Visualization 1

(a) Signal histograms of representative US images processed with the NL-p-DAS for various p values. Fixed dynamic ranges, independent of p, were applied in the conventional methods. (b), (c) Representative US (b) and PA (c) signal histograms to illustrate strategies to determine the adaptive dynamic ranges. First, we set a temporary dynamic range (D’) covering the effective signals in an image, and then set the top 80% of D’ as the final dynamic range (D). In the US image, D' is set from the bottom 10% to the top 1% due to the speckle background. In the PA image, D’ is set to be from the mode to the top 0.01% because the majority of background signal amplitudes are low. US, ultrasound; PA, photoacoustic; and NL-p-DAS, nonlinear p-th root delay-and-sum.