Dual-wavelength time-of-flight interferometric speckle-contrast optical spectroscopy (dual-wavelength TOF-iSCOS) for co-registered blood-flow and hemoglobin sensing
- 1Institute of Physical Chemistry PAS
Abstract
Diffuse optical measurements of blood flow, blood volume, and blood oxygenation often use separate devices and photon populations. Combining these contrasts within a common photon population would enable their direct co-registration while retaining time-of-flight-based depth discrimination. We introduce dual-wavelength time-of-flight interferometric speckle-contrast optical spectroscopy (TOF-iSCOS), built on an interferometric near-infrared spectroscopy (iNIRS) architecture that temporally multiplexes 780 and 852 nm swept lasers through a shared detection channel. It recovers co-registered flow-sensitive field dynamics and wavelength-resolved attenuation from the same complex-field acquisition. Three 50 ps TOF gates sample increasingly late-arriving photons. Within each gate, g1 was calculated directly as the normalized temporal autocorrelation of the reconstructed complex field.{kappa} 2(T) was reconstructed by finite-time integration of measured g1 and finite-integration fits yielded decorrelation rates. No camera speckle-variance contrast or Siegert substitution was used. Gate-integrated TPSF intensities yielded optical-density changes{Delta} OD, and division by the baseline-TPSF-weighted mean photon path length gave effective{Delta} {micro}a for two-wavelength hemoglobin inversion. In 12 forearm cuff-occlusion recordings from 11 adults, TOF-iSCOS detected flow suppression during occlusion and reactive hyperemia after release at both wavelengths. At 780 nm, the Late-minus-Early reactive-hyperemia amplitude in the relative blood-flow index (rBFI) was +0.647 (95% CI 0.194 to 1.124), whereas the Early-minus-Late cuff{Delta} {micro}a contrast was +0.196 cm-1 (95% CI 0.123 to 0.280). In the photon-limited 852 nm Late gate, the accepted-frame fraction was 0.994 for{kappa} 2-based fitting versus 0.831 for g1-based fitting. Exploratory phase-resolved analysis suggested that the initial hemoglobin response was concentrated in early-arriving photons, while later responses differed in magnitude and direction. Wavelength, field dynamics, and photon time-of-flight thus provide complementary physiological information; the largest response need not identify the phase of interest.
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BibTeX
@misc{nowackapieszak2026dualwavelength,
title = {{Dual-wavelength time-of-flight interferometric speckle-contrast optical spectroscopy (dual-wavelength TOF-iSCOS) for co-registered blood-flow and hemoglobin sensing}},
author = {K. Nowacka-Pieszak and M. Marzejon and N. Mogharari and D. Borycki},
howpublished = {medRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.02.26362024},
url = {https://www.medrxiv.org/content/10.64898/2026.09.02.26362024v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Dual-wavelength time-of-flight interferometric speckle-contrast optical spectroscopy (dual-wavelength TOF-iSCOS) for co-registered blood-flow and hemoglobin sensing
AU - K. Nowacka-Pieszak
AU - M. Marzejon
AU - N. Mogharari
AU - D. Borycki
PY - 2026
DA - 2026/09/02
PB - medRxiv
DO - 10.64898/2026.09.02.26362024
UR - https://www.medrxiv.org/content/10.64898/2026.09.02.26362024v1
AB - Diffuse optical measurements of blood flow, blood volume, and blood oxygenation often use separate devices and photon populations. Combining these contrasts within a common photon population would enable their direct co-registration while retaining time-of-flight-based depth discrimination. We introduce dual-wavelength time-of-flight interferometric speckle-contrast optical spectroscopy (TOF-iSCOS), built on an interferometric near-infrared spectroscopy (iNIRS) architecture that temporally multiplexes 780 and 852 nm swept lasers through a shared detection channel. It recovers co-registered flow-sensitive field dynamics and wavelength-resolved attenuation from the same complex-field acquisition. Three 50 ps TOF gates sample increasingly late-arriving photons. Within each gate, g1 was calculated directly as the normalized temporal autocorrelation of the reconstructed complex field.{kappa} 2(T) was reconstructed by finite-time integration of measured g1 and finite-integration fits yielded decorrelation rates. No camera speckle-variance contrast or Siegert substitution was used. Gate-integrated TPSF intensities yielded optical-density changes{Delta} OD, and division by the baseline-TPSF-weighted mean photon path length gave effective{Delta} {micro}a for two-wavelength hemoglobin inversion. In 12 forearm cuff-occlusion recordings from 11 adults, TOF-iSCOS detected flow suppression during occlusion and reactive hyperemia after release at both wavelengths. At 780 nm, the Late-minus-Early reactive-hyperemia amplitude in the relative blood-flow index (rBFI) was +0.647 (95% CI 0.194 to 1.124), whereas the Early-minus-Late cuff{Delta} {micro}a contrast was +0.196 cm-1 (95% CI 0.123 to 0.280). In the photon-limited 852 nm Late gate, the accepted-frame fraction was 0.994 for{kappa} 2-based fitting versus 0.831 for g1-based fitting. Exploratory phase-resolved analysis suggested that the initial hemoglobin response was concentrated in early-arriving photons, while later responses differed in magnitude and direction. Wavelength, field dynamics, and photon time-of-flight thus provide complementary physiological information; the largest response need not identify the phase of interest.
ER -