An ultrasound imaging system is equipped with two square transducers. One operates at 5 MHz and the other one operates at 12 MHz. The 5 MHz transducer is 2.0 cm by 2.0 cm and the 12 MHz one is 0.4 cm by 0.4 cm. The imaging system is tested in a medium having a speed of sound of 1,560 m/s at both frequencies. The amplitude attenuation factor of the medium satisfies

We want to image objects at ranges up to 20 cm.

(a) Find the system sensitivities L5MHz and L12MHz?

(b) What are the widths of the main lobes at the range of 20 cm? (Using the simple 3 dB model of a field pattern.)

(c) What is the maximum pulse repetition rate for the system?

(d) Suppose the transducers were scanned back and forth to obtain a B-mode image. What is the maximum frame rate if 128 lines are used to form an image?

(e) What will happen to the B-mode image if the speed of sound in the medium is nonuniform but we still use a uniform speed assumption?