In vivo cuff occlusion challenge in human forearm. (a) Experimental sketch. (b) Representative DTOF, showing the time gates, used for estimating the relative BFI trends (f,g). (c–e) Representative intensity ACFs of different stages of the measurement. At the baseline, intensity ACF decorrelates much faster (c) than at the cuff occlusion stage (d). Right after the cuff is released, the intensity ACF is composed of the two ACFs that decorrelate at different rates (e). The novel model depicts the depth-dependent reactive hyperemia (g), while conventional TD-DCS model does not (f).