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

Abstract

Monitoring of human tissue hemodynamics is invaluable in clinics as the proper blood flow regulates cellular-level metabolism. Time-domain diffuse correlation spectroscopy (TD-DCS) enables noninvasive blood flow measurements by analyzing temporal intensity fluctuations of the scattered light. With time-of-flight (TOF) resolution, TD-DCS should decompose the blood flow at different sample depths. For example, in the human head, it allows us to distinguish blood flows in the scalp, skull, or cortex. However, the tissues are typically polydisperse. So photons with a similar TOF can be scattered from structures that move at different speeds. Here, we introduce a novel approach that takes this problem into account and allows us to quantify the TOF-resolved blood flow of human tissue accurately. We apply this approach to monitor the blood flow index in the human forearm in vivo during the cuff occlusion challenge. We detect depth-dependent reactive hyperemia. Finally, we applied a controllable pressure to the human forehead in vivo to demonstrate that our approach can separate superficial from the deep blood flow. Our results can be beneficial for neuroimaging sensing applications that require short interoptode separation.

Influence of source–detector separation on diffuse correlation spectroscopy measurements of cerebral blood flow with a multilayered analytical model

“… 2 To minimize these extracerebral contributions, several approaches have been proposed that typically fall into one of two categories: (1) hardware modifications or (2) improved analytical modeling. On the hardware side, developments include methods that enhance depth sensitivity, either through time domain 3 , 4 or interferometric approaches, 5 , 6 or by moving to the second optical window at 1064 nm. 7 While these approaches are exciting and will likely be the future of DCS, limitations related to detector speed, availability, and cost currently limit widespread adoption.…”

Functional Time Domain Diffuse Correlation Spectroscopy

“…Previously reported TD-DCS systems ( Pagliazzi et al, 2017 ; Tamborini et al, 2019 ; Colombo et al, 2020 ; Samaei et al, 2021b ) face limitations with respect to detector efficiency and/or the characteristics of the IRF. To address these limitations, and building on our previous work demonstrating the benefits of DCS measurements at 1,064 nm ( Carp et al, 2020 ; Ozana et al, 2021 ), as well as simulation studies by our group ( Mazumder et al, 2021 ) and others ( Qiu et al, 2018 , 2021 ; Colombo et al, 2019 ) indicating the importance of optimizing laser source characteristics for TD-DCS, we developed a high-performance, next-generation TD-DCS system employing a custom 1,064 nm laser source and superconducting nanowire single photon detectors (SNSPDs, overall size of 69 × 49.5 × 113 cm for depth, width, and height, respectively) to maximize measurement performance and enable functional brain imaging.…”

Kernel Flow: a high channel count scalable time-domain functional near-infrared spectroscopy system

“…3 There have been many advancements in TD-fNIRS technology development in recent years that have generated enthusiasm for TD-fNIRS data. Increased numbers of measurement channels, 4 increased sampling frequencies, 5 wearable and wireless systems, 6,7 and integration of additional data collection methods, such as diffuse correlation spectroscopy, 8 have improved data quality and enabled broader application areas.…”