Orbital Mass Research Articles

Orbital tuberculosis mimicking an ocular malignancy: a case report

Background: Tuberculosis (TB), a multi-systemic disease caused by Mycobacterium tuberculosis, is associated with a high burden of morbidity and mortality worldwide. The diagnosis of TB in children is challenging, particularly when it presents in rarer sites such as the eye. We present a case of a female Ghanaian toddler with a right orbital mass which mimicked an orbital malignancy and was confirmed as TB on histopathology. This case report highlights the need for a high index of suspicion for TB among children who present with orbital masses, especially in TB-endemic regions.

Effects of a modified Reissner-Nordström spacetime

A modified Reissner-Nordström spacetime is considered here, where the central object (for example, a black hole or naked singularity) possesses a mass, with an “ordinary”, i.e., Standard Model (SM) electric charge, along with a “dark” electric charge associated with dark matter (DM). The inclusion of this dark charge modifies the gravitational properties of the spacetime, while not affecting ordinary electrodynamics. Geodesic motions of both charged and uncharged SM test particles are modified due to the presence of dark charge. The modifications may allow the detection and measrement of the dark charge. In particular, (1) the effective potential for orbiting particles is modified, and consequently, (2) the angular momenta and ISCOs of test masses in circular orbits are changed from those for the usual Reissner-Nordström case. (3) In the case of a naked singularity, it is possible that a “levitating atmosphere”, due to short distance repulsive gravity, forms at the zero gravity radius, which depends upon both SM and DM charges. A levitating atmosphere may then cloak the naked singularity.

An Eosinophilic Variant of Orbital Granulomatosis with Polyangiitis with Ocular Motility Disorder

Purpose: To present the case of a patient with localized orbital granulomatosis with polyangiitis (GPA) characterized by a significant ocular motility disorder, increased eosinophilia, and hyper-immunoglobulin E (hyper-IgE).Case Summary: A 61-year-old male, with no previous history of allergy, atopy, asthma, sinonasal disease, respiratory disease, or renal disease, came to our hospital due to a 2-day history of binocular diplopia. His left eye exhibited inward and upward deviation, along with gaze limitation. His vision was 20/20 in both eyes, and the pupillary light reflex and color test were normal. He had severe eyelid swelling and conjunctival injection without tenderness in his left eye, and retinal vessel congestion around the optic nerve, without proptosis. Laboratory tests revealed a positive cytoplasmic antineutrophil cytoplasmic antibody (cANCA), a normal WBC count, elevated eosinophils at 28.3% (2,462/mm<sup>3</sup>), and high serum levels of IgE (400 KU/L). Magnetic resonance imaging showed an inferolateral orbital mass with an enlarged lacrimal gland and myositis of the extraocular muscles. A biopsy of the lacrimal gland revealed nonspecific chronic inflammation with an eosinophilic infiltrate. The presence of cANCA, in combination with clinical and pathological findings, led to the diagnosis of an eosinophilic variant of localized orbital GPA. This variant was primarily confined to the orbital tissue, marked by elevated eosinophil and IgE levels, and was treated with oral steroids without requiring surgery for the ocular motility disorder.Conclusions: GPA may present as acute strabismus with orbital inflammation, even in the absence of systemic signs. Therefore, it should be considered in the differential diagnosis of unexplained acute orbital syndromes.

Gravity-based network traffic abstraction and laser ON/OFF control in optical satellite networks

As the cost of launching low Earth orbit satellites continuously decreases, satellite-based communications networks are emerging as a new area for both academia and industry. Lasers are already employed for building inter-satellite links, forming optical satellite networks. The orbiting nature of satellites determines that the optical satellite networks are usually uniformly distributed around the Earth, to provide seamless coverage to any place at all times. However, the end users on the Earth are non-uniformly distributed. As a result, many satellites with laser links might not be utilized efficiently. From the energy perspective, this work studies the energy-efficiency issues of the inter-satellite laser links. We first model the optical satellite networks by presenting the satellite constellation with inter-satellite laser design principles and introduce the laser ON/OFF control problem accordingly. To explore the possibility of saving energy in the massive satellite deployment, we further introduce the gravity-based network traffic model and propose a gravity-based network traffic abstraction (GNTA) model to evaluate the importance of each laser link. Accordingly, we further propose a GNTA-based ON/OFF control (GOOC) algorithm to improve the energy efficiency of inter-satellite laser links by switching OFF parts of the laser links that are less utilized. We evaluate the GOOC’s performance using simulation, and results show that switching OFF 20% of the laser terminals in the full-gridmesh topology can improve the energy efficiency by about 10%, with an acceptable cost of network performance degradation.

Binary planet formation through tides

ABSTRACT The search for satellites around exoplanets represents one of the greatest challenges in advancing the characterization of planetary systems. Currently, we can only detect massive satellites, which resemble additional planetary companions rather than rocky moons. It is not yet well understood whether such substellar pairs, known as binary planets, are common or how they form. In this study, we investigated the formation scenario for binary planets resulting from tidal dissipation during close encounters in the gravitational instability scenario. We conducted seven sets of simulations, varying the number of initial planets injected into the system from two to five, as well as the amount of energy lost due to tides. Our results demonstrate that this formation mechanism is quite efficient in producing binary planets, with an average occurrence rate for the simulated systems of 14.3 per cent. Additionally, we present the distribution of relevant physical parameters (semimajor axis, eccentricity, mass ratios, and formation time) for planet–planet pairs. We also provide comprehensive statistics for single planets and planet–planet pairs.

The outer low-α disc of the Milky Way – I: evidence for the first pericentric passage of Sagittarius?

ABSTRACT Phase-space data, chemistry, and ages together reveal a complex structure in the outer low-α disc of the Milky Way. The age-vertical velocity dispersion profiles beyond the Solar Neighbourhood show a jump at 6 Gyr for stars beyond the Galactic plane. Stars older than 6 Gyr are significantly hotter than younger stars. The chemistry and age histograms reveal a bump at [Fe/H] = −0.5, [α/Fe] = 0.1, and an age of 7.2 Gyr in the outer disc. Finally, viewing the stars beyond 13.5 kpc in the age-metallicity plane reveals a faint streak just below this bump, towards lower metallicities at the same age. Given the uncertainty in age, we believe these features are linked and suggest a pericentric passage of a massive satellite ∼6 Gyr ago that heated pre-existing stars, and led to a starburst in existing gas. New stars also formed from the metal-poorer infalling gas. The impulse approximation was used to characterize the interaction with a satellite, finding a mass of ∼1011 M⊙, and a pericentric position between 12 and 16 kpc. The evidence points to an interaction with the Sagittarius dwarf galaxy, likely its first pericentric passage.

Orientations of Dark Matter Halos in FIRE-2 Milky Way–mass Galaxies

The shape and orientation of dark matter (DM) halos are sensitive to the microphysics of the DM particles, yet in many mass models, the symmetry axes of the Milky Way’s DM halo are often assumed to be aligned with the symmetry axes of the stellar disk. This is well motivated for the inner DM halo, but not for the outer halo. We use zoomed-in cosmological baryonic simulations from the Latte suite of FIRE-2 Milky Way–mass galaxies to explore the evolution of the DM halo’s orientation with radius and time, with or without a major merger with a Large Magellanic Cloud analog, and when varying the DM model. In three of the four cold DM halos we examine, the orientation of the halo minor axis diverges from the stellar disk vector by more than 20° beyond about 30 galactocentric kpc, reaching a maximum of 30°–90°, depending on the individual halo’s formation history. In identical simulations using a model of self-interacting DM with σ = 1 cm2 g−1, the halo remains aligned with the stellar disk out to ∼200–400 kpc. Interactions with massive satellites (M ≳ 4 × 1010 M ⊙ at pericenter; M ≳ 3.3 × 1010 M ⊙ at infall) affect the orientation of the halo significantly, aligning the halo’s major axis with the satellite galaxy from the disk to the virial radius. The relative orientation of the halo and disk beyond 30 kpc is a potential diagnostic of self-interacting DM, if the effects of massive satellites can be accounted for.

Ocular and orbital manifestations of granulomatosis with polyangiitis: a systematic review of published cases.

Objective: Granulomatosis with polyangiitis (GPA) is an autoimmune disorder characterized by necrotizing granulomatous inflammation of small and medium-sized vessels. This systematic review aimed to highlight the most common ophthalmic manifestations and to uncover their associations with antineutrophil cytoplasmic antibody (ANCA) positivity and the presence of granulomas. Methods: A literature search of PubMed, Web of Science, and Scopus electronic databases was performed from journal inception to March 21, 2021, for case reports and a series of ophthalmic GPAs. Cytoplasmic-ANCA (c-ANCA), perinuclear-ANCA (p-ANCA), and granulomas were analyzed against many ophthalmic signs and symptoms. 306 patients with GPA were retrospectively studied. Results: Granulomas were present in 47.7% of our sample, c-ANCA in 59.2%, and p-ANCA in 10.8%. Scleritis was significantly associated with higher odds for c-ANCA positivity. Eye discharge, episcleritis, proptosis, and central nervous system (CNS) involvement were each significantly associated with lower odds for c-ANCA positivity. Orbital mass was significantly associated with lower odds for p-ANCA positivity. CNS involvement was significantly associated with higher odds for p-ANCA positivity (OR:3.08, 95% CI:1.02, 9.36, p=0.047) and orbital mass was significantly associated with lower odds for p-ANCA positivity. Conclusions: We recommend that clinicians should consider ocular or orbital GPA in patients presenting with non-specific eye complaints, such as vision impairment, orbital mass, or proptosis, and obtain further assessments to determine the possible presence of granuloma, c-ANCA, or p-ANCA. Abbreviations: GPA = Granulomatosis with Polyangiitis, ANCA = antineutrophil cytoplasmic antibody, c-ANCA = cytoplasmic-ANCA, p-ANCA = perinuclear-ANCA, CNS = central nervous system, AAVs = ANCA-associated vasculitides, SD = standard deviation, GU = genitourinary, ENT = ear nose and throat, OR = odds ratio, CI = confidence interval.

Presentation pattern and survival rate of retinoblastoma following chemotherapy: a prospective study

BackgroundThis study presents the clinical pattern of presentation and survival rate of retinoblastoma, which is the most prevalent form of pediatric intraocular cancer. The aim of this study is to provide baseline information about the clinical presentation and management of retinoblastoma at ECWA Eye Hospital. Additionally, the study identifies priority areas for enhancing medical care for children diagnosed with this cancer. ECWA Eye Hospital, situated in Kano State, Nigeria, is a specialized eye center located in the North-Western region of the country.MethodsA prospective study spanning five years was conducted at ECWA Eye Hospital to investigate clinically diagnosed cases of retinoblastoma. The study took place from January 2018 to December 2022. The patients received standardized pre-medication and chemotherapy protocols for retinoblastoma. Subsequently, a five-year follow-up was conducted to monitor the patients’ progress. The collected data was analyzed, descriptive statistics were generated, and the survival rate was calculated.ResultsDuring the five-year study period, a total of 35 cases of retinoblastoma were diagnosed. The patients had an average age of 3.21 ± 1.32 years. The most common presentation patterns observed were fungating ocular mass and proptosis. Among the cases, there were 10 instances of bilateral proptosis and 25 instances of unilateral proptosis. While no patients exhibited bilateral leukocoria, eight cases of unilateral leukocoria with anterior segment seedlings were identified. The additional patterns of presentation are proptosis, leukocoria, fungating orbital mass, redness and loss of vision. The mortality rate was 80% (28 cases), while the survival rate was 20% (7 cases). Notably, all the survivors had unilateral retinoblastoma.ConclusionThe majority of cases observed at ECWA Eye Hospital involve advanced retinoblastoma. In low-resource settings where alternative treatment options are limited, chemotherapy is considered a viable treatment option. Early presentation of retinoblastoma in patients may lead to a higher survival rate when chemotherapy is administered.

Ages and metallicities of stellar clusters using S-PLUS narrow-band integrated photometry: the Small Magellanic Cloud

ABSTRACT The Magellanic Clouds are the most massive and closest satellite galaxies of the Milky Way (MW), with stars covering ages from a few Myr up to 13 Gyr. This makes them important for validating integrated light methods to study stellar populations and star formation processes, which can be applied to more distant galaxies. We characterized a set of stellar clusters in the Small Magellanic Cloud (SMC), using the Southern Photometric Local Universe Survey. This is the first age (metallicity) determination for 11 (65) clusters of this sample. Through its seven narrow bands, centred on important spectral features, and five broad bands, we can retrieve detailed information about stellar populations. We obtained ages and metallicities for all stellar clusters using the Bayesian spectral energy distribution fitting code bagpipes. With a sample of clusters in the colour range −0.20 < r − z < +0.35, for which our determined parameters are most reliable, we modeled the age–metallicity relation of SMC. At any given age, the metallicities of SMC clusters are lower than those of both the Gaia Sausage-Enceladus disrupted dwarf galaxy and the MW. In comparison with literature values, differences are Δlog(age) ≈ 0.31 and Δ[Fe/H] ≈ 0.41, which is comparable to low-resolution spectroscopy of individual stars. Finally, we confirm a previously known gradient, with younger clusters in the centre and older ones preferentially located in the outermost regions. On the other hand, we found no evidence of a significant metallicity gradient.

Impact of orbiting satellites on star formation rate evolution and metallicity variations in Milky Way-like discs

ABSTRACT At least one major merger is currently taking place in the Milky Way (MW). The Sagittarius (Sgr) dwarf galaxy is being tidally destroyed while orbiting around the MW, whose close passages perturb the disc externally. In this work, using hydrodynamical simulations, we investigate how massive dwarf galaxies on quasi-polar Sgr-like orbits impact the star formation (SF) inside the MW-like discs. First, we confirm that interactions with orbiting satellites enhance the SF rate in the host. However, prominent SF bursts are detected during the very close passages (<20 kpc) of massive (2 × 1010 M⊙) gas-poor satellites. For gas-rich satellites, while we observe substantial enhancement of the SF, we do not detect prominent peaks in the SF history of the host. This can be explained by the steady gas accretion from the satellite smoothening short-term variations in the SF. The impact of the satellite perturbations, especially its first encounters, is seen mainly in the outer (>10 kpc) disc. We also found that the close passages of satellites cause the formation of low-metallicity stars in the host, and the effect is the most prominent for gas infall from the satellites resulting in the dilution of the mean stellar metallicity. Our simulations are in favour of causality between the recent passages of the Sgr and the bursts of the SF in the solar neighbourhood (≈1 and ≈2 Gyr ago); however, to reproduce the SF burst at its first infall (≈6 Gyr), we require a very close passage (<20 kpc) with subsequent substantial mass-loss of the Sgr precursor.

Huge Fast Spacecraft Travelling Our Solar System

Can you imagine a large space system leaving from an Earth space elevator in excess of 12.34 km/sec, ensuring quick travel within our solar system? How about if it had an additional 10 km/sec assist from a slingshot release with the ability to gain another 15 km/sec by doing gravity assists along the way? The total concept being discussed is fast enough to allow travelling around our solar system within months instead of decades. However, there is more for those seeking answers beyond Earth – how about the ability to send multi-hundreds of tonnes along this path in a huge space system with fuel for rendezvous and landing along the way? How? Forget the Rocket Equation! You assemble a large spacecraft above the gravity well of the Earth, add velocity to it by virtue of the Earth’s rotation and then release it with extra velocity as if from a giant slingshot. An extra-long space elevator could achieve these goals by 2038. This story should be told as part of future opportunities for space exploration and science. Solar system travel, and even into interstellar regions, becomes reality with space elevators designed to assemble massive satellites and enable high velocity releases. Keywords: Space elevators, Neptune, Apex Anchor, Interplanetary

Hypernova signatures of the first stars in dwarf galaxies in the local group

ABSTRACT Observing the first generation of stars, Population III (Pop III), is still a challenge even with the JWST due to their faintness. Instead, searching for fossil records of Pop III stars in nearby dwarf galaxies provides an alternative method for studying their physical properties. It is intriguing that a star recently discovered in the Sculptor dwarf galaxy, named AS0039, is considered to show the unique signature of a Pop III star. The detailed abundance patterns of AS0039 are well matched with those predicted by nucleosynthesis models for Pop III exploding as an energetic hypernova (HN), confirming its potential to provide insight into the properties of the first stars. This study aims to explore the environmental conditions required for the formation of such a unique star using cosmological hydrodynamic zoom-in simulations on dwarf galaxies with a mass of $M_{\rm vir}\approx 10^8{\ \mathrm{ M}_\odot }$ at z = 0 while varying the fraction of Pop III stars that undergo HNe. Our simulations identify rapid gas inflow ($\dot{M}_{\rm gas}\sim 0.08{\ \mathrm{ M}_\odot }$ $\rm yr^{-1}$) as a possible factor in facilitating the formation of stars similar to AS0039. Alternatively, the delayed formation of subsequent Population II (Pop II) stars in the gas-enriched environment may lead to low-metallicity stars like AS0039. Additionally, using the a-sloth code, we investigate the probability of finding remnants of Pop II stars with HN signatures in nearby dwarf satellite galaxies. We suggest that the most likely dwarf galaxies to contain HN signatures are massive satellites with a probability of 40 per cent in the range of $M_{\rm peak}\approx 10^{10}\ \mathrm{ to} \ 10^{11}{\ \mathrm{ M}_\odot }$ and $M_{\ast }\approx 10^7 \ \mathrm{ to} \ 10^8{\ \mathrm{ M}_\odot }$, considering observational limitations.

Seeding the CGM: how satellites populate the cold phase of milky way haloes

ABSTRACT The origin of the cold phase in the circumgalactic medium (CGM) is a highly debated question. We investigate the contribution of satellite galaxies to the cold gas budget in the CGM of a Milky Way-like host galaxy. We perform controlled experiments with three different satellite mass distributions and identify several mechanisms by which satellites can add cold gas to the CGM, including ram pressure stripping and induced cooling in the mixing layer of the stripped cold gas. These two mechanisms contribute a comparable amount of cold gas to the host CGM. We find that the less massive satellites (≤109M⊙) not only lose all of their cold gas in a short period (∼ 0.5–1 Gyr), but their stripped cold clouds also mix with the hot CGM gas and get heated up quickly. However, stellar feedback from these less massive satellites can hugely alter the fate of their stripped gas. Feedback speeds up the destruction of the stripped cold clouds from these satellites by making them more diffuse with more surface area. On the other hand, the more massive satellites (LMC or SMC-like ∼1010M⊙) can add cold gas to the total gas budget of the host CGM for several Gyr.

Large orbital masses due to longstanding hydrogel retinal explants.

To describe the features of orbital masses occurring as a late complication of hydrogel retinal explants. Retrospective review of patients presenting with orbital masses at decades after retinal surgery. Two patients with huge orbital masses are described, their presenting 25 and 28 years after retinal detachment repair with expansile hydrogel explants. In one case, the preoperative diagnosis was pleomorphic adenoma, and the other-with extreme distortion of the globe-was considered to be lymphoma or chronic inflammation arising around prior retinal explants. At orbitotomy, the masses were found to be grossly expanded hydrogel explants that were removed piecemeal from their fibrous capsules. Histopathology showed very mild inflammation with occasional multinucleate giant cells and patchy capsular calcification, and an eosinophilic amorphous material staining strongly with Alcian-blue. Surgery was uncomplicated and both orbits healed with marked functional improvement. Expansile hydrogel retinal explants were largely used in the 1980s and can present, often decades after the retinal surgery, with impaired orbital functions due to large parabulbar masses. The hydrophilic material appears to expand very slowly over decades, leading to gross distortion of neighbouring structures and a tumour-like mass.

Study on removal of oxytetracycline by KOH-modified chestnut shell biochar: Based on two-dimensional spectroscopy and molecular density functional theory

The adsorption type and mode of biochar have been extensive research. However, as an indispensable link to reveal the adsorption mechanism, the study of the adsorption sequence is greatly lacking, especially for different pollutants, the way of adsorption is different. In this study, the observation of the adsorption sequence was amplified by KOH modification and optimization of experimental conditions. Persistent radicals (PFRs) combined with liquid mass spectrometry (LC-MS) eliminated interference from oxidation-reduction. Notability, two-dimensional correlation spectroscopy (2D-COS), Raman and Fourier-transform infrared (FTIR) spectroscopy reveals that the vibration amplitude and velocity of the hydroxyl group are better than those of the carboxyl group, methyl group, and methylene group under time interference. Electrostatic adsorption (EA), H-bood (HB), and π-π* contribute 63.5 %, 35.3 %, and 1.2 %, respectively, to the adsorption of oxytetracycline (OTC). The density functional calculation shows that the nucleophilic and electrophilic reactions of OTC are easy to occur near oxygen atoms and nitrogen atoms. The Fukui function proves that the free radical weight of the N atom is 0.096, which is further confirmed the theoretical predictions by liquid chromatography and four-stage electrostatic field orbital trap mass spectrometry. Finally, this study provides a deeper insight into the biochar adsorption OTC.

When the well runs dry: modelling environmental quenching of high-mass satellites in massive clusters at z ≳ 1

ABSTRACT We explore models of massive (>1010 M⊙) satellite quenching in massive clusters at z ≳ 1 using an MCMC framework, focusing on two primary parameters: Rquench (the host-centric radius at which quenching begins) and τquench (the time-scale upon which a satellite quenches after crossing Rquench). Our MCMC analysis shows two local maxima in the 1D posterior probability distribution of Rquench at approximately 0.25 and 1.0 R200. Analysing four distinct solutions in the τquench–Rquench parameter space, nearly all of which yield quiescent fractions consistent with observational data from the GOGREEN survey, we investigate whether these solutions represent distinct quenching pathways and find that they can be separated between ‘starvation’ and ‘core quenching’ scenarios. The starvation pathway is characterized by quenching time-scales that are roughly consistent with the total cold gas (H2 + H i) depletion time-scale at intermediate z, while core quenching is characterized by satellites with relatively high line-of-sight velocities that quench on short time-scales (∼0.25 Gyr) after reaching the inner region of the cluster (<0.30 R200). Lastly, we break the degeneracy between these solutions by comparing the observed properties of transition galaxies from the GOGREEN survey. We conclude that only the ‘starvation’ pathway is consistent with the projected phase-space distribution and relative abundance of transition galaxies at z ∼ 1. However, we acknowledge that ram pressure might contribute as a secondary quenching mechanism.

Orbital mass in an anophthalmic socket: An unusual case with literature review

Malignant tumors in an anophthalmic socket are a rare phenomenon, which occurs when care of the anophthalmic socket and ocular prosthesis is overlooked. We report a 32-year-old male patient who developed an orbital mass in an anophthalmic socket 6 months following evisceration. The triggering factor in the present case was chronic irritation and trauma to the upper conjunctiva from wearing an ill-fitted ocular prosthesis. The patient had an eyelid-sparing exenteration, and histopathological examination showed the features of squamous cell carcinoma. This case illustrates the need of diligent examination of the anophthalmic socket and frequent follow-ups to detect untoward events at the earliest for timely intervention. A literature review was also performed to find out how rare is this disease and its time of onset after enucleation and evisceration.

Are smallsats taking over bigsats for land Earth observation?

In this work the evolution of the utilization of small satellites for land Earth observation missions is addressed. Scatter and “bubble” plots, supplemented by the calculation of correlation coefficients for pairs of selected variables, are used to identify, qualify and quantify trends. Optical and Synthetic Aperture RADAR (SAR) missions are considered separately. Systems are discriminated as single or constellation, and commercial or government owned. Trends coupling satellite mass to ground sample distance, and number of spectral bands, for optical satellites, and spatial resolution and microwave band for SARs, are also analyzed. The present analysis indicates that smallsats seems to be getting increasingly competitive, that is, they have become an alternative to bigger satellites, for most types of optical missions. On the other hand, the SAR arena still seems to pose a big challenge to satellite miniaturization, in spite of recent remarkable advances obtained on the fielding of smallsat X-band SAR constellations.

Can 18F-FDG PET/CT findings be used to predict orbital tumor histology?

To investigate whether 18F-FDG PET/CT might be useful to predict the histology of various orbital tumors based on the maximum standard uptake value (SUVmax) and the OMSUV (orbital max SUV)/MLSUV (mean liver SUV) ratio. A retrospective single-center study was conducted between May 2019 and December 2020. Patients with an orbital mass who underwent preoperative 18F-FDG PET/CT followed by an orbital biopsy were included. Tumor histology was classified as follows: orbital inflammation, solid tumor, low-grade lymphoid tumor, and high-grade lymphoid tumor. Orbital tumors were also classified as indolent or aggressive. Data recorded included the orbital SUVmax, OMSUV/MLSUV ratio and additional extra-orbital SUV sites. Forty-five patients (24 men) were included. There were 15 (33.3%), 14 (31.1%), 9 (20%), and 7 (15.5%) cases of orbital inflammation, solid tumor, low-grade lymphoid tumor, and high-grade lymphoid tumor, respectively. No correlation was found between the OMSUV/MLSUV ratio and orbital SUVmax and tumor histology (Z = -0.77, Z = -0.6, Z = -1.6, and Z =0.94, all P>0.05, respectively). No correlation was found between the OMSUV/MLSUV ratio (Z =-1.42, P>0.05) and orbital SUVmax (Z =-0.82, P>0.05) and tumor aggressiveness (indolent versus aggressive). Subgroup analyses showed that SUVmax was predictive of lymphoma aggressiveness (P=0.05) and was able to distinguish orbital cancers (all lymphomas+solid tumors) from benign tumors (P=0.02). 18F-FDG PET/CT could not be used to predict the underlying orbital tumor histology. However, more aggressive tumors, especially high-grade lymphomas and cancers, tended to have a higher orbital SUVmax compared to indolent lesions.