Which parameter remains constant as depth increases?

Which parameter remains constant as depth increases?

• A. Listening time
• B. Pulse duration
• C. Transmit time
• D. Depth

Answer: (C)

The main idea here is how ultrasound timing is split into two parts: the transmit phase and the listening phase. When you send a pulse, the transducer is active for a fixed duration—the transmit time. That length is determined by the transducer and its drive electronics and doesn’t depend on how deep you’re imaging. Depth affects how long echoes take to return, which is the listening time, so deep targets increase the time after emission before you hear the echo. Since the transmitted pulse length is fixed, the transmit time remains constant as depth increases.

The main idea here is how ultrasound timing is split into two parts: the transmit phase and the listening phase. When you send a pulse, the transducer is active for a fixed duration—the transmit time. That length is determined by the transducer and its drive electronics and doesn’t depend on how deep you’re imaging. Depth affects how long echoes take to return, which is the listening time, so deep targets increase the time after emission before you hear the echo. Since the transmitted pulse length is fixed, the transmit time remains constant as depth increases.