Effects of the instrument response function and the gate width in time-domain diffuse correlation spectroscopy: model and validations

Abstract

Time-domain diffuse correlation spectroscopy (TD-DCS) is an emerging noninvasive optical technique with the potential to resolve blood flow (BF) and optical coefficients (reduced scattering and absorption) in depth. Here, we study the effects of finite temporal resolution and gate width in a realistic TD-DCS experiment. We provide a model for retrieving the BF from gated intensity autocorrelations based on the instrument response function, which allows for the use of broad time gates. This, in turn, enables a higher signal-to-noise ratio that is critical for in vivo applications. In numerical simulations, the use of the proposed model reduces the error in the estimated late gate BF from 34% to 3%. Simulations are also performed for a wide set of optical properties and source-detector separations. In a homogeneous phantom experiment, the discrepancy between later gates BF index and ungated BF index is reduced from 37% to 2%. This work not only provides a tool for data analysis but also physical insights, which can be useful for studying and optimizing the system performance.

Time-domain diffuse correlation spectroscopy (TD-DCS) for noninvasive, depth-dependent blood flow quantification in human tissue in vivo

“…We also note that measured intensity autocorrelation functions, depends on the instrument response function or the IRF 28 , 29 . Then, to improve the signal-to-noise ratio, the experimental estimates are integrated over the photon TOF range, called the time gate.…”

Time Domain Diffuse Correlation Spectroscopy for Detecting Human Brain Function: Optimize System on Real Experimental Conditions by Simulation Method

“…However, in the real measurement using TD system, the role of IRF cannot be ignored. In the commonly used TD-DCS system, the full width at half maxima (FWHM) of the IRF in is about 100-300 ps [14,23]. In order to simulate the real TD-DCS measurement more realistically, we synthesized a right-tailed IRF with a FWHM of about 160 ps and a peak time of 2000 ps, as shown in the red curve in Fig.…”

“…2. The long right tail is a characteristic of the single-photon avalanche diode commonly used in TD systems [14,24]. The TPSF obtained from MMC simulation and the diffuse reflectance This work is licensed under a Creative Commons Attribution 4.0 License.…”

“…In other words, TD-DCS can provide higher sensitivity detection for deep dynamics. In recent years, TD-DCS technology has developed rapidly, including the proposal of various theoretical models, the verification of simulation and phantom experiments, as well as in vivo measurement of the human arm and head [11][12][13][14][15][16][17].…”

“…Regarding the effect of these two factors on TD-DCS measurement, Cheng et al have developed an analytical model of time-resolved 2 containing IRF and factors and applied it to semi-infinite medium [12]. In addition, Colombo et al [14] took the IRF into account and proposed a model for retrieving the blood flow from the gated intensity autocorrelation function, in which improved the in TD-DCS measurements. However, the above two studies were based on the semi-infinite model, and the effect on more complex heterogeneous media (such as human head) is not yet clear.…”