Track Length Research Articles

Shaping the turnout diverging track with nonlinear curvature for enhanced speed

Abstract: In the paper an attempt has been made to concentrate attention on shaping the variable curvature in the diverging track of the railway turnout. Making use of some earlier studies, solutions provided with a circular arc in the mid-zone, and in the extreme regions with segments of nonlinear curvature of equal length and zero curvature at the start and end of the turnout, have been assumed as models. The most advantageous choice of the type of curvature has been made taking into account the kinematic conditions. A presentation made includes an analytical record of the curvature and the tangent inclination angle in the diverging track length and the Cartesian coordinates of the track. The final part of the paper referred to the determination of a set of some basic magnitudes relating to geometric parameters appropriate for a given speed of trains and adequate to ensure the minimization of the length of the entire turnout at a given final ordinate. Keywords: Railway turnouts; Diverging track; Curvature modelling; Selection of geometrical parameters

Propofol Ameliorates Exaggerated Human Neutrophil Activation in a LPS Sepsis Model

BackgroundSepsis is a leading cause of morbidity and mortality worldwide. Many patients suffering from sepsis are treated on intensive care units and many of them require mechanical ventilation under sedation or general anesthesia. Propofol, a drug used for these purposes, is known to interact with polymorphonuclear granulocytes (PMNs). Therefore, the aim of this study was to investigate the influence of propofol on PMN functions after experimental Gram-negative induced sepsis using lipopolysaccharide (LPS) stimulation.MethodsA total of 34 granulocyte-enriched samples were collected from healthy subjects. PMNs were isolated by density gradient centrifugation and incubated simultaneously with either 6 µg/mL or 60 µg/mL propofol, or none (control). Additionally, the experimental sepsis samples were incubated with either 40 pg/mL or 400 pg/mL LPS. Live cell imaging was conducted in order to observe granulocyte chemotactic migration, ROS production, and NETosis. Flow cytometry was used to analyze viability and antigen expression.ResultsPropofol led to significantly reduced PMN track length (p < 0.001) and track speed (p < 0.014) after LPS-induced sepsis in a dose-dependent manner. NETosis (p = 0.018) and ROS production (p = 0.039) were accelerated by propofol without LPS incubation, indicating improved immune function. Propofol also ameliorated LPS-induced increased NETosis and ROS-production. Antigen expression for CD11b, CD62l and CD66b was unaffected by propofol.ConclusionPropofol improves LPS-induced exaggerated PMN activation in an ex vivo model. Beneficial effects due to restored immune function in septic patients might be possible, but needs further investigation.

Etching of fission tracks in monazite: Further evidence from optical and focused ion beam scanning electron microscopy

Abstract A series of experiments on monazites from Victoria, Australia, is presented to further understand their fission track etching properties. Using a 6 M HCl etchant at 90 °C, SEM images on crystal (100) pinacoid faces reveal well-etched rhombic spontaneous fission track openings. Average rhombic etch pit diameters Dpc and Dpb, parallel to the crystallographic c- and b-axes are 0.81 ± 0.20 µm and 0.73 ± 0.26 µm, respectively. An angular distribution experiment on (100) faces found that spontaneous fission tracks initially etch anisotropically, being preferentially revealed at an azimuth of 90° to the crystallographic c-axis up to ~60 min of etching. As etching continues, however, the distribution becomes progressively more uniform and is essentially isotropic by 90 min. Two experimental methods determined the rate at which the etchant penetrated along the lengths of implanted 252Cf fission tracks. This involved the application of a focused ion beam scanning electron microscope (FIB-SEM) to mill progressively into slightly etched monazite crystals followed by an etch-anneal-etch approach. Results indicate that at least the greater part of the etchable ranges of the latent fission tracks were penetrated by the 6 M HCl etchant within the first few minutes. Continued etching to 5 min indicates that track etching slows down toward the ends of the tracks, but the maximum ranges are estimated to be reached after 5–15 min, which represents the longest time the latent segments of the tracks are exposed to potential annealing at the etchant temperature. Taking into account that implanted 252Cf fission tracks in monazite anneal on average ~4% of their length at 90 °C after 1 h (Jones et al. 2019), suggests that a much shorter duration for exposure to this temperature causes less than ~1% of fission track length reduction during etching.

A Novel Snake-Like Model to Simulate Infinite Track for Vehicle–Track Coupling Vibration

The dynamic interaction between the vehicle and track is one of the most critical issues for railways, as it is closely related to running safety. Previously, many vehicle–track coupling models have been developed to study the vibration response of the system. Even though the track is periodic and infinitely extended, only a finite length of the track has often been used in the simulation, so as to reduce the effort of computation. For some special issues, it is necessary to consider the influence of long-wavelength track irregularities on the vehicle responses, and the characteristic track length can reach up to the scale of kilometer. In practice, the computational effort of using a model to accommodate kilometer-long tracks is costly and even unacceptable. To overcome this problem, this paper proposes a novel snake-like model inspired by the famous game Snake to simulate infinite tracks. In the snake-like model, each vehicle can travel on the track repeatedly via the transfer nodes installed at the end of the track. Two examples were presented to verify the accuracy and efficiency of the model proposed. The results showed that the accuracy of snake-like model is consistent with that of existing methods, but the computational effort has been reduced significantly.

Effects of the implementation of a mass rapid transit system on mortality rates attributed to cardiorespiratory complications in Taipei

ABSTRACT Although Taipei City has encountered a fall in ambient air pollutant levels since 1996, the year its mass rapid transit (MRT) system commenced operation, no apparent study investigated changes in risks of death attributed to respiratory, cardiovascular, and cerebrovascular diseases in Taipei during this 23-year period. In order to examine the relationship between MRT and occurrence of respiratory and cardiovascular illnesses attributed to air contaminants, exposure over the 23 year duration was subdivided into the following periods: reference period 1 (1992–1995); period 2 (1996–2004), a time when there was a total track length of 67 km; period 3 (2005–2015), when the total track length was lengthened to 131.1 km; and period 4 (2016–2020), when it was further extended to 146.2 km. Taichung City, no MRT system, was used as an external reference population. The effect of Taipei’s MRT system on rates of cause-specific death rates was analyzed using robust generalized Poisson regression models. After adjusting for age-standardized rates (ASRs), a decrease in relative risks (RRs) was found for non-trauma death and respiratory disease from periods 2 to 4. Even though the RRs were greater than 1.0 for cardiovascular and cerebrovascular diseases for periods 2 to 4, a downward trend was still noted in these RRs in Taipei. These findings suggest a relationship exists between air pollutant exposure and mortality. In addition, data demonstrated that implementation of the MRT in Taipei exerted beneficial health effects as evidenced by lower mortality rates.

When is enough, enough? Questions of sampling in vertebrate ichnology

AbstractSample size is a challenge for most field scientists determined not by the statistically ideal, but by the available. In vertebrate ichnology, track length is an important variable correlating well with the track‐maker’s biology. It is also key to estimating the minimum number of individuals (MNI) present on a trampled horizon. Broad assumptions on biometrics of the track‐makers are often made based on a few prints without consideration for intra‐trackway variability. In this study we use a simple bootstrapping algorithm to explore variance within sample size for a range of trackways with fossil and experimental examples to determine the minimum sample size required to extract linear measurements. Predictably, experimentation shows that inter‐step variability changes with track‐maker and substrate, but the degree of variance is not as marked as previously anticipated. Change‐point modelling suggests that a maximum sample size of 22–25 captures most of the variance present in track length at least; another threshold at 7–10 has been identified, which represents the reasonable sample size minimum. Samples of fewer than seven tracks are subject to large amounts of potential variance and are unlikely to provide reliable and consistent measurements. These sampling thresholds hold across a wide range of depositional environments and track‐makers. We calculate generic standard errors for human track‐makers which may assist the practitioner with small samples to estimate the likely errors, especially when making MNI estimates. The challenge is placed to the wider vertebrate ichnology to explore this issue for other track‐makers and develop similar guidance.

Electrification of Dielectric Satellites under the Influence of Electron Flows of the Earth\u2019s Radiation Belts

The effect of electron fluxes from the Earth’s radiation belts on satellites made of dielectric materials is studied theoretically. Spherical shaped nanosatellites of the BLITS and BLITS-M types are considered as a model. An analytical solution is obtained for the dependence of the electric field on the distance to the center of the satellite. Empirical formulas are used for the electron flux density and the track length in matter depending on the electron energy. The energy losses of incident electrons in the Debye shielding layer that surrounds the satellite, as well as the appearance of radiation conductivity in the surface layer of the dielectric, are taken into account. The reasons for the nonmonotonic dependence of the electric field on the satellite radius are established. Despite the fact that the electric field inside the satellite is smaller than the electrical breakdown threshold of the solid dielectric, it can be assumed that the dielectric micro-breakdown can occur in the surface layer of the dielectric and near inhomogeneities.

Visco-elastic contact spring in numerical simulations of train – track system vibrations

Abstract: In train – track coupled systems, interaction between subsystems occurs in wheel- rail contact. The most common contact model is perfectly elastic, linearized Hert’z spring. It has wide range of application in numerical simulations. In more detailed interaction models, the energy dissipation in wheel-rail contact is taken into account. There are no known comparisons of these models in the literature, that would indicate the effects of a specific solution application. In this paper, the main purpose is to analyze and compare the effects of two contact models in terms of numerical simulations of train – track vibrations. The reference contact model taken into account is linearized, perfectly elastic Hert’z spring. The second spring, proposed by the authors is enriched with viscous element based on hysteresis damping. Application of both models, and its effects were examined in plane, train – track vibrations simulations with threshold inequality excitation in the middle of the track length. Concluding from the analyzes performed, it was found that viscoelastic contact model application is important, when track stresses and fatigue are being investigated. In addition, it was found that neglecting the damping element in contact model reduces the probability of the wheel – rail contact loss phenomenon, and thus leads to incorrect identification of its occurrence. Keywords: Wheel/rail contact; Hertz contact; Linearized contact spring; Train/track dynamics

Discrete Modes of Migration Define Human NK Cell Development from Hematopoietic Stem Cells

Human innate lymphoid cells play a critical role in the control of infection and the shaping of the immune response. Furthermore, natural killer (NK) cells are the first reconstituting lymphocyte population after hematopoietic stem cell transplant and play a key role in shaping engraftment and moderating graft vs. leukemic effects. Relative to their adaptive immune counterparts, the molecular interactions that drive innate immune cell differentiation development are poorly understood. Human NK cells arise from bone marrow CD34+ hematopoietic stem cells (HSC) but undergo maturation in distal microenvironments, the best characterized of which is secondary lymphoid tissue. Human NK cells can also be derived in vitro from CD34+ HSC through co-culture with developmentally supportive stromal cells. Despite the requirement for direct stromal cell contact in NK cell maturation, the nature of these contacts is not known. We have previously shown that freshly isolated human NK cell developmental intermediates from in vitro culture, secondary lymphoid tissue or peripheral blood undergo spontaneous migration on the EL08.1D2 stromal cell line. We have further defined the NK cell ‘developmental synapse’, a site of productive and directional signaling in developmental intermediates arrested on stromal cells. Despite these interesting insights, the regulation of, and requirement for, NK cell migration during differentiation has not been defined.To determine the modes of migration associated with human NK cell differentiation, we performed highly resolved continuous live cell imaging of NK cells developing in vitro from CD34+ HSC over 28 days of culture. These analyses were performed in parallel with flow cytometry to monitor the progression of developmental intermediates towards a functionally mature NK cell phenotype. We found that while CD34+ HSC had constrained motility, progressive NK cell differentiation was associated with more directed migratory phenotype. NK cell maturation was associated with increased track length and velocity, and decreased frequency of time of cells spent in arrest on stromal cells. We further defined the acquisition of complex, Levy-walk behavior as has previously been described for mature T cells imaged within tissue. The consistency of these behaviors between in vitro derived cells and fresh ex vivo NK cells isolated from healthy human donors confirms that in vitro differentiation effectively recapitulates migratory phenotypes in addition to functional and cell surface phenotypes associated with NK cell maturation.Together, these data define distinct modes of migration that are acquired by human NK cells. We propose that this reflects a previously unappreciated requirement for cell migration that enables the functional maturation of human NK cells. Better defining the bidirectional signaling between developing NK cells and their microenvironment will enable a complete understanding of the signals that help shape the acquisition of key innate immune cell functions. This understanding is critical for better predicting and therapeutically enhancing lymphocyte reconstitution after transplant. DisclosuresNo relevant conflicts of interest to declare.

Measuring solar neutrinos over gigayear timescales with paleo detectors

Measuring the solar neutrino flux over gigayear timescales could provide a new window to inform the Solar Standard Model as well as studies of the Earth's long-term climate. We demonstrate the feasibility of measuring the time-evolution of the $^8$B solar neutrino flux over gigayear timescales using paleo detectors, naturally occurring minerals which record neutrino-induced recoil tracks over geological times. We explore suitable minerals and identify track lengths of 15--30 nm to be a practical window to detect the $^8$B solar neutrino flux. A collection of ultra-radiopure minerals of different ages, each some 0.1 kg by mass, can be used to probe the rise of the $^8$B solar neutrino flux over the recent gigayear of the Sun's evolution. We also show that models of the solar abundance problem can be distinguished based on the time-integrated tracks induced by the $^8$B solar neutrino flux.

Post-ore change and preservation of the late Paleozoic Tuwu porphyry Cu deposit in Eastern Tianshan, NW China: Constraints from geology and apatite fission track thermochronology

The late Paleozoic Tuwu porphyry Cu deposit is located in the Dananhu–Tousuquan arc in Eastern Tianshan, northwest China. In this study, we present new apatite fission track data of the intermediate-felsic intrusions (i.e., diorite porphyry, tonalite porphyry, quartz porphyry, and quartz albite porphyry) from Tuwu, together with inverse thermal modeling and previous study, to reveal exhumation and cooling history. Apatite fission track length analyses indicate that the track annealing type belongs to a transition from the undisturbed basement distribution to the mixed distribution. As a whole, two phases of cooling were recognized from inverse thermal modeling including a protracted slow cooling period with an average cooling rate of 0.32 ℃/Ma during late Cretaceous to Miocene and moderate slow cooling with a cooling rate of 1.89 ℃/Ma from Miocene to the present day. The first phase of cooling can be mainly attributed to a tectonically quiet and arid to semiarid climate whereas the later phases of cooling related to structural activation occurred at ~25–15 Ma in response to a distant effect of the India-Eurasia convergence. In addition, the exhumation rates of Tuwu intrusions from the two stages are 10.7 m/Ma and 63 m/Ma, respectively. The calculated total exhumation thickness at Tuwu is 1.2–2.3 km since late Cretaceous. Based on the integration of stratigraphic sequence, tectonic setting, paleogeographic, geochronology, and low temperature thermochronology study, we suggest that the thick deposition of coal-bearing stratum during the early and middle Jurassic, the extended duration slow cooling and exhumation controlled by arid to semiarid climate, and the differential lifting movement of fault blocks are key factors for preservation of the early Carboniferous Tuwu Cu deposit.

The influence of extracellular tissue on neutrophil function and its possible linkage to inflammatory diseases

Background: Migration, production of reactive oxygen species (ROS), release of myeloperoxidase (MPO), and NETosis are functional immunological reactions of elementary importance for polymorphonuclear neutrophils (PMN).Unregulated inflammatory response of PMN within tissues plays a key role in the pathophysiology of several diseases. However, little is known about the behavior of PMN after migration through blood vessel walls. Therefore, we investigated the influence of the extracellular matrix (ECM) on PMN function. Materials and Methods: We established an in vitro chemotaxis model of type I and III collagen, fibrin, and herbal agarose tissues using µ‐slide chemotaxis devices and N‐formylmethionine‐leucyl‐phenylalanine (fMLP). PMN within the matrices were assessed with a fluorescent time‐lapse microscope for live‐cell imaging. Results: PMN function was obviously influenced by the ECM. Type III collagen had an inhibitory effect on PMN migration regarding track length, direction, and targeting. Type III collagen also had an accelerating effect on neutrophil ROS production. Agarose had an inhibitory effect on MPO release and fibrin a retarding effect on NETosis. Conclusion: Because of the high abundance of type III collagen in lung and skin matrices, the interaction of PMN with the respective matrix could be an important mechanism in the pathophysiology of acute respiratory distress syndrome and pyoderma gangrenosum.

Tracking the invasive hornet Vespa velutina in complex environments by means of a harmonic radar

An innovative scanning harmonic radar has been recently developed for tracking insects in complex landscapes. This movable technology has been tested on an invasive hornet species (Vespa velutina) for detecting the position of their nests in the environment, in the framework of an early detection strategy. The new model of harmonic radar proved to be effective in tracking hornets either in open landscapes, hilly environments and areas characterised by the presence of more obstacles, such as woodlands and urban areas. Hornets were effectively tracked in complex landscapes for a mean tracking length of 96 ± 62 m with maximum values of ~ 300 m. The effectiveness of locating nests was 75% in new invasive outbreaks and 60% in highly density colonised areas. Furthermore, this technology could provide information on several aspects of insect’s ecology and biology. In this case, new insights were obtained about the mean foraging range of V. velutina (395 ± 208 m with a maximum value of 786 m) and flying features (ground speed), which was 6.66 ± 2.31 m s−1 for foraging individuals (hornets that are not carrying prey’s pellet) and 4.06 ± 1.34 m s−1 for homing individuals.

Tectonic Evolution of the SE West Siberian Basin (Russia): Evidence from Apatite Fission Track Thermochronology of Its Exposed Crystalline Basement

The West Siberian Basin (WSB) is one of the largest intracratonic Meso-Cenozoic basins in the world. Its evolution has been studied over the recent decades; however, some fundamental questions regarding the tectonic evolution of the WSB remain unresolved or unconfirmed by analytical data. A complete understanding of the evolution of the WSB during the Mesozoic and Cenozoic eras requires insights into the cooling history of the basement rocks as determined by low-temperature thermochronometry. We presented an apatite fission track (AFT) thermochronology study on the exposed parts of the WSB basement in order to distinguish tectonic activation episodes in an absolute timeframe. AFT dating of thirteen basement samples mainly yielded Cretaceous cooling ages and mean track lengths varied between 12.8 and 14.5 μm. Thermal history modeling based on the AFT data demonstrates several Mesozoic and Cenozoic intracontinental tectonic reactivation episodes affected the WSB basement. We interpreted the episodes of tectonic activity accompanied by the WSB basement exhumation as a far-field effect from tectonic processes acting on the southern and eastern boundaries of Eurasia during the Mesozoic–Cenozoic eras.

Реконструкция железнодорожной станции в условиях изменения конъюнктуры пассажирских перевозок

Objective: Drawing on the study of the situation in railway passenger traffic, to propose measures for the reconstruction of station M of the Murmansk transport hub and perform a consolidated estimate of the cost of implementing the proposed measures. Methods: The means and methods of general systems theory, system and economic analysis, terminalistics, logistics and management of the ope- rational work of railways are used. Results: Based on the results of the economic calculation, it was concluded that it is necessary to reconstruct the exhibition track N 2 to receive passenger trains of 25 cars and organize work with double-deck cars. A consolidated estimate of the cost of building an exhibition track N 2 has been made. Practical importance: Thanks to the increase in the useful track length, new opportunities will be opened for the development of promising passenger traffic at the station in question and, consequently, for an increase in the profit of the Russian Railways company. The results obtained can be applied in the implementation of the development concept of the Mur- mansk transport hub, in the design of individual elements and devices of the railway hub, as well as in the optimization of passenger service technology.

The Strip SiPM: a study of single photon time resolution

The Strip Silicon PhotoMultiplier (SiPM) allows a photosensitive area to be created that has excellent time resolution coupled to good position resolution. However, as the SiPM is made larger it becomes more difficult to extract the signal produced by a single photon; we thus are using the NINO ASIC as the front-end amplifier. The NINO ASIC dissipates 40 mW of heat per channel. SiPMs are sensitive to temperature; increasing the temperature leads to higher noise and a higher breakdown voltage. For the best timing performance the front-end electronics should be mounted as close to the SiPM as possible; however if, for example, the front-end electronics are mounted on the backside of the SiPM, it would be very difficult to control the temperature of the SiPM. Given this, we chose to mount the NINO ASIC on the printed circuit board (PCB) away from the strip SiPM so that a cooling system can be added. We present here the performance of an array of 16 strip SiPMs readout by 4 NINO ASICs coupled by ∼5 cm of PCB track length. The performance has been evaluated by the measurement of the Single Photon Time Resolution (SPTR) and also the position resolution along the strip determined from the time difference of the signals at each end.

Dynamic analysis of railway track on variable foundation under harmonic moving load

This paper aims to investigate the effect of variable foundation stiffness on the dynamic response of an infinite railway track under the action of a harmonic moving load. In this study, harmonic variation in the foundation stiffness along the track length is considered. Here, the dynamic response of the finite element (FE) model is obtained with the help of Newmark Beta method using programming in MATLAB. It is ascertained that in the central region of the long FE model, the response is repetitive, thereby ensuring that boundary conditions do not influence the response in the central region. In this problem, two frequencies, i.e. frequency of moving load and the spatial frequency of variable foundation stiffness, are involved. Their combined influence on the dynamic characteristics such as resonant frequency, critical velocity, displacement time history, displacement below load, and bifurcation curve are investigated. It is shown that the dynamic response is qualitatively and quantitatively affected by the wavelength (λ) and amplitude (ε) of the variation of foundation stiffness. It is also shown that the important dynamic properties, i.e., the critical velocity and the resonant frequency reduce with the increase in wavelength of stiffness variation. This reduction is significant for the large amplitude of harmonic stiffness variation.

Effect of laser jump speed on temperature distribution and thermal stress in laser powder bed fusion

A 3D thermo-mechanical finite element model was developed to study the effect of the laser jump speed on the temperature distribution and thermal stress in laser powder bed fusion (LPBF) of Ti6Al4V alloy. Gradient grid and gradient time step were used to further improve solution efficiency. It was found that the temperature of the scanned region rapidly increased as the laser jump speed increased from 100 mm/s to 1000 mm/s. The temperature distribution reached a stable state when the laser jump speed was above 5000 mm/s. The pre-heat peak, the heat peak and the post-heat peak increased with the laser jump speed. The effect of the laser jump speed on the post-heat peak was greater than the pre-heat peak. Compared with the long scan track, the thermal stress distribution varies more sharply with the laser jump speed when using the short scan track. The influence of the laser jump speed on the stress perpendicular to the scan direction was greater than that along the scan direction, whether in a short scan track or in a long scan track. To reduce the residual stress, the length of the scan track should be reduced while the laser jump speed should be increased as much as possible to make the post-heat peak close to the fusion temperature of the material. The simulated results were well validated by the experimental data. The findings of this research help to reduce the thermal stress in laser powder bed fusion.

Burial and exhumation of late paleozoic arc-related rocks in the Tulasu basin, Western Chinese Tianshan: Implication for the preservation of epithermal deposits in old orogenic belts

Epithermal deposits are susceptible to erosion owing to their shallow emplacement depth of 1 to 2 km, resulting in the observation that the majority of epithermal deposits worldwide are generally Cenozoic in age. Several large and super-large epithermal deposits likely associated with Late-Devonian to Carboniferous arc magmatism were recognized in the Tulasu volcanic-clastic sedimentary basin, western Chinese Tianshan. In order to further clarify the preservation processes of these old epithermal orebodies, apatite fission track (AFT) analysis has been undertaken in this study. Our AFT results gave a range of ages from 54.7 ± 6.3 Ma to 272.3 ± 8.7 Ma, and the mean confined fission track lengths are between 12.1 ± 0.2 μm and 13.5 ± 0.1 μm. Our new data, in combination with the 1:50,000 geological mapping, suggest that the ore-hosting Tulasu basin may have undergone multiple burial and exhumation episodes postdating the mineralization. The main burial scenario, probably occurring in the late Early Carboniferous (350–330 Ma) and Permian (300–250 Ma), may be related to subsidence on syn-volcanic faults concurrent with retreat of the Junggar Ocean and strong uplift of the neighboring mountain range induced by final closure of the Paleo-Asian Ocean, respectively. The calculated thickness of ca. 4.83 km of sedimentary rocks deposited during the burial events form a critical shield for the epithermal ore bodies that have been protected from substantial erosion by subsequent geological processes. Exhumation occurred in two episodes: Late Triassic-Cretaceous (ca. 240–100 Ma) and Oligocene (ca. 35 Ma). The Late Triassic-Cretaceous erosion is characterized by a slow exhumation rate (ca. 0.012 mm/y), corresponding to a total unroofing thickness of ca. 1.67 km. In contrast, the Oligocene event exhibits as a higher exhumation rate (up to ca. 0.057 mm/y), with removal of ca. 3.83 km of sedimentary cover. Therefore, the epithermal deposits have undergone a complex geological path from formation to final exposure. Initial burial and the following sluggish exhumation are two fundamental factors for the preservation of epithermal deposits in the old orogenic belts.

Neurite orientation dispersion and density imaging in evaluation of high-grade glioma-induced corticospinal tract injury

PurposeTo evaluate the application of neurite orientation dispersion and density imaging (NODDI) to brain glioma-induced corticospinal tract (CST) injury. Material and methodsTwenty-four patients with high-grade glioma (HGG) in or adjacent to the CST pathway and 12 matched healthy subjects underwent structural and diffusion MRI. The CSTs were reconstructed on the both sides. The CST features including morphological features (track number, average track length and track volume) and the diffusion parameter values including fractional anisotraphy (FA), mean diffusivity (MD), intracellular volume fraction (ICVF), isotropic or free water volume fraction (ISOVF) and orientation dispersion index (ODI) along the CST were calculated. The CST features were compared between the affected and healthy side for HGG patients and between the left and right side for healthy subjects. The relative CST features were compared across the healthy subjects, patients with motor weakness and patients with normal muscle strength. Receiver operating characteristic (ROC) curve was applied to evaluate the performance of each relative CST characteristic for HGG-induced CST changes. ResultsCompared with the CST features on the healthy side, the track number, track volume and FA along the CST changed significantly on the affected side for HGG patients (p < 0.05 for all), whereas MD and ICVF changed significantly on the affected side only for HGG patients with motor weakness (p = 0.012 for both). In patients with motor weakness, the relative MD was significantly higher (p < 0.001), whereas the relative FA and ICVF was significantly lower (p = 0.002 and <0.001) than those in patients with normal muscle strength. The relative ICVF had a similar area under curve (AUC) to that of MD (AUC=0.953 and 0.969). Compared with the relative CST features in the healthy subjects, only the relative ICVF was significantly lower in HGG patients with normal muscle strength (p = 0.012). ConclusionsNODDI seems to be useful in reflecting the HGG infiltration to CST, and can evaluate the CST destruction with a performance similar to DTI by providing additional information about neurite density for HGG-induced CST injury.