Publication

Autocorrelation Bias in Diffuse Correlation Spectroscopy Observable via SPAD Arrays

Claudio Bruschini
2025

Abstract

Diffuse correlation spectroscopy (DCS) is an emerging optical technique for non-invasive cerebral blood flow monitoring. Extraction of the DCS blood flow index typically involves calculating the temporal autocorrelation of the measured light intensity and then fitting its decay to a solution of the correlation diffusion equation. It is well-known that the experimental autocorrelation is a biased estimator of the true autocorrelation. This work explores this phenomenon as it relates to DCS, in particular implementations with single photon avalanche diode arrays (SPAD arrays). After deriving a first-order expression for the bias in DCS, we then quantify its impact as a function of sampling time in both simulation and experiment using SPAD array detection. We then present and explore two bias correction strategies to correct for its impact at fast sampling times (20-200 Hz) and in low-photon regimes.

Official source

https://infoscience.epfl.ch/entities/publication/cdf8188e-e22b-41f6-a0c2-8c6447ccc098

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Claudio Bruschini
2025

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/cdf8188e-e22b-41f6-a0c2-8c6447ccc098

About this result

Related concepts (32)

Sampling (statistics)

In statistics, quality assurance, and survey methodology, sampling is the selection of a subset or a statistical sample (termed sample for short) of individuals from within a statistical population to estimate characteristics of the whole population. Statisticians attempt to collect samples that are representative of the population. Sampling has lower costs and faster data collection compared to recording data from the entire population, and thus, it can provide insights in cases where it is infeasible to measure an entire population.

Spatial analysis

Spatial analysis is any of the formal techniques which studies entities using their topological, geometric, or geographic properties. Spatial analysis includes a variety of techniques using different analytic approaches, especially spatial statistics. It may be applied in fields as diverse as astronomy, with its studies of the placement of galaxies in the cosmos, or to chip fabrication engineering, with its use of "place and route" algorithms to build complex wiring structures.

Autocorrelation

Autocorrelation, sometimes known as serial correlation in the discrete time case, is the correlation of a signal with a delayed copy of itself as a function of delay. Informally, it is the similarity between observations of a random variable as a function of the time lag between them. The analysis of autocorrelation is a mathematical tool for finding repeating patterns, such as the presence of a periodic signal obscured by noise, or identifying the missing fundamental frequency in a signal implied by its harmonic frequencies.

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Autocorrelation Bias in Diffuse Correlation Spectroscopy Observable via SPAD Arrays

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