Diffuse Correlation Spectroscopy Beyond the Water Peak Enabled by Cross-Correlation of the Signals From InGaAs/InP Single Photon Detectors

Mitchell B. Robinson, Marco Renna, Nisan N. Ozana, Adriano Peruch, Sava Sakadzic, Megan L. Blackwell, Jonathan M. Richardson, Brian F. Aull, Stefan A. Carp, Maria Angela Franceschini

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Objective: Diffuse correlation spectroscopy (DCS) is an optical technique that allows for the non-invasive measurement of blood flow. Recent work has shown that utilizing longer wavelengths beyond the traditional NIR range provides a significant improvement to signal-to-noise ratio (SNR). However, current detectors both sensitive to longer wavelengths and suitable for clinical applications (InGaAs/InP SPADs) suffer from suboptimal afterpulsing and dark noise characteristics. To overcome these barriers, we introduce a cross correlation method to more accurately recover blood flow information using InGaAs/InP SPADs. Methods: Two InGaAs/InP SPAD detectors were used for during in vitro and in vivo DCS measurements. Cross correlation of the photon streams from each detector was performed to calculate the correlation function. Detector operating parameters were varied to determine parameters which maximized measurement SNR.State-space modeling was performed to determine the detector characteristics at each operating point. Results: Evaluation of detector characteristics was performed across the range of operating conditions. Modeling the effects of the detector noise on the correlation function provided a method to correct the distortion of the correlation curve, yielding accurate recovery of flow information as confirmed by a reference detector. Conclusion: Through a combination of cross-correlation of the signals from two detectors, model-based characterization of detector response, and optimization of detector operating parameters, the method allows for the accurate estimation of the true blood flow index. Significance: This work presents a method by which DCS can be performed at longer NIR wavelengths with existing detector technology, taking advantage of the increased SNR.

Original languageEnglish
Pages (from-to)1943-1953
Number of pages11
JournalIEEE Transactions on Biomedical Engineering
Volume69
Issue number6
DOIs
StatePublished - 1 Jun 2022
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 1964-2012 IEEE.

Funding

FundersFunder number
National Institute of Biomedical Imaging and BioengineeringT32EB001680

    Keywords

    • Fluid flow measurement
    • biomedical applications of optical radiation
    • infrared detectors
    • semiconductor device modeling

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