Application of the time correlated single photon counting and fluorescence spectroscopy methods for assessment of oxidative metabolism of biotissue
V.S. Yanushin1, E.V. Zharkikh1, Yu.I. Loktionova1, A.V. Dunaev1; 1Orel State University named after I.S. Turgenev
Abstract
Optical non-invasive diagnostic systems are becoming increasingly valuable for early detection of microcirculatory-tissue systems (MTS) changes preceding clinical manifestations in various diseases. This study employs laser Doppler flowmetry (LDF) and fluorescence spectroscopy (FS) to investigate blood microcirculation parameters and oxidative metabolism, focusing on the influence of blood filling on fluorescence signals under artificial ischemia conditions. Time correlated single photon counting (TCSPC) is utilized as a reference method to validate the wearable analyzer's FS channel.
The LDF method measures the index of blood microcirculation (Im), while FS assesses oxidative metabolism by capturing autofluorescence spectra of NADH at 365 nm excitation wavelength. Two "LAZMA PF" wearable analyzers equipped with LDF (850 nm) and FS channels are employed. NADH exists in free and bound forms with distinct fluorescence lifetimes crucial for cellular redox processes (0.4 ns and 2 ns, respectively). Parameters such as NADH fluorescence intensity, relative content of α1 and α2 components, and their lifetimes (τ1 and τ2) are extracted using TCSPC.
Five healthy volunteers underwent testing on the middle finger and forearm, involving baseline blood flow measurements, 3-minute arterial occlusion (200 mmHg), and recovery phase recordings. Im decreases during occlusion in both anatomical areas. NADH fluorescence intensity shows variable correlations between wearable and TCSPC methods: both positive and negative in the finger and negative in the forearm. Relative α1 and α2 content consistently correlates negatively, indicating dynamic NADH redistribution during occlusion. Lifetimes τ1 and τ2 exhibit negative correlations, suggesting interconversion between free and bound NADH forms with region-specific dynamics.
This study underscores the intricate relationship between microcirculation and NADH fluorescence intensity, emphasizing the need for area-specific analysis due to anatomical variability. Dynamic shifts in NADH forms under ischemic conditions suggest potential diagnostic relevance in non-invasively assessing tissue metabolic status.
Speaker
Vyacheslav
Orel State University named after I.S. Turgenev
Russia
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