Real-time, closed-loop dual-wavelength optical polarimetry for glucose monitoring

Abstract

Abstract. The development of a real-time, dual-wavelength optical polarimetric system to ultimately probe the aqueous humor glucose concentrations as a means of noninvasive diabetic glucose monitoring is the long-term goal of this research. The key impact of the work is the development of an approach for the reduction of the time-variant corneal birefringence due to motion artifact, which is still a limiting factor preventing the realization of such a device. Our dualwavelength approach utilizes real-time, closed-loop feedback that employs a classical three-term feedback controller and efficiently reduces the effect of motion artifact that appears as a common noise source for both wavelengths. In vitro results are shown for the openloop system, and although the dual-wavelength system helps to reduce the noise, it is shown that closed-loop control is necessary to bring the noise down to a sufficient level for physiological monitoring. Specifically, in vitro measurement results with the closed-loop dualwavelength approach demonstrate a sensitivity of 12.8 mg/ dl across the physiologic glucose range in the presence of time-variant test cell birefringence. Overall, it is shown that this polarimetric system has the potential to be used as a noninvasive measure of glucose for diabetes.

The dynamics of invasive and noninvasive blood glucose monitoring methods: Recent trends

“…Очевидным недостатком метода является движение тканей глаза, что служит источником постоянных арте-фактов. Кроме того, было рассчитано, что скорость про-дукции водянистой влаги составляет 2,4±0,6 мкл/мин, то есть около 1/100 общего объема в минуту, в связи с чем ценность метода значительно снижается ввиду значимой задержки между изменением уровня концентрации глю-козы в крови и водянистой влаге глаза [29].…”

A non-invasive photoacoustic and ultrasonic method for the measurement of glucose solution concentration

“…8,9 Cote et al also studied the correlation between the glucose levels with the depressing interference from corneal in Polarimetry. [10][11][12] But there are still two key issues not being solved for non-invasive blood glucose monitoring methodology. One is the specificity of blood glucose, the other is poor signal to noise ratio.…”

Dual-wavelength polarimetric glucose sensing in the presence of birefringence and motion artifact using anterior chamber of the eye phantoms

“…1 One of the main challenges with using polarimetry for glucose sensing in vivo is that most of the biological tissues are optically turbid. Polarimetric sensing of glucose in such media thus becomes challenging due to the presence of relatively high concentrations of chiral components, such as albumin, and multiple scattering events, which can significantly confound the state of polarization of the reflected or transmitted light.…”

“…1,20,21 Specifically, Cameron and Anumula utilized a dedicated birefringence compensator to attempt to account for corneal birefringence. 20 Their system includes a variable retarder that has the potential to compensate for birefringence by negating the contribution of sample birefringence.…”

“…Our group has utilized dual-wavelength polarimetry, which effectively uses two wavelengths to build a multiple linear regression (MLR) model to minimize the contribution of motion-induced birefringence to the total rotation of the state of polarization, yet remains sensitive to a change in rotation due to glucose. 1,21 This reduction in the effect of time-varying corneal birefringence is limited to a narrow but significant range of birefringence values.…”