scholarly journals Head phantoms for bioelectromagnetic applications: a material study

2020 ◽  
Author(s):  
Alexander Hunold ◽  
René Machts ◽  
Jens Haueisen
Keyword(s):  
Electrical Conductivity ◽  
White Matter ◽  
Ground Truth ◽  
Human Head ◽  
Transcranial Electrical Stimulation ◽  
Intracranial Volume ◽  
Nacl Solution ◽  
Anisotropic Conductivity ◽  
Synthetic Materials ◽  
Agarose Hydrogel

Abstract Background Assessments of source reconstruction procedures in electroencephalography and computations of transcranial electrical stimulation profiles require verification and validation with the help of ground truth configurations as implemented by physical head phantoms. For these phantoms, synthetic materials are needed, which are mechanically and electrochemically stable and possess conductivity values similar to the modeled human head tissues. Three-compartment head models comprise a scalp layer with a conductivity range of 0.137 S/m to 2.1 S/m, a skull layer with conductivity values between 0.066 S/m and 0.00275 S/m, and an intracranial volume with an often-used average conductivity value of 0.33 S/m. To establish a realistically shaped physical head phantom with a well-defined volume conduction configuration, we here characterize the electrical conductivity of synthetic materials for modeling head compartments. We analyzed agarose hydrogel, gypsum, and sodium chloride (NaCl) solution as surrogate materials for scalp, skull, and intracranial volume. We measured the impedance of all materials when immersed in NaCl solution using a four-electrode setup. The measured impedance values were used to calculate the electrical conductivity values of each material. Further, the conductivities in the longitudinal and transverse directions of reed sticks immersed in NaCl solution were measured to test their suitability for mimicking the anisotropic conductivity of white matter tracts.Results We obtained conductivities of 0.314 S/m, 0.30 S/m, 0.311 S/m (2 %, 3 %, 4 % agarose), 0.0425 S/m and 0.0017 S/m (gypsum with and without NaCl in the compound), and 0.332 S/m (0.17 % NaCl solution). These values are within the range of the conductivity values used for EEG and TES modeling. The reed sticks showed anisotropic conductivity with a ratio of 1:2.8. Conclusion We conclude that agarose, gypsum, and NaCl solution can serve as stable representations of the three main conductivity compartments of the head, i.e. scalp, skull, and intracranial volume. An anisotropic conductivity structure such as a fiber track in white matter can be modeled using tailored reed sticks inside a volume conductor.

scholarly journals Head phantoms for bioelectromagnetic applications: a material study

2020 ◽  
Author(s):  
Alexander Hunold ◽  
René Machts ◽  
Jens Haueisen
Keyword(s):  
Electrical Conductivity ◽  
White Matter ◽  
Ground Truth ◽  
Human Head ◽  
Transcranial Electrical Stimulation ◽  
Intracranial Volume ◽  
Nacl Solution ◽  
Anisotropic Conductivity ◽  
Synthetic Materials ◽  
Agarose Hydrogel

Abstract Background: Assessments of source reconstruction procedures in electroencephalography and computations of transcranial electrical stimulation profiles require verification and validation with the help of ground truth configurations as implemented by physical head phantoms.. For these phantoms, synthetic materials are needed, which are mechanically and electrochemically stable and possess conductivity values similar to the modeled human head tissues. Typical three-compartment head models comprise a scalp layer with a conductivity range from 0.137 S/m to 2.1 S/m, a skull layer with conductivity values between 0.066 S/m and 0.00275 S/m, and an intracranial volume with an often-used average conductivity value of 0.33 S/m. To establish a realistically shaped physical head phantom with a well-defined volume conduction configuration we here characterize the electrical conductivity of synthetic materials for modeling head compartments. We analyze agarose hydrogel, gypsum, and sodium chloride (NaCl) solution as surrogate materials for scalp, skull, and intracranial volume. We measure the impedance of all materials when immersed in NaCl solution using a four-electrode setup. The measured impedance values, temperature compensated to 25°C, were used to calculate the electrical conductivity values of each material. Further, the conductivities in the longitudinal and transversal directions of reed sticks immersed in NaCl solution were measured to test their suitability for mimicking the anisotropic conductivity of white matter tracts.Results: We obtained conductivities of 0.314 S/m, 0.30 S/m, 0.311 S/m (2 %, 3 %, 4 % agarose), 0.0425 S/m and 0.0017 S/m (gypsum with and without NaCl in the compound), and 0.332 S/m (0.17 % NaCl solution). These values are within the range of the conductivity values used for EEG and TES modeling. The reed sticks showed anisotropic conductivity with a ratio of 1:2.8. Conclusion: We conclude that the tested materials agarose, gypsum, and NaCl solution can serve as stable representations of the three main conductivity compartments of the head scalp, skull, and intracranial volume. An anisotropic conductivity structure such as a fiber track in white matter can be modeled using tailored reed sticks inside a volume conductor.

scholarly journals Head phantoms for bioelectromagnetic applications: a material study

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Alexander Hunold ◽  
René Machts ◽  
Jens Haueisen
Keyword(s):  
Electrical Conductivity ◽  
White Matter ◽  
Ground Truth ◽  
Human Head ◽  
Transcranial Electrical Stimulation ◽  
Intracranial Volume ◽  
Nacl Solution ◽  
Anisotropic Conductivity ◽  
Synthetic Materials ◽  
Agarose Hydrogel

Abstract Background Assessments of source reconstruction procedures in electroencephalography and computations of transcranial electrical stimulation profiles require verification and validation with the help of ground truth configurations as implemented by physical head phantoms. For these phantoms, synthetic materials are needed, which are mechanically and electrochemically stable and possess conductivity values similar to the modeled human head tissues. Three-compartment head models comprise a scalp layer with a conductivity range of 0.137 S/m to 2.1 S/m, a skull layer with conductivity values between 0.066 S/m and 0.00275 S/m, and an intracranial volume with an often-used average conductivity value of 0.33 S/m. To establish a realistically shaped physical head phantom with a well-defined volume conduction configuration, we here characterize the electrical conductivity of synthetic materials for modeling head compartments. We analyzed agarose hydrogel, gypsum, and sodium chloride (NaCl) solution as surrogate materials for scalp, skull, and intracranial volume. We measured the impedance of all materials when immersed in NaCl solution using a four-electrode setup. The measured impedance values were used to calculate the electrical conductivity values of each material. Further, the conductivities in the longitudinal and transverse directions of reed sticks immersed in NaCl solution were measured to test their suitability for mimicking the anisotropic conductivity of white matter tracts. Results We obtained conductivities of 0.314 S/m, 0.30 S/m, 0.311 S/m (2%, 3%, 4% agarose), 0.0425 S/m and 0.0017 S/m (gypsum with and without NaCl in the compound), and 0.332 S/m (0.17% NaCl solution). These values are within the range of the conductivity values used for EEG and TES modeling. The reed sticks showed anisotropic conductivity with a ratio of 1:2.8. Conclusion We conclude that agarose, gypsum, and NaCl solution can serve as stable representations of the three main conductivity compartments of the head, i.e., scalp, skull, and intracranial volume. An anisotropic conductivity structure such as a fiber track in white matter can be modeled using tailored reed sticks inside a volume conductor.

scholarly journals Head phantoms for bioelectromagnetic applications: a material study

2020 ◽  
Author(s):  
Alexander Hunold ◽  
René Machts ◽  
Jens Haueisen
Keyword(s):  
Electrical Conductivity ◽  
Ground Truth ◽  
Transcranial Electrical Stimulation ◽  
Intracranial Volume ◽  
Nacl Solution ◽  
Anisotropic Conductivity ◽  
Conductivity Structure ◽  
Agarose Hydrogel ◽  
Stable Representation ◽  
Material Study

Abstract Background Assessments of source reconstruction procedures in electroencephalography and computations of transcranial electrical stimulation profiles require verification and validation with the help of ground truth configurations as implemented by physical head phantoms. Phantoms provide well-defined volume conduction configurations with realistic geometries.We aim to characterize the electrical conductivity of materials for modeling head compartments to establish reproducible and stable physical head phantoms. We analyzed sodium chloride (NaCl) solution, agarose hydrogel, gypsum and reed sticks as surrogate materials for the intracranial volume, scalp, skull and anisotropic conductivity structures. We measured the impedance of all materials when immersed in NaCl solution using a four-point setup. The electrical conductivity values of each material were calculated from the temperature compensated impedances considering the sample geometries. Results We obtained conductivities of 0.332 S/m (0.17 % NaCl solution), 0.0425 S/m and 0.0017 S/m (gypsum with and without NaCl), 0.314 S/m, 0.30 S/m, 0.311 S/m (2 %, 3 %, 4 % agarose). The reed sticks were tested in longitudinal and transversal direction and showed anisotropic conductivity with a ratio of 1:2.8. Conclusion We conclude that the tested materials NaCl solution, gypsum and agarose can serve as stable representation of the three main conductivity compartments of the head, intracranial volume, skull and scalp. An anisotropic conductivity structure such as a piece of white matter can be modeled using tailored reed sticks inside a volume conductor.

scholarly journals Arterial stiffness and progression of cerebral white matter hyperintensities in patients with type 2 diabetes and matched controls: a 5-year cohort study

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Kristian L. Funck ◽  
Esben Laugesen ◽  
Pernille Høyem ◽  
Brian Stausbøl-Grøn ◽  
Won Y. Kim ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Cohort Study ◽  
White Matter ◽  
Arterial Stiffness ◽  
White Matter Hyperintensities ◽  
Cerebrovascular Diseases ◽  
Study Data ◽  
Cerebral White Matter ◽  
Intracranial Volume

Abstract Background Stroke is a serious complication in patients with type 2 diabetes (T2DM). Arterial stiffness may improve stroke prediction. We investigated the association between carotid-femoral pulse wave velocity [PWV] and the progression of cerebral white matter hyperintensities (WMH), a marker of stroke risk, in patients with T2DM and controls. Methods In a 5-year cohort study, data from 45 patients and 59 non-diabetic controls were available for analysis. At baseline, participants had a mean (± SD) age of 59  ±  10 years and patients had a median (range) diabetes duration of 1.8 (0.8–3.2) years. PWV was obtained by tonometry and WMH volume by an automated segmentation algorithm based on cerebral T2-FLAIR and T1 MRI (corrected by intracranial volume, cWMH). High PWV was defined above 8.94 m/s (corresponding to the reference of high PWV above 10 m/s using the standardized path length method). Results Patients with T2DM had a higher PWV than controls (8.8  ±  2.2 vs. 7.9  ±  1.4 m/s, p  <  0.01). WMH progression were similar in the two groups (p  =  0.5). One m/s increase in baseline PWV was associated with a 16% [95% CI 1–32%], p  <  0.05) increase in cWMH volume at 5 years follow-up after adjustment for age, sex, diabetes, pulse pressure and smoking. High PWV was associated with cWMH progression in the combined cohort (p  <  0.05). We found no interaction between diabetes and PWV on cWMH progression. Conclusions PWV is associated with cWMH progression in patients with type 2 diabetes and non-diabetic controls. Our results indicate that arterial stiffness may be involved early in the pathophysiology leading to cerebrovascular diseases.

Measurement of electrical conductivity of 0.001 mol NaCl solution under high pressures

1997 ◽  
Vol 42 (18) ◽  
pp. 1563-1566 ◽  
Author(s):  
Zheng Haifei ◽  
Xie Hongsen ◽  
Xu Yousheng ◽  
Song Maoshuang ◽  
Guo Jie ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
High Pressures ◽  
Nacl Solution

Influence of White Matter Hyperintensities on Baseline and Longitudinal Amyloid-β in Cognitively Normal Individuals

2021 ◽  
pp. 1-11
Author(s):  
Fennie Choy Chin Wong ◽  
Seyed Ehsan Saffari ◽  
Chathuri Yatawara ◽  
Kok Pin Ng ◽  
Nagaendran Kandiah ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Executive Function ◽  
White Matter ◽  
White Matter Hyperintensities ◽  
Small Vessel Disease ◽  
Amyloid Β ◽  
Intracranial Volume ◽  
Linear Regression Models ◽  
Cognitively Normal

Background: The associations between small vessel disease (SVD) and cerebrospinal amyloid-β1-42 (Aβ1-42) pathology have not been well-elucidated. Objective: Baseline (BL) white matter hyperintensities (WMH) were examined for associations with month-24 (M24) and longitudinal Aβ1-42 change in cognitively normal (CN) subjects. The interaction of WMH and Aβ1-42 on memory and executive function were also examined. Methods: This study included 72 subjects from the Alzheimer’s Disease Neuroimaging Initiative. Multivariable linear regression models evaluated associations between baseline WMH/intracranial volume ratio, M24 and change in Aβ1-42 over two years. Linear mixed effects models evaluated interactions between BL WMH/ICV and Aβ1-42 on memory and executive function. Results: Mean age of the subjects (Nmales = 36) = 73.80 years, SD = 6.73; mean education years = 17.1, SD = 2.4. BL WMH was significantly associated with M24 Aβ1-42 (p = 0.008) and two-year change in Aβ1-42 (p = 0.006). Interaction between higher WMH and lower Aβ1-42 at baseline was significantly associated with worse memory at baseline and M24 (p = 0.003). Conclusion: BL WMH was associated with M24 and longitudinal Aβ1-42 change in CN. The interaction between higher WMH and lower Aβ1-42 was associated with poorer memory. Since SVD is associated with longitudinal Aβ1-42 pathology, and the interaction of both factors is linked to poorer cognitive outcomes, the mitigation of SVD may be correlated with reduced amyloid pathology and milder cognitive deterioration in Alzheimer’s disease.

Abstract 47: White Matter Atrophy in Cerebral Amyloid Angiopathy

Stroke ◽  
2016 ◽  
Vol 47 (suppl_1) ◽  
Author(s):  
Panagiotis Fotiadis ◽  
Aaron Schultz ◽  
Trey Hedden ◽  
Sergi Martinez-Ramirez ◽  
Yael Reijmer ◽  
...  
Keyword(s):  
White Matter ◽  
Cerebral Amyloid Angiopathy ◽  
Cortical Thickness ◽  
Tissue Loss ◽  
White Matter Hyperintensity ◽  
Aging Brain ◽  
Amyloid Angiopathy ◽  
Intracranial Volume ◽  
White Matter Volume ◽  
Cerebral Amyloid

Background/Purpose: Cerebral Amyloid Angiopathy (CAA) leads to leukoaraiosis, lacunar infarcts and cortical tissue loss. We hypothesized that CAA is also associated with white matter atrophy (WMA). Methods: We have compared volumetric multimodal MRIs from 72 prospectively enrolled non-demented patients with probable CAA (per Boston criteria), to 3 other well-studied cohorts: 289 Healthy Controls (HC) from the Harvard Aging Brain (HAB) study, 231 HC and 198 patients with AD from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). Validated FreeSurfer algorithms were used to calculate White Matter Volume (WMV), white matter hyperintensity volume (WMHv), and cortical thickness. Microbleeds (MBs) were counted on SWI-MRI. Measures were obtained from the contralateral hemisphere if intracerebral hemorrhage present. All volumes were corrected for total intracranial volume (ICV), so reported as percent of ICV. Results: The CAA patients were significantly younger (mean age: 70.1) compared to both HC cohorts (ADNI-HC: 76.0, p<0.001, HAB-HC: 73.8, p < 0.001), and to patients with AD (75.5, p < 0.001). Despite being younger, patients with CAA presented significantly lower global WMV (28% ± 2.6) than both ADNI-HC (29.2% ± 2.2, p < 0.001), HAB-HC (29.0% ± 2.5, p = 0.001), and patients with AD (28.7% ± 2.2, p = 0.02) [Figure]. The association persisted after correcting for age, gender and WMHv. Within the CAA cohort, there was a negative correlation between WMV and lobar MB counts (rho = -0.26, p = 0.03), it remained significant after correcting for age, gender, WMHv (p=0.016). There were no significant associations however between WMV and neither WMHv, nor cortical thickness (both p>0.2). Conclusions: Patients with CAA show WMA when compared to older HC and AD. WMA independently correlates with MBs, a marker of CAA severity. Consistent spatial patterns of atrophy especially in posterior regions when compared to both HC and AD [Figure] might represent the “WMA signature of CAA”.

scholarly journals Blood-based bioenergetic profiling is related to differences in brain morphology in African Americans with Type 2 diabetes

2018 ◽  
Vol 132 (23) ◽  
pp. 2509-2518 ◽  
Author(s):  
Gargi Mahapatra ◽  
S. Carrie Smith ◽  
Timothy M. Hughes ◽  
Benjamin Wagner ◽  
Joseph A. Maldjian ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
White Matter ◽  
African Americans ◽  
Mitochondrial Function ◽  
Brain Morphology ◽  
Intracranial Volume ◽  
Peripheral Blood Mononuclear ◽  
Relationship Of ◽  
The Relationship

Blood-based bioenergetic profiling has promising applications as a minimally invasive biomarker of systemic bioenergetic capacity. In the present study, we examined peripheral blood mononuclear cell (PBMC) mitochondrial function and brain morphology in a cohort of African Americans with long-standing Type 2 diabetes. Key parameters of PBMC respiration were correlated with white matter, gray matter, and total intracranial volumes. Our analyses indicate that these relationships are primarily driven by the relationship of systemic bioenergetic capacity with total intracranial volume, suggesting that systemic differences in mitochondrial function may play a role in overall brain morphology.

scholarly journals Anatomy and white matter connections of the orbitofrontal gyrus

2018 ◽  
Vol 128 (6) ◽  
pp. 1865-1872 ◽  
Author(s):  
Joshua D. Burks ◽  
Andrew K. Conner ◽  
Phillip A. Bonney ◽  
Chad A. Glenn ◽  
Cordell M. Baker ◽  
...  
Keyword(s):  
White Matter ◽  
Diffusion Tensor ◽  
Diffusion Imaging ◽  
Internal Capsule ◽  
Ground Truth ◽  
Outcome Evaluation ◽  
Anterior Cingulate ◽  
Anatomical Dissection ◽  
Visual Spatial ◽  
Human Connectome Project

OBJECTIVEThe orbitofrontal cortex (OFC) is understood to have a role in outcome evaluation and risk assessment and is commonly involved with infiltrative tumors. A detailed understanding of the exact location and nature of associated white matter tracts could significantly improve postoperative morbidity related to declining capacity. Through diffusion tensor imaging–based fiber tracking validated by gross anatomical dissection as ground truth, the authors have characterized these connections based on relationships to other well-known structures.METHODSDiffusion imaging from the Human Connectome Project for 10 healthy adult controls was used for tractography analysis. The OFC was evaluated as a whole based on connectivity with other regions. All OFC tracts were mapped in both hemispheres, and a lateralization index was calculated with resultant tract volumes. Ten postmortem dissections were then performed using a modified Klingler technique to demonstrate the location of major tracts.RESULTSThe authors identified 3 major connections of the OFC: a bundle to the thalamus and anterior cingulate gyrus, passing inferior to the caudate and medial to the vertical fibers of the thalamic projections; a bundle to the brainstem, traveling lateral to the caudate and medial to the internal capsule; and radiations to the parietal and occipital lobes traveling with the inferior fronto-occipital fasciculus.CONCLUSIONSThe OFC is an important center for processing visual, spatial, and emotional information. Subtle differences in executive functioning following surgery for frontal lobe tumors may be better understood in the context of the fiber-bundle anatomy highlighted by this study.

Are Anesthesia and Surgery during Infancy Associated with Decreased White Matter Integrity and Volume during Childhood?

2017 ◽  
Vol 127 (5) ◽  
pp. 788-799 ◽  
Author(s):  
Robert I. Block ◽  
Vincent A. Magnotta ◽  
Emine O. Bayman ◽  
James Y. Choi ◽  
Joss J. Thomas ◽  
...  
Keyword(s):  
White Matter ◽  
Mean Diffusivity ◽  
White Matter Integrity ◽  
Cerebral Peduncle ◽  
Intracranial Volume ◽  
Healthy Children ◽  
Superior Cerebellar Peduncle ◽  
Control Subjects ◽  
Brain White Matter ◽  
Cerebellar Peduncle

AbstractBackgroundAnesthetics have neurotoxic effects in neonatal animals. Relevant human evidence is limited. We sought such evidence in a structural neuroimaging study.MethodsTwo groups of children underwent structural magnetic resonance imaging: patients who, during infancy, had one of four operations commonly performed in otherwise healthy children and comparable, nonexposed control subjects. Total and regional brain tissue composition and volume, as well as regional indicators of white matter integrity (fractional anisotropy and mean diffusivity), were analyzed.ResultsAnalyses included 17 patients, without potential confounding central nervous system problems or risk factors, who had general anesthesia and surgery during infancy and 17 control subjects (age ranges, 12.3 to 15.2 yr and 12.6 to 15.1 yr, respectively). Whole brain white matter volume, as a percentage of total intracranial volume, was lower for the exposed than the nonexposed group, 37.3 ± 0.4% and 38.9 ± 0.4% (least squares mean ± SE), respectively, a difference of 1.5 percentage points (95% CI, 0.3 to 2.8; P = 0.016). Corresponding decreases were statistically significant for parietal and occipital lobes, infratentorium, and brainstem separately. White matter integrity was lower for the exposed than the nonexposed group in superior cerebellar peduncle, cerebral peduncle, external capsule, cingulum (cingulate gyrus), and fornix (cres) and/or stria terminalis. The groups did not differ in total intracranial, gray matter, and cerebrospinal fluid volumes.ConclusionsChildren who had anesthesia and surgery during infancy showed broadly distributed, decreased white matter integrity and volume. Although the findings may be related to anesthesia and surgery during infancy, other explanations are possible.

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