Transmission versus reflectance spectroscopy for quantitation

Sawada, Jun‐ichi; Osawa, Ayumi; Takeuchi, Tomoki; Kaneda, Masato; Oishi, Shinya; Fujii, Nobutaka; Asai, Akira; Tanino, Keiji; Namba, Kosuke

doi:10.1117/1.jbo.23.1.018001

Cited by 6 publications

(2 citation statements)

References 32 publications

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“…Common sources used in commercial pulse oximeters are red light at approximately 660 nm and infrared (IR) light between 880 and 940 nm. This is due to both cost and the characteristics of the waves as larger wavelengths in the visible and near-IR spectrum transmit better through the skin [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

Equity-Driven Sensing System for Measuring Skin Tone–Calibrated Peripheral Blood Oxygen Saturation (OptoBeat): Development, Design, and Evaluation Study

Adams¹,

Mandel²,

Gao³

et al. 2022

JMIR Biomed Eng

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Background Many commodity pulse oximeters are insufficiently calibrated for patients with darker skin. We demonstrate a quantitative measurement of this disparity in peripheral blood oxygen saturation (SpO2) with a controlled experiment. To mitigate this, we present OptoBeat, an ultra–low-cost smartphone-based optical sensing system that captures SpO2 and heart rate while calibrating for differences in skin tone. Our sensing system can be constructed from commodity components and 3D-printed clips for approximately US $1. In our experiments, we demonstrate the efficacy of the OptoBeat system, which can measure SpO2 within 1% of the ground truth in levels as low as 75%. Objective The objective of this work is to test the following hypotheses and implement an ultra–low-cost smartphone adapter to measure SpO2: skin tone has a significant effect on pulse oximeter measurements (hypothesis 1), images of skin tone can be used to calibrate pulse oximeter error (hypothesis 2), and SpO2 can be measured with a smartphone camera using the screen as a light source (hypothesis 3). Methods Synthetic skin with the same optical properties as human skin was used in ex vivo experiments. A skin tone scale was placed in images for calibration and ground truth. To achieve a wide range of SpO2 for measurement, we reoxygenated sheep blood and pumped it through synthetic arteries. A custom optical system was connected from the smartphone screen (flashing red and blue) to the analyte and into the phone’s camera for measurement. Results The 3 skin tones were accurately classified according to the Fitzpatrick scale as types 2, 3, and 5. Classification was performed using the Euclidean distance between the measured red, green, and blue values. Traditional pulse oximeter measurements (n=2000) showed significant differences between skin tones in both alternating current and direct current measurements using ANOVA (direct current: F2,5997=3.1170 × 105, P<.01; alternating current: F2,5997=8.07 × 106, P<.01). Continuous SpO2 measurements (n=400; 10-second samples, 67 minutes total) from 95% to 75% were captured using OptoBeat in an ex vivo experiment. The accuracy was measured to be within 1% of the ground truth via quadratic support vector machine regression and 10-fold cross-validation (R2=0.97, root mean square error=0.7, mean square error=0.49, and mean absolute error=0.5). In the human-participant proof-of-concept experiment (N=3; samples=3 × N, duration=20-30 seconds per sample), SpO2 measurements were accurate to within 0.5% of the ground truth, and pulse rate measurements were accurate to within 1.7% of the ground truth. Conclusions In this work, we demonstrate that skin tone has a significant effect on SpO2 measurements and the design and evaluation of OptoBeat. The ultra-low-cost OptoBeat system enables smartphones to classify skin tone for calibration, reliably measure SpO2 as low as 75%, and normalize to avoid skin tone–based bias.

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Section: Introductionmentioning

confidence: 99%

Equity-Driven Sensing System for Measuring Skin Tone–Calibrated Peripheral Blood Oxygen Saturation (OptoBeat): Development, Design, and Evaluation Study

Adams¹,

Mandel²,

Gao³

et al. 2022

JMIR Biomed Eng

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“…The observed differences are that the absorbance values of the spectral data of single kernels are lower than for batch measurements. The absorbance value equals the -log transformation of the reflectance value (Gardner, 2018). Compared with single kernels scanning which has the largest scanning area, batch scanning probably has a partial scanning area because of the gap between peanuts caused by the samples' loading.…”

Section: The Establishment Of the Screening Methodsmentioning

confidence: 99%

Novel spectroscopic approaches for the characterisation of quality- and identity-related key features of peanuts and peanut butters

Yu¹

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Controlling the optical pathlength in continuous-wave reflectance spectroscopy using polarization

Macdonald

Sridhar

Hung

et al. 2021

Biomed. Opt. Express

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We investigate potential improvements of continuous-wave diffuse reflectance spectroscopy within highly scattering media by employing polarization gating. Simulations are used to show the extent at which the effective optical pathlength varies in a typical scattering medium as a function of the optical wavelength, the total level of absorption, and the selected polarization channels, including elliptical and circular polarization channels. Experiments then demonstrate that a wavelength dependent polarization gating scheme may reduce the prior knowledge required to solve the problem of chromophore quantification. This is achieved by finding combinations of polarization channels which have similar effective optical pathlengths through the medium at each wavelength.

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Transmission versus reflectance spectroscopy for quantitation

Cited by 6 publications

References 32 publications

Equity-Driven Sensing System for Measuring Skin Tone–Calibrated Peripheral Blood Oxygen Saturation (OptoBeat): Development, Design, and Evaluation Study

Equity-Driven Sensing System for Measuring Skin Tone–Calibrated Peripheral Blood Oxygen Saturation (OptoBeat): Development, Design, and Evaluation Study

Novel spectroscopic approaches for the characterisation of quality- and identity-related key features of peanuts and peanut butters

Controlling the optical pathlength in continuous-wave reflectance spectroscopy using polarization

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