Fig. 12.

Phantom 1 comparison of depth ranges for detectability of -- and for echo-free conditions of -- spheres for the model 770 25 MHz single-element transducer with the cases of the model 2100 20 MHz and 30 MHz linear arrays. The elevational focus of the 20 MHz linear array is most comparable to the fixed focus of the 770 transducer than that of the 30 MHz linear array. As expected, the depth range for detectability of spheres is much more restricted for the single element transducer than for the linear arrays. However, the single element transducer does a little better job of detecting the smallest detectable 300-μm spheres.