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. Author manuscript; available in PMC: 2009 May 4.
Published in final edited form as: IEEE Trans Ultrason Ferroelectr Freq Control. 2006 Aug;53(8):1412–1424. doi: 10.1109/tuffc.2006.1665098

Fig. 8.

Fig. 8

Definition of the ith initiated time (ITi) and the ith extinguished time (ETi). Diagram of backscatter temporal variability (backscatter energy moving standard deviation described in [2]) as a function of time is drawn to demonstrate the definition of ITi and ETi. ITi is the time interval between the ith initiation and the ith extinction. ETi is the time interval between the ith extinction and the (i + 1)th initiation. An initiating sequence containing N pulses was applied at the beginning of each ultrasound exposure. The applied initiating sequence was chosen to be 10 ms (200 pulses), 100 ms (2000 pulses), or 1 s (20,000 pulses). Consequently, the initiating sequence ends within 1 s after the beginning of each 480-s exposure (shown as arrow). Experimental observations show that the initiating sequence alone never created any visible erosion due to its short duration. The corresponding erosion depth could not be monitored in real time because of the interference from harmonics of the high-pressure therapy pulses due to nonlinear propagation and broadband noise generated by cavitating bubbles during the exposure.