Which statement about imaging probes is true?

Which statement about imaging probes is true?

• A. They have long pulses and narrow bandwidth
• B. They have short pulses and narrow bandwidth
• C. They have short pulses and wide bandwidth
• D. They have long pulses and wide bandwidth

Answer: (C)

Short pulses with wide bandwidth are what imaging probes use because pulse duration and spectral content are inversely related: a briefer pulse spreads across a broader range of frequencies. That broad bandwidth lets the system distinguish echoes that are very close in time, improving axial (depth) resolution. If the pulse were long and the bandwidth narrow, depth resolution would suffer. A short pulse with narrow bandwidth would have limited spectral content and poorer resolution, and a long pulse with wide bandwidth would contradict the usual inverse relationship between pulse length and bandwidth.

Short pulses with wide bandwidth are what imaging probes use because pulse duration and spectral content are inversely related: a briefer pulse spreads across a broader range of frequencies. That broad bandwidth lets the system distinguish echoes that are very close in time, improving axial (depth) resolution. If the pulse were long and the bandwidth narrow, depth resolution would suffer. A short pulse with narrow bandwidth would have limited spectral content and poorer resolution, and a long pulse with wide bandwidth would contradict the usual inverse relationship between pulse length and bandwidth.