{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2024,8,3]],"date-time":"2024-08-03T22:10:23Z","timestamp":1722723023493},"reference-count":19,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2022,8,13]],"date-time":"2022-08-13T00:00:00Z","timestamp":1660348800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"Background: Although both speckle plethysmography (SPG) and photoplethysmography (PPG) examine pulsatile changes in the vasculature using opto-electronics, PPG has a long history, whereas SPG is relatively new and less explored. The aim of this study was to compare the effects of integration time and light-source coherence on signal quality and waveform morphology for reflective and transmissive rSPG and rPPG. Methods: (A) Using time-domain multiplexing, we illuminated 10 human index fingers with pulsed lasers versus LEDs (both at 639 and 850 nm), in transmissive versus reflective mode. A synchronized camera (Basler acA2000-340 km, 25 cm distance, 200 fps) captured and demultiplexed four video channels (50 fps\/channel) in four stages defined by illumination mode. From all video channels, we derived rPPG and rSPG, and applied a signal quality index (SQI, scale: Good > 0.95; Medium 0.95\u20130.85; Low 0.85\u20130.8; Negligible < 0.8); (B) For transmission videos only, we additionally calculated the intensity threshold area (ITA), as the area of the imaging exceeding a certain intensity value and used linear regression analysis to understand unexpected similarities between rPPG and rSPG. Results: All mean SQI-values. Reflective mode: Laser-rSPG > 0.965, LED-rSPG < 0.78, rPPG < 0.845. Transmissive mode: 0.853\u20130.989 for rSPG and rPPG at all illumination settings. Coherent mode: Reflective rSPG > 0.951, reflective rPPG < 0.740, transmissive rSPG and rPPG 0.990\u20130.898. Incoherent mode: Reflective all <0.798 and transmissive all 0.92\u20130.987. Linear regressions revealed similar R2 values of rPPG with rSPG (R2 = 0.99) and ITA (R2 = 0.98); Discussion: Laser-rSPG and LED-rPPG produced different waveforms in reflection, but not in transmission. We created the concept of ITA to investigate this behavior. Conclusions: Reflective Laser-SPG truly originated from coherence. Transmissive Laser-rSPG showed a loss of speckles, accompanied by waveform changes towards rPPG. Diffuse spatial intensity modulation polluted spatial-mode SPG.<\/jats:p>","DOI":"10.3390\/s22166059","type":"journal-article","created":{"date-parts":[[2022,8,16]],"date-time":"2022-08-16T03:44:03Z","timestamp":1660621443000},"page":"6059","source":"Crossref","is-referenced-by-count":6,"title":["Camera-Derived Photoplethysmography (rPPG) and Speckle Plethysmography (rSPG): Comparing Reflective and Transmissive Mode at Various Integration Times Using LEDs and Lasers"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"http:\/\/orcid.org\/0000-0002-2347-401X","authenticated-orcid":false,"given":"Jorge","family":"Herranz Olaz\u00e1bal","sequence":"first","affiliation":[{"name":"IMEC, 3000 Leuven, Belgium"},{"name":"Faculty of Engineering Science, Katholieke Universiteit Leuven (KUL), 3000 Leuven, Belgium"}]},{"given":"Fokko","family":"Wieringa","sequence":"additional","affiliation":[{"name":"IMEC NL, 5656 AE Eindhoven, The Netherlands"},{"name":"Division of Internal Medicine, Department of Nephrology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands"}]},{"given":"Evelien","family":"Hermeling","sequence":"additional","affiliation":[{"name":"IMEC NL, 5656 AE Eindhoven, The Netherlands"}]},{"given":"Chris","family":"Van Hoof","sequence":"additional","affiliation":[{"name":"IMEC, 3000 Leuven, Belgium"},{"name":"Faculty of Engineering Science, Katholieke Universiteit Leuven (KUL), 3000 Leuven, Belgium"}]}],"member":"1968","published-online":{"date-parts":[[2022,8,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1211","DOI":"10.1007\/BF01778576","article-title":"Lichtelektrische Plethysmogramme","volume":"17","author":"Matthes","year":"1938","journal-title":"Klin. 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