Materials and Methods
The study was approved by the Guangdong Provincial People’s Hospital (Guangdong Academy of Medical Sciences). All of the data were acquired after obtaining authors permission.
The microbubbles were generated through standard reciprocating manual operation and measured with the microscopic shadow image technique. The details are as follows:
Preparation of the agitated saline microbubbles
The preparation of microbubbles is shown in Figure 1a. The experiment was carried out by hand pushing the syringe plugger reciprocating motion to create microbubbles. Each operator in each repeated experiment uses a 10 ml injector to extract 9 ml of 0.9% saline solution from the infusion bottle, then extract 1 ml of air. Then, each syringe plugger was pushed forward and backward ten times (Overall reciprocating motion 20 times) to mix the air with saline solution to activate the contrast agents (23) . Finally, the operator quickly and manually switched the three-way stopcock, injecting the saline-bubble mixture (within 1-2 seconds) into the flow test section. At the same time, the high-speed camera (Figure 1b) started taking images immediately. Six volunteers (M-1, M-2, M-3, M-4, M-5, and M-6) took part in the experiment, each completing ten repeated operations.