Polarimetric glucose sensing<i>in vitro</i>: a high frequency approach

Pirnstill, Casey W.; Grunden, Daniel T.; Coté, Gerard L.

doi:10.1117/12.2004481

Cited by 5 publications

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“…The motionless system was calibrated, and then the glucose concentrations were calculated using a simple linear regression model of the data acquired without motion. 37 In each experiment, three runs of data were recorded for the two wavelengths, 635 and 515 nm, respectively. As it was shown in Sec.…”

Section: System Performance Without Motionmentioning

confidence: 99%

Dual-modulation, dual-wavelength, optical polarimetry system for glucose monitoring

Pirnstill

Coté

2016

J. Biomed. Opt

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A dual modulation optical polarimetry system utilizing both laser intensity and polarization modulation was designed, built, and tested. The system was designed to reduce complexity and enhance the speed in order to facilitate the reduction of motion-induced time-varying birefringence, which is one of the major limitations to the realization of polarimetry for glucose monitoring in the eye. The high-speed less complex technique was tested using in vitro phantom studies with and without motion artifact introduced. The glucose concentration ranged from 0 to 600 mg/dl and the glucose measurements demonstrated a standard error of prediction to within 8.1 mg/dl without motion and to within 13.9 mg/dl with motion. Our feedback control systems took less than 10 ms to reach stabilization, which is adequately fast to eliminate the effect of time-varying birefringence. The results indicate that this new optical polarimetric approach has improved the speed and reduced the complexity, showing the potential for it to be used for noninvasive glucose measurements.

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Section: System Performance Without Motionmentioning

confidence: 99%

Dual-modulation, dual-wavelength, optical polarimetry system for glucose monitoring

Pirnstill

Coté

2016

J. Biomed. Opt

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“…However, optical polarimetry is unique in that it probes the anterior chamber of the eye [12]. Our group has proposed an optical polarimetric method for noninvasive glucose monitoring across the anterior chamber of the eye [12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

“…However, in these studies index coupling devices are utilized to overcome the index mismatch between the air-aqueous humor barrier [12][13][14][15][16][17][18]. It is well known through the process of vision that the eye is ideally suited to couple light to the back of the retina.…”

Section: Introductionmentioning

confidence: 99%

Modeling the optical coupling across the anterior chamber of the eye towards polarimetric glucose sensing

Pirnstill

Coté

2014

SPIE Proceedings

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Millions of people worldwide are affected by diabetes. While glucose sensing technology has come a long way over the past several decades, the current commercially available techniques are still invasive, often leading to poor patient compliance. To minimize invasiveness, focus has been placed on optical techniques to ascertain blood glucose concentrations. Optical polarimetry has shown promise and progress as a viable technique for glucose sensing. Recent developments in polarimetric glucose sensing have been focused on overcoming time varying corneal birefringence due to motion artifacts. Beyond corneal birefringence, the next hurdle toward making this approach viable is the ability to couple polarized light across the eye's anterior chamber. The eye is ideally suited to couple light to the retina. The index mismatch between the air and cornea is partially responsible for the beam bending toward the retina and, while good for vision, it complicates our ability to couple light across the anterior chamber without using an index matching device when performing polarimetric glucose monitoring. In this report, we have designed and modeled a non-index matched coupling scheme constructed with commercially available optics. The optical ray tracing model was performed using CODE V to verify the feasibility of a reflective based non-index matched coupling scheme with respect to index of refraction and anatomical restraints. The ray tracing model was developed for a dual-wavelength system and the effect of refraction and reflection at each optical interface within the setup was evaluated. The modeling results indicate a reflective based optical coupling design could be added to existing polarimetric glucose systems thus removing the need for placing an index matched eye-coupling mechanism over the eye prior to data collection.

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“…Therefore, the upper limit of the integration time from the lock-in amplifiers depends on the modulation frequency from the Faraday modulators. In other words, a higher Faraday modulation frequency provides the potential to create a faster output signal from the lock-in electronics, and a higher frequency modulation has the potential to improve the signal-to-noise ratio in the presence of motion artifacts(68).It is possible to procure a more accurate and repeatable standard error by obtaining more data over a shorter period of time(62). The output from the lock-in amplifier is input into a proportional-integral-derivative (PID) controller for the controlled feedback into the Faraday compensators.…”

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confidence: 99%

“…These air-core Faraday rotators were constructed from TGG crystals (Deltronic Crystals, Inc., Dover, New Jersey) inside bobbins wound with electric coils.After a beamsplitter/combiner (BS) (Optosigma Corp., Santa Ana, Califormia) combined the two linearly polarized beams, the polarization vector of both beams was modulated using the ferrite core Faraday modulator (FM). This approach replaced the previously used slower air-core Faraday modulator operating at 1.09 kHz(38,62) with the faster ferrite core Faraday modulator operating at a frequency between 30 and 75 kHz. For this aim, a combination of 3 capacitors yielding a net capacitance of 7.85 nF were placed in series with the ferrite core Faraday modulator for Series Resonance at 37 kHz modulation frequency.…”

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confidence: 99%

High-speed dual-wavelength optical polarimetry for glucose sensing

2014

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To non-invasively measure glucose concentrations across the aqueous humor of the eye, a high-speed, dual-wavelength optical polarimetric approach is proposed that addresses a key limitation of prior set-ups -system response time -while compensating for time-varying motion artifact due to corneal birefringence.This research is made up of three goals. The first goal is to design and construct a high-frequency, ferrite core Faraday rotator that can both rotate and modulate linearly polarized light in a frequency range of 30 to 75 kHz. The second goal is to implement a single ferrite core Faraday rotator into the current polarimetric approach. The third goal is to replace three air-core Faraday rotators with two ferrite core Faraday rotators for both modulation and compensation, allowing for two different signals to be measured on a single photodetector.In vitro phantom studies are performed with and without motion artifact. The sensor is shown to stabilize in ~2 msec and provide standard errors for glucose concentration of less than 13 mg/dL in the presence of motion. The results indicate that higher frequency modulation can reduce the overall system stabilization time with minimal loss of accuracy in the presence of motion artifact. iii ACKNOWLEDGEMENTS I would like to thank my committee chair, Dr. Gerard L. Coté, for his guidance, advice, and support through the course of this research. His professionalism and focus on various projects at the same time as performing his duties as department head have shown me the key qualities I strive for now and during my career. I couldn't have completed this work without him. I would also like to thank my committee members, Dr. Mary P. McDougall and Dr. Prasad Enjeti, for their support and their time. Their guidance through theory and design pointed me in the right directions. Mr. Erwin Thomas III and Dr. Bilal Malik both guided me in new and interesting directions as well.Thanks also go to my friends, including but not limited to

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Polarimetric glucose sensingin vitro: a high frequency approach

Cited by 5 publications

References 0 publications

Dual-modulation, dual-wavelength, optical polarimetry system for glucose monitoring

Dual-modulation, dual-wavelength, optical polarimetry system for glucose monitoring

Modeling the optical coupling across the anterior chamber of the eye towards polarimetric glucose sensing

High-speed dual-wavelength optical polarimetry for glucose sensing

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