Dominant Instability Research Articles

Resting-State Functional MRI Regional Homogeneity Correlates With Motor Scores in Parkinson's Disease.

This study investigated the neural mechanisms underlying Parkinson's disease (PD) subtypes-tremor dominant (TD) and postural instability gait difficulty (PIGD)-by analyzing regional homogeneity (ReHo) values from resting-state functional MRI. Fifty-nine PD patients (29 TD patients, 30 PIGD patients) and 30 healthy controls (HCs) were enrolled. ReHo values were analyzed via analysis of variance and a two-sample t-test, with age and sex as covariates. Correlations between ReHo values and clinical motor symptoms were also examined. Distinct ReHo patterns were observed in patients with the PD subtypes and HCs. TD patients presented decreased ReHo in the cerebellar-thalamic-cortical circuit, whereas PIGD patients presented lower ReHo in the striatum and supplementary motor area (SMA). TD patients had higher ReHo in the bilateral dorsolateral superior frontal gyrus and SMA but lower ReHo in the bilateral medial orbital part of the superior frontal gyrus and other regions on the left than PIGD patients. Specific brain area ReHo values were correlated with tremor scores, PIGD scores, and rigidity scores. Different motor subtypes of PD patients and HCs showed distinct ReHo patterns. ReHo correlation with clinical traits suggests its value as a biomarker for subtype-specific diagnostic strategies.

ELM-free enhanced D α H-mode with near zero NBI torque injection in DIII-D tokamak

Enhanced Dα H-mode (EDA H-mode), an ELM-free H-mode regime, and the concomitant quasi-coherent mode (QCM) are explored in neutral beam heated, lower single null plasmas with near zero external torque injection. This regime exhibits good energy confinement (H98y2 ∼ 1) with βN ∼ 2, high density, regime access at low input power, and no ELMs. New time–resolved measurements of electron and ion density, temperature, plasma rotation, and radial electric field as well as turbulence, flows, thermal and particle transport, and linear instability calculations examining the dynamics of the QCM are presented. Measurements using multiple fluctuation diagnostics reveal the QCM to be a separatrix spanning mode, peaking just inside the separatrix, existing in a wide range of k⊥ρs ∼ 0.1–1.2 with multiple harmonics, and propagating with a very small phase velocity in the plasma frame, where k⊥ is the binormal wavenumber and ρs is the ion sound radius. Linear gyrokinetic simulations of this EDA H-mode discharge with CGYRO indicate that the trapped electron mode (TEM) and electron temperature gradient mode are the dominant instabilities in the radial region where QCM is also unstable. Qualitative analysis indicates that the properties of TEM are consistent with the experimentally observed characteristics of the QCM. These similarities suggest that the QCM is consistent with a TEM instability existing in the edge region of the EDA H-mode plasmas.

Cortical complexity alterations in motor subtypes of Parkinson's disease: A surface-based morphometry analysis of fractal dimension.

Based on motor symptoms, Parkinson's disease (PD) can be classified into tremor dominant (TD) and postural instability gait difficulty (PIGD) subtypes. Few studies have examined cortical complexity differences in PD motor subtypes. This study aimed to investigate differences in cortical complexity and grey matter volume (GMV) between TD and PIGD. We enrolled 36 TD patients, 27 PIGD patients and 66 healthy controls (HC) from the PPMI (Parkinson's Progression Markers Initiative) database. Voxel-based morphometry (VBM) and surface-based morphometry (SBM) were utilized to assess differences in GMV, cortical thickness and cortical complexity. The structural MRI data of participants was analysed using CAT12/SPM12 (p < 0.05, FDR corrected). Additionally, correlations between clinical data and structural changes were examined (p < 0.05, Holm-Bonferroni corrected). In comparison to both HC and TD groups, PIGD patients exhibited a significant fractal dimension (FD) decrease in many cortical regions. A significant negative correlation between age and FD was observed in the left insula for the PIGD patients and in the bilateral insula for the TD patients. However, no significant differences were found in GMV, cortical thickness or other complexity indices. Altered FD in the bilateral insula indicates that postural instability and gait disturbances may result from a failure to integrate information from various structures, whereas parkinsonian rest tremor is not associated with this integration. Also, widespread decreases in cortical FD demonstrate that FD is more sensitive than other complexity measures and can serve as a novel biomarker for identifying subtle changes in cortical morphology in the PIGD subtype.

Electrogastrography in Adult Gastroparesis: A Systematic Review and Meta-Analysis

BackgroundGastroparesis is a delay in gastric emptying without mechanical obstruction, lacking a clear pathophysiological mechanism, but with multiple histological abnormalities including loss of interstitial cells of Cajal, which may alter slow waves. We can assess slow waves with electrogastrography.ObjectivesTo determine the prevalence and range of abnormalities in gastric slow waves in adults with gastroparesis using electrogastrography.MethodsWe systematically searched Medline, Embase, LILACS, Web of Science, and Cochrane Register of Controlled Trials. We included studies with patients older than 18 years with gastroparesis, assessed using electrogastrography. We evaluated the percentage of duration of the recording in which the dominant power was in normogastria, tachygastria, and bradygastria; dominant frequency; power ratio; change in post-stimulus dominant power; and dominant frequency instability coefficient. Methodological quality was assessed using the Joanna Briggs Institute tool. Data were synthesized using narrative summary and meta-analysis.ResultsA total of 3730 articles were reviewed, including 31 articles with 1545 patients and 340 controls. Compared to controls, gastroparetics patients had less normogastria (fasting: 50.3% versus 65.8%) (post-stimulus: 54.3% versus 66.5%), more bradygastria (fasting: 37.7% versus 13%) (post-stimulus: 31.9% versus 16.3%), and more tachygastria (fasting: 16.1% versus 4.6%) (post-stimulus: 18.3% versus 5.2%). Gastroparetics had less change in post-stimulus dominant power (1.45 dB versus 5.03 dB) and less power ratio (1.4 versus 5.26).ConclusionsGastroparetic patients present abnormalities in the frequency and changes in the post-stimulus power of slow waves, possibly secondary to a reduced number of interstitial cells of Cajal, as described in these patients.

Second-order analysis of hypersonic boundary-layer stability

The dominant mode instability in hypersonic boundary-layer transition is the so-called second-mode instability, which has a peculiar nature strongly coupled with thermoacoustic phenomena. In linear stability theory, the unstable wave is associated with one of the two eigenvalues that originate from the acoustic branches, referred to as slow and fast modes. Interestingly, the unstable mode (slow or fast) reaches its maximum amplification as the other mode (fast or slow) attains a minimum. The phase velocity of the two modes is then very close, and this phenomenon is called synchronization. The aim of the present study is to unravel the physical mechanism that explains the second-mode growth. To that aim, second-order nonlinear equations are written for the disturbances given by linear stability. In this framework, entropy, kinetic energy and temperature energy budgets are obtained up to second order. The budgets are scrutinized for various Mach numbers and for adiabatic and cold-wall thermal conditions. Perturbation entropy budgets clearly show the process is a reversible one. An energy exchange between kinetic energy and temperature energy of the weakly nonlinear modes is driven by pressure–dilatation terms. As underlined in previous studies, the unstable mode experiences an alternate heating and cooling near the wall, which is shown to be a rather nonlinear process. The change in fluctuating thermal energy in the form of a dilatational wave is sustained by pumping disturbance kinetic energy through the pressure–dilatation term, the direction of the conversion being driven by the relative phase between pressure and dilatation. This process is similar for the slow and fast modes, the unstable mode being amplified and the other being damped. No change in the process has been noted at the location of the synchronization, suggesting that the modes have the same nature but evolve independently.

Revisit compressible plane Couette and Poiseuille instability: Spectrum features of disturbances and dominant instability

Understanding the instability of compressible shear flows is of both academic interest and practical importance for predicting transition in such flows. In this paper, the linear stability of compressible plane Couette flow and Poiseuille flow in temporal mode is revisited, with emphasis on spectrum features of disturbances and dominant instability at different Mach numbers. The disturbance spectra of different discrete modes are presented, including acoustic modes (i.e., even modes II, IV, etc. and odd modes I, III, etc.) and viscous modes. The results show that as wavenumber increases, the even modes are first synchronized with the viscous branch when their phase velocities are a bit larger than zero, and subsequently synchronized with odd modes when their phase velocities coincide with each other. The synchronizations cause branching of the dispersion curves, and the even modes have several maxima of growth rate. The low-wavenumber maximum (with phase velocity close to zero) is associated with viscous instability and the higher-wavenumber maxima correspond to inviscid instability. Depending on the flow parameters, the branching topology may involve multimodes, which is different from the spectrum branching observed in hypersonic boundary layer. In compressible Couette flow, the mode-II viscous and inviscid instabilities dominate the instability at different Mach numbers. In compressible plane Poiseuille flow, multiple instability modes coexist, including the viscous Tollmien-Schlichting (TS) mode, the acoustic viscous instability modes II and IV and acoustic inviscid instability modes I and III. As Mach number increases (i.e., from incompressible to hypersonic), the mode TS, II, IV, and III would successively dominate the Poiseuille-flow instability. These results yield a comprehensive understanding of the disturbance spectrum and modal instability in compressible plane Couette and Poiseuille flows.

Crossflow-Induced Breakdown and Transition Correlation for a Hypersonic Swept Plate Flow

The crossflow-induced transition for a Mach 6 flow over a swept plate with a 35 mm nose radius and a sweep angle of 45 deg is investigated using direct numerical simulations (DNSs). In order to shed light on the complete transition process, the evolution of a stationary crossflow wave is first simulated. Then, unsteady wall blowing/suction perturbations are introduced to trigger transition to turbulence. The results show that both the type I and III secondary modes are excited, and they subsequently undergo a linear stage of amplification before breakdown. The type II mode is undetected despite its amplification predicted by the two-dimensional eigenvalue stability approach. Overall, the type I mode achieves a dominant amplitude and plays a key role in the transition. Furthermore, a transition correlation method is proposed based on the dominant secondary instability and threshold amplitude concept, and in order to verify and calibrate it, wall perturbations with different amplitudes are introduced to mimic the varying intensities of the background noise. The transition locations predicted by the most amplified secondary mode agree well with those by DNSs, validating the secondary-instability-based criterion for hypersonic crossflow transition.

Effect of central plasma pressure on high-order harmonics of 1/1 quasi-interchange instability in a central weak magnetic shear tokamak configuration

Abstract Numerical investigations of linear and nonlinear stages of quasi-interchange instability in a cylindrical tokamak geometry with a flat q-profile in the core region are conducted using eigenvalue and initial value codes, respectively. It is found that there exists a dependent relationship between the central plasma pressure p 0 (of the initial pressure profile) and the dominant harmonic of the quasi-interchange instability. As p 0 increases, m = n &gt; 1 mode would be dominant in the linear stage and even in the nonlinear stage, where m and n are the poloidal and toroidal mode number, respectively. In addition, with p 0 increasing, the fast growth of other harmonics is inevitable and will deeply affect the evolution of m = n dominant quasi-interchange instability.

Dualities of Paired Quantum Hall Bilayer States at ν_{T}=1/2+1/2.

Density-balanced, widely separated quantum Hall bilayers at ν_{T}=1 can be described as two copies of composite Fermi liquids (CFLs). The two CFLs have interlayer weak-coupling Bardeen-Cooper-Schrieffer instabilities mediated by gauge fluctuations, the resulting pairing symmetry of which depends on the CFL hypothesis used. If both layers are described by the conventional Halperin-Lee-Read (HLR) theory-based composite electron liquid (CEL), the dominant pairing instability is in the p+ip channel; whereas if one layer is described by CEL and the other by a composite hole liquid (CHL, in the sense of anti-HLR), the dominant pairing instability occurs in the s-wave channel. Using the Dirac composite fermion (CF) picture, we show that these two pairing channels can be mapped onto each other by particle-hole (PH) transformation. Furthermore, we derive the CHL theory as the nonrelativistic limit of the PH-transformed massive Dirac CF theory. Finally, we prove that an effective topological field theory for the paired CEL-CHL in the weak-coupling limit is equivalent to the exciton condensate phase in the strong-coupling limit.

Identification of dominant instability modes in power systems based on spatial‐temporal feature mining and TSOA optimization

AbstractThe recognition of the transient dominant instability mode is of great significance for rapidly and accurately formulating transient emergency decisions in power systems. In response to the challenge of accurately distinguishing between angle instability and voltage instability, which are coupled in actual power grids, this paper explores the mapping relationship between simulation data and the stable state of the system, as well as the dominant instability mode. The method enables real‐time identification of the dominant instability mode, which bypasses complex physical mechanisms. Firstly, spatio‐temporal feature mining is conducted, where convolutional neural networks are employed to learn crucial local features of transient curves, and bidirectional gated recurrent unit s utilized to learn transient features over time sequences. Next, a multihead attention mechanism is introduced to enhance sensitivity to important time steps in the sequence data. Finally, the transit search optimization algorithm optimizes the global model parameters, further increasing the accuracy of the model. Using the IEEE 10‐machine and 39‐node system as an example for simulation, the results validate that the proposed method exhibits significant advantages in terms of accuracy and applicability compared with other machine learning methods.

Ion-temperature- and density-gradient-driven instabilities and turbulence in Wendelstein 7-X close to the stability threshold

Electrostatic gyrokinetic instabilities and turbulence in the Wendelstein 7-X stellarator are studied. Particular attention is paid to the ion-temperature-gradient (ITG) instability and its character close to marginal stability [Floquet-type turbulence (Zocco et al., Phys. Rev. E, vol. 106, 2022, p. L013202) with no electron temperature gradient]. The flux tube version of the $\delta f$ code stella (Barnes et al., J. Comput. Phys., vol. 391, 2019, pp. 365–380) is used to run linear and nonlinear gyrokinetic simulations with kinetic electrons. The nature of the dominant instability depends on the wavelength perpendicular to the magnetic field, and the results are conveniently displayed in stability diagrams that take this dependence into account. This approach highlights the presence of universal instabilities, which are less unstable but have longer wavelengths than other modes. A quasi-linear estimate of the heat flux suggests they are relevant for transport. Close to the stability threshold, the linear eigenmodes and turbulence form highly extended structures along the computational domain if the magnetic shear is small. Numerical experiments and diagnostics are undertaken to assess the resulting radial localisation of the turbulence, which affects the interaction of the latter with zonal flows. Increasing the amplitude of the magnetic shear (e.g.through current drive) has a stabilising effect on the turbulence and, thus, reduces the nonlinear energy transport.

Gyrokinetic simulations of the kinetic electron effects on the electrostatic instabilities on the ITER baseline scenario

The linear and nonlinear simulations are carried out using the gyrokinetic code NLT for the electrostatic instabilities in the core region of a deuterium plasma based on the International Thermonuclear Experimental Reactor (ITER) baseline scenario. The kinetic electron effects on the linear frequency and nonlinear transport are studied by adopting the adiabatic electron model and the fully drift-kinetic electron model in the NLT code, respectively. The linear simulations focus on the dependence of linear frequency on the plasma parameters, such as the ion and electron temperature gradients , the density gradient and the ion–electron temperature ratio . Here, is the major radius, and and denote the electron and ion temperatures, respectively. is the gradient scale length, with denoting the density, the ion and electron temperatures, respectively. In the kinetic electron model, the ion temperature gradient (ITG) instability and the trapped electron mode (TEM) dominate in the small and large region, respectively, where is the poloidal wavenumber. The TEM-dominant region becomes wider by increasing (decreasing) ( ) or by decreasing . For the nominal parameters of the ITER baseline scenario, the maximum growth rate of dominant ITG instability in the kinetic electron model is about three times larger than that in the adiabatic electron model. The normalized linear frequency depends on the value of , rather than the value of or , in both the adiabatic and kinetic electron models. The nonlinear simulation results show that the ion heat diffusivity in the kinetic electron model is quite a lot larger than that in the adiabatic electron model, the radial structure is finer and the time oscillation is more rapid. In addition, the magnitude of the fluctuated potential at the saturated stage peaks in the ITG-dominated region, and contributions from the TEM (dominating in the higher region) to the nonlinear transport can be neglected. In the adiabatic electron model, the zonal radial electric field is found to be mainly driven by the turbulent energy flux, and the contribution of turbulent poloidal Reynolds stress is quite small due to the toroidal shielding effect. However, in the kinetic electron model, the turbulent energy flux is not strong enough to drive the zonal radial electric field in the nonlinear saturated stage. The kinetic electron effects on the mechanism of the turbulence-driven zonal radial electric field should be further investigated.

Amplification factor transport equation modelling of Mack mode disturbances in hypersonic boundary layers

In the hypersonic boundary layer, the streamwise instability modes are mainly the Mack first mode and the Mack second mode. After the Mach number exceeds 4.0, the Mack second mode becomes the dominant instability mode for boundary layer transition. Currently, there is no complete analytical method to establish an amplification factor transport equation for the second mode. In order to improve the application of the amplification factor transport (AFT) model in hypersonic boundary layer transition prediction, this paper employs boundary layer similarity solutions to conduct stability analysis on the second mode and introduces a function to calculate the growth rate of disturbances. Additionally, a transport equation for the amplification factor of the second mode is formulated. For the non-local variables appearing in the equation, a local calculation method is provided. Combined with the intermittency factor transport equation, a transition prediction model for the second mode is formed. Hypersonic flat plate, wedge, and flared wedge are selected for model validation. The computed results show good agreement with standard stability analysis or experimental results, demonstrating the rationality of the transition model and its high prediction accuracy and reliability.

Flutter in functionally graded conical shell under follower force

Truncated conical shells are essential components of rocket booster nozzles and thrust vector control (TVC) systems for the propulsion of multi-stage launch vehicles. The TVCs assist the ascent of launch vehicles by directing the resultant thrust from the boosters, acting as a follower force that might trigger instability. Previous studies on the instability of aerospace structures have mostly focused on beams, plates, and cylindrical shells. This study analyses a truncated conical shell under a follower force of constant magnitude, considering thickness-wise gradation of material properties employed for thermal management. The governing equations are derived following Hamilton's principle, considering first-order shear deformation theory, and solved using the finite element method. Clamped and free boundaries are assumed at the small and large ends. The influence of mass and stiffness proportional damping is considered. Although strong flutter appears as the dominant instability mode, instances of erratic weak instabilities are also observed for undamped and lightly damped cases. Damping enhances stability, but its effect becomes saturated. The flutter loads are presented for varying non-dimensional parameters, characterizing the shell geometry and material properties.

Intelligent Power System Stability Assessment and Dominant Instability Mode Identification Using Integrated Active Deep Learning.

Simulation analysis is critical for identifying possible hazards and ensuring secure operation of power systems. In practice, large-disturbance rotor angle stability and voltage stability are two frequently intertwined stability problems. Accurately identifying the dominant instability mode (DIM) between them is important for directing power system emergency control action formulation. However, DIM identification has always relied on human expertise. This article proposes an intelligent DIM identification framework that can discriminate among stable status, rotor angle instability, and voltage instability based on active deep learning (ADL). To reduce human expert efforts required to label the DIM dataset when building DL models, a two-stage batch-mode integrated ADL query strategy (preselection and clustering) is designed for the framework. It samples only the most helpful samples to label in each iteration and considers both information contents and diversity in them to improve query efficiency, significantly reducing the required number of labeled samples. Case studies conducted on a benchmark power system (China Electric Power Research Institute (CEPRI) 36-bus system) and a practical large-area power system (Northeast China Power System) reveal that the proposed approach outperforms conventional methods in terms of accuracy, label efficiency, scalability, and adaptability to operational variability.

Complex Deposit Slope Excavation Deformation Mechanism and Seismic Reinforcement Effect Evaluation

Background To further investigate the excavation deformation mechanism and remedial strategies for slope reinforcement in the southwest mountain area, the Baihetan-Jiangsu (Zhejiang) UHV transmission project deposit slope deformation reinforcement was used as a case study. Methods Deep displacement monitoring, on-site testing, and FLAC3D numerical simulation techniques were employed. The assessment of the deposit slope excavation deformation mechanism and the effectiveness of seismic reinforcement for different design options and pile parameters are conducted while analyzing the seismic reinforcement mechanism. Results and Discussions The results showed that (1) The deposit slope composed of “multi-genetic type soil” in the converter station is prone to deformation, where the dominant instability mode is “traction creep and tension failure mode.” (2) Both circular and rectangular anti-slide piles significantly reduce the amount of slope body deformation; employing circular anti-slide piles for addressing this type of deposit slope provides enhanced anti-slide retention and economic benefits. (3) Under the influence of an earthquake, the shear force and bending moment of the anti-slide pile first increase and then decrease with the increase of seismic intensity. Conclusion The distribution law of shear force and bending moment in a pile should be considered comprehensively in slope support design.

Plasmoid identification and statistics in two-dimensional Harris sheet and GRMHD simulations

ABSTRACT Magnetic reconnection is a ubiquitous phenomenon for magnetized plasma and leads to the rapid reconfiguration of magnetic field lines. During reconnection events, plasma is heated and accelerated until the magnetic field lines enclose and capture the plasma within a circular configuration. These so-called plasmoids could therefore observationally manifest themselves as hotspots, which are associated with flaring behaviour in supermassive black hole systems, such as Sagittarius A*. We have developed a novel algorithm for identifying plasmoid structures, which incorporates watershed and custom closed contouring steps. From the identified structures, we determine the plasmoids’ plasma characteristics and energetics in magnetohydrodynamical simulations. The algorithm’s performance is showcased for a high-resolution suite of axisymmetric ideal and resistive magnetohydrodynamical simulations of turbulent accretion discs surrounding a supermassive black hole. For validation purposes, we also evaluate several Harris current sheets that are well-investigated in the literature. We recover the characteristic power-law distribution of plasmoid sizes for both the black hole and Harris sheet simulations. This indicates that while the dynamics are vastly different, with different dominant plasma instabilities, the plasmoid creation characteristics are similar. Plasmoid formation rates for resistive general relativistic magnetohydrodynamical simulations are significantly higher than for their ideal counterpart. Moreover, the largest identified plasmoids are consistent with sizes typically assumed for semi-analytical interpretation of observations. We recover a positive correlation between the plasmoid formation rate and decreases in black-hole-horizon-penetrating magnetic flux, during which the accretion flow is temporarily halted. These results demonstrate the efficacy of the newly developed algorithm which has enabled an extensive quantitative analysis of plasmoid formation in black hole accretion simulations.

Inertia and slip effects on the instability of a liquid film coated on a fibre

To investigate the influence of inertia and slip on the instability of a liquid film on a fibre, a theoretical framework based on the axisymmetric Navier–Stokes equations is proposed via linear instability analysis. The model reveals that slip significantly enhances perturbation growth in viscous film flows, whereas it exerts minimal influence on flows dominated by inertia. Moreover, under no-slip boundary conditions, the dominant instability mode of thin films remains unaltered by inertia, closely aligning with predictions from a no-slip lubrication model. Conversely, when slip is introduced, the dominant wavenumber experiences a noticeable reduction as inertia decreases. This trend is captured by an introduced lubrication model with giant slip. Direct numerical simulations of the Navier–Stokes equations are then performed to further confirm the theoretical findings at the linear stage. For the nonlinear dynamics, no-slip simulations show complex vortical structures within films, driven by fluid inertia near surfaces. Additionally, in scenarios with weak inertia, a reduction in the volume of satellite droplets is observed due to slip, following a power-law relationship.

Plasma GFAP as a prognostic biomarker of motor subtype in early Parkinson’s disease

Parkinson’s disease (PD) is a heterogeneous movement disorder with different motor subtypes including tremor dominant (TD), indeterminate and postural instability, and gait disturbance (PIGD) motor subtypes. Plasma glial fibrillary acidic protein (GFAP) was elevated in PD patients and may be regarded as a biomarker for motor and cognitive progression. Here we explore if there was an association between plasma GFAP and different motor subtypes and whether baseline plasma GFAP level can predict motor subtype conversion. Patients with PD classified as TD, PIGD or indeterminate subtypes underwent neurological evaluation at baseline and 2 years follow-up. Plasma GFAP in PD patients and controls were measured using an ultrasensitive single molecule array. The study enrolled 184 PD patients and 95 control subjects. Plasma GFAP levels were significantly higher in the PIGD group compared to the TD group at 2-year follow-up. Finally, 45% of TD patients at baseline had a subtype shift and 85% of PIGD patients at baseline remained as PIGD subtypes at 2 years follow-up. Baseline plasma GFAP levels were significantly higher in TD patients converted to PIGD than non-converters in the baseline TD group. Higher baseline plasma GFAP levels were significantly associated with the TD motor subtype conversion (OR = 1.283, P = 0.033) and lower baseline plasma GFAP levels in PIGD patients were likely to shift to TD and indeterminate subtype (OR = 0.551, P = 0.021) after adjusting for confounders. Plasma GFAP may serve as a clinical utility biomarker in differentiating motor subtypes and predicting baseline motor subtypes conversion in PD patients.

The Analysis of relation to brain iron deposition of Parkinson’s Disease using Quantitative Susceptibility Mapping

Objectives: This study aimed to investigate the levels of brain iron deposition in Parkinson's disease (PD) patients using Quantitative Susceptibility Mapping (QSM) and to determine whether distinctions compared to the general population exist. Furthermore, we examined potential variations in iron deposition among different PD subtypes.Methods: Structural brain imaging was conducted on 75 participants at Gangdong Kyung Hee University Hospital between August 2017 and May 2020. PD patients were categorized into Tremor Dominant (TD) and Postural Instability and Gait Difficulty (PIGD) subtypes. Voxel-based morphometry and QSM were employed to compare voxel-wise magnetic susceptibility across the entire brain between Normal Controls (NC) and PD groups. Subsequently, QSM values were compared between TD and PIGD groups.Results: QSM values were compared among 46 PD patients and 23 normal controls, as well as between TD (n=22) and PIGD (n=24) groups. Voxel-based QSM analysis revealed no significant differences between groups. Similarly, ROI-based QSM analysis showed no significant distinctions.Conclusions: No significant variations were observed between the PD patient group, NC group, or PD subtypes. This study systematically compared QSM values across a broad range of brain regions potentially linked to PD pathology. Additionally, the subdivision of the PD group into TD and PIGD subtypes for QSM-based iron deposition analysis represents a meaningful and innovative approach.