Mid-infrared spectroscopy has been an important tool widely used for qualitative analysis in various fields. However, portable or personal use is size and cost prohibitive for either Fourier transform infrared or attenuated total reflectance (ATR) spectrophotometers. In this study, we developed an ultra-compact ATR spectrophotometer whose frequency band was 5.5–11.0 μm. We used miniature components, such as a light source fabricated by semiconductor technology, a linear variable filter, and a pyro-electric array detector. There were no moving parts. Optimal design based on two light sources, a zippered configuration of the array detector and ATR optics could produce absorption spectra that might be used for qualitative analysis. A microprocessor synchronized the pulsed light sources and detector, and all the signals were processed digitally. The size was 13.5×8.5×3.5 cm3 and the weight was 300 grams. Due to its low cost, our spectrophotometer can replace many online monitoring devices. Another application could be for a u-healthcare system installed in the bathroom or attached to a smartphone for monitoring substances in body fluids.
Measurement accuracy for predicting glucose in whole blood was studied based on near-infrared spectroscopy. Optimal wavelength regions, preprocessing, and the influence of hemoglobin were examined using partial least-squares regression. Spectra between 1100 and 2400 nm were measured from 98 whole blood samples. In order to study the influence of hemoglobin, which is the most dominant component in blood, 98 samples were arranged such that glucose and hemoglobin concentrations were distributed in their physiological ranges. Samples were grouped into three depending on hemoglobin level. The results showed that glucose prediction was influenced by hemoglobin concentrations in the calibration model. It was necessary for samples used in the calibration model to represent the entire range of hemoglobin level. The cross-validation errors were the smallest when the wavelength regions of 1390 to 1888 nm and 2044 to 2393 nm were used. However, prediction accuracy was not very dependent on preprocessing methods in this optimal region. The standard error of glucose prediction was 25.5 mg/dL and the coefficient of variation in prediction was 11.2%.
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.
In designing microelectromechanical systems (MEMS), the robustness of the system critically affects long-lasting system performance. In reality, fabrication errors, material property uncertainty, and environmental uncertainty such as temperature and humidity variations affect the performance of MEMS. These factors are usually referred to as noise factors. This investigation is mainly concerned with the robust design of micro electro-thermal actuators that are to be fabricated by the MEMS fabrication technology. The baseline design is found by topology optimization method which gives an initial optimal shape of an electro-thermal actuator giving the maximum output for a given input. By the mathematical topology optimization method alone, it is difficult or impossible to consider all noise factors in the final design stage. To take into account noise factors, we will employ the robust design methodology and modify the baseline design obtained by the topology optimization. In this work, robust design will be considered with micro electro-thermal actuators. The electro-thermal actuator is an actuating device using the thermal expansion by Joule’s heat, so its performance is affected by the temperature variation of surrounding air, convection, thermal expansion, and applied voltage among others. We consider these noise factors for the final design to improve its robustness against the noise factors. Several micro electro-thermal actuators were fabricated by the MEMS fabrication technology and a series of experiments were conducted to verify the effect of the robust design concept on the final design.
For noninvasive measurement of bio-fluid substances in human body based on optical spectroscopy, optical measurement system is one of the most important parts. We studied glucose specificities by analyzing the factors in the partial least squares regression models for the two cases of reflectance and transmittance measurements. Glucose -intralipid solutions were used as the samples whose scatterer's concentrations were varied. We used intralipid concentrations of 4%, 4.08% and 4.16% in the solution and these values were comparable to tissue scattering. Temperature was maintained at 30°C during measurement. Factor analysis for reflectance data didn't show glucose absorption feature and the factors were very noisy particularly in the combination band. It is speculated that light does not have enough information of glucose since the pathlength in reflectance is very short. On the other hand, the factors obtained from the PLS analysis of transmittance revealed glucose signatures. We suggest that transmittance measurement is preferred for in vivo glucose monitoring than reflectance measurement.
Photo-plethysmography measure pulsatile blood flow in real-time and non-invasively.One of widely known application of PPG is a measurement of saturated oxygen in arterial blood (SpO2). In our work , using several wave length more than those used in a pulse oximeter, an algorithm and instrument have been developed to measure hematocrit, saturated oxygen pulse and respiratory rates simultaneously.To predict hemotocrit, a dedicated algorithm is developed based on scattering of RBC and a protocall for detecting outlier signal is used to increase accuracy and reliability.Digital filtering techniques are used to exart respiratory rate signal. Utilization of wave length under 1000nm and a multi-wavelength LED array chip and digital-oriented electronic enable us to make a compact device. Our preliminary clinical trails shown that the achived percent errors are±8.2% for hematocrit when tested with 594 person ,r2 for SpO fitting is 0.99985 when tested with a Bi-Tek pulse oximeter simulator and the SPO2 error for in vivo test is ±2.5% over the range of 75~100%. The error of pulse rates is less than ±5%. We obtained a positive predictive value of 96% for respiratory rates in qualitative analysis.
Spontaneous ultraweak photon (biophoton) emissions from hands are measured for healthy subjects. The data provide basic reference information for diagnostic application of biophoton emission. The overall average of biophoton emissions from the hands is 226.4 ± 14.3 counts per second. The asymmetry of the biophoton emission rates between the left and the right hands could be significant for both western and oriental diagnosis.
The method and device for non-invasive measurement of blood glucose concentration based on the diffuse reflectance from the transcutaneous layers is proposed. Original normalizing ratio algorithm permitting to separate glucose absorption from absorption of other blood components is suggested. It was shown that the influence of water and some other components such as hemoglobin, albumin, globulin's and cholesterol concentration variations to the estimation of the glucose concentration can be compensated using spectral analysis of the reflection on several specially selected wavelengths and proposed algorithm. Device with optical geometry minimizing the effects of changes in the scattering background of biological tissues was developed. NIR spectral range 800 - 1800 nm was used because of its good transparency for biological tissue and presence of glucose absorption band. We used two kinds of light sources, namely LED array and Xe flash lamp. Tissue phantoms (different glucose concentration (0 - 1000 mg/dl) solutions with polystyrene beads or with milk) were used as samples. Scattering and absorption contribution to the dependence of diffuse reflection on glucose concentration was experimentally verified.
The importance and effects of data preprocessing and wavelength selection were investigated in predicting total hemoglobin concentrations form absorption spectra. Spectra of the 1 nm interval between 500-900nm were measured from the whole blood samples taken form 165 patients whose hemoglobin concentrations ranged between 7-17 g/dl. The concentrations were predicted using the partial least squares regression. A total of 18 different combinations of preprocessing were tested. The partial least squares regression analysis provided quite different results depending on preprocessing methods and a wide range of prediction accuracy was obtained. For example, the sum of squares of difference ranged from 6-18.6, R2 varied from 0.8333 to 0.9477 and the root mean squared errors were from 0.5504-0.966 g/dl. The best results was obtained from the data processed by linear regression baseline fitting, unit area correction, mean centering and variance scaling. Instead of using all wavelengths in the broad-band spectra, a discrete number of wavelengths were selected to predict the concentrations using our algorithm, which will be advantageous in developing compact and less expensive commercial devices. It proves that a careful selection of wavelengths can provide a comparable accuracy obtained from using the broad-band spectra. For our particular experimental data, the measurement form only three discrete wavelengths could provide excellent results.
A prototype pulsed laser of dual heads of Nd:YAG and Er:YAG has been developed. Nd:YAG laser emits 1.06 micrometers and 1.3 micrometers. Er:YAG laser generates 2.94 micrometers. This laser system is designed for treating both soft and hard tissues in dentistry. Nd:YAG laser has about 100 microseconds pulse duration and repetition rates are up to 100 Hz at 1.06 micrometer and up to 30 Hz at 1.3 micrometer. The average power at 50 Hz is up to 30 W at 1.06 micrometer. Up to 10 W at 30 Hz can be obtained at 1.3 micrometer. Er:YAG laser has about 100 microsecond pulse duration, repetition rates up to 5 Hz and the average power up to 5 W. Current 1.06 micrometer Nd:YAG dental lasers show some difficulties in treating soft tissue due to low absorption and higher penetration. Dye as absorbing medium is often applied on targets to enhance absorption. A 1.3 micrometer wavelength is expected to be valuable for soft tissue treatment since absorption at this wavelength is more than ten times higher than at 1.06 micrometer. A 2.94 micrometer wavelength is available for hard tissue surgery.
An open-loop temperature control was introduced to control evolution of the maximum
temperature on the tissue surface to be within upper and lower limits. For this purpose, the temperature
evolutions of sample shots were analyzed and optimal sequences of laser pulses were computed. The
1.06 tm pulsed Nd:YAG laser was used and the thermal camera measured temperature. Experiment
on animals in vivo and in vitro was performed to test the technique. Upper and lower temperature
limits during laser irradiation were set below 100 °C since thermal coagulation was ofprimary concern.
Usually, difference between the upper and lower limits was set to 1 5°C during experiment. However,
this difference depended on the laser specifications such as power, pulse width, and repetition rates, as
well as on tissue properties. Coagulation studies showed a clear relation of temperature versus
cogulation depth. Therefore, the heating temperature and the duration time can be used as primary
parameters instead of laser power and exposure time or energy.
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