Simple and affordable imaging of multiple physiological parameters with RGB camera-based diffuse reflectance spectroscopy

Izumi Nishidate; Masashi Minakawa; Daniel McDuff; Md Abdul Wares; Kazuya Nakano; Hideaki Haneishi; Yoshihisa Aizu; Kyuichi Niizeki

doi:10.1364/BOE.382270

Simple and affordable imaging of multiple physiological parameters with RGB camera-based diffuse reflectance spectroscopy

Biomed Opt Express. 2020 Jan 24;11(2):1073-1091. doi: 10.1364/BOE.382270. eCollection 2020 Feb 1.

Authors

Izumi Nishidate¹, Masashi Minakawa¹, Daniel McDuff², Md Abdul Wares^{1

3}, Kazuya Nakano⁴, Hideaki Haneishi⁴, Yoshihisa Aizu⁵, Kyuichi Niizeki⁶

Affiliations

¹ Tokyo University of Agriculture and Technology, Graduate School of Bio-Applications & Systems Engineering, 2-24-16 Naka-cho, Koganei, Tokyo, 184-8588, Japan.
² Microsoft Research, 4820 NE 36th Street, Building 99, Redmond, Washington 98052, USA.
³ Government of Bangladesh, Ministry of Fisheries and Livestock, Department of Livestock Services, Khamar Bari Road, Farmgate, Dhaka, 1209, Bangladesh.
⁴ Chiba University, Center for Frontier Medical Engineering, 1-33, Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan.
⁵ Muroran Institute of Technology, College of Design and Manufacturing Technology, 27-1 Mizumoto-cho, Muroran, Hokkaido, 050-8585, Japan.
⁶ Yamagata University, Graduate School of Bio-System Engineering, Jonan, Yonezawa-shi, Yamagata, 992-8510, Japan.

Abstract

We propose a simple and affordable imaging technique to evaluate transcutaneously multiple physiological parameters by using a digital red-green-blue camera. In this method, the RGB-values were converted into tristimulus values in the CIE (Commission Internationale de l'Eclairage) XYZ color space, which is compatible with the common color spaces. Monte Carlo simulation for light transport in biological tissue was then performed to specify the relationship among the XYZ-values and the concentrations of oxygenated hemoglobin, deoxygenated hemoglobin, bilirubin, and melanin. The concentration of total hemoglobin and tissue oxygen saturation were also calculated from the estimated concentrations of oxygenated and deoxygenated hemoglobin. In vivo experiments with bile duct ligation in rats demonstrated that the estimated bilirubin concentration increased after ligation of the bile duct and reached around 22 mg/dl at 116 h after the onset of ligation, which corresponds to the ground truth value of bilirubin measured by a commercially available transcutaneous bilirubinometer. Experiments with rats while varying the fraction of inspired oxygen demonstrated that oxygenated hemoglobin and deoxygenated hemoglobin decreased and increased, respectively, as the fraction of inspired oxygen decreased. Consequently, tissue oxygen saturation dramatically decreased. We further extended the method to a non-contact imaging photo-plethysmograph and estimation of the percutaneous oxygen saturation. An empirical formula to estimate percutaneous oxygen saturation was derived from the pulse wave amplitudes of oxygenated and deoxygenated hemoglobin. The estimated percutaneous oxygen saturation dropped remarkably when a faction of inspired oxygen was below 19%, indicating the onset of hypoxemia due to hypoxia, whereas the tissue oxygen saturation decreased gradually according to the reduction of the faction of inspired oxygen. The results in this study indicate the potential of this method for imaging of multiple physiological parameters in skin tissue and evaluating an optical biomedical imaging technique that enables cost-effective, easy-to-use, portable, remotely administered, and/or point-of-care solutions.