Particle Imaging Technique Research Articles

Construction of 3D-rendering imaging of an ischemic rat brain model using the planar FMMD technique

Occlusion of the major cerebral artery usually results in brain hypoxic-ischemic injury, which evokes neuroinflammation and microglial activation. Activated microglia are considered a source of multiple neurotoxic factors, such as reactive oxygen species (ROS), in the central nervous system (CNS). We herein present a 3D-rendering brain imaging technique in an experimental rodent model of cerebral ischemia based on 2D magnetic images of superparamagnetic iron oxide nanoparticles (SPIONs) using the planar frequency mixing magnetic detection (p-FMMD) technique. A rat model of cerebral ischemia was established by unilateral middle cerebral artery occlusion with reperfusion (MCAO/R) injury. 2,3,5-Triphenyltetrazolium chloride (TTC) staining was performed to demonstrate the irreversibly damaged ischemic brain tissues, and double immunofluorescent labeling of OX6 (activated microglial marker) and ethidium (ROS marker) was conducted to confirm ROS generation in the activated microglia in the infarcted brain region. The ischemic brain sections treated with OX6-conjugated SPIONs were scanned using our p-FMMD system, yielding 2D images on the basis of the nonlinear magnetic characteristics inherent in SPIONs. The p-FMMD signal images representing microglia activation show an infarct ratio of 44.6 ± 7.1% compared to the contralateral counterpart, which is smaller than observed by TTC (60.9 ± 4.9%) or magnetic resonance imaging (MRI, 65.7 ± 2.7%). Furthermore, we developed a 3D-rendering brain imaging process based on the 2D p-FMMD signal images. The 3D reconstructed model showed a decreased ratio of coincidence of the ischemic regions compared with MRI models. In this study, we successfully conducted a feasibility test on whether our p-FMMD technology, a technique for signaling and imaging based on the nonlinearity of SPIONs, can be used to visualize the ischemic brain region in real time by detecting activated microglia in an MCAO/R animal model. Therefore, our method might allow for a different approach to analyze the pathophysiology of ischemic stroke through molecular imaging. Furthermore, we propose that this magnetic particle imaging (MPI) technique that detects the nonlinear magnetization properties of SPIONs could be applied not only to a stroke model but also to various types of pathophysiological studies as a new bioimaging tool.

Dual-beam interferometric particle imaging for size and shape characterization of irregular coal micro-particle: Validation with digital inline holography

The size and shape characterization of irregular particles is of great significance in the comprehensive understanding of many natural and industrial processes. The dual-beam interferometric particle imaging (DIPI) technique is adapted from a dual-beam backward illumination configuration of interferometric particle imaging to access the size and 2D shape of an irregular particle from its interferogram. An experimental setup combining the digital inline holography (DIH) and DIPI techniques characterizes the same projection of the same particle with a color camera, permitting the accuracy evaluation and validation between these two techniques. The comparison results show a good agreement between the 2D-Fourier transform of DIPI interferogram and the 2D-autocorrelation of DIH reconstructed in-focus image. The DIH gives the reference result for the size measurement of the particles, and we observe a maximum difference as low as 9% with the DIPI measurement. The backward arrangement of the dual-beam interferometric particle imaging technique facilitates its further instrumental development and application to a variety of real circumstances, e.g., solid fuel particles and ice crystals.

Dual-beam interferometric particle imaging for size measurement of opaque metal droplet

Size measurement of micron-sized metal droplet is of great demand in industrial applications, e.g., 3D printing and metal propellant. A dual-beam interferometric particle imaging (DIPI) technique is developed to measure the size of opaque metal droplet, which is adapted from the traditional interferometric particle imaging (IPI) for transparent particles. In DIPI, the studied metal droplet is illuminated by two laser beams from different views, and the laser beams are reflected on the surface of the droplet. An interference pattern of the two reflections is yielded in the far-field that was capable to derive the size of aim droplet. The principle of DIPI is formulated in the framework of physical optics, with system configuration, modeling and data processing algorithm presented. A DIPI system is established to characterize the gallium droplet with size ranging from 300 μm to 500 μm experimentally, and the measured sizes with DIPI is compared with those obtained simultaneously by digital inline holography, which is a standard tool for particle measurement. Comparison shows that the measurements with these two methods are highly consistent, with a standard deviation of 1.7%. DIPI has been demonstrated with high measurement accuracy and flexible implementation of the one-sided arrangement.

Droplet Sizing in the Spray of a Fuel Injector Using Wavelet Analysis

The paper discusses the applied methods for studying the structure of the two-phase flow. Measurements of the size of liquid droplets in a spray of fuel injector were carried out using two methods: Interferometric Particle Imaging (IPI) and Glare Point Technique (GPT). The combined use of these methods allows to significantly expand the range of measured droplet sizes, and also provides an opportunity for cross-validation of methods and determining the level of errors. In this paper, we tested the IPI method using wavelet processing of interference drop images. As a result, it was shown that IPI images can have a highly inhomogeneous structure. This leads to a considerable variation in the period of the IPI-image and, as a consequence, to an increase of the error in determining the drop size. The proposed error estimation algorithm allows one to introduce an additional selection criterion and obtain statistically comparable results obtained by the IPI and GPT methods.

Corrected equations for the determination of a particle position using the interferometric particle imaging technique.

A new interferometric particle imaging (IPI) simulator is developed based on Fourier optics. With this model, the optical field distribution of any kind of IPI setup at any location, such as on the focused and the defocused image planes, can be easily generated. In addition, the geometric center of a particle image and the image of the particle center on focused and defocused image planes can then be assessed in detail with the IPI simulator by the optical ray tracing method. The size effect of the defocused image is investigated, and the new expression of the calculated defocused image size is given, which can produce higher accuracy in particle locating.

Integrated model of BP neural network and CNN algorithm for automatic wear debris classification

Mechanism-based wear debris classification (WDC) is important for root cause analysis and prediction of wear related faults. Compared to manual classifications, automatic WDC is more efficient and often more reliable for a wide range of industrial applications. However, existing methods unavoidably encounter some difficulties when dealing with those wear particles with highly geometric similarity, especially for fatigue particles and severe sliding particles. To meet the requirement for automatic WDC, an integrated, automated method for identifying typical wear debris is proposed with a two-level classification procedure. By referring to the traditional ferrography – a widely used wear particle imaging and analysis technique, the first-level classification is performed by a general back-propagation (BP) neural network with selected particle's morphological features. By doing this, three types of wear particles including rubbing, cutting, and spherical particles can be determined. In the second-level classification, a deep learning model of a 6-layer convolution neural network (CNN) is adopted to identify fatigue particles and severe sliding particles by analyzing their very slight surface details in pixel-level. The method is tested with over 100 images of real particles generated from an extruder machine in a petrochemical plant and identified by a ferrograph specialist. A high recognition rate of over 80% is achieved for the three types including rubbing, cutting, and spherical particles with the first procedure. Further, the identification rates are 85.7% and 80% for fatigue particles and severe sliding particles, respectively, which is distinctly improved from the reported values (they are 45.5% and 36.4%, respectively) of other intelligent methods.

Wide-range and accurate particle sizing using extended interferometric particle imaging technique.

Accurate measurement of particles of a wide size range is generally difficult in interferometric particle imaging (IPI). We propose an extended IPI technique with double or multiple imaging systems of different scattering angles and polarizations to achieve a wider measurable size range. The effects of particle size, scattering angle, polarization, and the comprehensive parameters of the imaging system on fringe patterns are thoroughly discussed. In the case of measuring water droplets, the measurable size range of the extended IPI enlarges to 10 μm-1 mm, with high-quality fringe patterns favoring the accuracy of measurement. The relative deviations of extracted diameters are no greater than 9%, demonstrating good accuracy of the particle sizing using the extended IPI technique.

Exploring and Monitoring of Methane Hydrate Deposits

Relatively, recently, in the last 20 years, it was discovered that methane hydrate (MH) deposits are globally distributed in the permafrost and oceans. Before 1960s, when first deposits were discovered in Siberian permafrost, former USSR, it was believed that MH can occur only in laboratory conditions or in vast parts of the Universe. Presently, it is presumed that this solid crystalline compounds in which CH4 molecules occupies the water ice lattices (nominal chemical formula of MH is C4H62O23) can serve as an energy source favorably to the all of the world remaining conventional hydrocarbon sources. Moreover, MH deposits can become vulnerable to climate changes, which were already occurring in geological past with tremendous consequences for the global life on earth. Thus, further development of advanced techniques is needed to enhance our abilities to better characterize, quantify, and monitor MH deposits. In this paper presented, 14-MeV neutrons with associated alpha particle imaging technique were used to quantify the amount of MH in the sample.

Influence of the time interval on image-based measurement of bed-load transport

ABSTRACTThe influence of the time interval (Δt) between two successive images on measurement of bed-load dynamics has been investigated both analytically and experimentally. The analytical approach is based on simplifying bed-load motion to follow a “flight-rest” pattern. The experimental work involves measuring bed-load transport in a closed channel with a particle imaging technique. The two approaches are consistent in revealing the influence of Δt on measurement results. It is shown that an increase in Δt leads to reduction in measured particle velocity and increase in the measured number of moving particles as well as the flight time. The measured flight length and bed-load transport rate are not directly affected by Δt. The influence of Δt needs to be fully addressed in image-based measurement of bed-load transport.

Modeling and Simulation Study for Solid Particles Detection in Gas–Oil Pipelines Using Field Free Line in Magnetic Particle Imaging and Its Hardware Realization

This paper suggests a new magnetic particle imaging (MPI) technique for 2-D tomographic imaging to detect the presence of flowing solid particles (i.e., black powder, which consist of paramagnetic nanoparticles) passing through gas-oil pipelines. The hardware consists of a ring of a modified Halbach array of 24 permanent magnets, in addition to two surrounding Helmholtz coil pairs, and a receiving coil, which are evenly distributed across a cross section of the probe. With the application of static and dynamically moving drive fields, the MPI utilizes the full benefit of superparamagnetic iron oxide nanoparticles (SPIONs) by providing a linear response when they are exposed to a relatively low magnetic field and no response when they are saturated. The scanning of region of interest with the field-free line (FFL) instead of the field-free point (FFP) is motivated by the fact that a high-intensity dc current is required for FFP, which is not tolerated in oil-gas pipelines where the maximal current should not exceed few amperes. With the presence of an oscillatory magnetic field, SPIONs react with a nonlinear magnetization response, which is further measured by the receiving coil. A 2-D image reconstruction is then performed using the frequency-based image reconstruction process. The hardware design, specifically the sizing of permanent magnets with regard to their relative position and dimensions, was refined following an optimization technique based on the particle swarm optimization technique. The assessment of the system using finite-element method indicates that the system can reconstruct the 2-D profile of the SPION with a mean absolute error of prediction of less than 4% and 12% using FFL and FFP methods, respectively.

Instant snapshot of the internal structure of Unzen lava dome, Japan with airborne muography.

An emerging elementary particle imaging technique called muography has increasingly been used to resolve the internal structures of volcanoes with a spatial resolution of less than 100 m. However, land-based muography requires several days at least to acquire satisfactory image contrast and thus, it has not been a practical tool to diagnose the erupting volcano in a real time manner. To address this issue, airborne muography was implemented for the first time, targeting Heisei-Shinzan lava dome of Unzen volcano, Japan. Obtained in 2.5 hours, the resultant image clearly showed the density contrast inside the dome, which is essential information to predict the magnitude of the dome collapse. Since airborne muography is not restricted by topographic conditions for apparatus placements, we anticipate that the technique is applicable to creating images of this type of lava dome evolution from various angles in real time.

On the Electrolyte Convection around a Hydrogen Bubble Evolving at a Microelectrode under the Influence of a Magnetic Field

Water electrolysis was carried out in a 1 M H2SO4 solution under different potentiostatic conditions in the presence of a magnetic field oriented normal to the horizontal microelectrode (100 μm in diameter). The imposed magnetohydrodynamic (MHD) electrolyte flow around the evolving hydrogen bubble was studied to clarify the effect on the detachment of the bubble from the electrode and the mass transfer toward the electrode. Different particle imaging and tracking techniques were applied to measure the three-dimensional flow in the bulk of the cell as well as in close vicinity of the evolving bubble. The periodic bubble growth cycle was analyzed by measurements of the current oscillations and microscopic high-speed imaging. In addition, a numerical study of the flow was conducted to support the experimental results. The results demonstrate that the MHD flow imposes only a small stabilizing force on the bubble. However, the observed secondary flow enhances the mass transfer toward the electrode and may reduce the local supersaturation of dissolved hydrogen.

Plasma membrane dynamics and tetrameric organisation of ABCG2 transporters in mammalian cells revealed by single particle imaging techniques

ABCG2 is one of three human ATP binding cassette (ABC) transporters involved in the export from cells of a chemically and structurally diverse range of compounds. This multidrug efflux capability, together with a broad tissue distribution in the body, means that ABCG2 exerts a range of effects on normal physiology such as kidney urate transport, as well as contributing towards the pharmacokinetic profiles of many exogenous drugs. The primary sequence of ABCG2 contains only half the number of domains required for a functioning ABC transporter and so it must oligomerise in order to function, yet its oligomeric state in intact cell membranes remains uncharacterized. We have analysed ABCG2 in living cell membranes using a combination of fluorescence correlation spectroscopy, photon counting histogram analysis, and stepwise photobleaching to demonstrate a predominantly tetrameric structure for ABCG2 in the presence or absence of transport substrates. These results provide the essential basis for exploring pharmacological manipulation of oligomeric state as a strategy to modulate ABCG2 activity in future selective therapeutics.

Harmonic phases of the nanoparticle magnetization: An intrinsic temperature probe

Magnetic fluid hyperthermia is a promising cancer therapy in which magnetic nanoparticles act as heat sources activated by an external AC magnetic field. The nanoparticles, located near or inside the tumor, absorb energy from the magnetic field and then heat up the cancerous tissues. During the hyperthermia treatment, it is crucial to control the temperature of different tissues: too high temperature can cause undesired damage in healthy tissues through an uncontrolled necrosis. However, the current thermometry in magnetic hyperthermia presents some important technical problems. The widely used optical fiber thermometers only provide the temperature in a discrete set of spatial points. Moreover, surgery is required to locate these probes in the correct place. In this scope, we propose here a method to measure the temperature of a magnetic sample. The approach relies on the intrinsic properties of the magnetic nanoparticles because it is based on monitoring the thermal dependence of the high order harmonic phases of the nanoparticle dynamic magnetization. The method is non-invasive and it does not need any additional probe or sensor attached to the magnetic nanoparticles. Moreover, this method has the potential to be used together with the magnetic particle imaging technique to map the spatial distribution of the temperature.

Evaluation of an in-line particle imaging tool for monitoring twin-screw granulation performance

Twin-screw granulation is an emerging continuous wet granulation technique in the pharmaceutical industry due to several advantages over batch granulation. However, for the implementation of a fully continuous line in an industrial environment, in-process measurement tools are required to monitor critical process parameters and (intermediate) product quality attributes, and trigger control actions based on such measurements. This study aimed at evaluating the feasibility of implementing an in-line particle imaging technique (Eyecon™) after continuous twin-screw granulation and before the drying system. Off-line sieving was used as reference particle size analysis method. A twin-screw granulator which is part of the Consigma system was used to granulate a placebo formulation composed of lactose and polyvinylpyrrolidone (PVP; 97.5:2.5% w/w). PVP was dissolved in water, which was used as granulation liquid at liquid-to-solid ratios ranging between 8 and 9%. The performance of the in-line measurement method at heterogeneous process conditions was tested by changing the liquid to solid ratio (8–9%), the material throughput (10–25kg/h) and the screw configuration (1×6 and 2×6 kneading discs). The volumetric size distribution obtained from the in-line measurements of the granules leaving the twin-screw granulator using the Eyecon™ camera was compared with the off-line measurements obtained by sieving of the granule samples collected before and after the drying unit operation. For the intermediate size range (diameter 250–1000μm), the Eyecon™ measurements showed to be promising as they were in agreement with off-line measurement results obtained before the drying unit. However, the image analysis algorithm and data post-processing of the Eyecon™ images for the fines and oversized ranges require modification for improvement in measurement results. In conclusion, the Eyecon™ provides very good in-line images despite a dense moving flow of granules. However, proper analysis of these images is crucial before application as standard in-line particle size monitoring tool and application for control purposes can be realized.

The correlation of single-particle diffraction patterns as a continuous function of particle orientation.

A statistical model for X-ray scattering of a non-periodic sample to high angles is introduced. It is used to calculate analytically the correlation of distinct diffraction measurements of a particle as a continuous function of particle orientation. Diffraction measurements with shot-noise are also considered. This theory provides a general framework for a deeper understanding of single particle imaging techniques used at X-ray free-electron lasers. Many of these techniques use correlations as a measure of diffraction-pattern similarity in order to determine properties of the sample, such as particle orientation.

Detecting chirality in molecules by imaging photoelectron circular dichroism

In this Perspective we discuss photoelectron circular dichroism (PECD), a relatively novel technique that can detect chiral molecules with high sensitivity. PECD has an enantiomeric sensitivity of typically 1-10%, which is two to three orders of magnitude larger than that of the widely employed technique of circular dichroism (CD). In PECD a chiral molecule is photoionized with circular polarized light, and the photoelectron angular scattering distribution is detected using particle imaging techniques. We present the general physical principles of photoelectron circular dichroism and we address both single- and multiphoton excitation. PECD has been measured with synchrotron radiation in single-photon ionization as well as, very recently, with femtosecond laser radiation in multiphoton ionization. We discuss the experimental implementation of PECD, focusing on velocity map coincidence imaging where the momentum distribution of both the electron and the coincident ion is measured. The coincident detection of the mass and momentum of the ion adds very powerful mass-correlated information to the PECD measurement of the chiral molecule. We illustrate the capabilities and the potential of PECD with various experimental examples and introduce computational methods that are able to model quantitatively experimental PECD results. We conclude with an outlook on novel developments and (analytical) implementations of PECD that may further broaden the application of PECD for the sensitive detection of chirality in molecules.

Particle characterization system for industrial and naval applications

Abstract The Interferometric Particle Imaging (IPI) technique was modified and adapted to provide particle size and particle concentration measurements in harsh environments. The development was forced by the challenge of nuclei concentration measurement in cavitation tunnels and full scale measurements in the wake flow of a vessel. Because only bubbles act as cavitation nuclei, discrimination between bubbles and other solid particles in the multi-phase flow is necessary. The size measurement and classification and can be realized by defocussed imaging and analysis of the scattered light from particles. A few measurement results demonstrate the feasibility of the new developed Nuclei Concentration Measurement (HDNC) technique and there advantages in terms of robustness, moderate hardware effort and reduced measurement time.

Simulations of Multi-Gamma Coincidences From Neutron-Induced Fission in Special Nuclear Materials

A study is presented on the detection of illicit special nuclear materials (SNM) in cargo containers using a conceptual neutron-based inspection system with xenon-doped liquefied argon (LAr(Xe)) scintillation detectors for coincidence gamma-ray detection. For robustness, the system is envisioned to exploit all fission signatures, namely both prompt and delayed neutron and gamma emissions from fission reactions induced in SNM. However, this paper focuses exclusively on the analysis of the prompt gamma ray emissions. The inspection system probes a container using neutrons produced either by (d, D) or (d, T) in pulsed form or from an associated particle neutron generator to exploit the associated particle imaging (API) technique, thereby achieving background reduction and imaging. Simulated signal and background estimates were obtained in MCNPX (2.7) for a 2 kg sphere of enriched uranium positioned at the center of a 1m × 1m × 1m container, which is filled uniformly with wood or iron cargos at 0.1 g/cc or 0.4 g/cc. Detection time estimates are reported assuming probabilities of detection of 95% and false alarm of 0.5%.

Timing Resolution Study of an Associated Particle Detector for Fast Neutron Imaging

D-T neutron generators have been used as an active interrogation source for associated particle imaging techniques. The D-T reaction yields a 14-MeV neutron and an alpha particle. The kinetics of the reaction allow the directionality and timing of the neutron to be determined utilizing position sensitive detectors for both the alpha and neutron. This information may be used for imaging applications. Since position and timing are required to form images, improved certainty in directional and timing will result in improved imaging performance. This requires maximum light transmission from its origin in the scintillator to conversion at the photosensor. This work is a study of the timing resolution of a first generation associated particle detector. An optical transport code, coupled with a timing model is also used to simulate the timing resolution. Good agreement is shown. Fundamental limits are presented with the aid of simulation and measurements. Based on these results, implications on the next-generation design are discussed.