Fig. 5. PACTER of human hand hemodynamics in vivo.
a, Schematic of the human hand imaging experiment. b,c, 3D PACTER images of the thenar vasculature of participant 1 (b) and participant 2 (c). Norm., normalized. d,e, Maximum amplitude projections of the 3D volumes from the 4D PACTER datasets along the z axis in b (d) and c (e) at the time instances before, during, and after cuffing. t0 = 17.44 s, t1 = 19.02 s. The solid lines flank the vessels under investigation. Differences from the images during cuffing are highlighted. f,g, PA amplitudes along the vessels (1D images) in d (f) and e (g) versus time, where the time instances in d and e are labeled with vertical gray lines. The blue and orange arrows indicate peak responses in the occlusion and recovery phases, respectively. h, Positions (solid circles) of the blood front along the blood vessel during the occlusion (left) and recovery (right) phases in f. The blue curve is an exponential fit with an occlusion rate of 1.3 ± 0.1 m/s, and the orange curve is a linear fit showing the blood flow speed of 16.5 ± 2.8 m/s. i, Comparison between the durations of the occlusion and recovery phases in f. ***P < 0.001, calculated by the two-sample t-test. j, Positions (solid circles) of the blood front along the blood vessel during the occlusion (left) and recovery (right) phases in g. The blue curve is an exponential fit with an occlusion rate of 2.4 ± 0.3 m/s, and the orange curve is a linear fit showing the blood flow speed of 32.9 ± 6.5 m/s. k, Comparison between the durations of the occlusion and recovery phases in g. ***P < 0.001, calculated by the two-sample t-test. l, Comparison between the blood flow speeds during recovery in f and g. *P < 0.05. Scale bars, 1 mm.