BIOSENSOR VALIDATION
Optical Integration Without Compromises
Dr. Janos Palhalmi (PhD) and Jan-Hein Broeders Analog Devices Instruments, Technical Articles
Abstract
Photoplethysmography (PPG) is a common technology for measuring oxygen saturation (SPO 2 ) levels in blood. Light is sent by a light emitter into the body, and the amount of reflective or unabsorbed light is measured with a photoreceiver. Depending on the ratio between two wavelengths, the amount of oxygenated haemoglobin can be measured. Comparable technologies are also used to measure heart rate with an optical technology or heart rate variability. All these systems require one or more photoemitters, which need to be controlled, and a photodetector to measure the amount of photocurrent as a measure for the received light. This receive signal finally needs to be amplified, conditioned, and digitized. Such an optical system might sound straightforward; however, with a missing dose of optical knowledge, it is very easy to retrieve an optical signal, which doesn’t have anything to do with the signals the user is looking for. To help companies achieve their optical objectives, a new, fully integrated optical module has been introduced. It has been tested and compared to a well-proven discrete optical system with outstanding results. You will read more about the results and methodologies behind this exercise.
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The Effect of Expanded Measurement Uncertainty on the Outcome of Blood
Pressure Measurement Validation Protocol Based on the ISO81060-2:2018
Guideline – A Monte Carlo Simulation Approach
Computing in Cardiology 2020
Janos Palhalmi – DataSenseLabs Ltd., Budapest
Abstract
The most common hemodynamic measurement technologies are the classical auscultatoric sphygmomanometric method and numerous solutions for automated sphygmomanometry. The classical method is the reference for testing the automated solutions according to the ISO81060-2:2018 guideline. Both of the above mentioned blood pressure estimations are indirect measurement methods according to the approach of metrology. According to the ISO81060-2:2018 guideline, two indirect measurement and estimation methods are compared with each other without the theoretical and technical consideration of the possible effect of the measurement uncertainty on the results. Within this simulation study several components of the
measurement uncertainty were implemented to test the reliability and confidence limit of the ISO guideline recommended process flow, experimental design and statistical analysis.
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A Statistical Metrology Approach to Compare the Quality of Optical Pulse Wave Signals
Dr. Janos Palhalmi (PhD) and Jan-Hein Broeders
Computing in Cardiology 2019
Abstract
Biometric metrology is becoming increasingly important as the wearable application specific biosensors are capable of generating accurate raw signals representing certain vital states. A comparative statistical approach has been worked out to answer questions arising from a biosensor testing measurement technology perspective. In this specific work two high quality optical solutions (Analog Devices’ ADPD107 and ADPD188GGZ) were compared to analyse the deep data level similarities or differences between the photo-plethysmography (PPG) raw biomedical signals generated by the two individual systems.
Two minutes long parallel recordings were carried out with the evaluation boards of both optical systems (EVAL-HCRWATCH and EVAL-ADPD188GGZ) on 11 healthy human subjects. Recordings were repeated on both wrists to avoid side specific influence. Both systems have been controlled by Analog Devices’ user-interface called “Application WaveTool”. For the test, configuration settings were optimized to achieve the highest signal quality and lowest power consumption (5.1 mW at 100 Hz sampling frequency). The physiologically and biometrically irrelevant frequency bands (<0.25 Hz,>40 Hz) were filtered before the data analysis.
A wavelet coherence-based method was worked out to compare the relevant frequency bands and two different correlation-based methods were developed to compare the wave-to-wave stability and similarity of the two compared signals. Magnitude squared coherence values were above 0.9 in all the explored frequency bands (0.25-40 Hz). Correlation coefficients were never under 0.9 while p values were always under 0.001 in case of the PPG wave-to-wave comparisons. Based on the results we can conclude, that the quality of the PPG signal recorded by the new ADPD188GGZ integrated optical module, reaches the same performance level as the ADPD107 discrete module, with key benefits such as small PCB area, ease of use (especially for companies with limited Optical expertise) and shorter Time to Market.
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A Computationally Efficient Method to Quantify the Biometric Properties of Ventricular Repolarization Irregularities in Healthy and Diseased Human Subjects
Dr. Janos Palhalmi (PhD)
Computing in Cardiology 2018
Abstract
Repolarization heterogeneity expressed by QT interval prolongation and abnormal temporal dynamics of the QT interval time series is an important factor in relation to coronary heart disease and lethal arrhythmias.
Based on our observations, the calculation of window correlation between the mean and variance of features extracted from QT interval time series can reveal natural and disease specific fluctuation patterns. Our algorithm is potentially a sensitive biometric measure to quantify personalized differences and the properties of repolarization heterogeneity, and also a potential biomarker to characterize disease specific QT interval temporal dynamics.
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https://ieeexplore.ieee.org/document/8744048/authors#authors
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