Fig. 1. Schematic diagram of the SampEn calculation sequence for LSI images.

Fig. 2. Comparison of speckle contrast and SampEn calculations from phantom flow experiments. (a) Both σ_t and SampEn show a similar exponential decrease with increasing flow rate. (b) Incorporating the 〈I〉 in the calculation of speckle contrast (1/K_t²) and SampEn contrast (1/K_SE²) results in a linear relationship with the rate of flow, as well as a greater range of values for SampEn contrast. (Each point is an average of 60 values taken over 1 min at a constant flow rate. Error bars indicate the standard deviation.)

Fig. 3. (a) Normalized 1/K_SE² from flow phantom experiments depending on the various threshold values r. Threshold values were determined by multiples of the standard deviation of the first 65 recorded speckle intensity values where m is two. (b) The values of average and standard deviation of 1/K_SE² when the window length (m) changes from 2 to 4, where r is std*0.5.

Fig. 4. Representative blood flow maps during the baseline, arm occlusion, motion, overshooting period, and recovery. Blood flow maps are generated from 1/K_SE² (left) and 1/K_t² (middle), and raw images are shown in the right column.

Fig. 5. Blood flow during arm occlusion accompanied by sudden hand movements from three different subjects (each row). The dashed region indicates the period of occlusion.

Fig. 6. (a) Blood flow estimates using 1/K_SE² and post-processed 1/K_t² with varying cutoff frequencies. (b) Magnified trace of the rapid blood flow change during cuff inflation. (c) Magnified trace of the motion artifact induced change. Traces were offset in the y axis to highlight the difference.