IEEE transactions on bio-medical engineering
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IEEE Trans Biomed Eng · Sep 2016
A Novel Algorithm for Remote Photoplethysmography: Spatial Subspace Rotation.
In this paper, we propose a conceptually novel algorithm, namely "Spatial Subspace Rotation" (2SR), that improves the robustness of remote photoplethysmography. Based on the assumption of 1) spatially redundant pixel-sensors of a camera, and 2) a well-defined skin mask, our core idea is to estimate a spatial subspace of skin-pixels and measure its temporal rotation for pulse extraction, which does not require skin-tone or pulse-related priors in contrast to existing algorithms. The proposed algorithm is thoroughly assessed on a benchmark dataset containing 54 videos, which includes challenges of various skin-tones, body-motions in complex illuminance conditions, and pulse-rate recovery after exercise. ⋯ When comparing the instant pulse-rate, 2SR improves on average the Pearson correlation and precision of ICA by 47% and 65%, CHROM by 22% and 23%, and PBV by 21% and 39%. ANOVA confirms the significant improvement of 2SR in peak-to-peak accuracy. The proposed 2SR algorithm is very simple to use and extend, i.e., the implementation only requires a few lines MATLAB code.
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IEEE Trans Biomed Eng · Sep 2016
Electrophysiological Source Imaging of Brain Networks Perturbed by Low-Intensity Transcranial Focused Ultrasound.
Transcranial focused ultrasound (tFUS) has been introduced as a noninvasive neuromodulation technique with good spatial selectivity. We report an experimental investigation to detect noninvasive electrophysiological response induced by low-intensity tFUS in an in vivo animal model and perform electrophysiological source imaging (ESI) of tFUS-induced brain activity from noninvasive scalp EEG recordings. ⋯ The present approach may lead to a new means of imaging brain activity using tFUS perturbation and a closed-loop ESI-guided tFUS neuromodulation modality.
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Photoplethysmography (PPG) is a noninvasive technique to measure the blood-volume pulse and derive various vital signs. Camera-based PPG imaging was recently proposed for clinical microvascular assessment, but motion robustness is still an issue for this technique. Our study aims to quantify cardiac-related, i.e., ballistocardiographic (BCG), motion as a source of artifacts in PPG imaging. ⋯ Our illumination recommendation provides a simple and effective means to improve the validity of remote PPG-imagers. We hope that it helps to prevent mistakes currently seen in many publications on remote PPG.