X-ray Domain Research Articles

Tunable and real-time automatic interventional x-ray collimation from semi-supervised deep feature extraction.

The use of endovascular procedures is becoming increasingly popular across multiple clinical domains. These procedures are generally performed under image guidance using an interventional c-arm x-ray system. Radiation exposure to both patients and interventional staff due to use of fluoroscopy is a health and occupational concern, but modifications to the interventional workflow to address radiation may come at the cost of procedure time orquality. Interventional x-ray collimation is a crucial task for improving image quality as well as reducing radiation exposure to both patients and operators who work in the x-ray domain. However, collimation is heavily underutilized due to its cumbersome nature and the difficulty of manually manipulating multiple parameters during fast-paced interventional procedures. Additionally, the widely varying collimation preferences of interventionalists across different procedure types, procedure phases, and anatomies makes the standardizing of collimation challenging for radiation technologist supportstaff. Automating collimation has the potential to bridge this gap, freeing up mental bandwidth for interventionalists and technologists and improving outcomes for patients. Here, we propose a tunable algorithm for automatic collimation based on a region-of-interest optimizer driven by a combination of image, system, device, and radiation based features and we illustrate its efficacy across varying personal preferences. Critically, we devise a method with a simple and easily understandable mapping between algorithm parameters and practicaloutcomes. We show a real-time implementation of this algorithm using deep feature extraction by a convolutional neural network and evaluate its performance in a custom dataset of simulated fluoroscopy and recorded fluoroscopy from clinical radial access procedures. We evaluate the effects of a practically implemented mixed supervision training strategy on model performance and show potential for radiation reduction in simulation. An uncertainty analysis indicates that the algorithm is robust to noise and anatomical variation across our clinical dataset. Clinical acceptability and quality is evaluated through a reader study with expert neuro-interventional radiologists, with participants indicating 100% clinical acceptability, high quality ratings, and improved radiation protection over their typicalpractice. The algorithm's modular design ensured that users' collimation requirements were met without disruption to the interventional workflow or procedure time, while exhibiting strong potential to reduce radiation risk to patients and operators. Evaluation in more varied clinical settings could support translation of this technology into theclinic.

Low-field-driven large strain in lead zirconate titanium-based piezoceramics incorporating relaxor lead magnesium niobate for actuation

Studies on the piezoelectric materials capable of efficiently outputting high electrostrains at low electric fields are driven by the demand for precise actuation in a wide range of applications. Large electrostrains of piezoceramics in operation require high driving fields, which limits their practical application due to undesirable nonlinearities and high energy consumption. Herein, a strategy is developed to enhance the electrostrains of piezoceramics while maintaining low hysteresis by incorporating lead magnesium niobate relaxors into lead zirconate titanium at the morphotropic phase boundary. An ultrahigh inverse piezoelectric coefficient d33*\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${d}_{33}^{*}$$\\end{document} of 1380 pm/V with a reduced hysteresis of 11.5% is achieved under a low electric field of 1 kV/mm, outperforming the major lead-based piezoelectric materials. In situ synchrotron X-ray diffraction and domain wall dynamics characterization with sub-microsecond temporal resolution reveal that the outstanding performances originate from facilitated domain wall movement, which in turn is due to reduced lattice distortion and miniaturized domain structures. These findings not only address the pending challenges of effective actuation under reduced driving conditions but also lay the foundation for a more systematic approach to exploring the origin of large electrostrains.

XMM-Newton Perspective of the Unique Magnetic Binary-ϵ Lupi

The ϵ Lupi A (HD 136504) system stands out among magnetic massive binaries as the only short-period binary system in which both components have detectable magnetic fields. The proximity of the magnetospheres of the components leads to magnetospheric interactions, which are revealed as periodic pulses in the radio light curve of this system. In this work, we aim to investigate the magnetospheric interaction phenomenon in the X-ray domain. We observed this system with the XMM-Newton telescope, covering its orbital period. We observe variable X-ray emission with maximum flux near periastron, showing similarity with radio observations. The X-ray spectra show significantly elevated hard X-ray flux during periastron. We attribute the soft X-ray emission to individual magnetospheres, while the hard X-ray emission is explained by magnetospheric interaction, particularly due to magnetic reconnection. However, unlike in the radio, we do not find any significant short-term X-ray bursts. This exotic system may be an ideal target to study magnetospheric interactions in close binaries with organized magnetospheres.

Cycle-Consistent Adversarial chest X-rays Domain Adaptation for pneumonia diagnosis

To deal with the challenge of limited annotated data for training target domain pneumonia classifier, domain adaptation methods leverage publicly available source dataset to enhance performance on the target domain. However, the existing methods lack effective feature representation to ensure a significant similarity between the source domain and the target domain. To address this problem, we propose a novel method, called Cycle-Consistent Adversarial chest X-rays Domain Adaptation (C2ADA) to diagnose pneumonia from Chest X-rays automatically, which can transfer knowledge from a publicly available large-scale source dataset to the small-scale target dataset and achieve high performance with fewer target domain samples. Specifically, C2ADA introduces the cycle-consistent adversarial module to enforce the feature extractor to learn domain-invariant features. Furthermore, unlike most existing domain adaptation methods that deal with the same tasks in the source domain and target domain, our perspective is that heterogeneous tasks can assist the target domain in learning more effectively. Therefore, C2ADA includes two subnetworks, one is for the source domain, which contains a multilabel classification task, and the other is for the target domain, which focuses on the binary classification task. To assess the effectiveness of our method, we conduct a comparative analysis with other domain adaptation approaches. The experimental results show that the proposed method can achieve 96.86% accuracy on the ChestXRay2017 dataset utilizing just 50 images.

Elevating electron energy gain and betatron x-ray emission in proton-driven wakefield acceleration

The long proton beams present at CERN have the potential to evolve into a train of microbunches through the self-modulation instability process. The resonant wakefield generated by a periodic train of proton microbunches can establish a high acceleration field within the plasma, facilitating electron acceleration. This paper investigates the impact of plasma density on resonant wakefield excitation, thus influencing the acceleration of a witness electron bunch and its corresponding betatron radiation within the wakefield. Various scenarios involving different plasma densities are explored through particle-in-cell simulations. The peak wakefield in each scenario is calculated by considering a long pre-modulated proton driver with a fixed peak current. Subsequently, the study delves into the witness beam acceleration in the peak wakefield and its radiation emission. Elevated plasma density increases both the number of microbunches and the accelerating gradient of each microbunch, consequently resulting in heightened resonant wakefield. Nevertheless, the scaling is disrupted by the saturation of the resonant wakefield due to the nonlinearities. The simulation results reveal that at high plasma densities, an intense and broadband radiation spectrum extending into the domain of the hard x-rays and gamma rays is generated. Furthermore, in such instances, the energy gain of the witness beam is significantly enhanced. The impact of wakefield on the witness energy gain and the corresponding radiation spectrum is clearly evident at elevated densities.

Prospects for Time-Domain and Multi-Messenger Science with AXIS

The Advanced X-ray Imaging Satellite (AXIS) promises revolutionary science in the X-ray and multi-messenger time domain. AXIS will leverage excellent spatial resolution (<1.5 arcsec), sensitivity (80× that of Swift), and a large collecting area (5–10× that of Chandra) across a 24-arcmin diameter field of view at soft X-ray energies (0.3–10.0 keV) to discover and characterize a wide range of X-ray transients from supernova-shock breakouts to tidal disruption events to highly variable supermassive black holes. The observatory’s ability to localize and monitor faint X-ray sources opens up new opportunities to hunt for counterparts to distant binary neutron star mergers, fast radio bursts, and exotic phenomena like fast X-ray transients. AXIS will offer a response time of <2 h to community alerts, enabling studies of gravitational wave sources, high-energy neutrino emitters, X-ray binaries, magnetars, and other targets of opportunity. This white paper highlights some of the discovery science that will be driven by AXIS in this burgeoning field of time domain and multi-messenger astrophysics. This White Paper is part of a series commissioned for the AXIS Probe Concept Mission; additional AXIS White Papers can be found at the AXIS website.

X-Ray Emission from Atomic Systems Can Distinguish between Prevailing Dynamical Wave-Function Collapse Models.

In this work the spontaneous electromagnetic radiation from atomic systems, induced by dynamical wave-function collapse, is investigated in the x-ray domain. Strong departures are evidenced with respect to the simple cases considered until now in the literature, in which the emission is either perfectly coherent (protons in the same nuclei) or incoherent (electrons). In this low-energy regime the spontaneous radiation rate strongly depends on the atomic species under investigation and, for the first time, is found to depend on the specific collapse model.

Soft X-ray wavefront sensing at an ellipsoidal mirror shell

A reliable `in situ' method for wavefront sensing in the soft X-ray domain is reported, developed for the characterization of rotationally symmetric optical elements, like an ellipsoidal mirror shell. In a laboratory setup, the mirror sample is irradiated by an electron-excited (4.4 keV), micrometre-sized (∼2 µm) fluorescence source (carbon K α, 277 eV). Substantially, the three-dimensional intensity distribution I(r) is recorded by a CCD camera (2048 × 512 pixels of 13.5 µm) at two positions along the optical axis, symmetrically displaced by ±21–25% from the focus. The transport-of-intensity equation is interpreted in a geometrical sense from plane to plane and implemented as a ray tracing code, to retrieve the phase Φ(r) from the radial intensity gradient on a sub-pixel scale. For reasons of statistical reliability, five intra-/extra-focal CCD image pairs are evaluated and averaged to an annular two-dimensional map of the wavefront error {\cal W}. In units of the test wavelength (C K α), an r.m.s. value \sigma_{\cal{W}} = ±10.9λ0 and a peak-to-valley amplitude of ±31.3λ0 are obtained. By means of the wavefront, the focus is first reconstructed with a result for its diameter of 38.4 µm, close to the direct experimental observation of 39.4 µm (FWHM). Secondly, figure and slope errors of the ellipsoid are characterized with an average of ±1.14 µm and ±8.8 arcsec (r.m.s.), respectively, the latter in reasonable agreement with the measured focal intensity distribution. The findings enable, amongst others, the precise alignment of axisymmetric X-ray mirrors or the design of a wavefront corrector for high-resolution X-ray science.

Ray-traced spectra of a hot neutron star for various metallicities

General relativity strongly affects the observed spectra of compact objects. New models of hot nonrotating neutron star (NS) atmospheres are presented for various chemical compositions. We demonstrate the influence of strong gravity on the value of the hardening factor measured by a distant observer. We prepare new xspec fitting packages based on our extended numerical models for hot NS atmospheres in order to use them for a spectral analysis in the X-ray domain. For the Schwarzschild metric, ray-tracing calculations were performed to determine the observational appearance of the continuum emission of an NS. The grid of intensity spectra emerging from the NS surface was computed with the code which solves the model atmosphere equations with an accurate treatment of the Compton scattering of photons on free electrons in fully relativistic thermal motion. For the single value of the surface gravity, $ =14.34$ (cgs), the emerging specific intensity spectra were then ray-traced from the surface to the distant observer with the code across the spacetime of a nonrotating NS obtained using the lo library. The color-correction factors were determined for a large grid of models of different chemical compositions for surface gravities from the critical gravity $ g_ crit $ up to $15.00$ (cgs), and for effective temperatures in the range of $10^ eff $ K. Comptonized spectra seen at the source rest frame display hardening factors in the range from 1.4 up to 2.0 in the case of a highly luminous metal-rich atmosphere. The ratio of the color temperature $T_ c $ to the effective temperature $T_ eff $ for ray-traced spectra is in the range $0.9-1.4$. In the strong gravity regime, the structure of a hot atmosphere strongly depends on the surface gravity, luminosity, and atmospheric metal abundance of the NS. The theoretical hardening factors of the ray-traced spectra are systematically lower then the hardening factors of spectra at the source by about 30<!PCT!> on average.

Investigating the Properties of the Relativistic Jet and Hot Corona in AGN with X-ray Polarimetry

X-ray polarimetry has been suggested as a prominent tool for investigating the geometrical and physical properties of the emissions from active galactic nuclei (AGN). The successful launch of the Imaging X-ray Polarimetry Explorer (IXPE) on 9 December 2021 has expanded the previously restricted scope of polarimetry into the X-ray domain, enabling X-ray polarimetric studies of AGN. Over a span of two years, IXPE has observed various AGN populations, including blazars and radio-quiet AGN. In this paper, we summarize the remarkable discoveries achieved thanks to the opening of the new window of X-ray polarimetry of AGN through IXPE observations. We will delve into two primary areas of interest: first, the magnetic field geometry and particle acceleration mechanisms in the jets of radio-loud AGN, such as blazars, where the relativistic acceleration process dominates the spectral energy distribution; and second, the geometry of the hot corona in radio-quiet AGN. Thus far, the IXPE results from blazars favor the energy-stratified shock acceleration model, and they provide evidence of helical magnetic fields inside the jet. Concerning the corona geometry, the IXPE results are consistent with a disk-originated slab-like or wedge-like shape, as could result from Comptonization around the accretion disk.

Generation of interferometrically stable pulse pairs from a free-electron laser using a birefringent interferometer

We present a compact, intrinsically stable common path interferometer for the seeding of free-electron lasers (FELs). The interferometer can handle the required ultraviolet seed wavelengths and features an excellent phase stability of 10 mrad at 265 nm. By seeding the FEL FERMI, we demonstrate the generation of extreme ultraviolet (XUV) pulse pairs with tunable delay and a delay stability of 6 as at 52.5 nm. Prospective applications are Fourier transform spectroscopy, nonlinear spectroscopy and coherent control experiments in the XUV and x-ray domain.

Nanoscale x-ray imaging with high spectral sensitivity using fluorescence intensity correlations.

This paper introduces spectral incoherent diffractive imaging (SIDI) as a novel method for achieving dark-field imaging of nanostructures with heterogeneous oxidation states. With SIDI, shifts in photoemission profiles can be spatially resolved, enabling the independent imaging of the underlying emitter distributions contributing to each spectral line. In the x-ray domain, this approach offers unique insights beyond the conventional combination of diffraction and x-ray emission spectroscopy. When applied at x-ray free-electron lasers, SIDI promises to be a versatile tool for investigating a broad range of systems, offering unprecedented opportunities for detailed characterization of heterogeneous nanostructures for catalysis and energy storage, including of their ultrafast dynamics.

Growth, Structure, and Electrical Properties of AgNbO3 Antiferroelectric Single Crystal

AgNbO3 (AN) lead-free antiferroelectric material has attracted great attention in recent years. However, little focus has been directed toward a single crystal that can provide more basic information. In this study, we successfully grew high-quality AN single crystals, using a flux method, with dimensions of 5 × 5 × 3 mm3. A systematic investigation into the crystal structure, domain structure, and electrical properties of a [001]-oriented AN single crystal was conducted. X-ray diffraction and domain structure analysis revealed an orthorhombic phase structure at room temperature. Stripe-like 90° domains aligning parallel to the [110] direction with a thickness of approximately 10–20 μm were observed using a polarized light microscope. The temperature dependence of dielectric permittivity showed M1-M2, M2-M3, and M3-O phase transitions along with increasing temperature, but the phase transition temperatures were slightly higher than those of ceramic. The AN single crystal also exhibited double polarization-electric field (P-E) hysteresis loops, which enabled good recoverable energy-storage density and efficiency comparable to ceramic. Additionally, double P-E loops were kept stable at various temperatures and frequencies, demonstrating robust stability and confirming typical antiferroelectric characteristics. Our work provides valuable insights into understanding the fundamental antiferroelectric properties of AN-based materials.

NuSTAR and Swift observations of two supergiant fast X-ray transients: AX J1841.0−0536 and SAX J1818.6−1703

ABSTRACT Supergiant fast X-ray transients are wind-fed binaries hosting neutron star accretors, which display a peculiar variability in the X-ray domain. Different models have been proposed to explain this variability and the strength of the compact object magnetic field is generally considered a key parameter to discriminate among possible scenarios. We present here the analysis of two simultaneous observational campaigns carried out with Swift and NuSTAR targeting the supergiant fast X-ray transient sources AX J1841.0−0536 and SAX J1818.6−1703. A detailed spectral analysis is presented for both sources, with the main goal of hunting for cyclotron resonant scattering features that can provide a direct measurement of the neutron star magnetic field intensity. AX J1841.0−0536 was caught during the observational campaign at a relatively low flux. The source broad-band spectrum was featureless and could be well-described by using a combination of a hot blackbody and a power-law component with no measurable cut-off energy. In the case of SAX J1818.6−1703, the broad-band spectrum presented a relatively complex curvature which could be described by an absorbed cut-off power law (including both a cut-off and a folding energy) and featured a prominent edge at ∼7 keV, compatible with being associated to the presence of a ‘screen’ of neutral material partly obscuring the X-ray source. The fit to the broad-band spectrum also required the addition of a moderately broad (∼1.6 keV) feature centred at ∼14 keV. If interpreted as a cyclotron resonant scattering feature, our results would indicate for SAX J1818.6−1703 a relatively low-magnetized neutron star (∼1.2 × 1012 G).

Validation of a Deep Learning Chest X-ray Interpretation Model: Integrating Large-Scale AI and Large Language Models for Comparative Analysis with ChatGPT.

This study evaluates the diagnostic accuracy and clinical utility of two artificial intelligence (AI) techniques: Kakao Brain Artificial Neural Network for Chest X-ray Reading (KARA-CXR), an assistive technology developed using large-scale AI and large language models (LLMs), and ChatGPT, a well-known LLM. The study was conducted to validate the performance of the two technologies in chest X-ray reading and explore their potential applications in the medical imaging diagnosis domain. The study methodology consisted of randomly selecting 2000 chest X-ray images from a single institution's patient database, and two radiologists evaluated the readings provided by KARA-CXR and ChatGPT. The study used five qualitative factors to evaluate the readings generated by each model: accuracy, false findings, location inaccuracies, count inaccuracies, and hallucinations. Statistical analysis showed that KARA-CXR achieved significantly higher diagnostic accuracy compared to ChatGPT. In the 'Acceptable' accuracy category, KARA-CXR was rated at 70.50% and 68.00% by two observers, while ChatGPT achieved 40.50% and 47.00%. Interobserver agreement was moderate for both systems, with KARA at 0.74 and GPT4 at 0.73. For 'False Findings', KARA-CXR scored 68.00% and 68.50%, while ChatGPT scored 37.00% for both observers, with high interobserver agreements of 0.96 for KARA and 0.97 for GPT4. In 'Location Inaccuracy' and 'Hallucinations', KARA-CXR outperformed ChatGPT with significant margins. KARA-CXR demonstrated a non-hallucination rate of 75%, which is significantly higher than ChatGPT's 38%. The interobserver agreement was high for KARA (0.91) and moderate to high for GPT4 (0.85) in the hallucination category. In conclusion, this study demonstrates the potential of AI and large-scale language models in medical imaging and diagnostics. It also shows that in the chest X-ray domain, KARA-CXR has relatively higher accuracy than ChatGPT.

A low noise CMOS camera system for 2D resonant inelastic soft X-ray scattering

Resonant Inelastic X-ray Scattering (RIXS) is a powerful spectroscopic technique to study quantum properties of materials in the bulk. A novel variant of RIXS, called 2D RIXS, enables concurrent measurement of the scattered X-ray spectrum for a wide range of input energies, improving on the typically low throughput of 1D RIXS. In the soft X-ray domain, 2D RIXS demands an X-ray camera system with small pixels, large area, high quantum efficiency and low noise to limit the false detection rate in long duration exposures. We designed and implemented a 7.5 Megapixel back-illuminated CMOS detector with 5 μm pixels and high quantum efficiency in the 200–1,000 eV X-ray energy range for the QERLIN 2D RIXS spectrometer at the Advanced Light Source. The QERLIN beamline and detector are currently in commissioning. The camera noise from in-situ 3 s long dark exposures is 7e− or less and the leakage current is 6.5 × 10−3 e−/(pixel ∙ s). For individual 500 eV X-rays, the expected efficiency is greater than 75% and the false detection rate is ∼1 × 10−5 per pixel.

Swift, NuSTAR, and INTEGRAL observations of the symbiotic X-ray binary IGR J16194-2810

ABSTRACT We report on a simultaneous observational campaign with both Swift/XRT and NuSTAR targeting the symbiotic X-ray binary (SyXB) IGR J16194-2810. The main goal of the campaign was to investigate the possible presence of cyclotron scattering absorption features in the broad-band spectrum of the source, and help advance our understanding of the process of neutron star formation via the accretion-induced collapse of a white dwarf. The 1–30 keV spectrum of the source, as measured during our campaign, did not reveal the presence of any statistically significant absorption feature. The spectrum could be well described using a model comprising a thermal black-body hot component, most likely emerging from the surface of the accreting neutron star, and a power law with no measurable cut-off energy (and affected by a modest absorption column density). Compared to previous analyses in the literature, we could rule out the presence of a colder thermal component emerging from an accretion disc, compatible with the idea that IGR J16194-2810 is a wind-fed binary (as most of the SyXBs). Our results were strengthened by exploiting the archival XRT and INTEGRAL data, extending the validity of the spectral model used up to 0.3–40 keV and demonstrating that IGR J16194-2810 is unlikely to undergo significant spectral variability over time in the X-ray domain.

GRANDMA and HXMT Observations of GRB 221009A: The Standard Luminosity Afterglow of a Hyperluminous Gamma-Ray Burst—In Gedenken an David Alexander Kann

Object GRB 221009A is the brightest gamma-ray burst (GRB) detected in more than 50 yr of study. In this paper, we present observations in the X-ray and optical domains obtained by the GRANDMA Collaboration and the Insight Collaboration. We study the optical afterglow with empirical fitting using the GRANDMA+HXMT-LE data sets augmented with data from the literature up to 60 days. We then model numerically using a Bayesian approach, and we find that the GRB afterglow, extinguished by a large dust column, is most likely behind a combination of a large Milky Way dust column and moderate low-metallicity dust in the host galaxy. Using the GRANDMA+HXMT-LE+XRT data set, we find that the simplest model, where the observed afterglow is produced by synchrotron radiation at the forward external shock during the deceleration of a top-hat relativistic jet by a uniform medium, fits the multiwavelength observations only moderately well, with a tension between the observed temporal and spectral evolution. This tension is confirmed when using the augmented data set. We find that the consideration of a jet structure (Gaussian or power law), the inclusion of synchrotron self-Compton emission, or the presence of an underlying supernova do not improve the predictions. Placed in the global context of GRB optical afterglows, we find that the afterglow of GRB 221009A is luminous but not extraordinarily so, highlighting that some aspects of this GRB do not deviate from the global known sample despite its extreme energetics and the peculiar afterglow evolution.

Long-term multi-wavelength study of 1ES 0647+250

Context. The BL Lac object 1ES 0647+250 is one of the few distant γ-ray emitting blazars detected at very high energies (VHEs; ≳100 GeV) during a non-flaring state. It was detected with the MAGIC telescopes during a period of low activity in the years 2009−2011 as well as during three flaring activities in the years 2014, 2019, and 2020, with the highest VHE flux in the last epoch. An extensive multi-instrument data set was collected as part of several coordinated observing campaigns over these years. Aims. We aim to characterise the long-term multi-band flux variability of 1ES 0647+250, as well as its broadband spectral energy distribution (SED) during four distinct activity states selected in four different epochs, in order to constrain the physical parameters of the blazar emission region under certain assumptions. Methods. We evaluated the variability and correlation of the emission in the different energy bands with the fractional variability and the Z-transformed discrete correlation function, as well as its spectral evolution in X-rays and γ rays. Owing to the controversy in the redshift measurements of 1ES 0647+250 reported in the literature, we also estimated its distance in an indirect manner through a comparison of the GeV and TeV spectra from simultaneous observations with Fermi-LAT and MAGIC during the strongest flaring activity detected to date. Moreover, we interpret the SEDs from the four distinct activity states within the framework of one-component and two-component leptonic models, proposing specific scenarios that are able to reproduce the available multi-instrument data. Results. We find significant long-term variability, especially in X-rays and VHE γ rays. Furthermore, significant (3−4σ) correlations were found between the radio, optical, and high-energy (HE) γ-ray fluxes, with the radio emission delayed by about ∼400 days with respect to the optical and γ-ray bands. The spectral analysis reveals a harder-when-brighter trend during the non-flaring state in the X-ray domain. However, no clear patterns were observed for either the enhanced states or the HE (30 MeV < E < 100 GeV) and VHE γ-ray emission of the source. The indirect estimation of the redshift yielded a value of z = 0.45 ± 0.05, which is compatible with some of the values reported in the literature. The SEDs related to the low-activity state and the three flaring states of 1ES 0647+250 can be described reasonably well with the both one-component and two-component leptonic scenarios. However, the long-term correlations indicate the need for an additional radio-producing region located about 3.6 pc downstream from the gamma-ray producing region.

Pelphix: Surgical Phase Recognition from X-ray Images in Percutaneous Pelvic Fixation.

Surgical phase recognition (SPR) is a crucial element in the digital transformation of the modern operating theater. While SPR based on video sources is well-established, incorporation of interventional X-ray sequences has not yet been explored. This paper presents Pelphix, a first approach to SPR for X-ray-guided percutaneous pelvic fracture fixation, which models the procedure at four levels of granularity - corridor, activity, view, and frame value - simulating the pelvic fracture fixation workflow as a Markov process to provide fully annotated training data. Using added supervision from detection of bony corridors, tools, and anatomy, we learn image representations that are fed into a transformer model to regress surgical phases at the four granularity levels. Our approach demonstrates the feasibility of X-ray-based SPR, achieving an average accuracy of 99.2% on simulated sequences and 71.7% in cadaver across all granularity levels, with up to 84% accuracy for the target corridor in real data. This work constitutes the first step toward SPR for the X-ray domain, establishing an approach to categorizing phases in X-ray-guided surgery, simulating realistic image sequences to enable machine learning model development, and demonstrating that this approach is feasible for the analysis of real procedures. As X-ray-based SPR continues to mature, it will benefit procedures in orthopedic surgery, angiography, and interventional radiology by equipping intelligent surgical systems with situational awareness in the operating room.