennycook, Timothy J., E-mail: tpennycook@gmail.com [EPSRC SuperSTEM Facility, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Lupini, Andrew R. [Oak Ridge National Laboratory, Materials Science and Technology Division, Oak Ridge, TN 37830 (United States); Yang, Hao [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Murfitt, Matthew F. [Nion Co., 1102 8th St., Kirkland, WA 98033 (United States); Jones, Lewys [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Nellist, Peter D. [EPSRC SuperSTEM Facility, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

2015-04-15

We demonstrate a method to achieve high efficiency phase contrast imaging in aberration corrected scanning transmission electron microscopy (STEM) with a pixelated detector. The pixelated detector is used to record the Ronchigram as a function of probe position which is then analyzed with ptychography. Ptychography has previously been used to provide super-resolution beyond the diffraction limit of the optics, alongside numerically correcting for spherical aberration. Here we rely on a hardware aberration corrector to eliminate aberrations, but use the pixelated detector data set to utilize the largest possible volume of Fourier space to create high efficiency phase contrast images. The use of ptychography to diagnose the effects of chromatic aberration is also demonstrated. Finally, the four dimensional dataset is used to compare different bright field detector configurations from the same scan for a sample of bilayer graphene. Our method of high efficiency ptychography produces the clearest images, while annular bright field produces almost no contrast for an in-focus aberration-corrected probe. - Highlights: • Ptychographic high efficiency phase contrast imaging is demonstrated in STEM. • We rely on a hardware aberration corrector to eliminate aberrations. • High efficiency is achieved by collecting all the relevant interference. • Use of a pixelated detector allows comparison of bright field modes post acquisition. • Ptychography provides the clearest images among the STEM bright field modes tested.

Diagnosis value of dual-phase contrast enhancement CT combined with virtual non-enhanced images by dual-energy CT in clear cell renal cell carcinoma

International Nuclear Information System (INIS)

Ma Zhoupeng; Zhou Jianjun; Liu Xueling; Wang Chun; Zhang Shunzhuang

2012-01-01

Objective: To explore the diagnostic value of dual-phase contrast enhancement CT combined with virtual non-enhanced images by dual-energy CT in clear cell renal cell carcinoma. Methods: Sixty patients who were suspected of clear cell renal cell carcinoma underwent non-enhanced CT and contrast enhancement CT of early interface-phase between cortex -medulla and parenchymal phase on a dual-energy CT. The true non-enhanced kidney CT (TNCT) was performed in a single-energy acquisition mode, but the dual-phase contrast enhancement CT were performed in a dual-energy mode of 80 kV and 140 kV respectively. The virtual non-enhanced CT (VNCT) images were derived from the data of early interface phase using liver virtual non-contrast software. The diagnose according to VNCT combined dual-phase contrast enhancement CT and dual-phase contrast enhancement CT only were made respectively and compared with χ 2 test. Between the true non-contrast CT and the virtual non-contrast CT, the image quality was compared with Wilcoxon test; The radiation dose of volume CT dose index (CTDIvol) and dose length product(DLP) in a single-phase and total examination, the mean CT HU values of the tumours were compared with t test. Results: The accuracy of VNCT combined dual-phase contrast enhancement CT was higher than that of dual-phase contrast enhancement CT only [93.3% (56/60) vs.78.3% (47/60); χ 2 =5.6, P<0.05]. The detective ability (score) of VNCT was near to that of TNCT and the difference was not obvious (Z=0.00, P>0.05). The radiation dose of volume CT dose index (CTDIvol) and dose length product (DLP) in a single phase and total examination of VNCT [(8.85 ± 1.28) mGy, (196.45 ±21.12) mGy·cm, (17.69±2.35) mGy, (392.90±42.25) mGy · cm] were lower than that of TNCT [(10.20 ± 1.44) mGy,(218.29 ± 29.60) mGy · cm, (30.61 ± 3.27) mGy and (654.86 ± 88.81) mGy ·cm], t=4.21, 3.58, 23.63, 16.12 respectively, P<0.05. The mean CT HU values of tumours on VNCT images was higher than that

Noise propagation in x-ray phase-contrast imaging and computed tomography

International Nuclear Information System (INIS)

Nesterets, Yakov I; Gureyev, Timur E

2014-01-01

Three phase-retrieval algorithms, based on the transport-of-intensity equation and on the contrast transfer function for propagation-based imaging, and on the linearized geometrical optics approximation for analyser-based imaging, are investigated. The algorithms are compared in terms of their effect on propagation of noise from projection images to the corresponding phase-retrieved images and further to the computed tomography (CT) images/slices of a monomorphous object reconstructed using filtered backprojection algorithm. The comparison is carried out in terms of an integral noise characteristic, the variance, as well as in terms of a simple figure-of-merit, i.e. signal-to-noise ratio per unit dose. A gain factor is introduced that quantitatively characterizes the effect of phase retrieval on the variance of noise in the reconstructed projection images and in the axial slices of the object. Simple analytical expressions are derived for the gain factor and the signal-to-noise ratio, which indicate that the application of phase-retrieval algorithms can increase these parameters by up to two orders of magnitude compared to raw projection images and conventional CT, thus allowing significant improvement in the image quality and/or reduction of the x-ray dose delivered to the patient. (paper)

Complete staining of human spermatozoa and immature germ cells combined with phase contrast microscopy

DEFF Research Database (Denmark)

Michael, A Y; Drejer, J O; Bagger, P V

1987-01-01

A method combining Janus green B and Thymol blue stains the anterior part of the head, the nuclear membrane, middle piece, and tail of spermatozoa light green and the nucleus deep purple. The method provides excellent stained preparations for the evaluation of sperm morphology by phase contrast...

Direct observation of phase transition of GeSbTe thin films by Atomic Force Microscope

Energy Technology Data Exchange (ETDEWEB)

Yang Fei [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Xu Ling, E-mail: xuling@nju.edu.cn [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Zhang Rui; Geng Lei; Tong Liang; Xu Jun [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Su Weining; Yu Yao [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Ma Zhongyuan; Chen Kunji [National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China)

2012-10-01

Graphical abstract: Nano-sized marks on GST thin film were fabricated using Conductive-AFM (Atomic Force Microscope). The AFM morphology images show that the marks are ablated at the center and a raised ring surrounding it. Highlights: Black-Right-Pointing-Pointer Microstructure of GeSbTe thin films was characterized by XRD and AFM. Black-Right-Pointing-Pointer Annealing and applying electrical field can induce crystallization on thin film. Black-Right-Pointing-Pointer Conductive-AFM was used to modify the surface of GeSbTe thin film. - Abstract: GeSbTe (GST) thin films were deposited on quartz substrates using electron beam evaporation system and then annealed in nitrogen atmosphere at different temperatures, ranging from 20 Degree-Sign C to 300 Degree-Sign C. X-ray diffraction (XRD) and Atomic Force microscope (AFM) measurements were used to characterize the as-deposited and post-annealed thin films. Annealing treatment was found to induce changes on microstructure, surface roughness and grain size, indicating that with the increase of annealing temperature, the amorphous GST films first changed to face-centered-cubic (fcc) phase and then the stable hexagonal (hex) phase. Meanwhile, conductive-AFM (C-AFM) was used to produce crystallized GST dots on thin films. I-V spectroscopy results show that GST films can switch from amorphous state to crystalline state at threshold voltage. After switching, I-V curve exhibits ohmic characteristic, which is usually observed in crystallized GST films. By applying repeated I-V spectroscopies on the thin films, crystallized nuclei were observed. As the times of I-V spectroscopies increases, the area of written dots increases, and the center of the mark begin to ablate. The AFM images show that the shape of marks is an ablated center with a raised ring surrounding it.

A theoretically exact reconstruction algorithm for helical cone-beam differential phase-contrast computed tomography

International Nuclear Information System (INIS)

Li Jing; Sun Yi; Zhu Peiping

2013-01-01

Differential phase-contrast computed tomography (DPC-CT) reconstruction problems are usually solved by using parallel-, fan- or cone-beam algorithms. For rod-shaped objects, the x-ray beams cannot recover all the slices of the sample at the same time. Thus, if a rod-shaped sample is required to be reconstructed by the above algorithms, one should alternately perform translation and rotation on this sample, which leads to lower efficiency. The helical cone-beam CT may significantly improve scanning efficiency for rod-shaped objects over other algorithms. In this paper, we propose a theoretically exact filter-backprojection algorithm for helical cone-beam DPC-CT, which can be applied to reconstruct the refractive index decrement distribution of the samples directly from two-dimensional differential phase-contrast images. Numerical simulations are conducted to verify the proposed algorithm. Our work provides a potential solution for inspecting the rod-shaped samples using DPC-CT, which may be applicable with the evolution of DPC-CT equipments. (paper)

Quantitative phase imaging of arthropods

Science.gov (United States)

Sridharan, Shamira; Katz, Aron; Soto-Adames, Felipe; Popescu, Gabriel

2015-11-01

Classification of arthropods is performed by characterization of fine features such as setae and cuticles. An unstained whole arthropod specimen mounted on a slide can be preserved for many decades, but is difficult to study since current methods require sample manipulation or tedious image processing. Spatial light interference microscopy (SLIM) is a quantitative phase imaging (QPI) technique that is an add-on module to a commercial phase contrast microscope. We use SLIM to image a whole organism springtail Ceratophysella denticulata mounted on a slide. This is the first time, to our knowledge, that an entire organism has been imaged using QPI. We also demonstrate the ability of SLIM to image fine structures in addition to providing quantitative data that cannot be obtained by traditional bright field microscopy.

Dynamic nano-imaging of label-free living cells using electron beam excitation-assisted optical microscope

Science.gov (United States)

Fukuta, Masahiro; Kanamori, Satoshi; Furukawa, Taichi; Nawa, Yasunori; Inami, Wataru; Lin, Sheng; Kawata, Yoshimasa; Terakawa, Susumu

2015-01-01

Optical microscopes are effective tools for cellular function analysis because biological cells can be observed non-destructively and non-invasively in the living state in either water or atmosphere condition. Label-free optical imaging technique such as phase-contrast microscopy has been analysed many cellular functions, and it is essential technology for bioscience field. However, the diffraction limit of light makes it is difficult to image nano-structures in a label-free living cell, for example the endoplasmic reticulum, the Golgi body and the localization of proteins. Here we demonstrate the dynamic imaging of a label-free cell with high spatial resolution by using an electron beam excitation-assisted optical (EXA) microscope. We observed the dynamic movement of the nucleus and nano-scale granules in living cells with better than 100 nm spatial resolution and a signal-to-noise ratio (SNR) around 10. Our results contribute to the development of cellular function analysis and open up new bioscience applications. PMID:26525841

Dynamic nano-imaging of label-free living cells using electron beam excitation-assisted optical microscope.

Science.gov (United States)

Fukuta, Masahiro; Kanamori, Satoshi; Furukawa, Taichi; Nawa, Yasunori; Inami, Wataru; Lin, Sheng; Kawata, Yoshimasa; Terakawa, Susumu

2015-11-03

Optical microscopes are effective tools for cellular function analysis because biological cells can be observed non-destructively and non-invasively in the living state in either water or atmosphere condition. Label-free optical imaging technique such as phase-contrast microscopy has been analysed many cellular functions, and it is essential technology for bioscience field. However, the diffraction limit of light makes it is difficult to image nano-structures in a label-free living cell, for example the endoplasmic reticulum, the Golgi body and the localization of proteins. Here we demonstrate the dynamic imaging of a label-free cell with high spatial resolution by using an electron beam excitation-assisted optical (EXA) microscope. We observed the dynamic movement of the nucleus and nano-scale granules in living cells with better than 100 nm spatial resolution and a signal-to-noise ratio (SNR) around 10. Our results contribute to the development of cellular function analysis and open up new bioscience applications.

Influence of heat treatment in β and γ phases on the microscopic structure of uranium

International Nuclear Information System (INIS)

Robillard, A.

1958-01-01

A new method of microscopic examination of uranium is described. Electrolytic polishing and etching are carried out in an acetic acid-chromic acid bath. Atmospheric or anodic oxidation of the polished surface produces films which follow exactly changes in the structure of the underlying metal. This method is very sensitive to small variations of orientation in polygonized crystals. Using this method of examination of uranium, it was found that annealing U in the γ phase followed by a cooling at a rate dependent of the annealing temperature, causes the formation of substructures different from those due to the polygonization of α-U. The substructures are indicated by the concentration of impurities on the dislocations induced by the stresses accompanying the allotropic transformation γ → β. Similar treatment of the U-1.4% Cr alloy in which the β phase is stabilized at room temperature, confirms this explanation. In addition to the polygonization substructures, sharp discontinuities can be observed in the network of sub- boundaries as a fine white edging. The comparison of these with the structure revealed by thermal etching in vacuum suggest that there are traces of the grain boundaries of the γ phase. The method of etching followed by oxidation shows a haloed phase identified as UH 3 . The conditions of appearance and disappearance of this phase are studied. The sensitivity of this method of detecting the last traces of H in U is very high. The dependence of the hydrogen content on the tensile properties of uranium metal was also studied. (author) [fr

IMIS: An intelligence microscope imaging system

Science.gov (United States)

Caputo, Michael; Hunter, Norwood; Taylor, Gerald

1994-01-01

Until recently microscope users in space relied on traditional microscopy techniques that required manual operation of the microscope and recording of observations in the form of written notes, drawings, or photographs. This method was time consuming and required the return of film and drawings from space for analysis. No real-time data analysis was possible. Advances in digital and video technologies along with recent developments in article intelligence will allow future space microscopists to have a choice of three additional modes of microscopy: remote coaching, remote control, and automation. Remote coaching requires manual operations of the microscope with instructions given by two-way audio/video transmission during critical phases of the experiment. When using the remote mode of microscopy, the Principal Investigator controls the microscope from the ground. The automated mode employs artificial intelligence to control microscope functions and is the only mode that can be operated in the other three modes as well. The purpose of this presentation is to discuss the advantages and disadvantages of the four modes of of microscopy and how the IMIS, a proposed intelligent microscope imaging system, can be used as a model for developing and testing concepts, operating procedures, and equipment design of specifications required to provide a comprehensive microscopy/imaging capability onboard Space Station Freedom.

Preliminary results for X-ray phase contrast micro-tomography on the biomedical imaging beamline at SSRF

International Nuclear Information System (INIS)

Chen Rongchang; Du Guohao; Xie Honglan; Deng Biao; Tong Yajun; Hu Wen; Xue Yanling; Chen Can; Ren Yuqi; Zhou Guangzhao; Wang Yudan; Xiao Tiqiao; Xu Hongjie; Zhu Peiping

2009-01-01

With X-ray phase contrast micro-tomography(CT), one is able to obtain edge-enhanced image of internal structure of the samples. This allows visualization of the fine internal features for biology tissues, which is not able to resolve by conventional absorption CT. After preliminary modulation, monochromatic X-rays (8-72.5 keV) are available for experiments on the experimental station of the biomedical imaging beamline at Shanghai Synchrotron Radiation Facility(SSRF). In this paper, we report the in line phase contrast micro-tomography(IL-XPCT) of biology sample (locust) on the beamline. The reconstruct slice images and three dimensional rendering images of the locust were obtained, with clearly visible images of locus's wing, surface texture and internal tissue distribution. (authors)

Quantitative optical microscopy: measurement of cellular biophysical features with a standard optical microscope.

Science.gov (United States)

Phillips, Kevin G; Baker-Groberg, Sandra M; McCarty, Owen J T

2014-04-07

We describe the use of a standard optical microscope to perform quantitative measurements of mass, volume, and density on cellular specimens through a combination of bright field and differential interference contrast imagery. Two primary approaches are presented: noninterferometric quantitative phase microscopy (NIQPM), to perform measurements of total cell mass and subcellular density distribution, and Hilbert transform differential interference contrast microscopy (HTDIC) to determine volume. NIQPM is based on a simplified model of wave propagation, termed the paraxial approximation, with three underlying assumptions: low numerical aperture (NA) illumination, weak scattering, and weak absorption of light by the specimen. Fortunately, unstained cellular specimens satisfy these assumptions and low NA illumination is easily achieved on commercial microscopes. HTDIC is used to obtain volumetric information from through-focus DIC imagery under high NA illumination conditions. High NA illumination enables enhanced sectioning of the specimen along the optical axis. Hilbert transform processing on the DIC image stacks greatly enhances edge detection algorithms for localization of the specimen borders in three dimensions by separating the gray values of the specimen intensity from those of the background. The primary advantages of NIQPM and HTDIC lay in their technological accessibility using "off-the-shelf" microscopes. There are two basic limitations of these methods: slow z-stack acquisition time on commercial scopes currently abrogates the investigation of phenomena faster than 1 frame/minute, and secondly, diffraction effects restrict the utility of NIQPM and HTDIC to objects from 0.2 up to 10 (NIQPM) and 20 (HTDIC) μm in diameter, respectively. Hence, the specimen and its associated time dynamics of interest must meet certain size and temporal constraints to enable the use of these methods. Excitingly, most fixed cellular specimens are readily investigated with

Phase- and size-adjusted CT cut-off for differentiating neoplastic lesions from normal colon in contrast-enhanced CT colonography

International Nuclear Information System (INIS)

Luboldt, W.; Kroll, M.; Wetter, A.; Vogl, T.J.; Toussaint, T.L.; Hoepffner, N.; Holzer, K.; Kluge, A.

2004-01-01

A computed tomography (CT) cut-off for differentiating neoplastic lesions (polyps/carcinoma) from normal colon in contrast-enhanced CT colonography (CTC) relating to the contrast phase and lesion size is determined. CT values of 64 colonic lesions (27 polyps 0 . The slope m was determined by linear regression in the correlation (lesion ∝[xA + (1 - x)V]//H) and the Y-intercept y 0 by the minimal shift of the line needed to maximize the accuracy of separating the colonic wall from the lesions. The CT value of the lesions correlated best with the intermediate phase: 0.4A+ 0.6V(r=0.8 for polyps ≥10 mm, r=0.6 for carcinomas, r=0.4 for polyps <10 mm). The accuracy in the differentiation between lesions and normal colonic wall increased with the height implemented as divisor, reached 91% and was obtained by the dynamic cut-off described by the formula: cut-off(A,V,H) = 1.1[0.4A + 0.6V]/H + 69.8. The CT value of colonic polyps or carcinomas can be increased extrinsically by scanning in the phase in which 0.4A + 0.6V reaches its maximum. Differentiating lesions from normal colon based on CT values is possible in contrast-enhanced CTC and improves when the cut-off is adjusted (normalized) to the contrast phase and lesion size. (orig.)

Monitoring stem cells in phase contrast imaging

Science.gov (United States)

Lam, K. P.; Dempsey, K. P.; Collins, D. J.; Richardson, J. B.

2016-04-01

Understanding the mechanisms behind the proliferation of Mesenchymal Stem cells (MSCs) can offer a greater insight into the behaviour of these cells throughout their life cycles. Traditional methods of determining the rate of MSC differentiation rely on population based studies over an extended time period. However, such methods can be inadequate as they are unable to track cells as they interact; for example, in autologous cell therapies for osteoarthritis, the development of biological assays that could predict in vivo functional activity and biological action are particularly challenging. Here further research is required to determine non-histochemical biomarkers which provide correlations between cell survival and predictive functional outcome. This paper proposes using a (previously developed) advanced texture-based analysis algorithm to facilitate in vitro cells tracking using time-lapsed microscopy. The technique was adopted to monitor stem cells in the context of unlabelled, phase contrast imaging, with the goal of examining the cell to cell interactions in both monoculture and co-culture systems. The results obtained are analysed using established exploratory procedures developed for time series data and compared with the typical fluorescent-based approach of cell labelling. A review of the progress and the lessons learned are also presented.

Phase-contrast x-ray computed tomography for biological imaging

Science.gov (United States)

Momose, Atsushi; Takeda, Tohoru; Itai, Yuji

1997-10-01

We have shown so far that 3D structures in biological sot tissues such as cancer can be revealed by phase-contrast x- ray computed tomography using an x-ray interferometer. As a next step, we aim at applications of this technique to in vivo observation, including radiographic applications. For this purpose, the size of view field is desired to be more than a few centimeters. Therefore, a larger x-ray interferometer should be used with x-rays of higher energy. We have evaluated the optimal x-ray energy from an aspect of does as a function of sample size. Moreover, desired spatial resolution to an image sensor is discussed as functions of x-ray energy and sample size, basing on a requirement in the analysis of interference fringes.

NMR multiple-echo phase-contrast blood flow imaging

International Nuclear Information System (INIS)

O'Donnell, M.

1986-01-01

A method is described for magnetic resonance imaging of fluid flow in a sample, comprising the steps of: (a) immersing the sample in a static magnetic field disposed in a first direction; (b) applying a first sequence of magnetic field gradients and radio-frequency signals to the sample to both define a slab, of the sample to be imaged, in a plane substantially orthogonal to a selected direction for which flow velocity is to be measured, and to obtain a plurality N of spin-echo response signals form that slab; (c) processing the plurality of first sequence spin-echo signals to obtain a complex value A/sub 1/(X,Y,Z) relating both the spin density rho'(X,Y,Z),... and the phase rotation phi(X,Y,Z), induced by the first sequence, for each of a selected number of sequential locations (X,Y,Z) in the sample slab; (d) applying a second sequence of magnetic field gradient and radio-frequency signals to both define the same sample slab as in step (b) and to obtain another plurality N of spin-echo response signals from that slab; (e) including a waveform in at least one of the magnetic field gradient and radio-frequency signals applied in step (d) for imparting to each of the spin-echo signal components from each slab location having a flowing material therein a phase rotation dependent upon the magnitude of the flow velocity therein in the selected direction; (f) processing the plurality of second sequence spin-echo signals to obtain a complex value A/sub 2/(X,Y,Z) relating the spin density rho'(X,Y,Z) and the imparted phase rotation of the sample material along the selected flow measurement direction for each of the sequential locations (X,Y,Z) in the sample slab; and (g) processing the complex values A/sub 1/(X,Y,Z) and A/sub 2/(X,Y,Z) for each sample location to obtain a differential phase-contrast value related to the velocity of the flowing material therein in the selected measurement direction

Enhancing the performance of the light field microscope using wavefront coding.

Science.gov (United States)

Cohen, Noy; Yang, Samuel; Andalman, Aaron; Broxton, Michael; Grosenick, Logan; Deisseroth, Karl; Horowitz, Mark; Levoy, Marc

2014-10-06

Light field microscopy has been proposed as a new high-speed volumetric computational imaging method that enables reconstruction of 3-D volumes from captured projections of the 4-D light field. Recently, a detailed physical optics model of the light field microscope has been derived, which led to the development of a deconvolution algorithm that reconstructs 3-D volumes with high spatial resolution. However, the spatial resolution of the reconstructions has been shown to be non-uniform across depth, with some z planes showing high resolution and others, particularly at the center of the imaged volume, showing very low resolution. In this paper, we enhance the performance of the light field microscope using wavefront coding techniques. By including phase masks in the optical path of the microscope we are able to address this non-uniform resolution limitation. We have also found that superior control over the performance of the light field microscope can be achieved by using two phase masks rather than one, placed at the objective's back focal plane and at the microscope's native image plane. We present an extended optical model for our wavefront coded light field microscope and develop a performance metric based on Fisher information, which we use to choose adequate phase masks parameters. We validate our approach using both simulated data and experimental resolution measurements of a USAF 1951 resolution target; and demonstrate the utility for biological applications with in vivo volumetric calcium imaging of larval zebrafish brain.

Simulation study of spatial resolution in phase-contrast X-ray imaging with Takagi-Taupin equation

International Nuclear Information System (INIS)

Koyama, Ichiro; Momose, Atsushi

2003-01-01

To evaluate attainable spatial resolution of phase-contrast X-ray imaging using an LLL X-ray interferometer with a thin crystal wafer, a computer simulation study with Takagi-Taupin equation was performed. Modulation transfer function of the wafer for X-ray phase was evaluated. For a polyester film whose thickness is 0.1 mm, it was concluded that the spatial resolution can be improved up to 3 μm by thinning the wafer, under our experimental condition

Molecular evaluation of thrombosis using X-ray phase contrast imaging with microbubbles targeted to P-selectin in mice

International Nuclear Information System (INIS)

Tang, Rongbiao; Chai, Wei-Min; Yan, Fuhua; Chen, Ke-Min; Yang, Guo-Yuan

2016-01-01

X-ray phase contrast imaging (PCI) provides excellent image contrast by utilizing the phase shift. The introduction of microbubbles into tissues can cause a phase shift to make microbubbles visibly identified on PCI. In this study, we assessed the feasibility of targeted microbubble-based PCI for the detection of thrombosis. The absorption and phase contrast images of P-selectin-targeted microbubbles (MB P ) were obtained and compared in vitro. MB P , control IgG-targeted microbubbles (MB C ), and unbound microbubbles (MB U ) were tested for binding specificity on thrombi expressing P-selectin. MB P were used as molecular PCI probes to evaluate P-selectin expression in a mouse model of arteriovenous shunt thrombosis that was created using PE tubes in the bypass outside of the mouse body. PCI clearly showed the microbubbles not viewable via absorption contrast imaging (ACI). In vitro attachment of MB P (91.60 ± 11.63) to thrombi was significantly higher than attachment of MB C (17.80 ± 4.02, P < 0.001) or MB U (9.80 ± 2.59, P < 0.001). In the mouse model of arteriovenous shunt thrombosis, the binding affinity of MB P (15.50 ± 6.25) was significantly greater than that of MB C (0.50 ± 0.84, P < 0.001) or MB U (0.33 ± 0.52, P < 0.001). Our results indicate that molecular PCI may be considered as a novel and promising imaging modality for the investigation of thrombosis. (orig.)

Hard x-ray microimaging techniques based on phase zone plates

International Nuclear Information System (INIS)

Lai, B.; Yun, W.B.; Legnini, D.; Xiao, Y.H.; Chrzas, J.

1992-01-01

Phase zone plates of high focusing efficiency and submicron resolution have been demonstrated in the hard x-ray region. A scanning microscope based on these focusing optics will create many new applications. Preliminary results in the applications of the microscope are reported here. In the area of imaging, we have utilized absorption contrast to clearly identify the locations of Au and Ni constituents in a sample of two interleaved grids. Micro-EXAFS spectra has also been obtained on a Ni foil. Fluorescence from a nuclear fuel sample, as an example of microanalysis, has revealed the elemental distribution at the interfaces. Lastly, microdiffraction from AgBr crystallites has been studied. 5 figs, 7 refs

Laser Light-field Fusion for Wide-field Lensfree On-chip Phase Contrast Microscopy of Nanoparticles

Science.gov (United States)

Kazemzadeh, Farnoud; Wong, Alexander

2016-12-01

Wide-field lensfree on-chip microscopy, which leverages holography principles to capture interferometric light-field encodings without lenses, is an emerging imaging modality with widespread interest given the large field-of-view compared to lens-based techniques. In this study, we introduce the idea of laser light-field fusion for lensfree on-chip phase contrast microscopy for detecting nanoparticles, where interferometric laser light-field encodings acquired using a lensfree, on-chip setup with laser pulsations at different wavelengths are fused to produce marker-free phase contrast images of particles at the nanometer scale. As a proof of concept, we demonstrate, for the first time, a wide-field lensfree on-chip instrument successfully detecting 300 nm particles across a large field-of-view of ~30 mm2 without any specialized or intricate sample preparation, or the use of synthetic aperture- or shift-based techniques.

Myocardial enhancement pattern in patients with acute myocardial infarction on two-phase contrast-enhanced Ecg-gated multidetector-row computed tomography

International Nuclear Information System (INIS)

Ko, S.M.; Seo, J.B.; Hong, M.K.; Do, K.H.; Lee, S.H.; Lee, J.S.; Song, J.W.; Park, S.J.; Park, S.W.; Lim, T.H.

2006-01-01

Aim: To evaluate the myocardial enhancement pattern of the left ventricle on two-phase contrast-enhanced electrocardiogram (ECG)-gated multidetector computed tomography (MDCT) images in patients with acute myocardial infarction (AMI). METHODS: Two-phase contrast-enhanced ECG-gated MDCT examinations were performed in 16 patients with AMI. The presence, location and pattern of myocardial enhancement were evaluated. MDCT findings were compared with the catheter angiographic results. RESULTS: Subendocardial (n=9) or transmural (n=6) area of early perfusion defects of the myocardium was detected in 15 of 16 patients (94%) on early-phase CT images. Variable delayed myocardial enhancement patterns on late-phase CT images were observed in 12 patients (75%): (1) subendocardial residual perfusion defect and subepicardial late enhancement (n=6); (2) transmural late enhancement (n=1); (3) isolated subendocardial late enhancement (n=1); and (4) isolated subendocardial residual perfusion defect (n=2). On catheter angiography, 14 of 15 corresponding coronary arteries showed significant stenosis. CONCLUSION: Variable abnormal myocardial enhancement pattern was seen on two-phase, contrast-enhanced ECG-gated MDCT in patients with AMI. Assessment of myocardial attenuation on CT angiography gives additional information of the location and extent of infarction

The measurement of tiny dew droplets at the initial deposition stage and dew point using a phase-shift interference microscope

Science.gov (United States)

Shigeaki, Matsumoto

2003-12-01

The shape of a dew droplet deposited on the mirror surface of a copper plate was measured accurately using an interference microscope that employed a phase-shift technique. The microscope was constructed by adding a piezoelectric transducer to an interference microscope. A simple method that uses a conventional speaker horn and an optical fibre cable was used to depress any speckle noise. The shape of a dew droplet deposited at dew point on the plate surface with average roughness of 0.1 µm was measured with an accuracy of ± 3 nm. The mass of a tiny dew droplet could be determined from the volume of its shape and was of the order of 10-9 g. The total mass of a dew droplet deposited per unit area and the deposition velocity under a gentle wind were also obtained in a similar way. The total mass was of the order of 10-5 g cm-2 at the beginning of deposition and the deposition velocity ranged from 1 × 10-5 to 6 × 10-5 g cm-2 min-1 at room temperature.

Quantitative measurement of normal and hydrocephalic cerebrospinal fluid flow using phase contrast cine MR imaging

International Nuclear Information System (INIS)

Katayama, Shinji; Asari, Shoji; Ohmoto, Takashi

1993-01-01

Measurements of the cerebrospinal fluid (CSF) flow using phase contrast cine magnetic resonance (MR) imaging were performed on a phantom, 12 normal subjects and 20 patients with normal pressure hydrocephalus (NPH). The phantom study demonstrated the applicability of phase contrast in quantitative measurement of the slow flow. The CSF flows of the normal subjects showed a consistent pattern with a to-and-fro movement of the flow in the anterior subarachnoid space at the C2/3 level, and they were dependent on the cardiac cycle in all subjects. However, the patients with NPH showed variable patterns of the CSF pulsatile flow and these patterns could be divided into four types according to velocity and amplitude. The amplitudes of each type were as follows: type 0 (n=1), 87.6 mm; type I (n=2), 58.2 mm (mean); type II (n=6), 48.0±5.0 mm (mean±SEM); and type III (n=11), 19.9±1.8 mm (mean±SEM). The decrease of the amplitudes correlated to a worsening of the clinical symptoms. After the shunting operation, the amplitude of to-and-fro movement of the CSF increased again in the patients with NPH who improved clinically. Some of the type III cases were reclassified type II, I and 0 and also one of the type II cases changed type I after the shunting operation. We conclude that the phase contrast cine MR imaging is a practically and clinically applicable technique for the quantitative measurement of the CSF flow. (author)

Phase contrast imaging: Effect of increased object-detector distances at X-ray diagnostic and megavoltage energies

Energy Technology Data Exchange (ETDEWEB)

Loveland, J.; Gundogdu, O. [Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Morton, E. [Rapiscan Systems, Units 2,3,4, Radnor Park Trading Estate, Congleton, Cheshire CW12 4XJ (United Kingdom); Wells, K. [CVSSP, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Bradley, D.A., E-mail: d.a.bradley@surrey.ac.uk [Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

2011-10-01

The effect of varying object to detector separation at constant and varying magnification has been investigated at an accelerating potential of 30 kVp. Edge-contrast enhancement provided by phase effects was investigated for a drinking straw and found to provide up to 2.52{+-}0.02x the contrast for a PVC Heaviside step function. An optimum magnification of 1.5x was found to apply for the microfocus X-ray tube setup used. Imaging at nominal megavoltage energies was investigated using a Rapiscan Systems Eagle M4500 series scanner. For a fixed source-detector separation, increased magnification improved edge contrast and spatial resolution.

Phase contrast imaging: Effect of increased object-detector distances at X-ray diagnostic and megavoltage energies

International Nuclear Information System (INIS)

Loveland, J.; Gundogdu, O.; Morton, E.; Wells, K.; Bradley, D.A.

2011-01-01

The effect of varying object to detector separation at constant and varying magnification has been investigated at an accelerating potential of 30 kVp. Edge-contrast enhancement provided by phase effects was investigated for a drinking straw and found to provide up to 2.52±0.02x the contrast for a PVC Heaviside step function. An optimum magnification of 1.5x was found to apply for the microfocus X-ray tube setup used. Imaging at nominal megavoltage energies was investigated using a Rapiscan Systems Eagle M4500 series scanner. For a fixed source-detector separation, increased magnification improved edge contrast and spatial resolution.

Augmented Quadruple-Phase Contrast Media Administration and Triphasic Scan Protocol Increases Image Quality at Reduced Radiation Dose During Computed Tomography Urography.

Science.gov (United States)

Saade, Charbel; Mohamad, May; Kerek, Racha; Hamieh, Nadine; Alsheikh Deeb, Ibrahim; El-Achkar, Bassam; Tamim, Hani; Abdul Razzak, Farah; Haddad, Maurice; Abi-Ghanem, Alain S; El-Merhi, Fadi

The aim of this article was to investigate the opacification of the renal vasculature and the urogenital system during computed tomography urography by using a quadruple-phase contrast media in a triphasic scan protocol. A total of 200 patients with possible urinary tract abnormalities were equally divided between 2 protocols. Protocol A used the conventional single bolus and quadruple-phase scan protocol (pre, arterial, venous, and delayed), retrospectively. Protocol B included a quadruple-phase contrast media injection with a triphasic scan protocol (pre, arterial and combined venous, and delayed), prospectively. Each protocol used 100 mL contrast and saline at a flow rate of 4.5 mL. Attenuation profiles and contrast-to-noise ratio of the renal arteries, veins, and urogenital tract were measured. Effective radiation dose calculation, data analysis by independent sample t test, receiver operating characteristic, and visual grading characteristic analyses were performed. In arterial circulation, only the inferior interlobular arteries in both protocols showed a statistical significance (P contrast-to-noise ratio than protocol A (protocol B: 22.68 ± 13.72; protocol A: 14.75 ± 5.76; P contrast media and triphasic scan protocol usage increases the image quality at a reduced radiation dose.

Operation of a separated-type x-ray interferometer for phase-contrast x-ray imaging

Science.gov (United States)

Yoneyama, Akio; Momose, Atsushi; Seya, Eiichi; Hirano, Keiichi; Takeda, Tohoru; Itai, Yuji

1999-12-01

Aiming at large-area phase-contrast x-ray imaging, a separated-type x-ray interferometer system was designed and developed to produce 25×20 mm interference patterns. The skew-symmetric optical system was adopted because of the feasibility of alignment. The rotation between the separated crystal blocks was controlled within a drift of 0.06 nrad using a feedback positioning system. This interferometer generated a 25×15 mm interference pattern with 0.07 nm synchrotron x-rays. A slice of a rabbit's kidney was observed, and its tubular structure could be revealed in a measured phase map.

X-ray phase-contrast tomography of renal ischemia-reperfusion damage.

Directory of Open Access Journals (Sweden)

Astrid Velroyen

Full Text Available The aim of the study was to investigate microstructural changes occurring in unilateral renal ischemia-reperfusion injury in a murine animal model using synchrotron radiation.The effects of renal ischemia-reperfusion were investigated in a murine animal model of unilateral ischemia. Kidney samples were harvested on day 18. Grating-Based Phase-Contrast Imaging (GB-PCI of the paraffin-embedded kidney samples was performed at a Synchrotron Radiation Facility (beam energy of 19 keV. To obtain phase information, a two-grating Talbot interferometer was used applying the phase stepping technique. The imaging system provided an effective pixel size of 7.5 µm. The resulting attenuation and differential phase projections were tomographically reconstructed using filtered back-projection. Semi-automated segmentation and volumetry and correlation to histopathology were performed.GB-PCI provided good discrimination of the cortex, outer and inner medulla in non-ischemic control kidneys. Post-ischemic kidneys showed a reduced compartmental differentiation, particularly of the outer stripe of the outer medulla, which could not be differentiated from the inner stripe. Compared to the contralateral kidney, after ischemia a volume loss was detected, while the inner medulla mainly retained its volume (ratio 0.94. Post-ischemic kidneys exhibited severe tissue damage as evidenced by tubular atrophy and dilatation, moderate inflammatory infiltration, loss of brush borders and tubular protein cylinders.In conclusion GB-PCI with synchrotron radiation allows for non-destructive microstructural assessment of parenchymal kidney disease and vessel architecture. If translation to lab-based approaches generates sufficient density resolution, and with a time-optimized image analysis protocol, GB-PCI may ultimately serve as a non-invasive, non-enhanced alternative for imaging of pathological changes of the kidney.

Phase-and-amplitude recovery from a single phase-contrast image using partially spatially coherent x-ray radiation

Science.gov (United States)

Beltran, Mario A.; Paganin, David M.; Pelliccia, Daniele

2018-05-01

A simple method of phase-and-amplitude extraction is derived that corrects for image blurring induced by partially spatially coherent incident illumination using only a single intensity image as input. The method is based on Fresnel diffraction theory for the case of high Fresnel number, merged with the space-frequency description formalism used to quantify partially coherent fields and assumes the object under study is composed of a single-material. A priori knowledge of the object’s complex refractive index and information obtained by characterizing the spatial coherence of the source is required. The algorithm was applied to propagation-based phase-contrast data measured with a laboratory-based micro-focus x-ray source. The blurring due to the finite spatial extent of the source is embedded within the algorithm as a simple correction term to the so-called Paganin algorithm and is also numerically stable in the presence of noise.

Near-field optical microscopy with a scanning tunneling microscope

International Nuclear Information System (INIS)