scholarly journals Computational Models of Brain Stimulation with Tractography Analysis

2020 ◽  
pp. 101-117
Author(s):  
Stefanie Riel ◽  
Mohammad Bashiri ◽  
Werner Hemmert ◽  
Siwei Bai
Keyword(s):  
White Matter ◽  
Electric Field ◽  
Brain Stimulation ◽  
Computational Models ◽  
Electrical Potential ◽  
Potential Gradient ◽  
Fe Model ◽  
Fibre Direction ◽  
Whole Brain ◽  
Activating Function

AbstractComputational human head models have been used in studies of brain stimulation. These models have been able to provide useful information that can’t be acquired or difficult to acquire from experimental or imaging studies. However, most of these models are purely volume conductor models that overlooked the electric excitability of axons in the white matter of the brain. We hereby combined a finite element (FE) model of electroconvulsive therapy (ECT) with a whole-brain tractography analysis as well as the cable theory of neuronal excitation. We have reconstructed a whole-brain tractogram with 2000 neural fibres from diffusion-weighted magnetic resonance scans and extracted the information on electrical potential from the FE ECT model of the same head. Two different electrode placements and three different white matter conductivity settings were simulated and compared. We calculated the electric field and second spatial derivatives of the electrical potential along the fibre direction, which describes the activating function for homogenous axons, and investigated sensitive regions of white matter activation. Models with anisotropic white matter conductivity yielded the most distinctive electric field and activating function distribution. Activation was most likely to appear in regions between the electrodes where the electric potential gradient is most pronounced.

scholarly journals White matter tracing combined with electric field simulation – A patient-specific approach for deep brain stimulation

2019 ◽  
Vol 24 ◽  
pp. 102026 ◽  
Author(s):  
Teresa Nordin ◽  
Peter Zsigmond ◽  
Sonia Pujol ◽  
Carl-Fredrik Westin ◽  
Karin Wårdell
Keyword(s):  
Deep Brain Stimulation ◽  
White Matter ◽  
Electric Field ◽  
Brain Stimulation ◽  
Patient Specific ◽  
Specific Approach ◽  
Field Simulation ◽  
Deep Brain

scholarly journals Whole-brain 3D MR fingerprinting brain imaging: clinical validation and feasibility to patients with meningioma

2021 ◽  
Author(s):  
Thomaz R. Mostardeiro ◽  
Ananya Panda ◽  
Robert J. Witte ◽  
Norbert G. Campeau ◽  
Kiaran P. McGee ◽  
...  
Keyword(s):  
White Matter ◽  
Statistical Significance ◽  
Relaxation Times ◽  
Brain Structures ◽  
Centrum Semiovale ◽  
In Vivo Evaluation ◽  
Whole Brain ◽  
Mean Values ◽  
Caudate Head

Abstract Purpose MR fingerprinting (MRF) is a MR technique that allows assessment of tissue relaxation times. The purpose of this study is to evaluate the clinical application of this technique in patients with meningioma. Materials and methods A whole-brain 3D isotropic 1mm3 acquisition under a 3.0T field strength was used to obtain MRF T1 and T2-based relaxometry values in 4:38 s. The accuracy of values was quantified by scanning a quantitative MR relaxometry phantom. In vivo evaluation was performed by applying the sequence to 20 subjects with 25 meningiomas. Regions of interest included the meningioma, caudate head, centrum semiovale, contralateral white matter and thalamus. For both phantom and subjects, mean values of both T1 and T2 estimates were obtained. Statistical significance of differences in mean values between the meningioma and other brain structures was tested using a Friedman’s ANOVA test. Results MR fingerprinting phantom data demonstrated a linear relationship between measured and reference relaxometry estimates for both T1 (r2 = 0.99) and T2 (r2 = 0.97). MRF T1 relaxation times were longer in meningioma (mean ± SD 1429 ± 202 ms) compared to thalamus (mean ± SD 1054 ± 58 ms; p = 0.004), centrum semiovale (mean ± SD 825 ± 42 ms; p < 0.001) and contralateral white matter (mean ± SD 799 ± 40 ms; p < 0.001). MRF T2 relaxation times were longer for meningioma (mean ± SD 69 ± 27 ms) as compared to thalamus (mean ± SD 27 ± 3 ms; p < 0.001), caudate head (mean ± SD 39 ± 5 ms; p < 0.001) and contralateral white matter (mean ± SD 35 ± 4 ms; p < 0.001) Conclusions Phantom measurements indicate that the proposed 3D-MRF sequence relaxometry estimations are valid and reproducible. For in vivo, entire brain coverage was obtained in clinically feasible time and allows quantitative assessment of meningioma in clinical practice.

scholarly journals Settlement process of radioactive dust to the ground inferred from the atmospheric electric field measurement

2012 ◽  
Vol 30 (1) ◽  
pp. 49-56 ◽  
Author(s):  
M. Yamauchi ◽  
M. Takeda ◽  
M. Makino ◽  
T. Owada ◽  
I. Miyagi
Keyword(s):  
Electric Field ◽  
Nuclear Power ◽  
Potential Gradient ◽  
Radioactive Material ◽  
Strong Wind ◽  
Fair Weather ◽  
Large Area ◽  
Radiation Dose Rate ◽  
Radioactive Dust ◽  
Cloudy Weather

Abstract. Radioactive materials from the accident at Fukushima Dai-ichi nuclear power plant (FNPP) in March 2011 spread over a large area, increasing the atmospheric electric conductivity by their ionizing effect, and reducing the vertical (downward) component of the DC electric field near the ground, or potential gradient (PG). PG data at Kakioka, 150 km away from the FNPP, showed independent changes compared to the radiation dose rate, and a comparison of these data revealed the local dynamics of the radioactive dust. (1) The initial drop of the PG to almost zero during 14–15 March is most likely due to radioactive dust suspended in the air near the ground during cloudy weather. (2) An episode of PG increase to more than 50 V m−1 on 16 March is most likely due to the re-suspension of the radioactive dust from the surface and subsequent removal from Kakioka by the strong wind from the non-contaminated area. (3) Low but finite values of the PG during 16–20 March most likely reflect a reduced amount of radioactive material near the ground after the above wind transported away the majority of the suspended radioactive dust. (4) Very low values of the PG after substantial rain on 20–22 March most likely reflect settlement of the radioactive material by rain-induced fallout. (5) Temporal recovery of daily variations from the end of March to the middle of April with low nighttime fair-weather baseline PG most likely reflects re-suspension of the radioactive dust into the air from the ground and trees, and subsequent transport to the other region or fallout to the ground until late April. (6) Weakening of the daily variation and gradual recovery of the nighttime fair-weather baseline after mid-April suggests a complete settlement of the radioactive material to the ground with partial migration to the subsurface.

Cerebral white matter injury and damage to myelin sheath following whole-brain ischemia

2013 ◽  
Vol 1495 ◽  
pp. 11-17 ◽  
Author(s):  
Yingzhu Chen ◽  
Qiong Yi ◽  
Gang Liu ◽  
Xue Shen ◽  
Lihui Xuan ◽  
...  
Keyword(s):  
White Matter ◽  
Brain Ischemia ◽  
Myelin Sheath ◽  
White Matter Injury ◽  
Cerebral White Matter ◽  
Whole Brain

Whole brain white matter integrity measures on patients with moderate to severe traumatic brain injury (TBI). FA and entropy analysis

2016 ◽  
Vol 32 ◽  
pp. 250
Author(s):  
Charalambos Yiannakkaras ◽  
Nikos Konstantinou ◽  
Eva Pettemeridou ◽  
Fofi Constantinidou ◽  
Eleni Eracleous ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
White Matter ◽  
Severe Traumatic Brain Injury ◽  
White Matter Integrity ◽  
Entropy Analysis ◽  
Whole Brain ◽  
Brain White Matter

Cause-and-effect relations between cosmic rays, electric field, aerosols and clouds

2021 ◽  
Author(s):  
Stavros Stathopoulos ◽  
Stergios Misios ◽  
Konstantinos Kourtidis
Keyword(s):  
Cosmic Rays ◽  
Electric Field ◽  
Causal Effect ◽  
Atmospheric Electricity ◽  
Potential Gradient ◽  
Galactic Cosmic Rays ◽  
The European Union ◽  
Development Education ◽  
Cause And Effect ◽  
Global Coordination

&lt;p&gt;Here we examine the cause-and-effect relations between galactic cosmic rays, electric field, aerosols and clouds over a region of Atlantic Ocean, during a Forbush Decrease (FD) event on 07/12/2015, using Convergent Cross Mapping (CCM) method. For this purpose, we used FD data from the Neuron Monitor Database (NMDB), Potential Gradient data (PG) from Global Coordination of Atmospheric Electricity Measurements (GLOCAEM) and remote sensing data from MODIS/Aqua, namely Aerosol Optical Depth at 550nm (AOD), Cloud Fraction (CF), Cloud Optical Thickness (COT), Cloud Top Pressure (CTP), Cirrus Reflectance (CR) and Cloud Effective Radius-Liquid (CERL). A cause-and-effect relation was found between FD and AOD, CERL, CF and PG, over the region. On the other hand, no causal effect was found between FD and COT, CTP and CR. This research is funded in the context of the project &quot;Cosmic and electric effects on aerosols and clouds&amp;#8221; (MIS: 5049552) under the call for proposals &amp;#8220;Support for researchers with emphasis on young researchers - Cycle B&amp;#8221; (EDULL 103). The project is co-financed by Greece and the European Union (European Social Fund - ESF) by the Operational Programme Human Resources Development, Education and Lifelong Learning 2014-2020.&lt;/p&gt;

Age Dependent and Anisotropic Material Properties of Immature Porcine Sclera

2013 ◽  
Author(s):  
Jami M. Saffioti ◽  
Brittany Coats
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Anisotropic Material ◽  
Computational Models ◽  
Fe Model ◽  
Ocular Tissues ◽  
Load Bearing ◽  
Anisotropic Properties ◽  
Age Dependent ◽  
Testing Protocols

Current finite element (FE) models of the pediatric eye are based on adult material properties [2,3]. To date, there are no data characterizing the age dependent material properties of ocular tissues. The sclera is a major load bearing tissue and an essential component to most computational models of the eye. In preparation for the development of a pediatric FE model, age-dependent and anisotropic properties of sclera were evaluated in newborn (3–5 days) and toddler (4 weeks) pigs. Data from this study will guide future testing protocols for human pediatric specimens.

scholarly journals Uncovering the underlying mechanisms and whole-brain dynamics of deep brain stimulation for Parkinson’s disease

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Victor M. Saenger ◽  
Joshua Kahan ◽  
Tom Foltynie ◽  
Karl Friston ◽  
Tipu Z. Aziz ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Deep Brain Stimulation ◽  
Brain Stimulation ◽  
Brain Dynamics ◽  
Whole Brain ◽  
Underlying Mechanisms ◽  
Deep Brain
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