Which statement best describes the function of time gain compensation in ultrasonography?

• A. It increases frame rate by rapid scanning.
• B. It adjusts the transducer frequency with depth.
• C. It provides depth-dependent gain compensation to produce uniform brightness with depth.
• D. It filters out high-frequency noise.

Answer: (C)

Time gain compensation is about depth-dependent amplification of the echoes. In ultrasound, signals attenuate as they travel deeper, so deeper tissues return weaker echoes. TGC boosts the amplification for those later-arriving signals (deeper depths) so the image brightness stays roughly uniform from near to far structures. This depth-focused control lets you compensate for natural attenuation and reveals deeper anatomy more clearly. It’s not about increasing frame rate, changing the transducer frequency with depth, or filtering noise—the gain is applied as a function of depth to balance brightness across the image.