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Jeong UH, Park JH, Choi JH, Lee WG, Park JG. Hybrid Organic-Si C-MOSFET Image Sensor Designed with Blue-, Green-, and Red-Sensitive Organic Photodiodes on Si C-MOSFET-Based Photo Signal Sensor Circuit. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:1066. [PMID: 38998671 PMCID: PMC11243616 DOI: 10.3390/nano14131066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2024] [Revised: 06/08/2024] [Accepted: 06/12/2024] [Indexed: 07/14/2024]
Abstract
The resolution of Si complementary metal-oxide-semiconductor field-effect transistor (C-MOSFET) image sensors (CISs) has been intensively enhanced to follow the technological revolution of smartphones, AI devices, autonomous cars, robots, and drones, approaching the physical and material limits of a resolution increase in conventional Si CISs because of the low quantum efficiency (i.e., ~40%) and aperture ratio (i.e., ~60%). As a novel solution, a hybrid organic-Si image sensor was developed by implementing B, G, and R organic photodiodes on four n-MOSFETs for photocurrent sensing. Photosensitive organic donor and acceptor materials were designed with cost-effective small molecules, i.e., the B, G, and R donor and acceptor small molecules were Coumarin6 and C_60, DMQA and MePTC, and ZnPc and TiOPc, respectively. The output voltage sensing margins (i.e., photocurrent signal difference) of the hybrid organic-Si B, G, and R image sensor pixels presented results 17, 11, and 37% higher than those of conventional Si CISs. In addition, the hybrid organic-Si B, G, and R image sensor pixels could achieve an ideal aperture ratio (i.e., ~100%) compared with a Si CIS pixel using the backside illumination process (i.e., ~60%). Moreover, they may display a lower fabrication cost than image sensors because of the simple image sensor structure (i.e., hybrid organic-Si photodiode with four n-MOSFETs).
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Affiliation(s)
- Ui-Hyun Jeong
- Department of Electronic Engineering, Hanyang University, Seoul 04763, Republic of Korea
| | - Joo-Hyeong Park
- Department of Electronic Engineering, Hanyang University, Seoul 04763, Republic of Korea
- Samsung Advanced Institute of Technology, 129, Samsung-ro, Yeongtong-gu, Suwon-si 16677, Republic of Korea
| | - Ji-Ho Choi
- Department of Electronic Engineering, Hanyang University, Seoul 04763, Republic of Korea
| | - Woo-Guk Lee
- Department of Nanoscale Semiconductor Engineering, Hanyang University, Seoul 04763, Republic of Korea
| | - Jea-Gun Park
- Department of Electronic Engineering, Hanyang University, Seoul 04763, Republic of Korea
- Advanced Semiconductor Materials & Devices Development Center, Hanyang University, Seoul 04763, Republic of Korea
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Badiola I, Blazek V, Jagadeesh Kumar V, George B, Leonhardt S, Hoog Antink C. Accuracy enhancement in reflective pulse oximetry by considering wavelength-dependent pathlengths. Physiol Meas 2022; 43. [PMID: 35959652 DOI: 10.1088/1361-6579/ac890c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 08/11/2022] [Indexed: 11/11/2022]
Abstract
Objective. Noninvasive measurement of oxygen saturation (SpO2) using pulse oximetry based on transmissive photoplethysmography (tPPG) is clinically accepted and widely employed. However, reflective photoplethysmography (rPPG) - present in smartwatches - has not become equally accepted, partially because the pathlengths of the red and infrared PPGs are patient-dependent. Thus, even the most popular "Ratio of Modulation" (R) method requires patient-dependent calibration to reduce the errors in the measurement of SpO2 using rPPGs.Approach. In this paper, a correction factor or "pathlength ratio" β is introduced in an existing calibration-free algorithm that compensates the patient-dependent pathlength variations, and improved accuracy is obtained in the measurement of SpO2 using rPPGs. The proposed β is derived through the analytical model of a rPPG signal. Using the new expression and data obtained from a human hypoxia study wherein arterial oxygen saturation values acquired through Blood Gas Analysis were employed as a reference, β is determined.Main results. The results of the analysis show that a specific combination of the β and the measurements on the pulsating part of the natural logarithm of the red and infrared PPG signals yields a reduced root-mean-square error (RMSE). It is shown that the average RMSE in measuring SpO2 values reduces to 1 %.Significance. The human hypoxia study data used for this work, obtained in a previous study, coversSpO2values in the range from 70 % to 100 %, and thus shows that the pathlength ratio β proposed here works well in the range of clinical interest. This work demonstrates that the calibration-free method applicable for transmission type PPGs can be extended to determineSpO2using reflective PPGs with the incorporation of the correction factor β. Our algorithm significantly reduces the number of parameters needed for the estimation, while keeping the RMSE below the clinically accepted 2 %.
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Affiliation(s)
- Idoia Badiola
- Medical Information Technology (MedIT), RWTH Aachen University, Schurzelter Strasse 570, Aachen, 52074, GERMANY
| | - Vladimir Blazek
- Medical Information Technology (MedIT), RWTH Aachen University, Pauwelsstrasse 20, Aachen, 52074, GERMANY
| | - V Jagadeesh Kumar
- Department of Electrical Engineering, Indian Institute of Technology Madras, Madras, Chennai, Tamil Nadu, 600036, INDIA
| | - Boby George
- Department of Electrical Engineering, Indian Institute of Technology Madras, Madras, Chennai, Tamil Nadu, 600036, INDIA
| | - Steffen Leonhardt
- Medical Information Technology (MedIT), RWTH Aachen University, Pauwelsstr 20, Aachen, 52074, GERMANY
| | - Christoph Hoog Antink
- Künstlich intelligente Systeme der Medizin (KISMED), TU Darmstadt, Magdalenenstraße 4, Darmstadt, Hessen, 64289, GERMANY
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Cabanas AM, Fuentes-Guajardo M, Latorre K, León D, Martín-Escudero P. Skin Pigmentation Influence on Pulse Oximetry Accuracy: A Systematic Review and Bibliometric Analysis. SENSORS 2022; 22:s22093402. [PMID: 35591092 PMCID: PMC9102088 DOI: 10.3390/s22093402] [Citation(s) in RCA: 45] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 04/15/2022] [Accepted: 04/20/2022] [Indexed: 02/04/2023]
Abstract
Nowadays, pulse oximetry has become the standard in primary and intensive care units, especially as a triage tool during the current COVID-19 pandemic. Hence, a deeper understanding of the measurement errors that can affect precise readings is a key element in clinical decision-making. Several factors may influence the accuracy of pulse oximetry, such as skin color, body temperature, altitude, or patient movement. The skin pigmentation effect on pulse oximetry accuracy has long been studied reporting some contradictory conclusions. Recent studies have shown a positive bias in oxygen saturation measurements in patients with darkly pigmented skin, particularly under low saturation conditions. This review aims to study the literature that assesses the influence of skin pigmentation on the accuracy of these devices. We employed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to conduct a systematic review retrospectively since February 2022 using WOS, PubMed, and Scopus databases. We found 99 unique references, of which only 41 satisfied the established inclusion criteria. A bibliometric and scientometrics approach was performed to examine the outcomes of an exhaustive survey of the thematic content and trending topics.
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Affiliation(s)
- Ana M. Cabanas
- Departamento de Física, Universidad de Tarapacá, Arica 1010069, Chile
- Correspondence:
| | | | - Katina Latorre
- Departamento de Tecnología Médica, Universidad de Tarapacá, Arica 1010069, Chile; (M.F.-G.); (K.L.)
| | - Dayneri León
- Departamento de Educación Física, Universidad de Tarapacá, Arica 1010069, Chile;
| | - Pilar Martín-Escudero
- Medical School of Sport Medicine, Faculty of Medicine, Universidad Complutense de Madrid, 28040 Madrid, Spain;
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Ochoa-Gutierrez V, Guerrero-Zuñiga S, Reboud J, Pazmino-Betancourth M, Harvey AR, Cooper JM. Changes in Oxygenation Levels During Moderate Altitude Simulation (Hypoxia-Induced): A Pilot Study Investigating the Impact of Skin Pigmentation in Pulse Oximetry. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1395:391-396. [PMID: 36527668 DOI: 10.1007/978-3-031-14190-4_64] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The current COVID-19 pandemic has shown us that the pulse oximeter is a key medical device for monitoring blood-oxygen levels non-invasively in patients with chronic or acute illness. It has also emphasised limitations in accuracy for individuals with darker skin pigmentation, calling for new methods to provide better measurements. The aim of our study is to identify the impact of skin pigmentation on pulse oximeter measurements. We also explored the benefits of a multi-wavelength approach with an induced change of arterial oxygen saturation. A total of 20 healthy volunteers were recruited. We used time domain diffuse reflectance spectroscopy (TDDRS) from a broad band light source, collecting spectra from the index finger along with three different pulse oximeters used simultaneously for monitoring purposes. Five acute hypoxic events were induced by administering 11% FiO2, produced by a Hypoxico altitude training system, for 120 sec through a face mask with a one-way valve. Our multi-wavelength approach revealed a correlation between the signature of skin pigmentation and the dynamic range of oxygen saturation measurements. Principal component analysis (PCA) showed separation between a range of different pigmented volunteers (PC1 = 56.00%) and oxygen saturation (PC2 = 22.99%). This emphasises the need to take into account skin pigmentation in oximeter measurements. This preliminary study serves to validate the need to better understand the impact of skin pigmentation absorption on optical readings in pulse oximeters. Multi-wavelength approaches have the potential to enable robust and accurate measurements across diverse populations.
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Khattak AF, Kakakhel SS, Wazir NK, Khattak M, Khattak T, Akbar F. Reliability of Smartphone Applications for the Quantification of Oxygen Saturation. Cureus 2021; 13:e19417. [PMID: 34926012 PMCID: PMC8654113 DOI: 10.7759/cureus.19417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/09/2021] [Indexed: 11/05/2022] Open
Abstract
Background Smartphone technology is rapidly evolving and advancing, with many of them offering health applications being used for oximetry purposes, including the Samsung Health/S Health application. Measuring oxygen saturation is one of the important indications to monitor patients with COVID-19, as well as other health conditions. These applications can be used for measuring oxygen saturation to provide a convenient solution for clinical decisions. Methods Oxygen saturation measurements were collected using the Samsung Health application for Samsung Galaxy smartphone with a sensor and camera flash and a low-cost portable digital display (liquid crystal display (LCD)) finger pulse oximeter. Intra-session reliability was established to determine the consistency between the measures. Intra-class correlation coefficients (ICCs) were calculated with 95% confidence intervals (CIs) reported for both methods. The Bland-Altman plot was used to compare the level of agreement between the two measurement methods. Results There was a statistically significant average difference between pulse oximeter and Samsung Health application measurements (t125 = 4.407, p < 0.001), and on average, pulse oximeter measurement was 0.510 points higher than Samsung Health application measurement (95% CI = 0.281-0.740). The pulse oximeter and Samsung Health application scores were moderately correlated (r = 0.462). The results of the intra-session reliability test produced an acceptable ICC value of 0.557, indicating moderate reliability and consistent results for the measurement of oxygen saturation with both methods. The Bland-Altman plot showed a consistently equal distribution of data points scattered above and below zero. Conclusion Smartphone health applications can be used with moderate reliability to measure oxygen saturation.
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Contactless Vital Signs Measurement System Using RGB-Thermal Image Sensors and Its Clinical Screening Test on Patients with Seasonal Influenza. SENSORS 2020; 20:s20082171. [PMID: 32294973 PMCID: PMC7218727 DOI: 10.3390/s20082171] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 04/08/2020] [Accepted: 04/10/2020] [Indexed: 11/17/2022]
Abstract
Background: In the last two decades, infrared thermography (IRT) has been applied in quarantine stations for the screening of patients with suspected infectious disease. However, the fever-based screening procedure employing IRT suffers from low sensitivity, because monitoring body temperature alone is insufficient for detecting infected patients. To overcome the drawbacks of fever-based screening, this study aims to develop and evaluate a multiple vital sign (i.e., body temperature, heart rate and respiration rate) measurement system using RGB-thermal image sensors. Methods: The RGB camera measures blood volume pulse (BVP) through variations in the light absorption from human facial areas. IRT is used to estimate the respiration rate by measuring the change in temperature near the nostrils or mouth accompanying respiration. To enable a stable and reliable system, the following image and signal processing methods were proposed and implemented: (1) an RGB-thermal image fusion approach to achieve highly reliable facial region-of-interest tracking, (2) a heart rate estimation method including a tapered window for reducing noise caused by the face tracker, reconstruction of a BVP signal with three RGB channels to optimize a linear function, thereby improving the signal-to-noise ratio and multiple signal classification (MUSIC) algorithm for estimating the pseudo-spectrum from limited time-domain BVP signals within 15 s and (3) a respiration rate estimation method implementing nasal or oral breathing signal selection based on signal quality index for stable measurement and MUSIC algorithm for rapid measurement. We tested the system on 22 healthy subjects and 28 patients with seasonal influenza, using the support vector machine (SVM) classification method. Results: The body temperature, heart rate and respiration rate measured in a non-contact manner were highly similarity to those measured via contact-type reference devices (i.e., thermometer, ECG and respiration belt), with Pearson correlation coefficients of 0.71, 0.87 and 0.87, respectively. Moreover, the optimized SVM model with three vital signs yielded sensitivity and specificity values of 85.7% and 90.1%, respectively. Conclusion: For contactless vital sign measurement, the system achieved a performance similar to that of the reference devices. The multiple vital sign-based screening achieved higher sensitivity than fever-based screening. Thus, this system represents a promising alternative for further quarantine procedures to prevent the spread of infectious diseases.
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van Gastel M, Stuijk S, de Haan G. New principle for measuring arterial blood oxygenation, enabling motion-robust remote monitoring. Sci Rep 2016; 6:38609. [PMID: 27924930 PMCID: PMC5141507 DOI: 10.1038/srep38609] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 11/10/2016] [Indexed: 11/27/2022] Open
Abstract
Finger-oximeters are ubiquitously used for patient monitoring in hospitals worldwide. Recently, remote measurement of arterial blood oxygenation (SpO2) with a camera has been demonstrated. Both contact and remote measurements, however, require the subject to remain static for accurate SpO2 values. This is due to the use of the common ratio-of-ratios measurement principle that measures the relative pulsatility at different wavelengths. Since the amplitudes are small, they are easily corrupted by motion-induced variations. We introduce a new principle that allows accurate remote measurements even during significant subject motion. We demonstrate the main advantage of the principle, i.e. that the optimal signature remains the same even when the SNR of the PPG signal drops significantly due to motion or limited measurement area. The evaluation uses recordings with breath-holding events, which induce hypoxemia in healthy moving subjects. The events lead to clinically relevant SpO2 levels in the range 80–100%. The new principle is shown to greatly outperform current remote ratio-of-ratios based methods. The mean-absolute SpO2-error (MAE) is about 2 percentage-points during head movements, where the benchmark method shows a MAE of 24 percentage-points. Consequently, we claim ours to be the first method to reliably measure SpO2 remotely during significant subject motion.
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Affiliation(s)
- Mark van Gastel
- Eindhoven University of Technology, Department of Electrical Engineering, Eindhoven, The Netherlands
| | - Sander Stuijk
- Eindhoven University of Technology, Department of Electrical Engineering, Eindhoven, The Netherlands
| | - Gerard de Haan
- Eindhoven University of Technology, Department of Electrical Engineering, Eindhoven, The Netherlands.,Philips Research, Philips Innovation Group, Eindhoven, The Netherlands
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Toward a Smartphone Application for Estimation of Pulse Transit Time. SENSORS 2015; 15:27303-21. [PMID: 26516861 PMCID: PMC4634485 DOI: 10.3390/s151027303] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 10/17/2015] [Accepted: 10/22/2015] [Indexed: 02/02/2023]
Abstract
Pulse transit time (PTT) is an important physiological parameter that directly correlates with the elasticity and compliance of vascular walls and variations in blood pressure. This paper presents a PTT estimation method based on photoplethysmographic imaging (PPGi). The method utilizes two opposing cameras for simultaneous acquisition of PPGi waveform signals from the index fingertip and the forehead temple. An algorithm for the detection of maxima and minima in PPGi signals was developed, which includes technology for interpolation of the real positions of these points. We compared our PTT measurements with those obtained from the current methodological standards. Statistical results indicate that the PTT measured by our proposed method exhibits a good correlation with the established method. The proposed method is especially suitable for implementation in dual-camera-smartphones, which could facilitate PTT measurement among populations affected by cardiac complications.
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