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Optical coherence tomography (OCT) provides noninvasive, high-resolution visualization of tissue microstructure and microvasculature. Functional extensions like Doppler OCT images blood flow, but are blind to static blood, while photothermal OCT (PTOCT) visualizes hemoglobin absorption without flow sensitivity. This incompatibility between modalities has hindered integrated vascular assessment. Herein, we present a dual-modality cross-correlation photothermal-Doppler OCT system enabled by what we believe to be a novel signal preprocessing scheme that unifies their signal extraction. By transforming the linear Doppler phase shift into a constructed velocity-modulated signal, it becomes compatible with the same cross-correlation demodulation algorithm used for PTOCT. This unified approach leverages the weak-signal enhancement and noise suppression of cross-correlation analysis. Consequently, the system seamlessly acquires simultaneous, co-registered high-resolution images of both microvasculature (via Doppler contrast) and static intravascular hemorrhage (via photothermal absorption) in vivo, achieving capillary-level resolution in mouse ear imaging. This work provides a unified framework for dual-contrast vascular imaging, demonstrating significant potential for noninvasive clinical diagnostics where comprehensive evaluation of both static and dynamic blood status is crucial.
Tang et al. (Tue,) studied this question.