Holographic Measurements Research Articles

Feasibility and accuracy of real-time 3D-holographic graft length measurement, a sub-study of the FAST-TRACK CABG trial

Abstract Background 3D Hologram is an emerging tool for intuitively manipulating and visualizing CT images. Mixed reality (MR) technology can display high-definition 3D holograms while preserving situational awareness. The new MR software offers the possibility to measure 3D objects using hand gestures and voice commands. However, these measurements made on 3D holograms have not been validated. Purpose We aimed to assess the feasibility and accuracy of using CT-derived 3D holograms for bypass graft length measurement. Methods Twenty-seven consecutive cases in the FAST TRACK CABG trial were included. The post-operative CT images performed at 30 days follow-up were analyzed in an independent core lab. Two analysts blinded to clinical information performed Holographic reconstruction and measurement using the CanaLife Holo software (Medapp, Krakow, Poland). (Figure 1) Inter-observer agreement was assessed in the first 20 cases. Another analyst with full access to clinical information performed the validation measurements on the CardIQ W8 system (GE Healthcare, Milwaukee, Wisconsin). (Figure 1) Results A total of 62 grafts (27 left internal mammary artery grafts, 27 saphenous vein grafts, and 8 right internal mammary artery grafts) were measured. There was an excellent inter-observer agreement between the analysts in the first 47 grafts analyzed (interclass correlation 0.9879 [0.9783-0.9933]). (Figure 2A, 2B) On average, holographic reconstruction and measurement of a case took 3 minutes and 36 seconds± 50.74 seconds compared to around 10 minutes per vessel on the traditional CT system. There was no significant difference between the graft length measured by hologram and CT (188.59±51.63 mm vs. 183.95±50.93 mm, p=0.616). The length measured by hologram and CT were similar across different graft types. The measurements of hologram and CT are highly correlated (r=0.973, p <0.001) with an excellent agreement (interclass correlation 0.9928 [0.9880-0.9957]). (Figure2C, 2D) Conclusion Holographic vessel length measurement is feasible, fast, and accurate even for tortuous coronary bypass grafts. This new methodology can empower surgeons to visualize and measure the results of their work by themselves and may provide insights for procedure evaluation. 3D Holograms can eventually empower surgeons to plan the precise length of the arterial and venous grafts to be harvested for every individual case.

Anomalous tumbling of colloidal ellipsoids in Poiseuille flows.

Shear flows cause aspherical colloidal particles to tumble so that their orientations trace out complex trajectories known as Jeffery orbits. The Jeffery orbit of a prolate ellipsoid is predicted to align the particle's principal axis preferentially in the plane transverse to the axis of shear. Holographic microscopy measurements reveal instead that colloidal ellipsoids' trajectories in Poiseuille flows strongly favor an orientation inclined by roughly π/8 relative to this plane. This anomalous observation is consistent with at least two previous reports of colloidal rods and dimers of colloidal spheres in Poiseuille flow and therefore appears to be a generic, yet unexplained feature of colloidal transport at low Reynolds numbers.

Convolutional and fourier neural networks for speckle denoising of wrapped phase in digital holographic interferometry

Owing to the unique non-Gaussian statistics and non-stationary properties, speckle denoising in digital holographic interferometry measurements is essential and challenging. Traditional Fourier-based frequency-domain filtering and deep-learning-based (DL-based) spatial-domain speckle denoising methods have realised significant achievements. However, these methods use different mechanisms and are applied separately. A deep learning-based algorithm combining the aforementioned methods is proposed, which simultaneously extracts features in the spatial and frequency domains via convolutional and Fourier neural networks (CFNN) for enhanced speckle denoising and minimising the phase unwrapping process error. Compared with the convolutional neural network (CNN), which provides spatial-domain features for the framework architecture to layer extraction operation, the Fourier neural operator (FNO) developed from traditional Fourier filtering provides the frequency-domain features. The differential gradient map of denoised wrapping is used as a loss function, further improving the smoothness of the denoised wrapped images and the subsequent phase-unwrapping performance. Compared to other algorithms, the proposed method achieves a relative improvement of 7.1% on the testing dataset and 5.0% on digital holographic deformation field experimental data. It can be extended to more fields of optical information processing, since it unifies the feature extraction and reconstruction in the spatial-domain and the frequency-domain in the same deep learning model.

Towards a classification of holographic multi-partite entanglement measures

In this paper, we systematically study the measures of multi-partite entanglement with the aim of constructing those measures that can be computed in probe approximation in the holographic dual. We classify and count general measures as invariants of local unitary transformations. After formulating these measures in terms of permutation group elements, we derive conditions that a probe measure should satisfy and find a large class of solutions. These solutions are generalizations of the multi-entropy introduced in [1]. We derive their holographic dual with the assumption that the replica symmetry is unbroken in the bulk and check our prescription with explicit computations in 2d CFTs. Analogous to the multi-entropy, the holographic dual of these measures is given by the weighted area of the minimal brane-web but with branes having differing tensions. We discuss the replica symmetry assumption and also how the already known entanglement measures, such as entanglement negativity and reflected entropy fit in our framework.

Digital holographic 3D surface topography measurement based on recording-plane rotation

In the present study, a three-dimensional (3D) surface topography measurement method based on digital holography is proposed that changes the observation vector by rotating a charge-coupled device(CCD) . Two digital holograms with different observation vectors were recorded by rotating the CCD at a small angle. In this paper, the 3D surface topographies of an irregular spheres with a radius of 16 mm and an surface relief denture with a dimensional of 10 mm ×10 mm were obtained. The results matches well with the real value of the hemisphere, which verifies the feasibility of the proposed method. At the same time, the surface topography measurement of the denture crown reflects its contour information well and can be used to guide dentists in the process of restorative teeth and denture making.

Feasibility and Accuracy of Holographic Graft Length Measurement, a Sub-study of the FAST TRACK CABG Trial

Feasibility and Accuracy of Holographic Graft Length Measurement, a Sub-study of the FAST TRACK CABG Trial

Holographic measurement in CFT thermofield doubles

We extend the results of arXiv:2209.12903 by studying local projective measurements performed on subregions of two copies of a CFT2 in the thermofield double state and investigating their consequences on the bulk double-sided black hole holographic dual. We focus on CFTs defined on an infinite line and consider measurements of both finite and semi-infinite subregions. In the former case, the connectivity of the bulk spacetime is preserved after the measurement. In the latter case, the measurement of two semi-infinite intervals in one CFT or of one semi-infinite interval in each CFT can destroy the Einstein-Rosen bridge and disconnect the bulk dual spacetime. In particular, we find that a transition between a connected and disconnected phase occurs depending on the relative size of the measured and unmeasured subregions and on the specific Cardy state the measured subregions are projected on. We identify this phase transition as an entangled/disentangled phase transition of the dual CFT system by computing the post-measurement holographic entanglement entropy between the two CFTs. We also find that bulk information encoded in one CFT in the absence of measurement can sometimes be reconstructed from the other CFT when a measurement is performed, or can be erased by the measurement. Finally, we show that a purely CFT calculation of the Renyi entropy using the replica trick yields results compatible with those obtained in our bulk analysis.

Digital holographic measurement of electron temperature and density of laser-produced plasmas with an ultrashort laserpulse.

Holography, which can provide the information of phase as well as amplitude of a laser probe, could be a powerful method to diagnose the electron density and temperature of a plasma simultaneously. In this paper, digital holography with an ultrashort laser pulse is applied to diagnose laser-produced aluminum plasmas. Detailed analyses show that the reconstruction of the wave amplitude could be profoundly affected by the difference between the phase and group velocity of the ultrashort laser pulse in the plasma, which makes it a challenge to accurately reconstruct the amplitude in the case when ultrashort laser pulses are utilized for high-temporal resolution of holography.

Phase-based reconstruction optimization method for digital holographic measurement of microstructures.

Digital holography has transformative potential in measuring stacked-chip microstructures due to its noninvasive, single-shot, full-field characteristics. However, uncertainties in reconstruction distance inevitably lead to resolving blur and reconstruction distortion. Herein, we propose a phase-based reconstruction optimization method that consists of a phase-evaluation function and a structured surface-characterization model. Our proposed method involves setting a reconstruction distance range, obtaining phase information using sliced numerical reconstruction, and optimizing the reconstruction distance by finding the extreme value of the function, which identifies the focal plane of the reconstructed image. The structure of the surface topography is then characterized using the characterization model. We perform simulations of the recording, reconstruction, and characterization to verify the effectiveness of the proposed method. To further demonstrate the approach, a simple holographic recording system is constructed to measure a standard resolution target, and the measurement results are compared with a commercial instrument. The simulation and experiment demonstrate, respectively, 31.16% and 34.41% improvement in step-height characterization accuracy.

Comparative Characterization of Nonlinear Ultrasound Fields Generated by Sonalleve V1 and V2 MR-HIFU Systems.

A Sonalleve magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) clinical system (Profound Medical, Mississauga, ON, Canada) has been shown to generate nonlinear ultrasound fields with shocks up to 100 MPa at the focus as required for HIFU applications such as boiling histotripsy of hepatic and renal tumors. The Sonalleve system has two versions V1 and V2 of the therapeutic array, with differences in focusing angle, focus depth, arrangement of elements, and the size of a central opening that is twice larger in the V2 system compared to the V1. The goal of this study was to compare the performance of the V1 and V2 transducers for generating high-amplitude shock-wave fields and to reveal the impact of different array geometries on shock amplitudes at the focus. Nonlinear modeling of the field in water using boundary conditions reconstructed from holography measurements shows that at the same power output, the V2 array generates 10-15-MPa lower shock amplitudes at the focus. Consequently, substantially higher power levels are required for the V2 system to reach the same shock-wave exposure conditions in histotripsy-type treatments. Although this difference is mainly caused by the smaller focusing angle of the V2 array, the larger central opening of the V2 array has a nontrivial impact. By excluding coherently interacting weakly focused waves coming from the central part of the source, the presence of the central opening results in a somewhat higher effective focusing angle and thus higher shock amplitudes at the focus. Axisymmetric equivalent source models were constructed for both arrays, and the importance of including the central opening was demonstrated. These models can be used in the "HIFU beam" software for simulating nonlinear fields of the Sonalleve V1 and V2 systems in water and flat-layered biological tissues.

Wavefront single-pixel imaging using a flexible SLM-based common-path interferometer

Wavefront single-pixel imaging (WSPI) is an important tool for simultaneously measuring the amplitude and phase of an unknown field, especially suitable for wavefront detecting in some special wavelengths where array detectors are immature or even unavailable. Here, a passive-detection-based WSPI method using a flexible SLM-based common-path interferometer is proposed, in which by detecting the zero-order diffraction of the SLM directly, the common-path phase-shift or off-axis technique can be flexibly realized by a “sandwich” structure consisting of a half-wave plate, a SLM, and a polarizer. The reference light can be conveniently chosen as the direct reflected light from the SLM, the unmodulated light from the pixels of the SLM, or the light from both of them. We experimentally verify the feasibility and advantages of the proposed method. We further demonstrate the method for wavefront measurement of a dragonfly wing, which suggests it can be used for quantitative phase imaging. It provides a high-resolution spatial wavefront passive detection technique, with a compact, stable, and flexible setup, which has lots of applications involving three-dimensional imaging, aberration correction, digital holographic measurement, and digital microscopy.

Comparison between shadow imaging and in-line holography for measuring droplet size distributions

A direct comparison of the droplet size and number measurements using in-line holography and shadow imaging is presented in three dynamically evolving laboratory scale experiments. The two experimental techniques and image processing algorithms used to measure droplet number and radii are described in detail. Droplet radii as low as r = 14 µm are measured using in-line holography and r = 50 µm using shadow imaging. The droplet radius measurement error is estimated using a calibration target (reticle) and it was found that the holographic technique is able to measure droplet radii more accurately than shadow imaging for droplets with r le 625 µm. Using the measurements of droplet number and size we quantitatively cross-validate and assess the accuracy of the two measurement techniques. The droplet size distributions, N(r), are measured in all three experiments and are found to agree well between the two measurement techniques. In one of the laboratory experiments, simultaneous measurements of droplets (r ge 14 µm, using holography) and dry aerosols (0.07 lessapprox r lessapprox 2 µm, using an scanning mobility particle sizer and 0.15 lessapprox r lessapprox 5 µm using an optical particle sizer) are reported, one of the first such comparison to the best of our knowledge. The total number and volume of droplets is found to agree well between both techniques in the three experiments. We demonstrate that a relatively simple shadow imaging technique can be just as reliable when compared to a more sophisticated holographic measurement technique over their common droplet radius measurement range. The agreement in results is shown to be valid over a large range of droplet concentrations, which include experiments with relatively sparse droplet concentrations as low as 0.02 droplets per image. Advantages and disadvantages for the two techniques are discussed in the context of our results. The main advantages to in-line holography are the greater accuracy in droplet radius measurement, greater spatial resolution, larger depth of field, and the high repetition rate and short pulse duration of the laser light source. In comparison, the main advantages to shadow imaging are the simpler experimental setup, image processing algorithm, and fewer computer resources necessary for image processing. Droplet statistics like number and size are found to be very reliable between the two methods for large range of droplet densities, {mathcal {P}}_{r>50}, ranging from 10^{-4} le {mathcal {P}}_{r>50} le 10^{-1} cm^{-3}, when the two techniques are implemented as shown in this paper.

Holographic confining-deconfining gauge theories and entanglement measures with a magnetic field

Holographic confining-deconfining gauge theories and entanglement measures with a magnetic field

TCTAP A-037 Feasibility and Accuracy of Holographic Graft Length Measurement, A Sub-study of the FAST TRACK CABG Trial

TCTAP A-037 Feasibility and Accuracy of Holographic Graft Length Measurement, A Sub-study of the FAST TRACK CABG Trial

Polarization-Maintaining Diffractive Elements for Off-Axis Terahertz Digital Holography

Off-axis digital holography in the terahertz waves allows three-dimensional visualizations of optically opaque volumetric objects in a single exposure and with angular separation of the zero-order component. Forming the tilted reference beam usually requires a set of mirrors, which can disturb the polarization, causing the loss of contrast in fringes at the detector. Here we present a mirror-less approach with 3D-printed transmissive diffractive optical elements, providing unaltered polarization and successful holographic measurements at 0.1 THz without any pre- or postprocessing of interference fringes.

Holographic measurement and quantum teleportation in the SYK thermofield double

According to holography, entanglement is the building block of spacetime; therefore, drastic changes of entanglement will lead to interesting transitions in the dual spacetime. In this paper, we study the effect of projective measurements on the Sachdev-Ye-Kitaev (SYK) model’s thermofield double state, dual to an eternal black hole in Jackiw-Teitelboim (JT) gravity. We calculate the (Renyi-2) mutual information between the two copies of the SYK model upon projective measurement of a subset of fermions in one copy. We propose a dual JT gravity model that can account for the change of entanglement due to measurement, and observe an entanglement wedge phase transition in the von Neumann entropy. The entanglement wedge for the unmeasured side changes from the region outside the horizon to include the entire time reversal invariant slice of the two-sided geometry as the number of measured Majorana fermions increases. Therefore, after the transition, the bulk information stored in the measured subsystem is not entirely lost upon projection in one copy of the SYK model, but rather teleported to the other copy. We further propose a decoding protocol to elucidate the teleportation interpretation, and connect our analysis to the physics of traversable wormholes.

CRT-100.07 Feasibility and Accuracy of Holographic Graft Length Measurement, a Sub-study of the FAST TRACK CABG Trial

CRT-100.07 Feasibility and Accuracy of Holographic Graft Length Measurement, a Sub-study of the FAST TRACK CABG Trial

MeerKAT Holography Measurements in the UHF, L, and S Bands

Radio holographic measurements using the MeerKAT telescope are presented for each of its supported observing bands, namely UHF (544–1087 MHz), L (856–1711 MHz), and S (1750–3499 MHz). Because the UHF-band receiver design is a scaled version of that of the L band, the electromagnetic performance in these two bands are expectedly similar to one another. Despite also being linearly polarized, S-band receivers have an entirely different design and distinct performance characteristics from the lower two bands. As introduced in previous work for the L band, evidence of higher order waveguide mode activation also appears in S-band measurements but there are differences in its manifestation. Frequency-dependent pointing (beam squint), beamwidth, beam ellipticity, error beam, instrumental polarization, and cross-polarization power measurements are illustrated for each of MeerKAT’s observational bands in a side-by-side style to facilitate the comparison of features. The derivation of collimation errors and main reflector surface errors from measurements made at these relatively low observation frequencies is also discussed. Results include elevation and ambient temperature effects on collimation, as well as the signatures of collimation degrading over time. The accompanying data release includes a snapshot of full Jones matrix primary beam patterns for all bands and antennas with corresponding derived metrics.

Probing phase structure of strongly coupled matter with holographic entanglement measures

We study the holographic entanglement measures such as the holographic mutual information, HMI, and the holographic entanglement of purification, EoP, in a holographic QCD model at finite temperature and zero chemical potential. This model can realize various types of phase transitions including crossover, first order and second order phase transitions. We use the HMI and EoP to probe the phase structure of this model and we find that at the critical temperature they can characterize the phase structure of the model. Moreover we obtain the critical exponent using the HMI and EoP.

Holographic study of reflected entropy in anisotropic theories

We evaluate reflected entropy in certain anisotropic boundary theories dual to nonrelativistic geometries using holography. It is proposed that this quantity is proportional to the minimal area of the entanglement wedge cross section. Using this prescription, we study in detail the effect of anisotropy on reflected entropy and other holographic entanglement measures. In particular, we study the discontinuous phase transition of this quantity for a symmetric configuration consisting of two disjoint strips. We find that in the specific regimes of the parameter space the critical separation is an increasing function of the anisotropy parameter and hence the correlation between the subregions becomes more pronounced. We carefully examine how these results are consistent with the behavior of other correlation measures including the mutual information. Finally, we show that the structure of the universal terms of entanglement entropy is corrected depending on the orientation of the entangling region with respect to the anisotropic direction.