Speaker
Description
Introduction: Brain tissue stiffness has emerged as a promising biomarker for early diagnosis of neurodegenerative changes. Diffuse Correlation Spectroscopy (DCS) has the potential to estimate tissue stiffness non-invasively, as the decorrelation time of scattered light speckles (Tau 2) correlates with Young’s Modulus. While decorrelation time is dominated by dynamic scatterers, Tau 2 in tissue still decorrelates from photon pathlength divergence induced by scattering. However, this relationship is likely influenced by more than one physical parameter. More specifically, Tau 2 is also dependent on tissue scattering coefficient (μ_s^'), which is influenced by density and size of microstructures and can be measured with time-resolved near-infrared spectroscopy (trNIRS). We hypothesize that changes in μ_s^' also alter Tau 2 independent of variations in tissue stiffness. The objective of this study is to investigate the relationship between Tau 2 and μ_s^', using Intralipid (IL) phantoms to mimic varying degrees of tissue scattering while stiffness remains constant.
Methods: The phantoms were prepared by mixing increasing concentrations of IL in distilled water (0.5% to 1.5% in steps of 0.1%). For DCS measurements, a 785-nm, long-coherence length laser was used for emission, and a single-photon counting module was used for detection. Measurements for trNIRS were acquired (760 nm) using a commercial system (PIONIRS). A constrained optimization routine was used to estimate Tau 2 from the intensity autocorrelation function measured with DCS and μ_s^' was measured from the distribution of times-of-flight measured with trNIRS, using an analytical model light propagation in turbid media.
Results: As IL concentration increased, Tau 2 and μ_s^' exhibited negative correlation, with μ_s^' increasing as Tau 2 decreased. R2 of 0.733 demonstrated changes in Tau 2 are strongly correlated with μ_s^'.
Conclusion: The preliminary findings of this study show a quantitative relationship between Tau 2 from DCS and μ_s^' from trNIRS. Therefore, optical assessment of tissue stiffness requires both measurements with DCS and trNIRS to provide a potential non-invasive tool for early detection of neurodegenerative diseases. Immediate future work will investigate the relationship between Tau 2, μ_s^', and Young’s Modulus in solid phantoms, mimicking variations in both scattering and stiffness.
| Keyword-1 | Optical Techniques |
|---|---|
| Keyword-2 | Scattering Coefficient |
| Keyword-3 | Tissue Stiffness |