CNT/PDMS-based canal-typed ear electrodes for inconspicuous EEG recording.

OBJECTIVE: Current electroencephalogram (EEG) monitoring systems typically require cumbersome electrodes that must be pasted on a scalp, making a private recording of an EEG in a public place difficult. We have developed a small, user friendly, biocompatible electrode with a good appearance for inconspicuous EEG monitoring. APPROACH: We fabricated carbon nanotube polydimethylsiloxane (CNT/PDMS)-based canal-type ear electrodes (CEE) for EEG recording. These electrodes have an additional function, triggering sound stimulation like earphones and recording EEG simultaneously for auditory brain-computer interface (BCI). The electrode performance was evaluated by a standard EEG measurement paradigm, including the detection of alpha rhythms and measurements of N100 auditory evoked potential (AEP), steady-state visual evoked potential (SSVEP) and auditory steady-state response (ASSR). Furthermore, the bio- and skin-compatibility of CNT/PDMS were tested. MAIN RESULTS: All feasibility studies were successfully recorded with the fabricated electrodes, and the biocompatibility of CNT/PDMS was also proved. SIGNIFICANCE: These electrodes could be used to monitor EEG clinically, in ubiquitous health care and in brain-computer interfaces.

Fractional anisotropy-based divisions of midsagittal corpus callosum.

The authors first divided the midsagittal corpus callosum of 22 healthy volunteers using three different subdivision methods: Witelson's geometric subdivision, boundary model-based subdivision, and medial model-based subdivision. Next, subdivisions of the corpus callosum were clustered on the basis of homogeneity of the fractional anisotropy values as produced from diffusion tensor images. Nine subregions of corpus callosum, similar in location and size, were successfully clustered when medial model-based or boundary model-based subdivisions were applied. These nine subregions of the corpus callosum were different from the seven subregions defined by Witelson's geometric subdivision, especially at the anterior and posterior tips of the corpus callosum. Our method of corpus callosum division can be potentially utilized to assess structural changes in the midsagittal corpus callosum.

A Preliminary Study for Unconstrained Pulse Arrival Time (PAT) Measurement on a Chair.

A method of measuring the pulse arrival time (PAT) non-consciously on a chair is proposed. In this method, the electrically non-contact ECG measurement system and the air cushion with balancing tubes are used. In this paper, the correlation between the typical PAT and the unconstrained PATs (A-PATs) are compared. The typical PAT is measured as the difference of R-peak of ECG and the steepest descent point of the PPG in toe. The three different A-PATs were measured from the pressure pulse of the air cushion (APP). The correlation between the typical PAT and the A-PAT from the steepest descent point of the APP was the highest (R=0.9663).

Unconstrained pulse transit time measurement system for computer users.

Pulse Transit Time (PTT) is a simple non-invasive method to evaluate vascular function using photoplethysmography(PPG) and electrocardiography(ECG). This study introduces unconstrained PTT measurement method for computer users and evaluates that. The proposed system consists of chair and mouse those can measure ECG and PPG respectability. PTT was defined as time delay between ECG R peak and PPG steepest point. The correlation coefficient between PTT that measured from this system and conventional PTT was 0.93. This work will provide many opportunities for ubiquitous health monitoring.

Common mode noise cancellation for electrically non-contact ECG measurement system on a chair.

Electrically non-contact ECG measurement system on a chair can be applied to a number of various fields for continuous health monitoring in daily life. However, the body is floated electrically for this system due to the capacitive electrodes and the floated body is very sensitive to the external noises or motion artifacts which affect the measurement system as the common mode noise. In this paper, the Driven-Seat-Ground circuit similar to the Driven-Right-Leg circuit is proposed to reduce the common mode noise. The analysis of this equivalent circuit is performed and the output signal waveforms are compared between with Driven-Seat-Ground and with capacitive ground. As the results, the Driven-Seat-Ground circuit improves significantly the properties of the fully capacitive ECG measurement system as the negative feedback.

Urine analysis in diluted situation using low-resolution Raman spectroscope.

We could get valuable information about various diseases by analyzing urine of patients. For the diabetics, it has been very important to know the glucose concentration in their urine. Until now, there have been many methods to estimate the concentration but they were invasive and annoyed patients. The Low-Resolution Raman Spectroscopy (LRRS) could be an alternative method to be non-invasive and unconscious for patients who want to check the amount of their urine components. LRRS is not expensive and smaller than laboratory Raman spectroscope. And we want to attach it to the common toilet bowl. For the reason, we got the spectrum of diluted urine and predicted the glucose concentration. In addition, we tried to find very small amount of glucose. LRRS was adequate for measuring Raman signal of diluted urine and could find very small amount of glucose. This system will realize the observation of one's health condition every day without awareness.

Nonlinear-analysis of human sleep EEG using detrended fluctuation analysis.

Quantification of the fractal scaling properties of human sleep EEG dynamics was sought and each normal sleep stage was compared with that of sleep apnea. The fractal scaling exponents that quantify power-law correlations were computed using detrended fluctuation analysis. Six healthy subjects, aged 30-35 years, participated and six recordings of the apnea were acquired from MIT/BIH polysomnography database. The data were 8-h baseline recordings (23:00-07:00 h). The EEG signals from the C4-A1 derivation were acquired with a resolution of 250 Hz. The sleep stages were visually scored for 30 s epochs, according to the criteria of Rechtschaffen and Kales. The mean scaling exponents increased from the awake stage to stages 1, 2 and 3-4, but decreased during rapid eye movement (REM) sleep. The scaling exponents of the apnea were lower than those of the healthy subject for all the stages. The scaling exponents could be attributed to the fractal nature of EEG, which would be more appropriate for describing the complexity of EEG due to its assumption of non-stationarity.

Regularized FOCUSS algorithm for EEG/MEG source imaging.

In this paper, we derived a generalized version of the regularized FOCUSS algorithm which was derived in [3]. It allows general forms of noise covariance and reduces depth effect when imaging focal neural sources from electroencephalography (EEG) / magnetoencephalography (MEG) data. We compared a depth-weighted regularized algorithm with FOCUSS and a regularized FOCUSS through simulation study. The suggested algorithm gave sparser and less spurious solutions than the others.

A study on the factor number determination methods in the partial least squares model for the urinalysis using Raman spectroscopy.

As an effort for the development of the nonintrusive measurement system, Raman spectroscopy was applied for the urinalysis. By using Raman spectroscopy, the concentration of the urine components could be measured. As a multivariate method, the partial least squares method was performed. When composing a calibration model, the determination of the appropriate number of factors was very important for the accurate prediction of the constituent concentration. In this study, the number of factors was determined by observing the minimum PRESS (prediction residual error sum of squares) value and the biggest correlation coefficient between the predicted values and the original values of the training set. After obtaining the most suitable number of factors by the two methods, the unknown constituent concentration was predicted with those factors, and the correlation coefficients between the pre-examined value and the predicted results from the unknown spectra were calculated. The analysis results using the two factor number determination methods were compared in order to determine which one is more suitable for the accurate urine component concentration prediction. The selected method will be used in the urinalysis using Raman spectroscopy system which will be one of the non-intrusive measurement systems in a live-alone patient's house.