Disc Location Research Articles

Disk wakes in nonlinear stratification

Nonlinearity of density stratification modulates buoyancy effects. We report results from a body-inclusive large eddy simulation of a wake in nonlinear stratification, specifically for a circular disk at diameter-based Reynolds number ( ${\it Re} $ ) of $5000$ . Five density profiles are considered; the benchmark has linear stratification and the other four have hyperbolic tangent profiles of the same thickness to model a pycnocline. The disk moves inside the central core of the pycnocline in two of those four cases and, in the other two cases with a shifted density profile, the disk moves partially/completely outside the pycnocline. The maximum buoyancy frequency ( $N_{max}$ ) for all the profiles is the same. The first part of the study investigates the centred cases. Non-uniform stratification results in increasing wake turbulence relative to the benchmark owing to reduced suppression of turbulence production as well as wave trapping in the pycnocline. Steady lee waves are also quantified to understand the limitations of linear theory. The second part pays attention to the effect of a relative shift between the pycnocline and the disk. The wake defect velocity decays substantially faster in the cases with a shift and the wake has higher turbulence level. The effect of disk location on the Kelvin wake waves (a family of steady waves within the pycnocline) and its modal form is obtained and explained by solving the Taylor–Goldstein equation. The family of unsteady internal gravity waves that are generated by the wake is also studied and the effect of disk shift is quantified.

Role of time in binding features in visual working memory.

Previous research on feature binding in visual working memory has supported a privileged role for location in binding an object's nonspatial features. However, humans are able to correctly recall feature conjunctions of objects that occupy the same location at different times. In a series of behavioral experiments, we investigated binding errors under these conditions, and specifically tested whether ordinal position can take the role of location in mediating feature binding. We performed two dual report experiments in which participants had to memorize three colored shapes presented sequentially at the screen center. When participants were cued with the ordinal position of one item and had to report its shape and color, report errors for the two features were largely uncorrelated. In contrast, when participants were cued, for example, with an item's shape and reported an incorrect ordinal position, they had a high chance of making a corresponding error in the color report. This pattern of error correlations closely matched the predictions of a model in which color and shape are bound to each other only indirectly via an item's ordinal position. In a third experiment, we directly compared the roles of location and sequential position in feature binding. Participants viewed a sequence of colored disks displayed at different locations and were cued either by a disk's location or its ordinal position to report its remaining properties. The pattern of errors supported a mixed strategy with individual variation, suggesting that binding via either time or space could be used for this task. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Cold Deuterium Fractionation in the Nearest Planet-forming Disk

Deuterium fractionation provides a window into the thermal history of volatiles in the solar system and protoplanetary disks. While evidence of active molecular deuteration has been observed toward a handful of disks, it remains unclear whether this chemistry affects the composition of forming planetesimals due to limited observational constraints on the radial and vertical distribution of deuterated molecules. To shed light on this question, we introduce new Atacama Large Millimeter/submillimeter Array observations of DCO+ and DCN J = 2–1 at an angular resolution of 0.″5 (30 au) and combine them with archival data of higher energy transitions toward the protoplanetary disk around TW Hya. We carry out a radial excitation analysis assuming both LTE and non-LTE to localize the physical conditions traced by DCO+ and DCN emission in the disk, thus assessing deuterium fractionation efficiencies and pathways at different disk locations. We find similar disk-averaged column densities of 1.9 × 1012 and 9.8 × 1011 cm−2 for DCO+ and DCN, with typical kinetic temperatures for both molecules of 20–30 K, indicating a common origin near the comet- and planet-forming midplane. The observed DCO+/DCN abundance ratio, combined with recent modeling results, provide tentative evidence of a gas-phase C/O enhancement within <40 au. Observations of DCO+ and DCN in other disks, as well as HCN and HCO+, will be necessary to place the trends exhibited by TW Hya in context, and fully constrain the main deuteration mechanisms in disks.

Fatigue crack propagation analysis in an aero-engine turbine disc using computational methods and spin test

This article presents a study on applying the fracture mechanics-based method to predict the fatigue crack growth (FCG) characteristics of the turbine disc in a turboshaft engine. According to the stress analysis results, the electric discharge machining (EDM) method introduced notches for initiating cracks of a specific size into the critical locations of the turbine disc. The FCG of these cracks under cyclic load was predicted utilising a three-dimensional (3D) numerical analysis method and a simplified rectangular plate model with relevant fracture mechanics properties. Meanwhile, the full-scale spin test was performed using a pre-flawed turbine disc under intentional loads at an isothermal temperature. After the test, the crack surface fractography and the quantitative fracture striation analysis revealed the practical crack propagation behaviour. There was a relatively small difference between the experimental results and the 3D finite element method, which indicated the good predictability of FEM for turbine disc crack growth. Furthermore, the rectangular plate models could predict the front stage of steady-state crack growth but were overall conservative due to their inability to precisely calculate the effects of crack growth and structure geometry on the stress intensity factor.

Optic disc localization using graph traversal algorithm along blood vessel in polar retinal image

The optic disc (OD) is an important landmark of the retina and its location is essential for computer-aided diagnosis of diabetic retinopathy and glaucoma. This paper presented a new method that applies the proposed graph traversal algorithm for vertical vascular infrastructure to detect root nodes representing the location of optical discs. The proposed algorithms were designed to process the terrific view of blood vessels from a polar image without depending on the prominent OD characteristic of circular/elliptical shape and brightness. Before constructing the vascular infrastructure, the new multi-scale and multi-orientation top-hat filters were proposed to properly approximate blood vessels of different sizes and directions. The proposed method provided efficiency and certainty for complex retinal images such as low contrast OD with low illumination and distorted OD shape due to complex vascular structure. The algorithms evaluation was performed on five public fundus image databases for retinal image analysis. Experimental results revealed that the proposed algorithm identified valid optical discs with high accuracy as 91.21%, 95.09%, 88.45%, 91.66%, and 95.01% for the five corresponding data sets and outperformed comparison methods.

Rock Magnetic Characterization of Returned Samples From Asteroid (162173) Ryugu: Implications for Paleomagnetic Interpretation and Paleointensity Estimation

AbstractIn this study, systematic rock magnetic measurements and saturation isothermal remanent magnetization (SIRM) paleointensity calibration experiments were conducted for the returned samples from C‐type asteroid (162173) Ryugu and two carbonaceous chondrites (Orgueil and Tagish Lake) to evaluate the remanence carriers of the Ryugu sample and its ability as a paleomagnetic recorder. Our magnetic measurements show that Ryugu samples exhibit signatures for framboidal magnetite, coarse‐grained magnetite, and pyrrhotite, and that framboidal magnetite is the dominant remanence carrier of Ryugu samples in the middle‐coercivity range. The SIRM paleointensity constant was obtained for two Ryugu samples, and the median value was 3,318 ± 1,038 μT, which is close to the literature's value based on the average among magnetite, titanomagnetite, pyrrhotite, and FeNi alloys and is widely used for SIRM paleointensity experiments. The paleointensity values estimated using the obtained SIRM paleointensity constant indicate a strong magnetic field of the protoplanetary disk, suggesting that Sun's protoplanetary disk existed at the disk location of Ryugu's parent planetesimal when framboidal magnetite precipitated from the aqueous fluid.

Magnetic resonance imaging features of canine intradural/extramedullary intervertebral disc extrusion in seven cases

Intervertebral disc disease, including intervertebral disc extrusions and protrusions, is the most common spinal cord disorder in dogs. Atypical and uncommon intervertebral disc herniations include intradural/intramedullary disc extrusion, intervertebral foraminal disc extrusion and intervertebral disc herniation (Schmorl's node). Intradural/extramedullary disc extrusion is the least common type of intervertebral disc herniation in veterinary medicine, characterized by extruded disc material within the intradural space. To date, only one study has been published in veterinary medicine reporting intradural/extramedullary disc extrusions. In this study, low field MRI was used, and the authors could not find any MRI features to diagnose with confidence an intradural/extramedullary disc location of the extruded disc material. The aim of this study was to describe the high field (1.5T) MRI characteristics of surgically confirmed intradural/extramedullary disc extrusions. This is a retrospective, multicentric and descriptive study. Inclusion criteria was surgical confirmation of intradural/extramedullary disc extrusion by durotomy and complete MRI study of the spine. Seven cases were included. Images were reviewed by a radiology resident and a certified radiologist, with emphasis on the following signs: “Golf-tee sign” (widening of the subarachnoid space cranial and caudal to the lesion), “Beak sign” (pointed and sharp compressive lesion) and “Y sign” (division of the dura and arachnoid layers). MRI showed a “Y sign” in all the cases (7/7) seen from the T2-weighted sagittal views, while “Golf-tee sign” was not recognized in any of the cases (0/7). Additionally, “beak sign” was present in half of the cases (4/7). “Y sign” maybe a reliable MRI feature for identifying intradural/medullary disc extrusions from the MRI study. As the arachnoid is peeled from the dura by the disc herniation there is a splitting of the arachnoid mater and the ventral dura. The intradural disc material will be surrounded by CSF signal intensity margin, giving the appearance of a Y, which can be identified from the T2-weighted sagittal images.

Detectability of category 3 or higher microcalcifications on digital mammograms: a comparative study between 5-MP color and monochrome liquid crystal display monitors.

This study explored the detectability of category 3 or higher microcalcifications using 5-MP color and monochrome monitors. Contrast detail mammography phantom with polymethyl methacrylate (PMMA) images were observed in color and monochrome by five radiographers, and the image quality figures (IQF) were calculated based on the gold disc locations identified. Five radiographers and two radiologists observed 200 mammograms from 100 patients (including 36 with microcalcifications) and rated the microcalcifications. The results were analyzed using area under the curve (AUC) and jackknife resampling. A paired t test was used for statistical analysis (p < 0.05). The mean IQF of color and monochrome monitors were 10.73 and 10.49 (30mm PMMA, p = 0.653) and 8.47 and 8.74 (50mm PMMA, p = 0.774), respectively. The mean AUC of color and monochrome monitors were 0.917 and 0.936 (p = 0.335), respectively, with windowing and magnification. The detectability of microcalcifications was not significantly different between the monitors.

Unsteady flow over a rotating and vertically moving disk with variable fluid properties

A numerical solution is worked out for unsteady flow around a revolving disk exhibiting upward/downward motion. A temperature-dependent viscosity model is introduced that yields a system in which momentum and energy equations are coupled in terms of a parameter [Formula: see text]. The disk revolves with the time-dependent angular velocity [Formula: see text] and vertically moves with the axial velocity [Formula: see text], where [Formula: see text] denotes the location of disk at any time t. The considered expressions of [Formula: see text] and [Formula: see text] suggest that upward/downward motion of the rotating disk leads to the case of accelerated/decelerated disk. Solutions are worked out by a widely employed routine bvp4c of MATLAB. The vertical motion of the disk leads to a two-dimensional flow problem when the disk is nonrotating. However, simultaneous vertical movement and rotation of the disk impart a three-dimensional motion. A marked variation in solution profiles is detected whenever temperature dependency in fluid viscosity is retained. In addition, the deceleration phenomenon of the disk declines heat transfer rate from the surface.

Planetesimal Dynamics in the Presence of a Giant Planet. II. Dependence on Planet Mass and Eccentricity

The presence of an early-formed giant planet in the protoplanetary disk has mixed influence on the growth of other planetary embryos. Gravitational perturbation from the planet can increase the relative velocities of planetesimals at the mean motion resonances to very high values and impede accretion at those locations. However, gas drag can also align the orbital pericenters of equal-size planetesimals in certain disk locations and make them dynamically quiet and “accretion-friendly” locations for planetesimals of similar sizes. Following the previous paper, where we investigated the effect of a Jupiter-like planet on an external planetesimal disk, we generalize our findings to extrasolar planetary systems by varying the planet parameters. In particular, we focus on the dependence of the planetesimal relative velocities on the mass and eccentricity of the existing planet. We found that the velocity dispersion of identical-mass particles increases monotonically with increasing planet mass. Meanwhile, the dependence of the relative velocity between different-mass planetesimals on their mass ratio becomes weaker as the planet mass increases. While the relative velocities generally increase with increasing planet eccentricity, the velocity dispersion of lower-mass particles (m ≲ 1018 g) is almost independent of planet eccentricity owing to their strong coupling to gas. We find that the erosion limits are met for a wider range of parameters (planet mass/eccentricity, planetesimal mass ratio) when the planetesimal size decreases. Our results could provide some clues for the formation of Saturn’s core, as well as the architecture of some exoplanetary systems with multiple cold giant planets.

Growth after the streaming instability: The radial distance dependence of the planetary growth

Streaming instability is hypothesized to be triggered at particular protoplanetary disk locations where the volume density of the solid particles is enriched comparable to that of the gas. A ring of planetesimals thus forms when this condition is fulfilled locally. These planetesimals collide with each other and accrete inward drifting pebbles from the outer disk to further increase masses. We investigate the growth of the planetesimals that form in a ring-belt at various disk radii. Their initial mass distributions are calculated based on the formula summarized from the streaming instability simulations. We simulate the subsequent dynamical evolution of the planetesimals with a protoplanetary disk model based either on the minimum mass solar nebula (MMSN) or on the Toomre stability criterion. For the MMSN model, both pebble accretion and planetesimal accretion are efficient at a close-in orbit of 0.3 AU, resulting in the emergence of several super-Earth mass planets after 1 Myr. For comparison, only the most massive planetesimals undergo substantial mass growth when they are born at r = 3 AU, while the planetesimals at r = 30 AU experience little or no growth. On the other hand, in the denser Toomre disk, the most massive forming planets can reach Earth mass at t = 1 Myr and reach a mass between that of Neptune and that of Saturn within 3 Myr at 30 AU and 100 AU. Both the pebble and planetesimal accretion rate decrease with disk radial distance. Nevertheless, planetesimal accretion is less pronounced than pebble accretion at more distant disk regions. Taken together, the planets acquire higher masses when the disk has a higher gas density, a higher pebble flux, and/or a lower Stokes number of pebbles.

The emergence of diffused gamma-ray burst afterglows from the discs of active galactic nuclei

ABSTRACT The discs of active galactic nuclei (AGNs) have emerged as rich environments for the production and capture of stars and the compact objects that they leave behind. These stars produce long gamma-ray bursts (GRBs) at their deaths, while frequent interactions among compact objects form binary neutron stars and neutron star–black hole binaries, leading to short GRBs upon their merger. Predicting the properties of these transients as they emerge from the dense environments of AGN discs is key to their proper identification and to better constrain the star and compact object population in AGN discs. Some of these transients would appear unusual because they take place in much higher densities than the interstellar medium. Others, which are the subject of this paper, would additionally be modified by radiation diffusion, since they are generated within optically thick regions of the accretion discs. Here, we compute the GRB afterglow light curves for diffused GRB sources for a representative variety of central black hole masses and disc locations. We find that the radiation from radio to ultraviolet and soft X-rays can be strongly suppressed by synchrotron self-absorption in the dense medium of the AGN disc. In addition, photon diffusion can significantly delay the emergence of the emission peak, turning a beamed, fast transient into a slow, isotropic, and dimmer one. These would appear as broad-band correlated AGN variability with a dominance at the higher frequencies. Their properties can constrain both the stellar populations within AGN discs and the disc structure.

Assessment of downy mildew in grapevine using computer vision and fuzzy logic. Development and validation of a new method

Downy mildew is a major disease of grapevine. Conventional methods for assessing crop diseases are time-consuming and require trained personnel. This work aimed to develop and validate a new method to automatically estimate the severity of downy mildew in grapevine leaves using fuzzy logic and computer vision techniques. Leaf discs of two grapevine varieties were inoculated with Plasmopara viticola and subsequently, RGB images were acquired under indoor conditions. Computer vision techniques were applied for leaf disc location in Petri dishes, image pre-processing and segmentation of pre-processed disc images to separate the pixels representing downy mildew sporulation from the rest of the leaf. Fuzzy logic was applied to improve the segmentation of disc images, rating pixels with a degree of infection according to the intensity of sporulation. To validate the new method, the downy mildew severity was visually evaluated by eleven experts and averaged score was used as the reference value. A coefficient of determination (R2) of 0.87 and a root mean squared error (RMSE) of 7.61 % was observed between the downy mildew severity obtained by the new method and the visual assessment values. Classification of the severity of the infection into three levels was also attempted, achieving an accuracy of 86 % and an F1 score of 0.78. These results indicate that computer vision and fuzzy logic can be used to automatically estimate the severity of downy mildew in grapevine leaves. A new method has been developed and validated to assess the severity of downy mildew in grapevine. The new method can be adapted to assess the severity of other diseases and crops in agriculture.

Identifying Those at Risk of Glaucoma: A Deep Learning Approach for Optic Disc and Cup Segmentation and Their Boundary Analysis.

Glaucoma is a leading cause of irreversible vision loss that gradually damages the optic nerve. In ophthalmic fundus images, measurements of the cup to optic disc (CD) ratio, CD area ratio, neuroretinal rim to optic disc (RD) area ratio, and rim thickness are key measures to screen for potential glaucomatous damage. We propose an automatic method using deep learning algorithms to segment the optic disc and cup and to estimate the key measures. The proposed method comprises three steps: The Region of Interest (ROI) (location of the optic disc) detection from a fundus image using Mask R-CNN, the optic disc and cup segmentation from the ROI using the proposed Multiscale Average Pooling Net (MAPNet), and the estimation of the key measures. Our segmentation results using 1099 fundus images show 0.9381 Jaccard Index (JI) and 0.9679 Dice Coefficient (DC) for the optic disc and 0.8222 JI and 0.8996 DC for the cup. The average CD, CD area, and RD ratio errors are 0.0451, 0.0376, and 0.0376, respectively. The average disc, cup, and rim radius ratio errors are 0.0500, 0.2257, and 0.2166, respectively. Our method performs well in estimating the key measures and shows potential to work within clinical pathways once fully implemented.

Does the sagittal spinal profile differ between the elderly Chinese populations with and without lumbar disc herniation?

To explore the characteristics of the sagittal spinopelvic profile in the elderly Chinese population with lumbar disc herniation (LDH) and to evaluate its influence on the severity, location and number of disc degeneration. A retrospective analysis was conducted on 212 elderly Chinese patients with LDH and 213 asymptomatic volunteers with matched age and sex. Sagittal spinopelvic parameters were measured on the full-length X-ray and the sagittal profiles were determined according to the Roussouly classification. The severity, location and number of lumbar disc degeneration were evaluated from the L12 to L5S1 discs on the MRI images. There were no significant differences in BMI between the two groups. Patients with LDH were found to have significantly smaller TK, LL, and SS than those in the asymptomatic population (P<0.05), while contradicting observations were obtained of PT and TPA (P<0.05). In the LDH group, Roussouly type 1 and type 2 (50.4% and 28.7%, respectively) were predominant and the proportion of type 1 in the elderly LDH population was further increased compared to the younger LDH population. LDH population with Roussouly type 1 and 2 showed more caudal herniated locations and fewer herniated numbers than those with type 3 and 4. The sagittal spinopelvic profile was significantly different between the elderly Chinese population with and without LDH. There were significant differences in the Roussouly distribution between the elderly and the younger groups and different Roussouly types have different effects on the lumbar disc degeneration patterns.

Snails across Scales: Local and Global Phase-mixing Structures as Probes of the Past and Future Milky Way

Abstract Signatures of vertical disequilibrium have been observed across the Milky Way’s (MW’s) disk. These signatures manifest locally as unmixed phase spirals in z–v z space (“snails-in-phase”), and globally as nonzero mean z and v z , wrapping around the disk into physical spirals in the x–y plane (“snails-in-space”). We explore the connection between these local and global spirals through the example of a satellite perturbing a test-particle MW-like disk. We anticipate our results to broadly apply to any vertical perturbation. Using a z–v z asymmetry metric, we demonstrate that in test-particle simulations: (a) multiple local phase-spiral morphologies appear when stars are binned by azimuthal action J ϕ , excited by a single event (in our case, a satellite disk crossing); (b) these distinct phase spirals are traced back to distinct disk locations; and (c) they are excited at distinct times. Thus, local phase spirals offer a global view of the MW’s perturbation history from multiple perspectives. Using a toy model for a Sagittarius (Sgr)–like satellite crossing the disk, we show that the full interaction takes place on timescales comparable to orbital periods of disk stars within R ≲ 10 kpc. Hence such perturbations have widespread influence, which peaks in distinct regions of the disk at different times. This leads us to examine the ongoing MW–Sgr interaction. While Sgr has not yet crossed the disk (currently, z Sgr ≈ −6 kpc, v z,Sgr ≈ 210 km s−1), we demonstrate that the peak of the impact has already passed. Sgr’s pull over the past 150 Myr creates a global v z signature with amplitude ∝ M Sgr, which might be detectable in future spectroscopic surveys.

Dynamical origin of the Dwarf Planet Ceres

The Dwarf Planet Ceres revealed the presence of ammonia and other unique properties compared to other asteroids in the main belt which suggests that it was not formed in situ. We model the early dynamical evolution of the outer Solar System to study possible dynamical mechanisms to implant a Ceres-sized planetesimal in the asteroid belt from the trans-Saturnian region. We calculate that the fraction of the population of Ceres-sized planetesimals that are captured in the asteroid belt is in the range of 2.8×10−5 to 1.2×10−3 depending on the initial location in the outer planetesimal disk. The captured bodies have a 70% probability to have a semimajor axis between 2.5 and 3 au, a 33% probability to have an eccentricity smaller than 0.2 and a 45% probability to have an orbital inclination smaller than 10°. Assuming the existence of 3,600 Ceres-size planetesimals in the inner part of the trans-Saturnian disk, consistent with the estimate of Nesvorný and Vokrouhlický (2016) for the trans-Neptunian disk, our estimated capture probability and a final 80% depletion of the asteroid belt during the subsequent giant planet instability, lead to capture ∼ 1 Ceres in the asteroid belt, with a probability of 15%, 34%, and 51% to be located in the inner, middle and outer belt respectively.

Comparison of Unremoved Intervertebral Disc Location Between 2 Lateral Lumbar Interbody Fusion (LLIF) Techniques

To compare location and amount of unremoved intervertebral disc between extreme lateral lumbar interbody fusion (XLIF) and oblique lateral lumbar interbody fusion (OLIF). Postoperative magnetic resonance images of patients who underwent XLIF and OLIF for degenerative spine diseases were reviewed. An axial cut T2-weighted image that was the middle cut of operated disc space was selected. We divided the disc area into 5 zones: central, left anterior, left posterior, right anterior, and right posterior. Disc area was measured using a picture archiving and communication system program. The angle of intervertebral cage was also measured. A total of 61 levels of XLIF from 51 patients and 62 levels of OLIF from 34 patients were included. The area of unremoved disc at left anterior, right anterior, and left posterior zones of OLIF were significantly greater than XLIF (55.7 ± 41.5 vs. 29.8 ± 33.3 mm2, 57.9 ± 43.6 vs. 34.1 ± 33.1 mm2, and 50.5 ± 41.8 vs. 31.5 ± 35.9 mm2, respectively; P < 0.01). No significant differences were found at the right posterior and central zones. A 9.2° ± 6.1° and 0.7° ± 4.9° cage angulation from left anterior to right posterior was found in OLIF and XLIF, respectively, with statistical significance. Our study found a greater area of unremoved disc in OLIF compared with XLIF. The common locations were in the contralateral side of the surgical approach-right anterior in OLIF, and right posterior in XLIF. The greater area of the unremoved disc in the anterior zone after OLIF due to oblique corridor to disc space may cause cage malposition. Meticulous disc removal should be performed, especially in OLIF, to prevent complications.

Alterations in dynamics of counterjet injection technique in presence of real gas effects

Large wave drag is common problem encountered for flights driving at high speeds. It should be dealt with utmost care for better design of long range flights cruising at high speeds. Studies found in the literature only deals with computations or experiment that are carried at lower stagnation temperature or considering perfect gas flow. Thus, the present work incorporates the real gas effects on various flow features like Mach disk diameter, Mach disk location and recirculation pressure. Further the effect of various freestream Mach number (M∞) and freestream total enthalpy (Ho) are observed on wall pressure for blunt body hemisphere considering real gas reactions by means of in house perfect and real gas solvers at hypersonic speeds. Pressure ratio of opposing jet is fixed as 15 while temperature ratio is fixed as 1. Results reveals that the pressure on the object lowers with the increase in M∞ especially upstream of maximum surface pressure point both for the reacting as well as the perfect solver. Surface pressure is found to be much higher at elevated freestream total enthalpy in comparison of smaller freestream total enthalpy for reacting solver while surface pressure almost shows similar trend at all Freestream total enthalpy for perfect solver case. Surface pressure for perfect solver is found to be lower than surface pressure for reacting solver for all the cases studied and this reduction is significant at higher M∞. Drag on body is rising with Freestream total enthalpy but this rate of drag enhancement diminishes at higher M∞.

Is condyle morphology a factor for anterior temporomandibular disc displacement?

To investigate morphological features of the mandibular condyle and its association with anterior temporomandibular disc displacement on sagittal oblique MRI plane. One hundred and twenty patients with temporomandibular MRI examination were retrospectively involved in the study. Patients aged less than 18 years and those with severe osteoarthritis, posterior disk displacement, tumor, abscess, history of a rheumatic disease, facial trauma, and motion artifacts on images were excluded. Three radiologists evaluated all images in consensus. Temporomandibular disc locations were classified as normal, anteriorly displaced with reduction (ADr), and anteriorly displaced without reduction (ADwr) on sagittal oblique T1-weighted images. Condylar shapes were classified as flat, rounded, and angled, and condyle anteroposterior width (c-APW) was measured on these images in closed-mouth position. Ninety six discs were in normal position (40%), 70 discs were ADr (29%), and 74 discs were ADwr (31%). Eighty-four condyles were flat (35%), 100 condyles were rounded (42%), and 56 condyles were angled (23%). Mean c-APW was 7 mm in normal joints, 5.9 mm in ADr, and 5.8 mm in ADwr joints, and it was smaller in joints with anterior disc displacement (p < 0.001). In normal joints, flat and rounded type condylar shape was more common and almost equally prevalent (44% and 43%); however, rounded type was more common among ADr (%47) and angled type was more common among ADwr joints (36%) (p = 0.008). Patients with anterior disc displacement were significantly younger from normal cases and anterior disc displacement was more common among female sex. Mandibular condyle shape alterations and condyle size on sagittal oblique MRI plane are associated with anterior disc displacement. Angled shape was more common among ADwr joints. Joints with anterior disc displacement had smaller c-APW than normal joints.