Figure 4:

Breathing waveforms as a function of tissue depth. a,b) For several subjects, such as Subject A5 shown in (a), waveforms at different depths differed mostly in terms of motion amplitude, with larger motion detected at deeper locations. In contrast, for Subject B4 shown in (b), deeper tissues moved in the opposite direction relative to shallower subcutaneous tissues. c) Motion amplitude is shown for all 37 datasets obtained in 13 volunteers, and useful depth information was obtained in all subjects but A3, B5 and B8.