Cuffing-based photoacoustic flowmetry in humans in the optical diffusive regime

Measuring blood flow speed in the optical diffusive re- gime in humans has been a long standing challenge for photoacoustic tomography. In this work, we proposed a cuffing-based method to quantify blood flow speed in hu- mans with a handheld photoacoustic probe. By cuffing and releasing the blood vessel, we can measure the blood flow speed downstream. In phantom experiments, we de- monstrated that the minimum and maximum measurable flow speeds were 0.035 mm/s and 42 mm/s, respectively. In human experiments, flow speeds were measured in three different blood vessels: a radial artery in the right forearm, a radial artery in the index finger of the right hand, and a radial vein in the right forearm. Taking ad- vantage of the handheld probe, our method can poten- tially be used to monitor blood flow speed in the clinic and at the bedside.