Resolved Images Research Articles

The Zap-X Radiosurgical System in the Treatment of Intracranial Tumors: A Technical Case Report.

BACKGROUND AND IMPORTANCEThe Zap-X system (Zap Surgical Systems Inc, San Carlos, California) is a radically new surgical robot designed for brain and head and neck radiosurgery. It represents the first new dedicated brain stereotactic radiosurgery platform in almost half a century optimizing the goals of safety, speed, and accuracy. The Zap-X system was used in a required Chinese National Medical Products Administration clinical study. In early January 2020, 2 patients were treated with the Zap-X robot prior to a national COVID-19 lockdown. Both were closely followed via clinical exam and magnetic resonance imaging (MRI) imaging. Prospectively collected data were used to generate this report.CLINICAL PRESENTATIONTwo female patients, each harboring either a trigeminal schwannoma or petroclival meningioma, were treated with the Zap-X robot. Respective tumor volumes were 2.60 and 4.02 cm3. A radiation dose of 13 Gy was prescribed to the 50% isodose line. At 8 mo of follow-up, preoperative symptoms were either resolved or stable and MRI imaging demonstrated a 31% and 56% reduction in lesion volume, respectively. In both patients, symptoms improved, and tumor volumes decreased, whereas no major complication was observed.CONCLUSIONGiven only 2 patients and short-term follow-up, any conclusions about the safety and efficacy of the Zap-X radiosurgery robot are preliminary. However, in the absence of any other published outcomes to date, this small case series may be of interest to many radiosurgical specialists.

Discharge modes and characteristics optimization of nanosecond pulsed discharge in packed bed reactor

In this study, comparisons of spatiotemporal resolved images, optical emission spectroscopy technology, and electrical characteristics diagnosis were used to investigate the conversion and optimization of the discharge modes in a packed bed reactor (PBR) in which dielectric materials with different dielectric constants were employed under different peak voltages. The effects of the peak voltages and dielectric materials on the production of reactive species, such as and , were also studied for plasma applications. The results show that, when a polytetrafluoroethylene (PTFE) column is employed, with an increase in the peak voltages, the form and modes of the discharge both change. First, the discharge channel becomes ‘wider’ and the discharge volume becomes larger, which results in more reactive species. Second, the discharge mode changes from surface discharge to diffuse discharge during the falling edge of the voltage pulse. When the dielectric constant of the dielectric material is increased, the intensity of the surface streamer decreases during its shorter propagation path because of more electron collision losses. Moreover, a different discharge mode, called ‘local discharge’, was observed at the contact point. Under the same experimental conditions, the numbers of nitrogen molecules distributed at different vibrational levels and the reactive species produced in the alumina PBR were fewer than those in the PTFE PBR.

A novel energy resolved neutron imaging detector based on a time stamping optical camera for the CSNS

The China Spallation Neutron Source (CSNS) operates in pulsed mode and has a high neutron flux. This provides opportunities for energy resolved neutron imaging by using the TOF (Time Of Flight) approach. An Energy resolved neutron imaging instrument (ERNI) is being built at the CSNS but significant challenges for the detector persist because it simultaneously requires a spatial resolution of less than 100 μm, as well as a microsecond-scale timing resolution. This study constructs a prototype of an energy resolved neutron imaging detector based on the fast optical camera, TPX3Cam coupled with an image intensifier. To evaluate its performance, a series of proof of principle experiments were performed in the BL20 at the CSNS to measure the spatial resolution and the neutron wavelength spectrum, and perform neutron imaging with sliced wavelengths and Bragg edge imaging of the steel sample. A spatial resolution of 57 μm was obtained for neutron imaging by using the centroiding algorithm, the timing resolution was on the microsecond scale and the measured wavelength spectrum was identical to that measured by a beam monitor. In addition, any wavelengths can be selected for the neutron imaging of the given object, and the detector can be used for Bragg edge imaging. The results show that our detector has good performances and can satisfy the requirements of ERNI for detectors at the CSNS.

MuRNet: A deep recursive network for super resolution of bicubically interpolated images

In many real-world cases such as printer devices and in-camera interpolation, only the interpolated versions of the low-resolution images are available. In this paper, a new low-complexity high-performance image super resolution network is proposed that starting from the bicubic interpolated version of the low resolution image produces a high quality super resolved image. The main idea in the proposed scheme is the development of a feature generating block that is capable of producing features using multiple local spatial ranges and multiple resolution levels, fusing them in order to provide a rich set of feature maps, and using them in a recursive framework. The objective in designing such a recursive block is not simply to provide a light-weight network, as is traditionally done in the design of such a network, but also to provide a low count on the number of multiply-accumulate operations with high performance. The experimental results are provided to show that the proposed network outperforms other recursive super resolution networks when their super resolution capability, the number of parameters and number of multiply-accumulate operations are simultaneously taken into consideration.

Reconstruction of a small acoustic inclusion via time-dependent polarization tensors

Abstract This paper aims at introducing the concept of time-dependent polarization tensors (TDPTs) for the wave equation associated to a diametrically small acoustic inclusion, with constitutive parameters different from those of the background and size smaller than the operating wavelength. Firstly, the solution to the Helmholtz equation is considered, and a rigourous systematic derivation of a complete asymptotic expansion of the scattered field due to the presence of the inclusion is presented. Then, by applying the Fourier transform, the corresponding time-domain expansion is readily obtained after truncating the high frequencies. The new concept of TDPTs is shown to be promising for performing imaging. In particular, the optimization approach proposed by Ammari et al. (Ammari, H., Kang, H., Kim, & E. Lee, J.-Y. (2012)The generalized polarization tensors for resolved imaging. Part II: shape and electromagnetic parameters reconstruction of an electromagnetic inclusion from multistatic measurements. Math. Comp., 81, 839–860.) is extended to TDPTs. Numerical simulations are presented, showing that the TDPTs reconstructed from noisy measurements allow to image fine shape details of the inclusion.

Quantitative estimation of atom-scaled ripple structure using transmission electron microscopy images

Atom-scaled ripple structure can be intrinsically formed because of thermal instability or induced stress in graphene or two-dimensional (2D) materials. However, it is difficult to estimate the period, amplitude, and shape of such a ripple structure. In this study, by applying the geometrical phase analysis method to atomically resolved transmission electron microscopy images, we demonstrate that the atom-scaled ripple structure of MoS2 nanosheet can be quantitatively analyzed at the subnanometer scale. Furthermore, by analyzing the observed ripple structure of the MoS2 nanosheet, we established that it is inclined by approximately 7.1° from the plane perpendicular to the incident electron beam; it had 5.5 and 0.3 nm in period and amplitude, respectively. For quantitative estimation of ripple structure, our results provide an effective method that contributes to a better understanding of 2D materials in the sub-nanometre scale.

Debris discs in binaries: morphology and photometric signatures

Context. Since about half of all main-sequence stars reside in multiple star systems, it is important to consider the effect of binarity on the evolution of planetesimal belts in these complex systems. Aims. We aim to see whether debris belts evolving between two stars may be impacted by the presence of the companion and whether this leaves any detectable signature that could be observed with current or future instruments. Methods. We consider a circumprimary parent body (PB) planetesimal belt that is placed just inside the stability limit between the two stars and we use the state-of-the-art DyCoSS code to follow the coupled dynamical and collisional evolution of the dust produced by this PB belt. We explore several free parameters, such as the belt’s mass and the binary’s mass ratio as well as its orbital eccentricity. We use the GraTeR package to produce 2D luminosity maps and system-integrated spectral energy distributions (SEDs). Results. We confirm a preliminary result obtained by previous DyCoSS studies, which is that the coupled effect of collisional activity, binary perturbations, and stellar radiation pressure is able to place and maintain a halo of small grains in the dynamically unstable region between the two stars. In addition, we identify several prominent spatial structures, notably, a single spiral arm stretching all the way from the PB belt to the companion star. We also identify a fainter and more compact disc around the secondary star, which is non-native and feeds off small grains from the unstable halo. The halo, spiral arm, and secondary disc should all be detectable on resolved images by instruments with capacities on the level of SPHERE. The system as a whole is depleted of small grains when compared to a companion-free case. This depletion leaves an imprint on the system’s integrated SED, which appears colder than for the same parent body belt around a single star. This new finding could explain why the SED-derived location, rdisc, of some unresolved discs-in-binaries places their primary belt in the dynamically ’forbidden’ region between the two stars: indeed, this apparent paradox could be due to an overestimation of rdisc when using empirical prescriptions that are valid for the case of a single star.

Single-cell resolved imaging reveals intra-tumor heterogeneity in glycolysis, transitions between metabolic states, and their regulatory mechanisms

SummaryInter-cellular heterogeneity in metabolic state has been proposed to influence many cancer phenotypes, including responses to targeted therapy. Here, we track the transitions and heritability of metabolic states in single PIK3CA mutant breast cancer cells, identify non-genetic glycolytic heterogeneity, and build on observations derived from methods reliant on bulk analyses. Using fluorescent biosensors in vitro and in tumors, we have identified distinct subpopulations of cells whose glycolytic and mitochondrial metabolism are regulated by combinations of phosphatidylinositol 3-kinase (PI3K) signaling, bromodomain activity, and cell crowding effects. The actin severing protein cofilin, as well as PI3K, regulates rapid changes in glucose metabolism, whereas treatment with the bromodomain inhibitor slowly abrogates a subpopulation of cells whose glycolytic activity is PI3K independent. We show how bromodomain function and PI3K signaling, along with actin remodeling, independently modulate glycolysis and how targeting these pathways affects distinct subpopulations of cancer cells.

Daikenchuto increases blood flow in the superior mesenteric artery in humans: A comparison study between four-dimensional phase-contrast vastly undersampled isotropic projection reconstruction magnetic resonance imaging and Doppler ultrasound

Respiratory-gated four-dimensional phase-contrast vastly undersampled isotropic projection reconstruction (4D PC-VIPR) is magnetic resonance (MR) imaging technique that enables analysis of vascular morphology and hemodynamics in a single examination using cardiac phase resolved 3D phase-contrast magnetic resonance imaging. The present study aimed to assess the usefulness of 4D PC-VIPR for the superior mesenteric artery (SMA) flowmetry before and after flow increase was induced by the herbal medicine Daikenchuto (TJ-100) by comparing it with Doppler ultrasound (DUS) as a current standard. Twenty healthy volunteers were enrolled in this prospective single-arm study. The peak cross-sectionally averaged velocity was measured by 4D PC-VIPR, peak velocity was measured by DUS, and flow volume (FV) of SMA and aorta were measured by 4D PC-VIPR and DUS 25 min before and after the peroral administration of TJ-100. The peak cross-sectionally averaged velocity, peak velocity, and FV of SMA measured by 4D PC-VIPR and DUS significantly increased after administration of TJ-100 (4D PC-VIPR: the peak cross-sectionally averaged velocity; p = 0.004, FV; p = 0.035, DUS: the peak velocity; p = 0.003, FV; p = 0.010). Furthermore, 4D PC-VIPR can analyze multiple blood vessels simultaneously. The ratio of the SMA FV to the aorta, before and after oral administration on the 4D PC-VIPR test also increased (p = 0.015). The rate of change assessed by 4D PC-VIPR and DUS were significantly correlated (the peak cross-sectionally averaged velocity and peak velocity: r = 0.650; p = 0.005, FV: r = 0.659; p = 0.004). Retrospective 4D PC-VIPR was a useful modality for morphological and hemodynamic analysis of SMA.

Observation of Pauli Crystals.

The Pauli exclusion principle is a fundamental law underpinning the structure of matter. Because of their antisymmetric wave function, no two fermions can occupy the same quantum state. Here, we report on the direct observation of the Pauli principle in a continuous system of up to six particles in the ground state of a two-dimensional harmonic oscillator. To this end, we sample the full many-body wave function by applying a single atom resolved imaging scheme in momentum space. We find so-called Pauli crystals as a manifestation of higher order correlations. In contrast to true crystalline phases, these unique high-order density correlations emerge even without any interactions present. Our work lays the foundation for future studies of correlations in strongly interacting systems of many fermions.

Adaptive-SFSDAF for Spatiotemporal Image Fusion that Selectively Uses Class Abundance Change Information

Many spatiotemporal image fusion methods in remote sensing have been developed to blend highly resolved spatial images and highly resolved temporal images to solve the problem of a trade-off between the spatial and temporal resolution from a single sensor. Yet, none of the spatiotemporal fusion methods considers how the various temporal changes between different pixels affect the performance of the fusion results; to develop an improved fusion method, these temporal changes need to be integrated into one framework. Adaptive-SFSDAF extends the existing fusion method that incorporates sub-pixel class fraction change information in Flexible Spatiotemporal DAta Fusion (SFSDAF) by modifying spectral unmixing to select spectral unmixing adaptively in order to greatly improve the efficiency of the algorithm. Accordingly, the main contributions of the proposed adaptive-SFSDAF method are twofold. One is to address the detection of outliers of temporal change in the image during the period between the origin and prediction dates, as these pixels are the most difficult to estimate and affect the performance of the spatiotemporal fusion methods. The other primary contribution is to establish an adaptive unmixing strategy according to the guided mask map, thus effectively eliminating a great number of insignificant unmixed pixels. The proposed method is compared with the state-of-the-art Flexible Spatiotemporal DAta Fusion (FSDAF), SFSDAF, FIT-FC, and Unmixing-Based Data Fusion (UBDF) methods, and the fusion accuracy is evaluated both quantitatively and visually. The experimental results show that adaptive-SFSDAF achieves outstanding performance in balancing computational efficiency and the accuracy of the fusion results.

Probing Luminescent Radiation of Positive Streamer in Atmospheric Air: Experiments at Low Temperature

A photo-charge measurement system based on large dynamic photomultiplier tube (PMT) and current integration method is set up to capture the transient optical signal generated by the positive streamer in the test chamber of which the temperature is adjustable. The results of the luminescent radiation, including the photo-charge quantity, propagation velocity and morphology of the streamer, for the three-electrode and the rod-plate electrode arrangements are presented at different temperatures. The influence trend of temperature on streamer is similar in both arrangements. The pronounced feature of luminescent radiation in the low temperature air ranging from 173 to 293 K is that it has a positive correlation with the temperature. The photo-charge amount of the uniform and non-uniform field increases approximately linearly with the increase of external electric field and voltage, respectively. It is remarkable that the streamer channels become much clearer and brighter with the increase of the temperature. Furthermore, the real luminescent radiation intensity of streamer and the feather-like structure were also displayed by the nanosecond resolved ICCD images.

Two-photon fluorescence imaging of subsurface tissue structures with volume holographic microscopy.

.Significance: Two-photon (2P) fluorescence imaging can provide background-free high-contrast images from the scattering tissues. However, obtaining a multiplane image is not straightforward. We present a two-photon volume holographic imaging (2P-VHI) system for multiplane imaging.Aim: Our goal was to design and implement a 2P-VHI system that can provide the high-contrast optically sectioned images at multiple planes.Approach: A 2P-VHI system is presented that incorporates angularly multiplexed volume holographic gratings and a femtosecond laser source for fluorescence excitation for multiplane imaging. A volume hologram with multiplexed gratings provides multifocal observation, whereas nonlinear excitation using a femtosecond laser helps in significantly enhancing both depth resolution and contrast of images.Results: Standard fluorescent beads are used to demonstrate the imaging performance of the 2P-VHI system. Two-depth resolved optical-sectioning images of fluorescently labeled thick mice intestine samples were obtained. In addition, the optical sectioning capability of our system is measured and compared with that of a conventional VHI system.Conclusions: Results demonstrated that 2P excitation in VHI systems provided the optical sectioning ability that helps in reducing background noise in the images. Integration of nonlinear fluorescence excitation in the VHI provides some unique advantages to the system and has potential to design multidepth optical sectioned spatial–spectral imaging systems.

Lunar optical interferometry and hypertelescope for direct imaging at high resolution.

Following earlier proposals for optical stellar interferometer concepts in space and on the Moon, the improved 'hypertelescope' version capable of direct high-resolution imaging with a high limiting magnitude became tested on Earth, proposed for space, and is now also proposed for the Moon. Many small mirrors can be dilutely arrayed in a lunar impact crater spanning 10-25 km. And a larger version, modified for a flat lunar site and spanning up to several hundred kilometres can be built later if needed for a higher resolution and limiting magnitude. Even larger versions, at the scale of many thousand kilometres, also appear feasible in space at some stage, in the form of a controlled flotilla of mirrors. Among the varied science targets considered with the imaging resolution expected, reaching 100 nano-arcseconds on the Moon, are: (a) the early detection and resolved imaging of Near Earth Objects, and their monitoring for eventual collision avoidance by orbital deflection; (b) multi-pixel imaging of exoplanets as part of the search for exolife by mapping local seasonal spectral variations; (c) the physics of neutron stars and black holes at the galactic centre and in other Active Galactic Nuclei; and (d) distant galaxies of cosmological interest. This article is part of a discussion meeting issue 'Astronomy from the Moon: the next decades'.

Progress in biomedical photoacoustic imaging instrumentation toward clinical application

Photoacoustic (optoacoustic) imaging is able to generate highly resolved images of structures with optical absorption contrast in biological tissues. This is made possible by excitation of ultrasound through the absorption of pulsed or rapidly modulated optical radiation. Since the resolution is mainly determined by the ultrasound waves, which are detected at multiple locations outside the tissue, absorbing structures such as blood vessels can be resolved at a depth of several centimeters with sub-millimeter resolution. Furthermore, spectroscopic measurements allow the extraction of functional parameters including blood oxygenation. These favorable properties have generated a lot of hope for improved diagnostics of diseases that involve changes in vasculature, such as breast tumors. After more than two decades of instrumentation development and encouraging clinical trials, photoacoustic imaging techniques are about to enter clinical practice. In this Perspective, we give an overview of recent achievements in the fields of photoacoustic tomography, microscopy, and endoscopy and try to anticipate further developments that will take advantage of the unique properties of this technology on its way to a variety of clinical applications.

Hints for Icy Pebble Migration Feeding an Oxygen-rich Chemistry in the Inner Planet-forming Region of Disks

Abstract We present a synergic study of protoplanetary disks to investigate links between inner-disk gas molecules and the large-scale migration of solid pebbles. The sample includes 63 disks where two types of measurements are available: (1) spatially resolved disk images revealing the radial distribution of disk pebbles (millimeter to centimeter dust grains), from millimeter observations with the Atacama Large Millimeter/Submillimeter Array or the Submillimeter Array, and (2) infrared molecular emission spectra as observed with Spitzer. The line flux ratios of H2O with HCN, C2H2, and CO2 all anticorrelate with the dust disk radius R dust, expanding previous results found by Najita et al. for HCN/H2O and the dust disk mass. By normalization with the dependence on accretion luminosity common to all molecules, only the H2O luminosity maintains a detectable anticorrelation with disk radius, suggesting that the strongest underlying relation is between H2O and R dust. If R dust is set by large-scale pebble drift, and if molecular luminosities trace the elemental budgets of inner-disk warm gas, these results can be naturally explained with scenarios where the inner disk chemistry is fed by sublimation of oxygen-rich icy pebbles migrating inward from the outer disk. Anticorrelations are also detected between all molecular luminosities and the infrared index n 13–30, which is sensitive to the presence and size of an inner-disk dust cavity. Overall, these relations suggest a physical interconnection between dust and gas evolution, both locally and across disk scales. We discuss fundamental predictions to test this interpretation and study the interplay between pebble drift, inner disk depletion, and the chemistry of planet-forming material.

Resolution enhanced photothermal imaging by high-order correlation.

Laser scanning photothermal imaging offers a powerful non-destructive testing tool to visualize subsurface structures of opaque materials, but it suffers the resolution limit imposed by thermal diffusion. To overcome this physical obstacle, a tightly focused excitation beam with a high repetition rate is usually used to improve the spatial resolution. Here, we demonstrate that the resolution of photothermal imaging could be enhanced using the high-order correlation imaging method inspired by correlated optical imaging. By carefully designing the laser scanning and modulation behavior, we can individually control the statistical properties of isolated hotspots induced by lasers. Imaging reconstructions of subsurface structures are performed afterward by reading out time-fluctuated thermal images. Moreover, the resolution can be further enhanced by using the high-order correlation, which enables a new way for highly resolved thermal imaging and metrology applications.

Super-resolution and denoising of 4D-Flow MRI using physics-Informed deep neural nets

Background and Objective: Time resolved three-dimensional phase contrast magnetic resonance imaging (4D-Flow MRI) has been used to non-invasively measure blood velocities in the human vascular system. However, issues such as low spatio-temporal resolution, acquisition noise, velocity aliasing, and phase-offset artifacts have hampered its clinical application. In this research, we developed a purely data-driven method for super-resolution and denoising of 4D-Flow MRI.Methods: The flow velocities, pressure, and the MRI image magnitude are modeled as a patient-specific deep neural net (DNN). For training, 4D-Flow MRI images in the complex Cartesian space are used to impose data-fidelity. Physics of fluid flow is imposed through regularization. Creative loss function terms have been introduced to handle noise and super-resolution. The trained patient-specific DNN can be sampled to generate noise-free high-resolution flow images. The proposed method has been implemented using the TensorFlow DNN library and tested on numerical phantoms and validated in-vitro using high-resolution particle image velocitmetry (PIV) and 4D-Flow MRI experiments on transparent models subjected to pulsatile flow conditions.Results: In case of numerical phantoms, we were able to increase spatial resolution by a factor of 100 and temporal resolution by a factor of 5 compared to the simulated 4D-Flow MRI. There is an order of magnitude reduction of velocity normalized root mean square error (vNRMSE). In case of the in-vitro validation tests with PIV as reference, there is similar improvement in spatio-temporal resolution. Although the vNRMSE is reduced by 50%, the method is unable to negate a systematic bias with respect to the reference PIV that is introduced by the 4D-Flow MRI measurement.Conclusions: This work has demonstrated the feasibility of using the readily available machinery of deep learning to enhance 4D-Flow MRI using a purely data-driven method. Unlike current state-of-the-art methods, the proposed method is agnostic to geometry and boundary conditions and therefore eliminates the need for tedious tasks such as accurate image segmentation for geometry, image registration, and estimation of boundary flow conditions. Arbitrary regions of interest can be selected for processing. This work will lead to user-friendly analysis tools that will enable quantitative hemodynamic analysis of vascular diseases in a clinical setting.

The effects of resolution on black hole accretion simulations of jets

ABSTRACT We perform three general-relativistic magnetohydrodynamic simulations of black hole accretion designed to test how sensitive results are to grid resolution in the jet region. The cases differ only in numerics, modelling the same physical scenario of a radiatively inefficient, geometrically thick, magnetically arrested flow on to a rapidly spinning black hole. Properties inferred with the coarsest grid generally agree with those found with higher resolutions, including total jet power and its decomposition into different forms, velocity structure, non-axisymmetric structure, and the appearance of resolved millimetre images. Some measures of variability and magnetization are sensitive to resolution. We conclude that most results obtained by limiting resolution near the jet for computational expediency should still be reliable, at least in so far as they would not be improved with a finer grid.

Experimental study of fluid-structure interaction at a model wind turbine blade using optical measurement techniques

Experimental studies of fluid-structure interaction on a single blade of the model wind turbine MoWiTO 1.8, which has been designed as an aerodynamically downscaled wind tunnel model of the NREL 5 MW turbine, were performed. Tailored inflow generated by means of a 2D active grid is used to induce dynamic stall through periodic angle of inflow changes. The interactions at the model wind turbine blade are investigated using two high-speed and non intrusive optical measurement techniques. The aerodynamics around the turbine blade is measured using temporal highly resolved particle image velocimetry (PIV) measurements at the suction side of the blade. Synchronized measurements with a high-speed photogrammetric system are linking the aerodynamic events to high accuracy measurements of the blade deflections.