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Frontiers in Human Neuroscience 2024Volume conduction models of the human head are used in various neuroscience fields, such as for source reconstruction in EEG and MEG, and for modeling the effects of...
INTRODUCTION
Volume conduction models of the human head are used in various neuroscience fields, such as for source reconstruction in EEG and MEG, and for modeling the effects of brain stimulation. Numerous studies have quantified the accuracy and sensitivity of volume conduction models by analyzing the effects of the geometrical and electrical features of the head model, the sensor model, the source model, and the numerical method. Most studies are based on simulations as it is hard to obtain sufficiently detailed measurements to compare to models. The recording of stereotactic EEG during electric stimulation mapping provides an opportunity for such empirical validation.
METHODS
In the study presented here, we used the potential distribution of volume-conducted artifacts that are due to cortical stimulation to evaluate the accuracy of finite element method (FEM) volume conduction models. We adopted a widely used strategy for numerical comparison, i.e., we fixed the geometrical description of the head model and the mathematical method to perform simulations, and we gradually altered the head models, by increasing the level of detail of the conductivity profile. We compared the simulated potentials at different levels of refinement with the measured potentials in three epilepsy patients.
RESULTS
Our results show that increasing the level of detail of the volume conduction head model only marginally improves the accuracy of the simulated potentials when compared to sEEG measurements. The mismatch between measured and simulated potentials is, throughout all patients and models, maximally 40 microvolts (i.e., 10% relative error) in 80% of the stimulation-recording combination pairs and it is modulated by the distance between recording and stimulating electrodes.
DISCUSSION
Our study suggests that commonly used strategies used to validate volume conduction models based solely on simulations might give an overly optimistic idea about volume conduction model accuracy. We recommend more empirical validations to be performed to identify those factors in volume conduction models that have the highest impact on the accuracy of simulated potentials. We share the dataset to allow researchers to further investigate the mismatch between measurements and FEM models and to contribute to improving volume conduction models.
PubMed: 38410258
DOI: 10.3389/fnhum.2024.1279183 -
Journal of Electrical Bioimpedance Jan 2023Biomedical engineering stands at the forefront of medical innovation, with electroencephalography (EEG) signal analysis providing critical insights into neural...
Biomedical engineering stands at the forefront of medical innovation, with electroencephalography (EEG) signal analysis providing critical insights into neural functions. This paper delves into the utilization of EEG signals within the MILimbEEG dataset to explore their potential for machine learning-based task recognition and diagnosis. Capturing the brain's electrical activity through electrodes 1 to 16, the signals are recorded in the time-domain in microvolts. An advanced feature extraction methodology harnessing Hjorth Parameters-namely Activity, Mobility, and Complexity-is employed to analyze the acquired signals. Through correlation analysis and examination of clustering behaviors, the study presents a comprehensive discussion on the emergent patterns within the data. The findings underscore the potential of integrating these features into machine learning algorithms for enhanced diagnostic precision and task recognition in biomedical applications. This exploration paves the way for future research where such signal processing techniques could revolutionize the efficiency and accuracy of biomedical engineering diagnostics.
PubMed: 38162817
DOI: 10.2478/joeb-2023-0009 -
Data in Brief Oct 2023Biomedical Electroencephalography (EEG) signals are the result of measuring the electric potential difference generated on the scalp surface by neural activity...
Biomedical Electroencephalography (EEG) signals are the result of measuring the electric potential difference generated on the scalp surface by neural activity corresponding to each brain area. Accurate and automatic detection of neural activity from the upper and lower limbs using EEG may be helpful in rehabilitating people suffering from mobility limitations or disabilities. This article presents a dataset containing 7440 CSV files from 60 test subjects during motor and motor imagery tasks. The motor and motor imagery tasks performed by the test subjects were: Closing Left Hand (CLH), Closing Right Hand (CRH), Dorsal flexion of Left Foot (DLF), Plantar flexion of Left Foot (PLF), Dorsal flexion of Right Foot (DRF), Plantar flexion of Right Foot (PRF) and Resting in between tasks (Rest). The volunteers were recruited from research colleagues at ESPOL and patients at the Luis Vernaza Hospital in Guayaquil, Ecuador. Each CSV file has 501 rows, of which the first one lists the electrodes from 0 to 15, and the remaining 500 rows correspond to 500 data recorded during the task is performed due to sample rate. In addition, each file has 17 columns, of which the first one indicates the sampling number and the remaining 16 columns represent 16 surface EEG electrodes. As a data recording equipment, the OpenBCI is used in a monopolar setup with a sampling rate of 125 Hz. This work includes statistical measures about the demographic information of all recruited test subjects. Finally, we outline the experimental methodology used to record EEG signals during upper and lower limb task execution. This dataset is called MILimbEEG and contains microvolt (µV) EEG signals acquired during motor and motor imagery tasks. The collected data may facilitate the evaluation of EEG signal detection and classification models dedicated to task recognition.
PubMed: 37727590
DOI: 10.1016/j.dib.2023.109540 -
Arquivos Brasileiros de Cardiologia 2023Sudden cardiac death (SCD) resulting from ventricular arrhythmia is the main complication of hypertrophic cardiomyopathy (HCM). Microvolt T-wave alternans (MTWA) is...
BACKGROUND
Sudden cardiac death (SCD) resulting from ventricular arrhythmia is the main complication of hypertrophic cardiomyopathy (HCM). Microvolt T-wave alternans (MTWA) is associated with the occurrence of ventricular arrhythmias in several heart diseases, but its role in HCM remains uncertain.
OBJECTIVE
To evaluate the association of MTWA with the occurrence of SCD or potentially fatal ventricular arrhythmias in HCM patients in a long-term follow-up.
METHODS
Patients diagnosed with HCM and NYHA functional class I-II were consecutively selected. At the beginning of the follow-up, the participants performed the MTWA evaluation using the modified moving average during the stress test. The results were classified as altered or normal. The composite endpoint of SCD, ventricular fibrillation, sustained ventricular tachycardia (SVT) or appropriate implantable cardiac defibrillation (ICD) therapy was assessed. The level of significance was set at 5%.
RESULTS
A total of 132 patients (mean age of 39.5 ± 12.6 years) were recruited and followed for a mean of 9.5 years. The MTWA test was altered in 74 (56%) participants and normal in 58 (44%). Nine events (6.8%) occurred during the follow-up, with a prevalence of 1.0%/year - six SCDs, two appropriate ICD shocks and one episode of (SVT). Altered MTWA was associated with non-sustained ventricular tachycardia on Holter (p = 0.016), septal thickness ≥30 mm (p < 0.001) and inadequate blood pressure response to effort (p = 0.046). Five patients with altered MTWA (7%) and four patients with normal MTWA (7%) had the primary outcome [OR = 0.85 (95% CI: 0.21 - 3.35, p=0.83)]. Kaplan-Meir event curves showed no differences between normal and altered MTWA.
CONCLUSION
Altered MTWA was not associated with the occurrence of SCD or potentially fatal ventricular arrhythmias in HCM patients, and the low rate of these events during long-term follow-up suggests the good prognosis of this heart disease.
Topics: Humans; Adult; Middle Aged; Prognosis; Follow-Up Studies; Arrhythmias, Cardiac; Cardiomyopathy, Hypertrophic; Death, Sudden, Cardiac; Tachycardia, Ventricular; Ventricular Fibrillation; Anti-Arrhythmia Agents; Cardiotonic Agents; Diuretics
PubMed: 37672406
DOI: 10.36660/abc.20220833 -
Cardiology Research Feb 2023Cardiac arrhythmias are significantly associated with poor outcomes in coronavirus disease 2019 (COVID-19) patients. Microvolt T-wave alternans (TWA) can be...
BACKGROUND
Cardiac arrhythmias are significantly associated with poor outcomes in coronavirus disease 2019 (COVID-19) patients. Microvolt T-wave alternans (TWA) can be automatically quantified and has been recognized as a representation of repolarization heterogeneity and linked to arrhythmogenesis in various cardiovascular diseases. This study aimed to explore the correlation between microvolt TWA and COVID-19 pathology.
METHODS
Patients suspected of COVID-19 in Mohammad Hoesin General Hospital were consecutively evaluated using Alivecor Kardiamobile 6L™ portable electrocardiogram (ECG) device. Severe COVID-19 patients or those who are unable to cooperate in active ECG self-recording were excluded from the study. TWA was detected and its amplitude was quantified using the novel enhanced adaptive match filter (EAMF) method.
RESULTS
A total of 175 patients, 114 COVID-19 patients (polymerase chain reaction (PCR)-positive group), and 61 non-COVID-19 patients (PCR-negative group) were enrolled in the study. PCR-positive group was subdivided according to the severity of COVID-19 pathology into mild and moderate severity subgroups. Baseline TWA levels were similar between both groups during admission (42.47 ± 26.52 µV vs. 44.72 ± 38.21 µV), but higher TWA levels were observed during discharge in the PCR-positive compared to the PCR-negative group (53.45 ± 34.42 µV vs. 25.15 ± 17.64 µV, P = 0.03). The correlation between PCR-positive result in COVID-19 and TWA value was significant, after adjustment of other confounding variables (R = 0.081, P = 0.030). There was no significant difference in TWA levels between mild and moderate severity subgroups in patients with COVID-19, both during admission (44.29 ± 27.14 µV vs. 36.75 ± 24.46 µV, P = 0.34) and discharge (49.47 ± 33.62 µV vs. 61.09 ± 35.99 µV, P = 0.33).
CONCLUSIONS
Higher TWA values can be observed on follow-up ECG obtained during discharge in the PCR-positive COVID-19 patients.
PubMed: 36896221
DOI: 10.14740/cr1458 -
Journal of Cardiovascular Development... Jan 2023Atrial fibrillation (AF) is the most persistent arrhythmia today, with its prevalence increasing exponentially with the rising age of the population. Particularly at... (Review)
Review
Atrial fibrillation (AF) is the most persistent arrhythmia today, with its prevalence increasing exponentially with the rising age of the population. Particularly at elevated heart rates, a functional abnormality known as cardiac alternans can occur prior to the onset of lethal arrhythmias. Cardiac alternans are a beat-to-beat oscillation of electrical activity and the force of cardiac muscle contraction. Extensive evidence has demonstrated that microvolt T-wave alternans can predict ventricular fibrillation vulnerability and the risk of sudden cardiac death. The majority of our knowledge of the mechanisms of alternans stems from studies of ventricular electrophysiology, although recent studies offer promising evidence of the potential of atrial alternans in predicting the risk of AF. Exciting preclinical and clinical studies have demonstrated a link between atrial alternans and the onset of atrial tachyarrhythmias. Here, we provide a comprehensive review of the clinical utility of atrial alternans in identifying the risk and guiding treatment of AF.
PubMed: 36826532
DOI: 10.3390/jcdd10020036 -
Clinical Breast Cancer Jun 2023Breast cancer survivors (BCS) frequently show upper limb dysfunctions. The forearm muscle activity measured by surface electromyography (sEMG) in this population has not...
INTRODUCTION/BACKGROUND
Breast cancer survivors (BCS) frequently show upper limb dysfunctions. The forearm muscle activity measured by surface electromyography (sEMG) in this population has not been studied. This study aimed to describe forearm muscle activity in BCS, as well as to assess its possible relationship with other variables related to upper limb functionality and cancer-related fatigue (CRF).
MATERIALS AND METHODS
A cross-sectional study was carried out including 102 BCS as volunteers at a secondary care in Malaga, Spain. BCS were included if they were aged between 32 and 70 years old, without evidence of cancer recurrence at the time of recruitment. The forearm muscle activity (microvolts, µV) was assessed by sEMG during the handgrip test. The handgrip strength was assessed by dynamometry (kg), the upper limb functionality (%) was measured by the upper limb functional index (ULFI) questionnaire and the CRF was also assessed by revised Piper Fatigue Scale (0-10 points).
RESULTS
BCS reported reduced forearm muscle activity (287.88 µV) and reduced handgrip strength (21.31 Kg), a good upper limb functionality (68.85%), and a moderate cancer-related fatigue (4.74). Forearm muscle activity showed a poor significant correlation (r = -0.223, P = .038) with the CRF. Handgrip strength showed a poor correlation with the upper limb functionality (r = 0.387, P < .001) and age (r=-0.200, P = .047).
CONCLUSION
BCS showed a reduced forearm muscle activity. BCS also presented a poor correlation between forearm muscle activity and handgrip strength. Both outcomes tended to lower values with higher levels of CRF, while preserving a good upper limb functionality.
Topics: Humans; Adult; Middle Aged; Aged; Female; Forearm; Breast Neoplasms; Hand Strength; Cross-Sectional Studies; Cancer Survivors; Neoplasm Recurrence, Local; Fatigue; Muscles
PubMed: 36803839
DOI: 10.1016/j.clbc.2023.01.008 -
MedLife Clinics 2022There is a need to accurately identify pregnant women at risk for preterm birth as early as possible. Recent developments in technology enable the recording of uterine...
BACKGROUND
There is a need to accurately identify pregnant women at risk for preterm birth as early as possible. Recent developments in technology enable the recording of uterine electrical activity (electrohysterogram) from the anterior abdominal wall in a non-invasive way.
OBJECTIVE
To investigate whether uterine activity recorded under resting conditions at a gestational age of 34 weeks could identify a risk of preterm birth.
STUDY DESIGN
A commercial antenatal holter device with its dedicated software was used to record and store raw data of the maternal and fetal electrocardiograms and uterine activity for the Safe Passage Study. Uterine activity was recorded under resting conditions from 34 weeks' gestation in epochs of 250 ms (millisecond) for at least 30 min. From this database the raw data, recorded at a mean gestational age of 34 weeks, of 50 women who had preterm deliveries were selected for comparison with data of women who had term deliveries. Mean uterine activity, expressed in microvolt (μV)/epoch, was used for the comparison.
RESULTS
After exclusion of 25 participants where labour was induced or augmented and another three for other reasons, 36 remained in each group. The participants in each group were comparable in respect of maternal age, gravidity, parity, gestational age at recruitment and duration of recording. Uterine activity in the preterm group (60.3 μV/epoch) differed significantly (p<0.01) from that of the comparison group (52.4 μV/epoch). Using a cut-off point of 52.3 μV/epoch as obtained from receiver operator characteristic curves (area under the curve 0.72), the sensitivity and specificity of identifying risks of preterm labour were 81% and 50% respectively.
CONCLUSION
Results of this small study are promising but need to be confirmed in larger studies and preferably at earlier gestational age.
PubMed: 36660227
DOI: No ID Found -
Scientific Reports Dec 2022Sudden cardiac death is impactful. There has been an increase in the search for tools capable of identifying individuals who are most susceptible, such as the microvolt...
Sudden cardiac death is impactful. There has been an increase in the search for tools capable of identifying individuals who are most susceptible, such as the microvolt T-wave alternans. This study aims to analyze the applicability of the modified moving average methodology to obtain the microvolt T-wave alternans using treadmill specific protocols. Medical records of patients during the period August 2006-December 2014 were retrospectively analyzed. Five hundred and thirty nine exams were then included, divided into groups according to the protocol and updating factor used: Ellestad factor 8 or 32, Naughton factor 8 or 32. The topics for analysis were the alternans behavior, noise and confirmation according to the groups of leads analyzed (frontal, transversal and orthogonal planes). The greater microvolt T-wave alternans was found during the stress phase in most of the tests. Group Naughton 8 presented lower noise in this phase for the transverse and orthogonal planes (p = 0.0082 and p < 0.0001), with greater confirmation of frontal and orthogonal planes in comparison with group Ellestad 8 (p = 0.0002 and 0.0008). The results indicate the viability of simultaneous performance of the stress test and measurement of the T wave alternans with Naughton protocol with 1/8 updating factor.
Topics: Humans; Exercise Test; Retrospective Studies; Factor VIII; Arrhythmias, Cardiac; Death, Sudden, Cardiac; Electrocardiography
PubMed: 36575194
DOI: 10.1038/s41598-022-26535-x