Development and characterization of a multidistance and multiwavelength diffuse correlation spectroscopy system.

Bernhard Zimmermann,David A Boas,Davide Tamborini,Kuan-Cheng Wu,Maria Angela Franceschini,Parisa Farzam

doi:10.1117/1.nph.5.1.011015

Abstract

.This paper presents a multidistance and multiwavelength diffuse correlation spectroscopy (DCS) approach and its implementation to simultaneously measure the optical proprieties of deep tissue as well as the blood flow. The system consists of three long coherence length lasers at different wavelengths in the near-infrared, eight single-photon detectors, and a correlator board. With this approach, we collect both light intensity and DCS data at multiple distances and multiple wavelengths, which provide unique information to fit for all the parameters of interest: scattering, blood flow, and hemoglobin concentration. We present the characterization of the system and its validation with phantom measurements.

Highlights

Diffuse correlation spectroscopy (DCS) is a relatively new nearinfrared spectroscopy (NIRS) method that is being increasingly adopted because of its ability to directly measure an index of microvascular blood flow (BFi)
We characterized the potential impact of the nonlinearity of the detector at high count rates on the autocorrelation function to find the maximum count rate able to guarantee a negligible distortion in the g2 curve
We demonstrated the capabilities of the multidistance and multiwavelength (MD-MW) DCS method by measuring the optical properties and dynamics of liquid phantoms

Summary

Introduction

Diffuse correlation spectroscopy (DCS) is a relatively new nearinfrared spectroscopy (NIRS) method that is being increasingly adopted because of its ability to directly measure an index of microvascular blood flow (BFi). By fitting the equation to the measured autocorrelation function, we can derive a quantitative blood flow index (BFi, cm2∕s)[6] only if we know or assume absorption and scattering. It has been demonstrated that the cross talk between static (absorption and scattering) and dynamic (flow) properties of the tissue does not permit fitting for multiple parameters using a single autocorrelation function.[7] To correctly estimate absolute BFi, it is customary to use NIRS in conjunction with DCS8,9 and to simultaneously quantify tissue optical properties and BFi. The need for combining two modalities makes the approach more complex

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Conclusion