We report the time kinetics of fluorescently labelled microbubbles in capillary-level microvasculature as measured via confocal microscopy and compare these results to ultrasound localization microscopy. The observed 19.4 1 4.2 microbubbles per confocal field-of-view (212 lm x 212 lm) is in excellent agreement with the expected count of 19.1 microbubbles per frame. The estimated time to fully perfuse this capillary network was 193 seconds, which corroborates the values reported in literature.

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... then modeled the capillary network as an empirically determined discrete-time Markov chain with adjustable microbubble transition probabilities though individual capillaries. Monte Carlo random walk simulations found perfusion times ranging from 24.5 seconds for unbiased Markov chains up to 182 seconds for heterogeneous flow distributions. This pilot study confirms a probability-derived explanation for the long acquisition times required for super-resolution ultrasound localization microscopy.