transdermal optical imaging

{{short description|Method of detecting blood flow in face}}

Transdermal optical imaging, also known as transdermal optical imagery or TOI, is a method of detecting blood flow of the face by measuring hemoglobin concentration using a digital video camera.{{Cite web|title=Camera-Based Health Readings|url=https://www.trendhunter.com/trends/transdermal-optical-imaging|access-date=2021-02-10|website=TrendHunter.com|language=en}} Because of the translucent property of skin, light can travel beneath the skin and re-emit.{{Cite journal|last1=Liu|first1=Jiangang|last2=Luo|first2=Hong|last3=Zheng|first3=Paul Pu|last4=Wu|first4=Si Jia|last5=Lee|first5=Kang|date=2018-07-12|title=Transdermal optical imaging revealed different spatiotemporal patterns of facial cardiovascular activities|url= |journal=Scientific Reports|language=en|volume=8|issue=1|pages=10588|doi=10.1038/s41598-018-28804-0|pmid=30002447|pmc=6043515|bibcode=2018NatSR...810588L|issn=2045-2322}} The re-emitted light from underneath the skin is affected by chromophores, mainly hemoglobin and melanin,{{Cite journal|last1=Nishidate|first1=Izumi|last2=Aizu|first2=Yoshihisa|last3=Mishina|first3=Hiromichi|date=July 2004|title=Estimation of melanin and hemoglobin in skin tissue using multiple regression analysis aided by Monte Carlo simulation|journal=Journal of Biomedical Optics|volume=9|issue=4|pages=700–710|doi=10.1117/1.1756918|pmid=15250756|bibcode=2004JBO.....9..700N|issn=1083-3668|doi-access=free}} which differ in color.{{Cite web|last=Emilio|first=Maurizio Di Paolo|date=2018-07-30|title=Transdermal Optical Imaging Is the Best Diagnosis Technology Yet|url=https://www.engineerstribune.com/transdermal-optical-imaging-is-the-best-option-for-non-contact-diagnosis/|access-date=2021-02-10|website=The Engineers' Tribune|language=en-US}} The color difference allows TOI machine learning software to separate the images into layers, which are known as bitplanes. It extracts signals rich in hemoglobin and signals rich in melanin, then discards the melanin-rich signals to obtain a recording of hemoglobin changes under the skin.{{Cite journal|last1=Wei|first1=Jing|last2=Luo|first2=Hong|last3=Wu|first3=Si J.|last4=Zheng|first4=Paul P.|last5=Fu|first5=Genyue|last6=Lee|first6=Kang|date=2018-02-08|title=Transdermal Optical Imaging Reveal Basal Stress via Heart Rate Variability Analysis: A Novel Methodology Comparable to Electrocardiography|journal=Frontiers in Psychology|volume=9|page=98|doi=10.3389/fpsyg.2018.00098|issn=1664-1078|pmc=5809462|pmid=29472879|doi-access=free}}{{Cite journal|last1=Luo|first1=Hong|last2=Yang|first2=Deye|last3=Barszczyk|first3=Andrew|date=2019|title=Smartphone-Based Blood Pressure Measurement Using Transdermal Optical Imaging Technology|journal=Circulation: Cardiovascular Imaging |url=http://statics.drvoice.cn/uploadfile/2019/0811/20190811035538407.pdf|access-date=|volume=12 |issue=8 |pages=e008857 |doi=10.1161/CIRCIMAGING.119.008857 |pmid=31382766 }} Transdermal optical imaging has been proposed as an alternative to cuff-based methods of measuring blood pressure because it is able to measure heart rate accurately in a "contactless and non-invasive" way.{{Cite web|title=Blood pressure monitoring may one day be easy as taking a video selfie|url=https://newsroom.heart.org/news/blood-pressure-monitoring-may-one-day-be-easy-as-taking-a-video-selfie|access-date=2021-02-10|website=American Heart Association|language=en-us}} Transdermal optical imaging may be able to detect hidden emotions using the patterns of blood flow in the face.{{Cite web|title=How Scientists Will Turn Your Smartphone Into a Lie Detector|url=https://www.vice.com/en/article/nuralogix-smartphone-lie-detector-toronto/|access-date=2021-02-08|website=Vice.com|date=4 July 2016 |language=en}}{{Cite web|last=|first=|date=|title=Transdermal Optical Imagery (TOI) Hidden Emotions|url=https://autm.net/about-tech-transfer/better-world-project/bwp-stories/transdermal-optical-imaging-%C2%A0(toi)|access-date=|website=}}