Theme 7. Biomedical Sensors and Wearable Systems

Innovations in Photoplethysmography


John Allen, Coventry University, United Kingdom
Panayiotis Kyriacou , City, University of London, United Kingdom
Haipeng Liu, Coventry University, United Kingdom
Peter Charlton, University of Cambridge, United Kingdom

Photoplethysmography (PPG) is a low-cost vascular optics technique that can detect blood volume changes in the microvascular bed of tissue, usually from measurements collected non-invasively at the skin surface. The PPG waveform comprises a pulsatile ('AC') physiological waveform which is attributed to cardiac synchronous blood volume changes, superimposed on a slowly varying ('DC') baseline with various lower frequency components attributed to respiration, sympathetic nervous system activity and thermoregulation. Although the origins of these key components are not fully understood, it is generally accepted that they can provide valuable cardiovascular information. There has been considerable interest in PPG in recent years and this is attributed to developments in wearable sensors, demands for low-cost portable technology, availability of low- cost/miniature semiconductor components, and advances in computer-based pulse wave analysis techniques including AI. PPG has been used in a wide range of devices, including for measuring oxygen saturation, blood pressure and cardiac output, assessing autonomic function and assessing peripheral vascular disease. Considerable work continues across the globe in advancing the technologies involved, creating innovations in PPG sensing, pulse analysis and applications.

Kyriacou and Allen, as co-editors, are proud to announce a new holistic and state-of-the- art book on Photoplethysmography (published by Elsevier, November 2021) covering the history, scientific principles, genesis of the PPG waveform, technology, pulse analysis, cardiovascular applications and clinical monitoring, cuffless blood pressure measurement, imaging, and future trends and directions. This mini-symposium will include talks by leading PPG experts on some of the key topics covered in the book, including tissue oxygen measurement, assessments of vascular disease and autonomic function, cuffless blood pressure measurement, as well as wearable sensors.

Trends on On-Scalp Magnetoencephalography


Stefania Della Penna, University of Chieti-Pescara, Italy Tilmann Sander Thömmes, PTB, Germany
Justin F. Schneiderman, University of Gothenburg, Sweden
Sara Spadone, University of Chieti-Percara, Italy

In the latest years, technological advancements in sensor fabrication are allowing the implementation of novel MEG systems allowing to record cerebral magnetic fields closer to the scalp than standard MEG systems based on the well assessed Low Tc SQUIDs. The advantages of on-scalp MEG are i) increase of the measured magnetic fields, ii) higher spatial resolution at the channel level, iii) system flexibility to open the recordings to larger cohorts of subjects, iv) reduction of maintenance costs. The most popular technologies allowing on-scalp MEG rely Optically Pumped Magnetometers (OPM) and High Tc SQUID magnetometers. The first commercial systems based on OPMs were launched on the market since last year, while the possibility of implementing multichannel High Tc SQUID- based system was recently demonstrated. Notably, triggered by these achievements, other devices based on unconventional technologies in biomagnetism were recently proposed. In this symposium the latest news on the status of on-scalp MEG will be presented. Different aspects, from technology to applications in non-invasive brain imaging will be covered by experts in the field. Specifically, Tilmann Sanders will present and discuss recordings obtained OPM for wearable-MEG. Justin Schneiderman will outline technical developments and applications of a modular channel arrays based on High Tc SQUIDs for on-scalp recordings. Stefania Della Penna will present the recent results of the OXiNEMS project aiming at developing a new technology to implement field-tolerant devices for on scalp MEG. Sara Spadone will present simulations addressing the effects of pick-up loop size on the analysis of activity and connectivity at the source level obtained from on-scalp MEG.

Also of Interest…

The following sessions may be applicable to the theme Biomedical Sensors and Wearable Systems although they are primarily listed under a different theme.

Session title Primary theme
Signal Processing and Machine Learning Paradigms for Enabling the Digital Health Ecosystem 9