Table 1.

The parameters of different phased array probes.

Phased Array Probe	The Number of Elements	Excitation Frequency	Element Width	Element Pitch
probe A	16	1.0 MHz	1.8 mm	2.0 mm
probe B	32	2.5 MHz	0.9 mm	1.0 mm
probe C	32	5.0 MHz	0.9 mm	1.0 mm