Final answer:
The statement is true; in a diagnostic ultrasound system, deeper imaging requires longer pulse repetition times to allow echoes to return before the next pulse is emitted.
Step-by-step explanation:
When the system is imaging more deeply, the time from one pulse to the next, known as the pulse repetition time, is indeed longer. This is true because the pulses must travel a greater distance to reach deeper tissues and then return to the transducer. The pulse repetition time must be sufficient to allow echoes from the deepest tissue of interest to return before the next pulse is emitted, ensuring that the echoes can be correctly attributed to the corresponding emitted pulse and that accurate imaging is achieved. This is essential in diagnostic ultrasound procedures.