Images of a tissue mimicking phantom with (a) 800-, (b) 530-, (c) 400-, and (d) 300-μm-diameter anechoic cysts using the 30-MHz array and custom-designed imaging system. A single transmit and receive focus of 6.4 mm was used and the displayed dynamic range for this image is 40 dB. The contrast-to-noise ratios for these images at a range of 6.5 mm were estimated to be 2.6, 2.0, 2.0, and 1.1, respectively [31].