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Investigating optical path and differential pathlength factor in reflectance photoplethysmography for the assessment of perfusion

Chatterjee, S., Abay, T. Y., Phillips, J. P. ORCID: 0000-0003-3486-3704 & Kyriacou, P. A. ORCID: 0000-0002-2868-485X (2018). Investigating optical path and differential pathlength factor in reflectance photoplethysmography for the assessment of perfusion. Journal of Biomedical Optics, 23(7), 0.075005. doi: 10.1117/1.JBO.23.7.075005


Photoplethysmography (PPG) is an optical noninvasive technique with the potential for assessing tissue perfusion. The relative time-change in the concentration of oxyhemoglobin and deoxyhemoglobin in the blood can be derived from DC part of the PPG signal. However, the absolute concentration cannot be determined due to the inadequate data on PPG optical paths. The optical path and differential pathlength factor (DPF) for PPG at red (660 nm) and infrared (880 nm) wavelengths were investigated using a heterogeneous Monte Carlo model of the human forearm. Using the simulated DPFs, the absolute time-change in concentrations were determined from PPG signals recorded from the same tissue site. Results were compared with three conditions of approximated DPFs. Results showed the variation of the optical-path and DPF with different wavelengths and source-detector separations. Approximations resulted in significant errors, for example, using NIRS DPF in PPG led to "cross talk" of -0.4297 and 0.060 and an error of 15.16% to 25.18%. Results confirmed the feasibility of using the PPG (DC) for the assessment of tissue perfusion. The study also identified the inappropriateness of the assumption that DPF is independent of wavelength or source-detector separations and set the platform for further studies on investigating optical pathlengths and DPF in PPG.

Publication Type: Article
Additional Information: © 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this publication for a fee or for commercial purposes, or modification of the contents of the publication are prohibited.
Publisher Keywords: photoplethysmography; Beer–Lambert law; Monte Carlo model; optical path; near-infrared spectroscopy; oxy/deoxy hemoglobin.
Subjects: R Medicine > R Medicine (General)
T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments: School of Science & Technology > Engineering
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