Tunable laser diode system for noninvasive blood glucose measurements

Optical Science and Technology Center and the Department of Chemistry, 100 IATL, University of Iowa, Iowa City, Iowa 52242, USA.
Applied Spectroscopy (Impact Factor: 2.01). 01/2006; 59(12):1480-4. DOI: 10.1366/000370205775142485
Source: PubMed

ABSTRACT Optical sensing of glucose would allow more frequent monitoring and tighter glucose control for people with diabetes. The key to a successful optical noninvasive measurement of glucose is the collection of an optical spectrum with a very high signal-to-noise ratio in a spectral region with significant glucose absorption. Unfortunately, the optical throughput of skin is low due to absorption and scattering. To overcome these difficulties, we have developed a high-brightness tunable laser system for measurements in the 2.0-2.5 microm wavelength range. The system is based on a 2.3 microm wavelength, strained quantum-well laser diode incorporating GaInAsSb wells and AlGaAsSb barrier and cladding layers. Wavelength control is provided by coupling the laser diode to an external cavity that includes an acousto-optic tunable filter. Tuning ranges of greater than 110 nm have been obtained. Because the tunable filter has no moving parts, scans can be completed very quickly, typically in less than 10 ms. We describe the performance of the present laser system and avenues for extending the tuning range beyond 400 nm.

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    ABSTRACT: Since the external cavity quantum dot laser was first demonstrated, the performances have been improved in terms of operation temperature, output power, pulse generator and tuneability based on the naturally size fluctuation of quantum dot. Nowadays, the external cavity quantum dot sources have been successfully used in different absorption spectroscope techniques, in industry, biomedical and research. In this paper we reviewed the recent developments of quantum dot lasers operated in a grating-coupled external cavity system where a single frequency and wide tunable wavelength range were easily obtained by adjusting the grating angle. In all cases, we mainly stressed the significant progresses in understanding of basic optical and electronic properties to enable the importance steps forward. The prospects for further progress directed towards stability, mode-hoping-free tuning range, miniaturization and integration of the external cavity quantum dot lasers also reviewed.
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    ABSTRACT: Background and Objective There is a growing body of evidence suggesting that the accurate measurement of blood glucose concentration can be perturbed by many factors. Current literature is limited in describing the influence of cholesterol on non-invasive blood glucose measurements by near-infrared spectroscopy (NIRS). This study aims to investigate the influence of cholesterol on blood glucose measurement through clinical oral glucose tolerance test (OGTT) and NIRS. Further, a method to reduce the prediction errors induced by cholesterol is proposed, facilitating the clinical application of non-invasive blood glucose sensing by NIRS.Study Design/Material and Methods We obtained clinical data of glucose and cholesterol concentrations at specific time points (0, 0.5, 1, 2, and 3 h) during OGTTs from 115 subjects. The subjects were grouped into: Norm for normal control, IGT for Impaired Glucose Tolerance, and Diabetes. In addition, spectral data between 1200 and 1800 nm were collected from 130 phantom samples, which are separated into seven groups depending on glucose and cholesterol levels. Statistical methods including One Sample T-test (OSTT), Pearson Correlation Analysis(PCA), and Unary Linear Regression (ULR) were used to analyze clinical data and spectral data to determine the relationship between glucose and cholesterol concentrations with the time course of OGTT. Reference wavelength-based method (RWM) was introduced to diminish the influence of cholesterol on glucose measurement and further the prediction error induced by cholesterol was reduced when using partial least square (PLS) model.ResultsClinical results statistically show that there is a strong negative correlation between the changes of glucose and cholesterol concentrations in the diabetes group. The spectra of cholesterol exhibit similar absorbance peaks to those of glucose within NIR range. PLS modelling results demonstrate that glucose prediction is influenced by cholesterol concentrations in a calibration model. Furthermore, a model expression (R2 = 0.993) is fitted to quantitatively describe the glucose prediction increment () due to cholesterol concentration (). The results show that glucose prediction accuracy can be improved up to 38.36% by using RWM when using NIRS.Conclusions The cholesterol has an effect on blood glucose sensing. RWM is useful to help realize non-invasive blood glucose sensing by NIRS. Lasers Surg. Med. © 2015 Wiley Periodicals, Inc.
    Lasers in Surgery and Medicine 01/2015; DOI:10.1002/lsm.22317 · 2.61 Impact Factor

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