Enhancing diffuse correlation spectroscopy pulsatile cerebral blood flow signal with near-infrared spectroscopy photoplethysmography

Kuan Cheng Wu, Alyssa Martin, Marco Renna, Mitchell Robinson, Nisan Ozana, Stefan A. Carp, Maria Angela Franceschini

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Significance: Combining near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS) allows for quantifying cerebral blood volume, flow, and oxygenation changes continuously and non-invasively. As recently shown, the DCS pulsatile cerebral blood flow index (pCBFi) can be used to quantify critical closing pressure (CrCP) and cerebrovascular resistance (CVRi). Aim: Although current DCS technology allows for reliable monitoring of the slow hemodynamic changes, resolving pulsatile blood flow at large source-detector separations, which is needed to ensure cerebral sensitivity, is challenging because of its low signal-to-noise ratio (SNR). Cardiac-gated averaging of several arterial pulse cycles is required to obtain a meaningful waveform. Approach: Taking advantage of the high SNR of NIRS, we demonstrate a method that uses the NIRS photoplethysmography (NIRS-PPG) pulsatile signal to model DCS pCBFi, reducing the coefficient of variation of the recovered pulsatile waveform (pCBFi-fit) and allowing for an unprecedented temporal resolution (266 Hz) at a large source-detector separation (>3 cm). Results: In 10 healthy subjects, we verified the quality of the NIRS-PPG pCBFi-fit during common tasks, showing high fidelity against pCBFi (R2 0.98 ± 0.01). We recovered CrCP and CVRi at 0.25 Hz, >10 times faster than previously achieved with DCS. Conclusions: NIRS-PPG improves DCS pCBFi SNR, reducing the number of gate-averaged heartbeats required to recover CrCP and CVRi.

Original languageEnglish
Article number035008
Issue number3
StatePublished - 1 Jul 2023
Externally publishedYes

Bibliographical note

Publisher Copyright:
© The Authors.


John Sunwoo assisted with the processing of the physiological data. Zachary Starkweather 3D-printed the optical probe casings for both NIRS and DCS devices. This study was supported by Dr. Franceschini’s Research Sundry fund and in part by the National Institutes of Health (Grant Nos. U01EB028660 and R21EB028626).

FundersFunder number
National Institutes of HealthR21EB028626, U01EB028660


    • cerebral blood flow
    • cerebrovascular resistance
    • critical closing pressure
    • diffuse correlation spectroscopy
    • near-infrared spectroscopy


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