Which parameter changes when a system's maximum imaging depth is adjusted?

Which parameter changes when a system's maximum imaging depth is adjusted?

• A. PRP
• B. Frequency
• C. Wavelength
• D. Amplitude

Answer: (A)

The key idea is that maximum imaging depth is determined by how long the system waits between emitted pulses, known as the pulse repetition period. Echoes must return before the next pulse is fired, so the listening window (PRP) sets how deep you can sample. Depth in ultrasound is tied to the round-trip travel time of sound, so maximum depth is roughly (speed of sound in tissue × PRP) / 2. Therefore, to image deeper structures, you lengthen PRP, which lowers the pulse repetition frequency and reduces frame rate, but allows echoes from greater depths to be received. The other parameters don’t directly set this depth limit: frequency (and thus wavelength) governs resolution and penetration but isn’t adjusted to change the depth window; amplitude relates to transmitted power and brightness, not the listening time between pulses.

The key idea is that maximum imaging depth is determined by how long the system waits between emitted pulses, known as the pulse repetition period. Echoes must return before the next pulse is fired, so the listening window (PRP) sets how deep you can sample. Depth in ultrasound is tied to the round-trip travel time of sound, so maximum depth is roughly (speed of sound in tissue × PRP) / 2. Therefore, to image deeper structures, you lengthen PRP, which lowers the pulse repetition frequency and reduces frame rate, but allows echoes from greater depths to be received.

The other parameters don’t directly set this depth limit: frequency (and thus wavelength) governs resolution and penetration but isn’t adjusted to change the depth window; amplitude relates to transmitted power and brightness, not the listening time between pulses.