Direct Imaging Method Research Articles

Volumetric imaging of myelin in vivo using 3D inversion recovery-prepared ultrashort echo time cones magnetic resonance imaging.

Direct myelin imaging is promising for characterization of multiple sclerosis (MS) brains at diagnosis and in response to therapy. In this study, a 3D inversion recovery-prepared ultrashort echo time cones (IR-UTE-Cones) sequence was used for both morphological and quantitative imaging of myelin on a clinical 3 T scanner. Myelin powder phantoms with different myelin concentrations were imaged with the 3D UTE-Cones sequence and it showed a strong correlation between concentrations and UTE-Cones signals, demonstrating the ability of the UTE-Cones sequence to directly image myelin in the brain. Quantitative myelin imaging with multi-echo IR-UTE-Cones sequences show similar T2 * values for a D2 O-exchanged myelin phantom (T2 * = 0.33 ± 0.04 ms), ex vivo brain specimens (T2 * = 0.20 ± 0.04 ms) and in vivo healthy volunteers (T2 * = 0.254 ± 0.023 ms), further confirming the feasibility of 3D IR-UTE-Cones sequences for direct myelin imaging in vivo. In ex vivo MS brain study, signal loss is observed in MS lesions, which was confirmed with histology. For the in vivo study, the lesions in MS patients also show myelin signal loss using the proposed direct myelin imaging method, demonstrating the clinical potential for MS diagnosis. Furthermore, the measured IR-UTE-Cones signal intensities show a significant difference between normal-appearing white matter in MS patients and normal white matter in volunteers, which cannot be found in clinical used T2 -FLAIR sequences. Thus, the proposed 3D IR-UTE-Cones sequence showed clinical potential for MS diagnosis with the capability of direct myelin detection of the whole brain.

Direct imaging method of frequency response of capacitance in dual bias modulation electrostatic force microscopy

We have proposed and demonstrated a direct imaging method in dual bias modulation electrostatic force microscopy (DI-DEFM) to observe the frequency response of the capacitance between a conductive tip and a sample in a single scan. In DI-DEFM, dual ac biases with different frequencies are simultaneously applied between the tip and the sample to generate an electrostatic force; the frequencies are switched between two pairs of frequency conditions, with a switching frequency . Then, the component in the electrostatic force is detected, similar to a heterodyne method, to analyze the frequency response of the capacitance. The validity of DI-DEFM is assessed through the image acquisition on a Cu(In,Ga)Se2 sample.

Direct hyperspectral dual-comb imaging

Even though dual-comb-based systems are employed almost routinely nowadays in an ever-increasing number of applications, an efficient combination of this effective technique with an imaging arrangement, which would undoubtedly revolutionize hyperspectral imaging, had not yet been demonstrated. Here we present, to our knowledge, the first hyperspectral dual-comb imaging system in which interferograms are directly detected by a video camera. The system, based on a dual-comb scheme capable of consistently generating interferograms at a rate of 1 Hz and below, combines fast hyperspectral imaging with unprecedented optical resolution and fully multiplex operation. Various proof-of-principle experiments demonstrating hyperspectral imaging of molecular resonances have proved that the direct hyperspectral dual-comb imaging method presented here is capable of characterizing a scene with super-fine resolution in a narrow optical span within 1 s.

Imaging of singlet oxygen feedback delayed fluorescence and lysosome permeabilization in tumor in vivo during photodynamic therapy with aluminum phthalocyanine.

.Significance: Singlet oxygen is a key cytotoxic agent in photodynamic therapy (PDT). As such, its imaging is highly desirable, but existing direct imaging methods are still limited by the exceptionally low yield of the luminescence signal. Singlet oxygen feedback delayed fluorescence (SOFDF) of the photosensitizer is a higher yield alternative for indirect measurement of this signal.Aim: The aim was to explore feasibility of SOFDF imaging in vivo in tumor-bearing mice during PDT and investigate how SOFDF images can be transformed into images of singlet oxygen. In addition, we study whether lysosome permeabilization can be visualized through fluorescence lifetime.Approach: Mice were intravenously injected with 2.5 mg/kg of photosensitizer aluminum(III) phthalocyanine tetrasulfonate () 20 h prior to experiments, having subcutaneous BxPC3 pancreas tumors. Time-resolved delayed fluorescence and prompt fluorescence (PF) were imaged using an intensified time-gated camera with 10-Hz pulsed laser excitation at 690 nm.Results: Delayed emission from was detected with lifetimes 7 to , which was attributed to SOFDF and shown to be oxygen-dependent. Singlet oxygen images were approximated by the ratio of SOFDF/PF at each pixel. SOFDF images of a good quality could be captured within several seconds with a radiant exposure of . In addition, lifetime images of PF in ns-time domain enabled us to visualize the event of lysosome permeabilization, as the lifetime increased from to 5.2 ns.Conclusions: Imaging of SOFDF in vivo in mouse tumor during PDT with is feasible, and it is a promising method for singlet molecular oxygen monitoring. Moreover, the time-gated approach also enables visualization of the lysosome permeabilization that alters the PF lifetime.

Recovering Unbounded Rough Surfaces with a Direct Imaging Method

In this paper, we consider the inverse acoustic scattering problem by an unbounded rough surface. A direct imaging method is proposed to reconstruct the rough surfaces from scattered-field data for incident plane waves and the performance analysis is also presented. The reconstruction method is very robust to noises of measured data and does’t need to know the type of the boundary conditions of the surfaces in advance. Finally, numerical examples are carried out to illustrate that our method is fast, accurate and stable even for the case of multiple-scale profiles.

In vivo and in situ real-time fluorescence imaging of peripheral nerves in the NIR-II window

The peripheral nervous system (PNS) is essential for performing and maintaining various motor and sensory functions. Abnormalities can lead to a series of peripheral neurological conditions, such as paraesthesia, pain, or spasms, which are debilitating and lowering the quality of life. The current guidelines for diagnosis rely predominantly on clinical symptoms resulting from PNS dysfunction, which occur already at an advanced stage. There are currently no effective methods that visually reflect the extent of peripheral neuropathy. In our study, we present a novel in vivo and in situ real-time imaging of peripheral nerves based on the second near-infrared window (NIR-II) fluorescence. In NIR-II system, PbS Qds with NIR-II fluorescence specifically bound to motor neuron-specific protein agrin, acting as image contrast. In mice model, peripheral nerves were visible as soon as after 2 h post injection. We provide evidence for the efficacy of this approach, which allows to directly demonstrate peripheral nerves, their structure, and potential damage sites and degree. Furthermore, our products were of good biocompatibility, while the neural fluorescence signal was solid, bright and stable for 4 h in vivo. Thus, overall, our results suggest that NIR-II is an effective new method for direct imaging of peripheral nerves in vivo, opening new horizons on early, improved and more precise, targeted diagnosis. A resulting more rapid installation of personalized therapy facilitates a better prognosis of clinical peripheral neuropathy.

Direct wide-field radio imaging in real-time at high time resolution using antenna electric fields

ABSTRACTThe recent demonstration of a real-time direct imaging radio interferometry correlator represents a new capability in radio astronomy. However, wide-field imaging with this method is challenging since wide-field effects and array non-coplanarity degrade image quality if not compensated for. Here, we present an alternative direct imaging correlation strategy using a direct Fourier transform (DFT), modelled as a linear operator facilitating a matrix multiplication between the DFT matrix and a vector of the electric fields from each antenna. This offers perfect correction for wide field and non-coplanarity effects. When implemented with data from the Long Wavelength Array (LWA), it offers comparable computational performance to previously demonstrated direct imaging techniques, despite having a theoretically higher floating point cost. It also has additional benefits, such as imaging sparse arrays and control over which sky coordinates are imaged, allowing variable pixel placement across an image. It is in practice a highly flexible and efficient method of direct radio imaging when implemented on suitable arrays. A functioning electric field direct imaging architecture using the DFT is presented, alongside an exploration of techniques for wide-field imaging similar to those in visibility-based imaging, and an explanation of why they do not fit well to imaging directly with the digitized electric field data. The DFT imaging method is demonstrated on real data from the LWA telescope, alongside a detailed performance analysis, as well as an exploration of its applicability to other arrays.

Adult brain aging investigated using BMC-mcDESPOT–based myelin water fraction imaging

The relationship between regional brain myelination and aging has been the subject of intense study, with magnetic resonance imaging perhaps the most effective modality for elucidating this. However, most of these studies have used nonspecific methods to probe myelin content, including diffusion tensor imaging, magnetization transfer ratio, and relaxation times. In the present study, we used the BMC-mcDESPOT analysis, a direct and specific method for imaging of myelin water fraction (MWF), a surrogate of myelin content. We investigated age-related differences in MWF in several brain regions in a large cohort of cognitively unimpaired participants, spanning a wide age range. Our results indicate a quadratic, inverted U-shape, relationship between MWF and age in all brain regions investigated, suggesting that myelination continues until middle age followed by decreases at older ages. We also observed that these age-related differences vary across different brain regions, as expected. Our results provide evidence for nonlinear associations between age and myelin in a large sample of well-characterized adults, using a direct myelin content imaging method.

Synchronization of dual diffusion flame in co-flow

In this study, the interaction of two adjacent diffusion flames (dual flame) were experimentally investigated using the direct imaging method and particle image velocimetry (PIV) measurements for varied distances between the two flames under the influence of the co-flow. The direct imaging method indicates the presence of various synchronization modes, such as merging, in-phase synchronization, amplitude death, anti-phase synchronization, and desynchronization, as the distance between the flames was increased. The dual flame synchronization was characterized using an image analysis of the time-series variation of flame heights summarized by the mean flame height, root-mean-square of the flame height, Strouhal number, and the cross-correlation coefficient of flame heights against the burner distance. Furthermore, the unsteady velocity fields of the synchronized flames were measured using PIV combined with the proper orthogonal decomposition (POD) analysis to extract the flow structure of the dual flame. The experimental results indicated that the in-phase mode is characterized by the formation of symmetrical vortices, whereas the anti-phase mode features the formation of asymmetrical vortices inside and outside of the flame. The POD analysis demonstrated higher fluctuating energy in the anti-phase mode than in the in-phase mode, which suggested the formation of a highly organized flame structure in the anti-phase mode.

(Invited) Multiscale Analysis of Battery Materials Using X-Ray Microscopy

Battery electrodes are inherently multiscale, functional material systems that provide sites for chemical reactions and pathways for charge and reactant transport. A greater understanding of the interaction between transport phenomena, electrochemistry, and electrode structures is critical to advance battery performance and reliability. Direct microstructural imaging methods provide a unique capability for the multiscale observation of electrode structures and the material changes that occur during battery operation. The microstructural image data produced by these methods also facilitates physics-based simulation informed by real device structures. Applications of X-ray microscopy to battery electrodes at multiple scales are presented. X-ray nanotomography (XNT) and microtomography (µCT) of battery electrode materials are presented for high capacity metallic anode materials and transition metal oxide cathode materials. First, X-ray imaging is presented as a means of assessing the impact of processing methods on electrode structure at nano- and micro-scales. Ex situ and in operando spectroscopic imaging using µCT and nano-scale X-ray absorption near edge structure (XANES) are then presented as a means of assessing multiscale chemical and structural changes in electrodes during cycling. The data obtained through these imaging efforts facilitates modeling of real electrode structures. Modeling efforts informed by the microstructural data obtained are discussed with a focus on Li-ion cathode materials. Observations from modeling are complemented by microstructural analysis that permits description of cathode performance in terms of dimensionless parameters.

Simulasi Analisis Bukti Digital Pada Layanan Cloud Computing Menggunakan Metode NIST 800-86

Ease and support for cloud-based data storage It has supported an increase in the number of cloud services. The increasing number of uses for cloud services also increases the number of digital-based criminal actions related to the addition of facilities to cloud services. The cloud service feature designed to store data to support the smooth running of business processes can be misused by criminal assistance to store crime data. Accurate digital evidence is one way to prove a digital crime, which can then be used as supporting evidence in the trial. This study discusses the analysis of digital evidence from a cloud service. The analysis process using the NIST 800-86 method is carried out on digital evidence from 5 previously prepared scenarios related to the use of cloud service features that use being misused. Data acquisition techniques use the method of direct acquisition and physical imaging to obtain digital evidence. The experimental results showed that after scenario 1 and scenario 3, information on the file name and directory of the paths downloaded by client 1 and client 2 were obtained with information on the IP address, mac address, user name, password and time stamp. After scenario 2, digital evidence has been obtained that contains information on the name and location of the folder on the cloud server. After scenario 4, information on the name of the file and the shared folder is successfully obtained, equipped with client information that has the right to access the files and folders. After scenario 5, information about the file name and directory of the file path is successfully obtained.

A direct imaging method for half-space inverse elastic scattering problems

We propose a direct imaging method based on reverse-time migration in order to reconstruct extended obstacles in the half space with finite aperture elastic scattering data at a fixed frequency. We demonstrate the resolution of the reconstruction method in terms of the aperture and the depth of the obstacle embedded in the half space. The resolution analysis is studied via the point spread function and implies that the imaginary part of the cross-correlation imaging function always peaks on the upper boundary of the obstacle. Numerical examples are included to illustrate the effectiveness of the method.

Near-Field Imaging of an Unbounded Elastic Rough Surface with a Direct Imaging Method

This paper is concerned with the inverse scattering problem of time-harmonic elastic waves by an unbounded rigid rough surface. A direct imaging method is developed to reconstruct the unbounded rou...

Uniqueness and Direct Imaging Method for Inverse Scattering by Locally Rough Surfaces with Phaseless Near-Field Data

This paper is concerned with inverse scattering of plane waves by a locally perturbed infinite plane (which is called a locally rough surface) with the modulus of the total-field data (also called the phaseless near-field data) at a fixed frequency in two dimensions. We consider the case where a Dirichlet boundary condition is imposed on the locally rough surface. This problem models inverse scattering of plane acoustic waves by a one-dimensional sound-soft, locally rough surface; it also models inverse scattering of plane electromagnetic waves by a locally perturbed, perfectly reflecting, infinite plane in the transverse electric polarization case. We prove that the locally rough surface is uniquely determined by the phaseless near-field data generated by a countably infinite number of plane waves and measured on an open domain above the locally rough surface. Further, a direct imaging method is proposed to reconstruct the locally rough surface from the phaseless near-field data generated by plane waves and measured on the upper part of the circle with a sufficiently large radius. Theoretical analysis of the imaging algorithm is derived by making use of properties of the scattering solution and results from the theory of oscillatory integrals (especially the method of stationary phase). Moreover, as a by-product of the theoretical analysis, a similar direct imaging method with full far-field data is also proposed to reconstruct the locally rough surface. Finally, numerical experiments are carried out to demonstrate that the imaging algorithms with phaseless near-field data and full far-field data are fast, accurate, and very robust with respect to noise in the data.

Quantitative Analysis of Structure and Dynamics in AFM Images of Lipid Membranes.

AFM is now established as a powerful and direct technique for studying lipid membranes, and is highly complementary with other techniques. It is the only method for direct imaging and mechanical probing of lipid phase structure in a liquid environment down to the nanometer level. In order to understand the structure, function, and interactions of membranes at this level, we must be able to reliably and quantitatively measure the AFM images. Here we describe the methods used to process and analyze AFM images of phase-separated supported lipid bilayers . This initially takes a static approach, where we simply quantify the % of domain area, number of domains, and morphology, and quantify how many images must be taken to obtain reliable statistics. We then look at dynamics, describing the methods we use to study the nanometer scale motion of the domain perimeter as observed using Fast Scan AFM, and hence extract a quantitative line tension.

Imaging with ghostly electrons

Electron Imaging Ghost imaging is a computational imaging approach that uses correlations between a signal beam that interacts with a sample and a reference beam that doesn't. The correlations are then used to reconstruct an image of the sample and can, in principle, be used to image samples with very weak signal beams that might otherwise be damaged with a typical probe beam. Already demonstrated for optics and atoms, Li et al. now extend the method of ghost imaging to electrons. To circumvent the difficulty of splitting an electron beam, they instead used a structured electron beam to probe the sample. They show that a reconstructed image of a sample with a lower electron dose than that used in direct imaging methods can be faithfully produced. This technique could reduce acquisition time and avoid damaging sensitive samples in electron imaging applications. Phys. Rev. Lett. 121 , 114801 (2018).

Transverse beam profile measurement system for the Duke storage ring

The transverse beam emittance is a crucial parameter determining the brightness of an electron storage ring based synchrotron radiation source. The beam emittance is typically determined using the transverse electron beam size and the beta function at a particular location. For a low energy storage ring, the direct imaging method using visible/UV light has many advantages, including being simple, straightforward, and cost-effective. The resolution of such a system can be quite adequate for measuring electron beams with a reasonably large transverse beam size. In this work, we present the development of a new transverse beam profile measurement system for the Duke storage ring. This new system has been characterized to allow absolute measurements of the electron beam size while achieving better system resolution than previously thought possible for the direct imaging technique. The preliminary measurement results show that this system is capable of measuring the horizontal beam size over a wide range of the electron beam energies and currents. The system has also been demonstrated as a useful tool to study the intra-beam scattering related emittance increase in the storage ring.

Structural Analysis of Cellulose-Coated Oil-in-Water Emulsions Fabricated from Molecular Solution.

Natural cellulose has been used as a coating to stabilize oil-in-water (o/w) emulsions by exploiting the amphiphilic character of the cellulose chains molecularly dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate. Its cellulose coating exhibits a continuous amorphous structure which differs significantly from the cellulose particle stabilization used in Pickering emulsions. The structure of these cellulose-coated o/w emulsion particles, in particular the cellulose coating shell characteristics (thickness, porosity, and composition), is studied by using a combination of direct imaging methods such as cryogenic electron microscopy and fluorescence microscopy with small-angle neutron scattering measurements. This work suggests a unique multicompartment structure of the emulsion particles: an oil core, surrounded by an inner shell composed of a porous cellulose gel, encapsulated by a dense outer cellulose shell, a few nanometers in thickness. The thickness of the inner cellulose shell varies significantly. The nanoscale emulsion droplets exhibit a thickness of 10 ± 3 nm, whereas the larger micron-sized droplets exhibit a thicker inner cellulose shell of 500-750 nm. It is also inferred that the cellulose shells contain water rather than oil.

Weighting function effects in a direct regularization method for image-guided near-infrared spectral tomography of breast cancer.

Structural image-guided near-infrared spectral tomography (NIRST) has been developed as a way to use diffuse NIR spectroscopy within the context of image-guided quantification of tissue spectral features. A direct regularization imaging (DRI) method for NIRST has the value of not requiring any image segmentation. Here, we present a comprehensive investigational study to analyze the impact of the weighting function implied when weighting the recovery of optical coefficients in DRI based NIRST. This was done using simulations, phantom and clinical patient exam data. Simulations where the true object is known indicate that changes to this weighting function can vary the contrast by 10%, the contrast to noise ratio by 20% and the full width half maximum (FWHM) by 30%. The results from phantoms and human images show that a linear inverse distance weighting function appears optimal, and that incorporation of this function can generally improve the recovered total hemoglobin contrast of the tumor to the normal surrounding tissue by more than 15% in human cases.

Rapid optical imaging of polycrystalline material structures.

The physical properties of polycrystalline materials that are widely used in various optical applications are determined by their structure, wherein grain size and form and grain boundaries play a crucial role. Currently, there is no simple and fast method to generate a direct image of polycrystalline material structures. In this study, we propose a method for direct optical imaging of a crystalline material structure based on the difference between the optical properties of the grains and grain boundaries near the fundamental absorption edge of the material. Our results indicate the possible utility of the method in diverse imaging applications.