ABSTRACT
A two-electrode biopotential amplifier, though simpler than a three-electrode amplifier, has problems rejecting 60 Hz power-line interference due to the imbalance of electrode-skin impedance. A direct interference canceling (DIC) scheme to reject 60 Hz interference for a two-electrode biopotential amplifier is proposed. The DIC scheme cancels differential-mode interference directly by adding to the interference to be canceled a feedback signal that has the same magnitude and frequency as the interference, but that has phase shifted 180 degrees. When the DIC is started by closing a switch, transient interference appears, which decreases within several seconds. In steady state, the DIC amplifier rejects a very narrow bandwidth (BW) centered at the interference frequency. The proposed circuit was implemented and the DIC operation yielded 54 dB interference canceling with 0.6 Hz rejection BW.
Subject(s)
Amplifiers, Electronic , Electrodes , Electrodiagnosis/instrumentation , Electronics, Medical/instrumentation , Algorithms , Electrodiagnosis/methods , Feedback , HumansABSTRACT
In this study, we present the possibility of the fat thickness measurement using the miniaturized chip LEDs sensor module for the twelve healthy women. The newly developed sensor module consisted of four different source-detector distances. The measurement sites are the five parts of biceps, triceps, upper abdomen, front thigh, and calf and the range of fat thickness is from 3.5 mm to 39.0 mm. The fitting curve for each measurement sites is separately obtained. We obtained the correlation coefficient of 0.932 compared with the fat thickness of CT measurement for biceps site. For the three measurement sites of biceps, front thigh, and calf of twelve persons and namely 36 data points, the mean absolute difference thickness and % error for the measured thickness compared with that of reference CT thickness are 1.08 mm and 11.49%, respectively. Based on this preliminary experiment, it is confirmed that the fat thickness measurement is possible with proper curve fitting procedure using slope analysis.
Subject(s)
Abdominal Fat , Adiposity , Optics and Photonics , HumansABSTRACT
Glucose determination based on near-IR spectroscopy is investigated for reflectance and transmittance measurement. A wavelength range is 1100 to 2500 nm, which includes both the combination and overtone bands of glucose absorption. Intralipid solutions are used as samples, where glucose concentrations vary between 0 and 1000 mg/dl. Sample thickness for reflectance is 10 cm and 1- and 2-mm-thick samples are used for transmission. Partial least-squares regression (PLSR) analyses are performed to predict glucose concentrations. The standard errors of calibration are comparable between reflectance and 2-mm-thick transmittance. The reflectance method is inferior to the transmittance method in terms of the standard errors of prediction. Loading vector analysis for reflectance does not show glucose absorption features. Reflected light may not have enough information of glucose since a major portion of detected light has a short optical path length. In addition, prediction becomes more dependent on medium scattering rather than glucose, compared with transmission measurement. Loading vectors obtained from a PLSR transmittance analysis have glucose absorption profiles. The 1-mm-thick samples give better results than the 2-mm-thick samples for both calibration and prediction models. The transmittance setup is recommended for noninvasive glucose monitoring.
Subject(s)
Algorithms , Glucose/analysis , Nephelometry and Turbidimetry/methods , Photometry/methods , Spectrophotometry, Infrared/methods , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
We tested the feasibility of noninvasive fat thickness measurements by using a diffuse optical method with variable source-detector pairs. A light source module composed of 770 nm low-power chip LEDs and a photodetector were used in this study. The tissue phantoms are composed of a fat and a muscle layer made with gels with appropriate absorption/scattering coefficients. The fat thickness was varied from several to 30 mm. Based on this preliminary study, it is concluded that the noninvasive fat thickness measurement is possible with proper curve fitting procedure.
